text:
HTTPS
From Wikipedia, the free encyclopedia
Jump to: navigation, search
HTTPS (also called HTTP over Transport Layer Security [TLS],[1] HTTP over SSL,[2] and HTTP Secure[3][4]) is a communications protocol for secure communication over a computer network which is widely used on the Internet. HTTPS consists of communication over Hypertext Transfer Protocol (HTTP) within a connection encrypted by Transport Layer Security, or its predecessor, Secure Sockets Layer. The main motivation for HTTPS is authentication of the visited website and protection of the privacy and integrity of the exchanged data.
In its popular deployment on the internet, HTTPS provides authentication of the website and associated web server with which one is communicating, which protects against man-in-the-middle attacks. Additionally, it provides bidirectional encryption of communications between a client and server, which protects against eavesdropping and tampering with or forging the contents of the communication.[5] In practice, this provides a reasonable guarantee that one is communicating with precisely the website that one intended to communicate with (as opposed to an impostor), as well as ensuring that the contents of communications between the user and site cannot be read or forged by any third party.
Historically, HTTPS connections were primarily used for payment transactions on the World Wide Web, e-mail and for sensitive transactions in corporate information systems. In the late 2000s and early 2010s, HTTPS began to see widespread use for protecting page authenticity on all types of websites, securing accounts and keeping user communications, identity and web browsing private.
Contents
[hide]
1 Overview
1.1 Usage in websites
1.2 Browser integration
2 Security
3 Technical
3.1 Difference from HTTP
3.2 Network layers
3.3 Server setup
3.3.1 Acquiring certificates
3.3.2 Use as access control
3.3.3 In case of compromised secret (private) key
3.4 Limitations
4 History
5 See also
6 References
7 External links
Overview[edit]
For more details on this topic, see Transport Layer Security.
Illustration of the networking protocol https and the www letters
The HTTPS Uniform Resource Identifier (URI) scheme has identical syntax to the standard HTTP scheme, aside from its scheme token. However, HTTPS signals the browser to use an added encryption layer of SSL/TLS to protect the traffic. SSL/TLS is especially suited for HTTP, since it can provide some protection even if only one side of the communication is authenticated. This is the case with HTTP transactions over the Internet, where typically only the server is authenticated (by the client examining the server's certificate).
HTTPS creates a secure channel over an insecure network. This ensures reasonable protection from eavesdroppers and man-in-the-middle attacks, provided that adequate cipher suites are used and that the server certificate is verified and trusted.
Because HTTPS piggybacks HTTP entirely on top of TLS, the entirety of the underlying HTTP protocol can be encrypted. This includes the request URL (which particular web page was requested), query parameters, headers, and cookies (which often contain identity information about the user). However, because host (website) addresses and port numbers are necessarily part of the underlying TCP/IP protocols, HTTPS cannot protect their disclosure. In practice this means that even on a correctly configured web server, eavesdroppers can infer the IP address and port number of the web server (sometimes even the domain name e.g. www.example.org, but not the rest of the URL) that one is communicating with, as well as the amount (data transferred) and duration (length of session) of the communication, though not the content of the communication.[5]
Web browsers know how to trust HTTPS websites based on certificate authorities that come pre-installed in their software. Certificate authorities (such as Symantec, Comodo, GoDaddy and GlobalSign) are in this way being trusted by web browser creators to provide valid certificates. Therefore, a user should trust an HTTPS connection to a website if and only if all of the following are true:
The user trusts that the browser software correctly implements HTTPS with correctly pre-installed certificate authorities.
The user trusts the certificate authority to vouch only for legitimate websites.
The website provides a valid certificate, which means it was signed by a trusted authority.
The certificate correctly identifies the website (e.g., when the browser visits "https://example.com", the received certificate is properly for "example.com" and not some other entity).
The user trusts that the protocol's encryption layer (SSL/TLS) is sufficiently secure against eavesdroppers.
HTTPS is especially important over insecure networks (such as public Wi-Fi access points), as anyone on the same local network can packet-sniff and discover sensitive information not protected by HTTPS. Additionally, many free to use and paid WLAN networks engage in packet injection in order to serve their own ads on webpages. However, this can be exploited maliciously in many ways, such as injecting malware onto webpages and stealing users' private information.[6]
HTTPS is also very important for connections over the Tor anonymity network, as malicious Tor nodes can damage or alter the contents passing through them in an insecure fashion and inject malware into the connection. This is one reason why the Electronic Frontier Foundation and the Tor project started the development of HTTPS Everywhere,[5] which is included in the Tor Browser Bundle.[7]
As more information is revealed about global mass surveillance and criminals stealing personal information, the use of HTTPS security on all websites is becoming increasingly important regardless of the type of Internet connection being used.[8][9] While metadata about individual pages that a user visits is not sensitive, when combined, they can reveal a lot about the user and compromise the user's privacy.[10][11][12]
Deploying HTTPS also allows the use of HTTP/2 (or its predecessor, the now-deprecated protocol SPDY), that are new generations of HTTP, designed to reduce page load times and latency.
It is recommended to use HTTP Strict Transport Security (HSTS) with HTTPS to protect users from man-in-the-middle attacks, especially SSL stripping.[12][13]
HTTPS should not be confused with the little-used Secure HTTP (S-HTTP) specified in RFC 2660.
Usage in websites[edit]
As of November 2017[update], 27.7% of Alexa top 1,000,000 websites use HTTPS as default,[14] 43.1% of the Internet's 141,387 most popular websites have a secure implementation of HTTPS,[15] and 45% of page loads (measured by Firefox Telemetry) use HTTPS.[16]
According to Mozilla since January 2017 more than half of the Web traffic is encrypted.[17][18]
Browser integration[edit]
Most browsers display a warning if they receive an invalid certificate. Older browsers, when connecting to a site with an invalid certificate, would present the user with a dialog box asking whether they wanted to continue. Newer browsers display a warning across the entire window. Newer browsers also prominently display the site's security information in the address bar. Extended validation certificates turn the address bar green in newer browsers. Most browsers also display a warning to the user when visiting a site that contains a mixture of encrypted and unencrypted content.
Comparison between different kinds of SSL/TLS certificates
(Using Firefox as an example)
Many web browsers, including Firefox (shown here), use the address bar to tell the user that their connection is secure, often by coloring the background.
When accessing a site only with a common certificate, the address bar of Firefox turns green. For some other browsers, a "lock" sign may appear.
Most web browsers alert the user when visiting sites that have invalid security certificates.
Firefox uses HTTPS for Google searches as of version 14,[19] to "shield our users from network infrastructure that may be gathering data about the users or modifying/censoring their search results".[20]
The Electronic Frontier Foundation, opining that "In an ideal world, every web request could be defaulted to HTTPS", has provided an add-on called HTTPS Everywhere for Mozilla Firefox that enables HTTPS by default for hundreds of frequently used websites. A beta version of this plugin is also available for Google Chrome and Chromium.[21][22]
Security[edit]
Main article: Transport Layer Security § Security
The security of HTTPS is that of the underlying TLS, which typically uses long-term public and private keys to generate a short-term session key, which is then used to encrypt the data flow between client and server. X.509 certificates are used to authenticate the server (and sometimes the client as well). As a consequence, certificate authorities and public key certificates are necessary to verify the relation between the certificate and its owner, as well as to generate, sign, and administer the validity of certificates. While this can be more beneficial than verifying the identities via a web of trust, the 2013 mass surveillance disclosures drew attention to certificate authorities as a potential weak point allowing man-in-the-middle attacks.[23][24] An important property in this context is forward secrecy, which ensures that encrypted communications recorded in the past cannot be retrieved and decrypted should long-term secret keys or passwords be compromised in the future. Not all web servers provide forward secrecy.[25][needs update]
A site must be completely hosted over HTTPS, without having part of its contents loaded over HTTP – for example, having scripts loaded insecurely – or the user will be vulnerable to some attacks and surveillance. Also having only a certain page that contains sensitive information (such as a log-in page) of a website loaded over HTTPS, while having the rest of the website loaded over plain HTTP, will expose the user to attacks. On a site that has sensitive information somewhere on it, every time that site is accessed with HTTP instead of HTTPS, the user and the session will get exposed. Similarly, cookies on a site served through HTTPS have to have the secure attribute enabled.[12]
Technical[edit]
Difference from HTTP[edit]
HTTPS URLs begin with "https://" and use port 443 by default, whereas HTTP URLs begin with "http://" and use port 80 by default.
HTTP is not encrypted and is vulnerable to man-in-the-middle and eavesdropping attacks, which can let attackers gain access to website accounts and sensitive information, and modify webpages to inject malware or advertisements. HTTPS is designed to withstand such attacks and is considered secure against them (with the exception of older, deprecated versions of SSL).
Network layers[edit]
HTTP operates at the highest layer of the TCP/IP model, the Application layer; as does the TLS security protocol (operating as a lower sublayer of the same layer), which encrypts an HTTP message prior to transmission and decrypts a message upon arrival. Strictly speaking, HTTPS is not a separate protocol, but refers to use of ordinary HTTP over an encrypted SSL/TLS connection.
Everything in the HTTPS message is encrypted, including the headers, and the request/response load. With the exception of the possible CCA cryptographic attack described in the limitations section below, the attacker can only know that a connection is taking place between the two parties and their domain names and IP addresses.
Server setup[edit]
To prepare a web server to accept HTTPS connections, the administrator must create a public key certificate for the web server. This certificate must be signed by a trusted certificate authority for the web browser to accept it without warning. The authority certifies that the certificate holder is the operator of the web server that presents it. Web browsers are generally distributed with a list of signing certificates of major certificate authorities so that they can verify certificates signed by them.
Acquiring certificates[edit]
Authoritatively signed certificates may be free[26][27] or cost between 8 USD[28] and 70 USD[29] per year (in 2012–2014).
Organizations may also run their own certificate authority, particularly if they are responsible for setting up browsers to access their own sites (for example, sites on a company intranet, or major universities). They can easily add copies of their own signing certificate to the trusted certificates distributed with the browser.
There also exists a peer-to-peer certificate authority, CACert. However, it is not included in the trusted root certificates of many popular browsers (e.g. Firefox, Chrome, Internet Explorer), which may cause warning messages to be displayed to end users.
Let's Encrypt, launched in April 2016,[30] provides free and automated SSL/TLS certificates to websites.[31] According to the Electronic Frontier Foundation, "Let's Encrypt" will make switching from HTTP to HTTPS "as easy as issuing one command, or clicking one button."[32]
Use as access control[edit]
The system can also be used for client authentication in order to limit access to a web server to authorized users. To do this, the site administrator typically creates a certificate for each user, a certificate that is loaded into their browser. Normally, that contains the name and e-mail address of the authorized user and is automatically checked by the server on each reconnect to verify the user's identity, potentially without even entering a password.
In case of compromised secret (private) key[edit]
An important property in this context is perfect forward secrecy (PFS). Possessing one of the long-term asymmetric secret keys used to establish an HTTPS session should not make it easier to derive the short-term session key to then decrypt the conversation, even at a later time. Diffie–Hellman key exchange (DHE) and Elliptic curve Diffie–Hellman key exchange (ECDHE) are in 2013 the only ones known to have that property. Only 30% of Firefox, Opera, and Chromium Browser sessions use it, and nearly 0% of Apple's Safari and Microsoft Internet Explorer sessions.[25] Among the larger internet providers, only Google supports PFS since 2011 (State of September 2013).[citation needed]
A certificate may be revoked before it expires, for example because the secrecy of the private key has been compromised. Newer versions of popular browsers such as Firefox,[33] Opera,[34] and Internet Explorer on Windows Vista[35] implement the Online Certificate Status Protocol (OCSP) to verify that this is not the case. The browser sends the certificate's serial number to the certificate authority or its delegate via OCSP and the authority responds, telling the browser whether the certificate is still valid.[36]
Limitations[edit]
SSL/TLS comes in two options, simple and mutual. The mutual version is more secure, but requires the user to install a personal client certificate into their web browser in order to authenticate themselves.[37]
Whether the strategy is simple or mutual, the level of protection strongly depends on the correctness of the implementation of the web browser and the server software and the actual cryptographic algorithms supported.
SSL/TLS does not prevent the entire site from being indexed using a web crawler, and in some cases the URI of the encrypted resource can be inferred by knowing only the intercepted request/response size.[38] This allows an attacker to have access to the plaintext (the publicly available static content), and the encrypted text (the encrypted version of the static content), permitting a cryptographic attack.
Because TLS operates below HTTP and has no knowledge of higher-level protocols, TLS servers can only strictly present one certificate for a particular IP/port combination.[39] In the past, this meant that it was not feasible to use name-based virtual hosting with HTTPS. A solution called Server Name Indication (SNI) exists, which sends the hostname to the server before encrypting the connection, although many very old browsers do not support this extension. Support for SNI is available since Firefox 2, Opera 8, Safari 2.1, Google Chrome 6, and Internet Explorer 7 on Windows Vista.[40][41][42]
From an architectural point of view:
An SSL/TLS connection is managed by the first front machine that initiates the TLS connection. If, for any reasons (routing, traffic optimization, etc.), this front machine is not the application server and it has to decipher data, solutions have to be found to propagate user authentication information or certificate to the application server, which needs to know who is going to be connected.
For SSL/TLS with mutual authentication, the SSL/TLS session is managed by the first server that initiates the connection. In situations where encryption has to be propagated along chained servers, session timeOut management becomes extremely tricky to implement.
With mutual SSL/TLS, security is maximal, but on the client-side, there is no way to properly end the SSL/TLS connection and disconnect the user except by waiting for the server session to expire or closing all related client applications.
A sophisticated type of man-in-the-middle attack called SSL stripping was presented at the Blackhat Conference 2009. This type of attack defeats the security provided by HTTPS by changing the https: link into an http: link, taking advantage of the fact that few Internet users actually type "https" into their browser interface: they get to a secure site by clicking on a link, and thus are fooled into thinking that they are using HTTPS when in fact they are using HTTP. The attacker then communicates in clear with the client.[43] This prompted the development of a countermeasure in HTTP called HTTP Strict Transport Security.
HTTPS has been shown vulnerable to a range of traffic analysis attacks. Traffic analysis attacks are a type of side-channel attack that relies on variations in the timing and size of traffic in order to infer properties about the encrypted traffic itself. Traffic analysis is possible because SSL/TLS encryption changes the contents of traffic, but has minimal impact on the size and timing of traffic. In May 2010, a research paper by researchers from Microsoft Research and Indiana University discovered that detailed sensitive user data can be inferred from side channels such as packet sizes. More specifically, the researchers found that an eavesdropper can infer the illnesses/medications/surgeries of the user, his/her family income and investment secrets, despite HTTPS protection in several high-profile, top-of-the-line web applications in healthcare, taxation, investment and web search.[44] Although this work demonstrated vulnerability of HTTPS to traffic analysis, the approach presented by the authors required manual analysis and focused specifically on web applications protected by HTTPS.
In June 2014, a team of researchers at UC Berkeley and Intel led by Brad Miller demonstrated a generalized approach to HTTPS traffic analysis based on machine learning.[45][46] The researchers demonstrated that the attack applied to a range of websites, including Mayo Clinic, Planned Parenthood and YouTube.[47] The attack assumes that the attacker is able to visit the same webpages as the victim to gather Network traffic which serves as training data. The attacker is then able to identify similarities in the packet sizes and orderings between the victim traffic and the training data traffic which frequently allow the attacker to infer the exact page the victim is visiting. For example, this attack could be used to determine whether a user browsing the Planned Parenthood website is looking for information about preventative health screening or an abortion. Note that the attack can not be used to discover user specific values embedded in a webpage. For example, many banks offer web interfaces which allow users to view account balances. While the attacker would be able to discover that the user was viewing an account balance page, they would be unable to learn the user's exact account balance or account number.
History[edit]
Netscape Communications created HTTPS in 1994 for its Netscape Navigator web browser.[48] Originally, HTTPS was used with the SSL protocol. As SSL evolved into Transport Layer Security (TLS), HTTPS was formally specified by RFC 2818 in May 2000.
See also[edit]
Bullrun (decryption program) – a secret anti-encryption program run by the U.S. National Security Agency
Computer security
curl-loader
Diameter protocol
HTTPsec
Moxie Marlinspike
Opportunistic encryption
Stunnel
References[edit]
Jump up ^ Network Working Group (May 2000). "HTTP Over TLS". The Internet Engineering Task Force. Retrieved February 27, 2015.
Jump up ^ "Enabling HTTP Over SSL". Adobe Systems Incorporated. Retrieved February 27, 2015.
Jump up ^ "Secure your site with HTTPS". Google Support. Google, Inc. Retrieved February 27, 2015.
Jump up ^ "What is HTTPS?". Comodo CA Limited. Retrieved February 27, 2015. Hyper Text Transfer Protocol Secure (HTTPS) is the secure version of HTTP [...]
^ Jump up to: a b c "HTTPS Everywhere FAQ". Retrieved 3 May 2012.
Jump up ^ "Hotel Wifi JavaScript Injection". Retrieved 24 July 2012.
Jump up ^ The Tor Project, Inc. "Tor". torproject.org.
Jump up ^ Konigsburg, Eitan; Pant, Rajiv; Kvochko, Elena (November 13, 2014). "Embracing HTTPS". The New York Times. Retrieved February 27, 2015.
Jump up ^ Gallagher, Kevin (September 12, 2014). "Fifteen Months After the NSA Revelations, Why Aren't More News Organizations Using HTTPS?". Freedom of the Press Foundation. Retrieved February 27, 2015.
Jump up ^ "HTTPS as a ranking signal". Google Webmaster Central Blog. Google Inc. August 6, 2014. Retrieved February 27, 2015. You can make your site secure with HTTPS (Hypertext Transfer Protocol Secure) [...]
Jump up ^ Grigorik, Ilya; Far, Pierre (June 26, 2014). "Google I/O 2014 - HTTPS Everywhere". Google Developers. Retrieved February 27, 2015.
^ Jump up to: a b c "How to Deploy HTTPS Correctly". Retrieved 13 June 2012.
Jump up ^ "HTTP Strict Transport Security". Mozilla Developer Network.
Jump up ^ "HTTPS usage statistics on top websites". statoperator.com. Retrieved 2017-11-03.
Jump up ^ "SSL Pulse". Trustworthy Internet Movement. 2015-10-03. Retrieved 2015-10-19.
Jump up ^ Aas, Josh (22 June 2016). "Progress Towards 100% HTTPS, June 2016". Lets Encrypt. Retrieved 23 July 2016.
Jump up ^ "We're Halfway to Encrypting the Entire Web". Electronic Frontier Foundation. 21 February 2017. Retrieved 3 May 2017.
Jump up ^ Finley, Klint (January 31, 2017). "Half the Web Is Now Encrypted. That Makes Everyone Safer". WIRED. Retrieved 1 May 2017.
Jump up ^ "Firefox 14.0.1 Release Notes". Retrieved 24 July 2012.
Jump up ^ "Firefox Rolling Out HTTPS Google search". Retrieved 24 July 2012.
Jump up ^ Peter Eckersley: Encrypt the Web with the HTTPS Everywhere Firefox Extension EFF blog, 17 June 2010
Jump up ^ HTTPS Everywhere EFF projects
Jump up ^ Law Enforcement Appliance Subverts SSL, Wired, 2010-04-03.
Jump up ^ New Research Suggests That Governments May Fake SSL Certificates, EFF, 2010-03-24.
^ Jump up to: a b SSL: Intercepted today, decrypted tomorrow, Netcraft, 2013-06-25.
Jump up ^ "Free SSL Certificates from a Free Certificate Authority". sslshopper.com. Retrieved 2009-10-24.
Jump up ^ Justin Fielding (2006-07-16). "Secure Outlook Web Access with (free) SSL: Part 1". TechRepublic. Retrieved 2009-10-24.
Jump up ^ "Namecheap.com SSL Services". namecheap. Retrieved 30 Jan 2012.
Jump up ^ "Secure Site Pro with SSL Certificate". Retrieved August 23, 2014.
Jump up ^ Catalin Cimpanu. "Let's Encrypt Launched Today, Currently Protects 3.8 Million Domains". Softpedia News. Retrieved April 12, 2016.
Jump up ^ Kerner, Sean Michael (November 18, 2014). "Let's Encrypt Effort Aims to Improve Internet Security". eWeek.com. Quinstreet Enterprise. Retrieved February 27, 2015.
Jump up ^ Eckersley, Peter (November 18, 2014). "Launching in 2015: A Certificate Authority to Encrypt the Entire Web". Electronic Frontier Foundation. Retrieved February 27, 2015.
Jump up ^ "Mozilla Firefox Privacy Policy". Mozilla Foundation. 27 April 2009. Archived from the original on 26 May 2009. Retrieved 13 May 2009.
Jump up ^ "Opera 8 launched on FTP". Softpedia. 19 April 2005. Retrieved 13 May 2009.
Jump up ^ Lawrence, Eric (31 January 2006). "HTTPS Security Improvements in Internet Explorer 7". MSDN. Retrieved 13 May 2009.
Jump up ^ Myers, M; Ankney, R; Malpani, A; Galperin, S; Adams, C (June 1999). "Online Certificate Status Protocol – OCSP". Internet Engineering Task Force. Retrieved 13 May 2009.
Jump up ^ "Manage client certificates on Chrome devices - Chrome for business and education Help". support.google.com. Retrieved 2016-10-13.
Jump up ^ Pusep, Stanislaw (31 July 2008). "The Pirate Bay un-SSL". Archived from the original on 8 March 2009. Retrieved 6 March 2009.
Jump up ^ "SSL/TLS Strong Encryption: FAQ". apache.org.
Jump up ^ Lawrence, Eric (22 October 2005). "Upcoming HTTPS Improvements in Internet Explorer 7 Beta 2". Microsoft. Retrieved 12 May 2009.
Jump up ^ "Server Name Indication (SNI)". inside aebrahim's head.
Jump up ^ Pierre, Julien. "Browser support for TLS server name indication" (2001-12-19). Bugzilla. Mozilla Foundation. Retrieved 2010-12-15.
Jump up ^ "sslstrip". Retrieved 2011-11-26.
Jump up ^ Shuo Chen; Rui Wang; XiaoFeng Wang; Kehuan Zhang (May 2010). "Side-Channel Leaks in Web Applications: a Reality Today, a Challenge Tomorrow" (PDF). IEEE Symposium on Security & Privacy 2010.
Jump up ^ "Statistical Tricks Extract Sensitive Data from Encrypted Communications". MIT Technology Review. 2014-06-19.
Jump up ^ "Researchers Use Big Data to Get Around Encryption". The Wall Street Journal. 2014-06-23.
Jump up ^ Brad Miller; Ling Huang; Anthony D. Joseph; J.D. Tygar. "I Know Why You Went to the Clinic: Risks and Realization of HTTPS Traffic Analysis" (PDF).
Jump up ^ Walls, Colin (2005). Embedded software. Newnes. p. 344. ISBN 0-7506-7954-9.
External links[edit]
Wikimedia Commons has media related to HTTPS.
RFC 2818: HTTP Over TLS
RFC 5246: The Transport Layer Security Protocol 1.2
RFC 6101: The Secure Sockets Layer (SSL) Protocol Version 3.0
[show]
v
t
e
Uniform Resource Identifier (URI) schemes
Official
about
acct
crid
data
file
geo
gopher
http
https
info
ldap
mailto
sip / sips
tag
tel
urn
view-source
wais
ws / wss
Unofficial
coffee
ed2k
feed
irc / irc6 / ircs
ldaps
magnet
ymsgr
Protocol list
[show]
v
t
e
Web browsers
Comparison
lightweight
History
List
for Unix
Timeline
Usage share
Features
Ad filtering
Augmented browsing
Bookmarks
Bookmarklet
Live bookmark
Smart Bookmarks
Browser extension
Browser security
Browser synchronizer
comparison
Cookies
Download manager
Favicon
Incremental search
Plug-in
Privacy mode
Tabs
Universal Edit Button
Web standards
Acid tests
Cascading Style Sheets
HTML
HTML5
JavaScript
MathML
OCSP
SVG
WebGL
XHTML
Related topics
BrowserChoice.eu
CRL
HTTP
HTTPS
iLoo
Internet suite
Man-in-the-browser
Mobile Web
Offline reader
PAC
Pwn2Own
Rich Internet application
Site-specific browser
SPDY
SSL/TLS
WebSocket
Widget
World Wide Web
WPAD
XML
[show]
Desktop
Blink-based
Chromium
Brave
Chrome
Dragon
Opera
QupZilla
Sleipnir
Slimjet
SRWare Iron
UC Browser
Vivaldi
Yandex Browser
Sputnik
SafeZone
Gecko-based
AT&T Pogo
Avant
Camino
Firefox
Conkeror
GNU IceCat
IceDragon
Swiftfox
Swiftweasel
TenFourFox
Timberwolf
Tor Browser
Waterfox
xB Browser
Galeon
Ghostzilla
K-Meleon
Kazehakase
Kirix Strata
Lotus Symphony
Lunascape
Mozilla
Beonex Communicator
Classilla
Netscape
SeaMonkey
Trident-based
AOL Explorer
Avant
Deepnet Explorer
GreenBrowser
Internet Explorer
Lunascape
Maxthon
MediaBrowser
MenuBox
NeoPlanet
NetCaptor
SlimBrowser
SpaceTime
UltraBrowser
WebbIE
ZAC Browser
WebKit-based
Arora
Avant
Dooble
Epic
Flock
Fluid
iCab
Konqueror
Lunascape
Maxthon
Midori
OmniWeb
Origyn Web Browser
Otter Browser
QtWeb
rekonq
Safari
Shiira
SlimBoat
surf
Torch
Uzbl
Epiphany
WebPositive
xombrero
Text-based
ELinks
Emacs/W3
Line Mode Browser
Links
Lynx
w3m
Other
abaco
Amaya
Arachne
Arena
Charon
Dillo
eww
Gazelle
HotJava
IBM Home Page Reader
IBrowse
KidZui
Microsoft Edge
Mosaic
Mothra
NetPositive
NetSurf
Pale Moon
Qihoo 360 Secure Browser
[show]
Mobile
Blink-based
Android Browser
Chromium
Brave
Chrome for Android
Opera Mobile
Silk
Gecko-based
Firefox for Android
MicroB
Minimo
Presto-based
Opera Mini
Trident-based
Maxthon
WebKit-based
BOLT
Dolphin Browser
Chrome for iOS
Firefox for iOS
Maxthon
Mercury Browser
Nokia Browser for Symbian
Rockmelt
Safari
Steel
Other
Blazer
CM Browser
Deepfish
ibisBrowser
Internet Explorer Mobile
Iris Browser
Konqueror Embedded
Microsoft Edge
NetFront
Nokia Xpress
Skweezer
Skyfire
Teashark
ThunderHawk
UC Browser
Vision
WinWAP
[show]
Television and video game console
Gecko-based
Kylo
Presto-based
Internet Channel
WebKit-based
Google TV
Nintendo 3DS Internet Browser
Nintendo DS & DSi Browser
NetFront
Steam Overlay
Wii U Internet Browser
Other
MSN TV
Software no longer in development shown in italics
Category
Commons
Internet portal
Software portal
[show]
v
t
e
TLS and SSL
Protocols and technologies
Transport Layer Security / Secure Sockets Layer (TLS/SSL)
Datagram Transport Layer Security (DTLS)
DNS Certification Authority Authorization (CAA)
DNS-based Authentication of Named Entities (DANE)
HTTPS
HTTP Public Key Pinning (HPKP)
HTTP Strict Transport Security (HSTS)
OCSP stapling
Perfect forward secrecy
Server Name Indication (SNI)
STARTTLS
Application-Layer Protocol Negotiation (ALPN)
Public-key infrastructure
Automated Certificate Management Environment (ACME)
Certificate authority (CA)
CA/Browser Forum
Certificate policy
Certificate revocation list (CRL)
Domain-validated certificate (DV)
Extended Validation Certificate (EV)
Online Certificate Status Protocol (OCSP)
Public key certificate
Public-key cryptography
Public key infrastructure (PKI)
Root certificate
Self-signed certificate
See also
Domain Name System Security Extensions (DNSSEC)
Internet Protocol Security (IPsec)
Secure Shell (SSH)
History
Export of cryptography from the United States
Server-Gated Cryptography
Implementations
Bouncy Castle
BoringSSL
Botan
CryptoComply by SafeLogic
cryptlib
GnuTLS
JSSE
LibreSSL
MatrixSSL
mbed TLS
NSS
OpenSSL
RSA BSAFE
SChannel
SSLeay
stunnel
wolfSSL
Notaries
Certificate Transparency
Convergence
HTTPS Everywhere / SSL Observatory
Perspectives Project
Vulnerabilities
Theory
Man-in-the-middle attack
Padding oracle attack
Cipher
Bar mitzvah attack
Protocol
BEAST
BREACH
CRIME
DROWN
Logjam
POODLE (in regards to SSL 3.0)
Implementation
Certificate authority compromise
Random number generator attacks
FREAK
goto fail
Heartbleed
Lucky Thirteen attack
POODLE (in regards to TLS 1.0)
[show]
v
t
e
Internet censorship circumvention technologies
Background
Internet censorship
Internet censorship in China
National intranet
Censorship and blocking technologies
IP address blocking
DNS cache pollution
Wordfilter
Great Firewall of China
Blocks on specific websites
Wikipedia
Facebook
Twitter
Principles
With a proxy server
P2P
Web proxies
SSH
VPN
PAC
Without a proxy server
HTTPS
IPv6
hosts
DNSCrypt
Anti-censorship software
Free software
Lantern
Psiphon
GoAgent
GoProxy
Shadowsocks
V2Ray
VPN Gate
Proprietary software
Freegate
Ultrasurf
Hotspot Shield
fqrouter
GPass
Xiaoyaoyou
Huofenghuang
Garden Networks
Puff
West Wing plan
Telex
FreeBrowser
Integrated into browsers
X browser (supporting Android only)
Xingyuan browser (supporting Windows only)
Changyou Wuxian browser
Xskywalker (Tianxing browser)
Browser extensions
uProxy
Hongxing
Anonymity
Anonymous software
Tor
I2P
JAP
Anonymous P2P network
ZeroNet
Freenet
StealthNet
Relevant organizations
GreatFire
FreeWeibo
FreeBrowser
Turkey Blocks
Relevant events
2016 Chinese meme war on Facebook
Reference
Program Think Blog
Great Cannon
Strike through: the maintainers have stopped maintenance
Retrieved from "https://en.wikipedia.org/w/index.php?title=HTTPS&oldid=809029762"
Categories:
Hypertext Transfer Protocol
Cryptographic protocols
Secure communication
URI schemes
Transport Layer Security
Hidden categories:
Articles containing potentially dated statements from November 2017
All articles containing potentially dated statements
Wikipedia articles in need of updating from February 2015
All Wikipedia articles in need of updating
All articles with unsourced statements
Articles with unsourced statements from September 2013
Pages using RFC magic links
Navigation menu
Personal tools
Not logged in
Talk
Contributions
Create account
Log in
Namespaces
Article
Talk
Variants
Views
Read
Edit
View history
More
Search
Navigation
Main page
Contents
Featured content
Current events
Random article
Donate to Wikipedia
Wikipedia store
Interaction
Help
About Wikipedia
Community portal
Recent changes
Contact page
Tools
What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Wikidata item
Cite this page
Print/export
Create a book
Download as PDF
Printable version
In other projects
Wikimedia Commons
Meta-Wiki
Wikibooks
Languages
Afrikaans
العربية
Azərbaycanca
বাংলা
Беларуская
Български
Català
Čeština
Dansk
Deutsch
Eesti
Ελληνικά
Español
Euskara
فارسی
Føroyskt
Français
Galego
한국어
Հայերեն
Hrvatski
Bahasa Indonesia
Italiano
עברית
Қазақша
Latviešu
Magyar
Монгол
မြန်မာဘာသာ
Nederlands
日本語
Norsk
Oʻzbekcha/ўзбекча
Polski
Português
Română
Русский
Scots
Slovenčina
Slovenščina
Српски / srpski
Srpskohrvatski / српскохрватски
Suomi
Svenska
Tagalog
தமிழ்
ไทย
Türkçe
Українська
Tiếng Việt
粵語
中文
Edit links
This page was last edited on 6 November 2017, at 18:37.
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Privacy policy
About Wikipedia
Disclaimers
Contact Wikipedia
Developers
Cookie statement
Mobile view
Enable previews

values: mw-page-base noprint

values: mw-head-base noprint

values: firstHeading firstHeading en

values: siteSub noprint

values: jump-to-nav mw-jump

value: sup

attrs: alt src width height class srcset data-file-width data-file-height

values:
nofollow
external free
https://example.com

values:
external mw-magiclink-rfc
nofollow
//tools.ietf.org/html/rfc2660

values:
plainlinks noprint asof-tag update
display:none;

values:
/wiki/Extended_validation_certificate
mw-redirect
Extended validation certificate

values: min-height:4.6em;width:307px;line-height:1.3em;padding:2px 6px 1px 6px;margin:0px;border:none;border-width:0px

values:
/wiki/Mozilla_Firefox
mw-redirect
Mozilla Firefox

values: Does this still hold in 2015? (February 2015)

values: Wikipedia:Manual of Style/Dates and numbers

values:
/wiki/Secure_cookie
mw-redirect
Secure cookie

values:
/wiki/TCP/IP_model
mw-redirect
TCP/IP model

values: Edit section: In case of compromised secret (private) key

values:
/wiki/Perfect_forward_secrecy
mw-redirect
Perfect forward secrecy

values: There appears to be referenced basis for this claim; Additionally, a cursory test indicates that at least Facebook and Twitter use ECDHE(alexa top 10) (September 2013)

values:
noprint Inline-Template Template-Fact
white-space:nowrap;

values:
/wiki/Uniform_resource_identifier
mw-redirect
Uniform resource identifier

values:
nofollow
external text
http://bradmiller.io

values:
/wiki/Netscape_Communications
mw-redirect
Netscape Communications

values:
/wiki/Secure_Sockets_Layer
mw-redirect
Secure Sockets Layer

values:
external mw-magiclink-rfc
nofollow
//tools.ietf.org/html/rfc2818

values:
/wiki/Diameter_protocol
mw-redirect
Diameter protocol

values:
nofollow
external text
https://tools.ietf.org/html/rfc2818

values:
/wiki/Lets_Encrypt
mw-redirect
Lets Encrypt

values:
nofollow
external text
https://www.eff.org/https-everywhere

values:
nofollow
external text
https://tools.ietf.org/html/rfc2560

values:
nofollow
external text
http://sysd.org/stas/node/220

values: Institute of Electrical and Electronics Engineers

values: -moz-column-width: 33em; -webkit-column-width: 33em; column-width: 33em; list-style-type: decimal;

values:
nofollow
external text
https://tools.ietf.org/html/rfc5246

values:
nofollow
external text
https://tools.ietf.org/html/rfc6101

values:
/wiki/Uniform_resource_name
mw-redirect
Uniform resource name

values: nowraplinks collapsible autocollapse navbox-inner

values: List of web browsers for Unix and Unix-like operating systems

values:
/wiki/Ad_filtering
mw-redirect
Ad filtering

values:
/wiki/Revocation_list
mw-redirect
Revocation list

values:
/wiki/Graphical_control_element
mw-redirect
Graphical control element

values:
/wiki/Web_Proxy_Autodiscovery_Protocol
mw-redirect
Web Proxy Autodiscovery Protocol

values:
/wiki/Blink_(layout_engine)
mw-redirect
Blink (layout engine)

values:
/wiki/Epiphany_(GNOME)
mw-redirect
Epiphany (GNOME)

values:
/wiki/Mothra_(web_browser)
mw-redirect
Mothra (web browser)

values: nowraplinks collapsible collapsed navbox-subgroup

values:
/wiki/Android_Browser
mw-redirect
Android Browser

attrs: alt src title width height srcset data-file-width data-file-height

values: nowraplinks hlist collapsible autocollapse navbox-inner

values: DNS Certification Authority Authorization

values: DNS-based Authentication of Named Entities

values: Automated Certificate Management Environment

values:
/wiki/Internet_Protocol_Security
mw-redirect
Internet Protocol Security

values: Export of cryptography from the United States

values:
/wiki/Perspectives_Project
mw-redirect
Perspectives Project

values:
/wiki/BEAST_(security_exploit)
mw-redirect
BEAST (security exploit)

values: Template:Internet censorship circumvention technologies

values: Template talk:Internet censorship circumvention technologies (page does not exist)

values: DNS cache pollution (page does not exist)

values:
/wiki/Great_Firewall_of_China
mw-redirect
Great Firewall of China

values:
/wiki/Web_proxies
mw-redirect
Web proxies

values: Puff (proprietary internet censorship circumvention software) (page does not exist)

values: Changyou Wuxian browser (page does not exist)

values: nowraplinks collapsible collapsed navbox-inner

values: Category:Articles containing potentially dated statements from November 2017

values: Category:All articles containing potentially dated statements

values: Category:Wikipedia articles in need of updating from February 2015

values: Category:All Wikipedia articles in need of updating

values: Category:All articles with unsourced statements

values: Category:Articles with unsourced statements from September 2013

values: Discussion about edits from this IP address [ctrl-alt-n]

values: A list of edits made from this IP address [ctrl-alt-y]

values:
/wiki/HTTPS
View the content page [ctrl-alt-c]
c

values:
/w/index.php?title=HTTPS&action=edit
Edit this page [ctrl-alt-e]
e

values: Find background information on current events

values:
/wiki/Special:Random
Load a random article [ctrl-alt-x]
x

values: portal navigation p-navigation p-navigation-label

values: Guidance on how to use and edit Wikipedia

values: About the project, what you can do, where to find things

values: A list of recent changes in the wiki [ctrl-alt-r]

values: portal navigation p-interaction p-interaction-label

values: List of all English Wikipedia pages containing links to this page [ctrl-alt-j]

values: Recent changes in pages linked from this page [ctrl-alt-k]

values:
/wiki/Wikipedia:File_Upload_Wizard
Upload files [ctrl-alt-u]
u

values: A list of all special pages [ctrl-alt-q]

values: Permanent link to this revision of the page

values: Link to connected data repository item [ctrl-alt-g]

values: Printable version of this page [ctrl-alt-p]

values: portal navigation p-wikibase-otherprojects p-wikibase-otherprojects-label

values:
uls-settings-trigger
Language settings
0
button
true

values:
https://af.wikipedia.org/wiki/HTTPS
HTTPS – Afrikaans
af
af
interlanguage-link-target

values: بروتوكول نقل النص التشعبي الآمن – Arabic

values:
https://az.wikipedia.org/wiki/HTTPS
HTTPS – Azerbaijani
az
az
interlanguage-link-target

values: হাইপারটেক্সট ট্রান্সফার প্রোটোকল সিকিউর – Bangla

values:
https://be.wikipedia.org/wiki/HTTPS
HTTPS – Belarusian
be
be
interlanguage-link-target

values:
https://bg.wikipedia.org/wiki/HTTPS
HTTPS – Bulgarian
bg
bg
interlanguage-link-target

values:
https://ca.wikipedia.org/wiki/HTTPS
HTTPS – Catalan
ca
ca
interlanguage-link-target

values:
https://cs.wikipedia.org/wiki/HTTPS
HTTPS – Czech
cs
cs
interlanguage-link-target

values:
https://da.wikipedia.org/wiki/HTTPS
HTTPS – Danish
da
da
interlanguage-link-target

values: Hypertext Transfer Protocol Secure – German

values:
https://et.wikipedia.org/wiki/HTTPS
HTTPS – Estonian
et
et
interlanguage-link-target

values:
https://el.wikipedia.org/wiki/HTTPS
HTTPS – Greek
el
el
interlanguage-link-target

values: Protocolo seguro de transferencia de hipertexto – Spanish

values:
https://eu.wikipedia.org/wiki/HTTPS
HTTPS – Basque
eu
eu
interlanguage-link-target

values: پروتکل امن انتقال ابرمتن – Persian

values: interlanguage-link interwiki-fa badge-Q17437798 badge-goodarticle

values:
https://fo.wikipedia.org/wiki/Https
Https – Faroese
fo
fo
interlanguage-link-target

values: HyperText Transfer Protocol Secure – French

values: Hypertext Transfer Protocol Secure – Galician

values:
https://ko.wikipedia.org/wiki/HTTPS
HTTPS – Korean
ko
ko
interlanguage-link-target

values:
https://hy.wikipedia.org/wiki/HTTPS
HTTPS – Armenian
hy
hy
interlanguage-link-target

values:
https://hr.wikipedia.org/wiki/HTTPS
HTTPS – Croatian
hr
hr
interlanguage-link-target

values:
https://it.wikipedia.org/wiki/HTTPS
HTTPS – Italian
it
it
interlanguage-link-target

values:
https://lv.wikipedia.org/wiki/HTTPS
HTTPS – Latvian
lv
lv
interlanguage-link-target

values:
https://hu.wikipedia.org/wiki/Https
Https – Hungarian
hu
hu
interlanguage-link-target

values:
https://mn.wikipedia.org/wiki/HTTPS
HTTPS – Mongolian
mn
mn
interlanguage-link-target

values:
https://my.wikipedia.org/wiki/HTTPS
HTTPS – Burmese
my
my
interlanguage-link-target

values: HyperText Transfer Protocol Secure – Dutch

values:
https://ja.wikipedia.org/wiki/HTTPS
HTTPS – Japanese
ja
ja
interlanguage-link-target

values:
https://no.wikipedia.org/wiki/HTTPS
HTTPS – Norwegian
no
no
interlanguage-link-target

values:
https://uz.wikipedia.org/wiki/HTTPS
HTTPS – Uzbek
uz
uz
interlanguage-link-target

values:
https://pl.wikipedia.org/wiki/HTTPS
HTTPS – Polish
pl
pl
interlanguage-link-target

values: Hyper Text Transfer Protocol Secure – Portuguese

values:
https://ro.wikipedia.org/wiki/HTTPS
HTTPS – Romanian
ro
ro
interlanguage-link-target

values:
https://ru.wikipedia.org/wiki/HTTPS
HTTPS – Russian
ru
ru
interlanguage-link-target

values: Zabezpečený hypertextový prenosový protokol – Slovak

values:
https://sl.wikipedia.org/wiki/HTTPS
HTTPS – Slovenian
sl
sl
interlanguage-link-target

values:
https://sr.wikipedia.org/wiki/HTTPS
HTTPS – Serbian
sr
sr
interlanguage-link-target

values:
https://sh.wikipedia.org/wiki/HTTPS
HTTPS – Serbo-Croatian
sh
sh
interlanguage-link-target

values:
https://fi.wikipedia.org/wiki/HTTPS
HTTPS – Finnish
fi
fi
interlanguage-link-target

values: Hypertext Transfer Protocol Secure – Swedish

values:
https://tl.wikipedia.org/wiki/HTTPS
HTTPS – Tagalog
tl
tl
interlanguage-link-target

values: பாதுகாப்பான மீயுரை பரிமாற்ற நெறிமுறை – Tamil

values: เอชทีทีพีเอส – Thai

values:
https://tr.wikipedia.org/wiki/HTTPS
HTTPS – Turkish
tr
tr
interlanguage-link-target

values:
https://uk.wikipedia.org/wiki/HTTPS
HTTPS – Ukrainian
uk
uk
interlanguage-link-target

values:
https://vi.wikipedia.org/wiki/HTTPS
HTTPS – Vietnamese
vi
vi
interlanguage-link-target

values:
https://zh-yue.wikipedia.org/wiki/HTTPS
HTTPS – Cantonese
zh-yue
zh-yue
interlanguage-link-target

values: 超文本传输安全协议 – Chinese

values: mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-HTTPS rootpage-HTTPS vector-experimental-print-styles vector-nav-directionality skin-vector action-view


text:
Oxygen–hemoglobin dissociation curve
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2009) (Learn how and when to remove this template message)
The oxygen–hemoglobin dissociation curve, also called the oxyhemoglobin dissociation curve or oxygen dissociation curve (ODC), is a curve that plots the proportion of hemoglobin in its saturated (oxygen-laden) form on the vertical axis against the prevailing oxygen tension on the horizontal axis. This curve is an important tool for understanding how our blood carries and releases oxygen. Specifically, the oxyhemoglobin dissociation curve relates oxygen saturation (SO2) and partial pressure of oxygen in the blood (PO2), and is determined by what is called "hemoglobin affinity for oxygen"; that is, how readily hemoglobin acquires and releases oxygen molecules into the fluid that surrounds it.
Contents
[hide]
1 Background
2 Sigmoidal shape
3 Factors that affect the standard dissociation curve
3.1 pH
3.2 Carbon dioxide
3.3 2,3-BPG
3.4 Temperature
3.5 Carbon monoxide
3.6 Effects of methemoglobinaemia
3.7 Effects of ITPP
4 Fetal hemoglobin
5 See also
6 Notes
7 References
8 External links
Background[edit]
Hemoglobin (Hb) is the primary vehicle for transporting oxygen in the blood. Oxygen is also carried dissolved in the blood's plasma, but to a much lesser degree. Haemoglobin is contained in red blood cells. Under certain conditions, oxygen bound to the hemoglobin is released into the blood's plasma and absorbed into the tissues. Each hemoglobin molecule has the capacity to carry four oxygen molecules. These molecules of oxygen bind to the iron of the Heme group [1]. The binding of the first oxygen molecule induces a conformational change of hemoglobin that increases the affinity for the remaining three oxygen molecules.
How much of that capacity is filled by oxygen at any time is called the oxygen saturation. Expressed as a percentage, the oxygen saturation is the ratio of the amount of oxygen bound to the hemoglobin, to the oxygen-carrying capacity of the hemoglobin. The oxygen-carrying capacity of hemoglobin is determined by the type of hemoglobin present in the blood. The amount of oxygen bound to the hemoglobin at any time is related, in large part, to the partial pressure of oxygen to which the hemoglobin is exposed. In the lungs, at the alveolar–capillary interface, the partial pressure of oxygen is typically high, and therefore the oxygen binds readily to hemoglobin that is present. As the blood circulates to other body tissue in which the partial pressure of oxygen is less, the hemoglobin releases the oxygen into the tissue because the hemoglobin cannot maintain its full bound capacity of oxygen in the presence of lower oxygen partial pressures.
Sigmoidal shape[edit]
Hemoglobin saturation curve.
The curve is usually best described by a sigmoid plot, using by a formula of the kind:
S ( t ) = 1 1 + e − t . {\displaystyle S(t)={\frac {1}{1+e^{-t}}}.}
A hemoglobin molecule can bind up to four oxygen molecules in a reversible way.
The shape of the curve results from the interaction of bound oxygen molecules with incoming molecules. The binding of the first molecule is difficult. However, this facilitates the binding of the second, third and fourth, this is due to the induced conformational change in the structure of the hemoglobin molecule induced by the binding of an oxygen molecule.
In its most simple form, the oxyhemoglobin dissociation curve describes the relation between the partial pressure of oxygen (x axis) and the oxygen saturation (y axis). Hemoglobin's affinity for oxygen increases as successive molecules of oxygen bind. More molecules bind as the oxygen partial pressure increases until the maximum amount that can be bound is reached. As this limit is approached, very little additional binding occurs and the curve levels out as the hemoglobin becomes saturated with oxygen. Hence the curve has a sigmoidal or S-shape. At pressures above about 60 mmHg, the standard dissociation curve is relatively flat, which means that the oxygen content of the blood does not change significantly even with large increases in the oxygen partial pressure. To get more oxygen to the tissue would require blood transfusions to increase the hemoglobin count (and hence the oxygen-carrying capacity), or supplemental oxygen that would increase the oxygen dissolved in plasma. Although binding of oxygen to hemoglobin continues to some extent for pressures about 50 mmHg, as oxygen partial pressures decrease in this steep area of the curve, the oxygen is unloaded to peripheral tissue readily as the hemoglobin's affinity diminishes. The partial pressure of oxygen in the blood at which the hemoglobin is 50% saturated, typically about 26.6 mmHg (3.5 kPa) for a healthy person, is known as the P50. The P50 is a conventional measure of hemoglobin affinity for oxygen. In the presence of disease or other conditions that change the hemoglobin's oxygen affinity and, consequently, shift the curve to the right or left, the P50 changes accordingly. An increased P50 indicates a rightward shift of the standard curve, which means that a larger partial pressure is necessary to maintain a 50% oxygen saturation. This indicates a decreased affinity. Conversely, a lower P50 indicates a leftward shift and a higher affinity.
The 'plateau' portion of the oxyhemoglobin dissociation curve is the range that exists at the pulmonary capillaries (minimal reduction of oxygen transported until the p(O2) falls 50 mmHg).
The 'steep' portion of the oxyhemoglobin dissociation curve is the range that exists at the systemic capillaries (a small drop in systemic capillary p(O2) can result in the release of large amounts of oxygen for the metabolically active cells).
To see the relative affinities of each successive oxygen as you remove/add oxygen from/to the hemoglobin from the curve compare the relative increase/decrease in p(O2) needed for the corresponding increase/decrease in s(O2).
Factors that affect the standard dissociation curve[edit]
The strength with which oxygen binds to hemoglobin is affected by several factors. These factors shift or reshape the oxyhemoglobin dissociation curve. A rightward shift indicates that the hemoglobin under study has a decreased affinity for oxygen. This makes it more difficult for hemoglobin to bind to oxygen (requiring a higher partial pressure of oxygen to achieve the same oxygen saturation), but it makes it easier for the hemoglobin to release oxygen bound to it. The effect of this rightward shift of the curve increases the partial pressure of oxygen in the tissues when it is most needed, such as during exercise, or hemorrhagic shock. In contrast, the curve is shifted to the left by the opposite of these conditions. This leftward shift indicates that the hemoglobin under study has an increased affinity for oxygen so that hemoglobin binds oxygen more easily, but unloads it more reluctantly. Left shift of the curve is a sign of hemoglobin's increased affinity for oxygen (e.g. at the lungs). Similarly, right shift shows decreased affinity, as would appear with an increase in either body temperature, hydrogen ions, 2,3-bisphosphoglycerate (2,3-BPG) concentration or carbon dioxide concentration.
Control factors
Change
Shift of curve
Temperature ↑ →
↓ ←
2,3-BPG ↑ →
↓ ←
pCO2 ↑ →
↓ ←
Acidity [H+] ↑ →
↓ ←
Note:
Left shift: higher O2 affinity
Right shift: lower O2 affinity
fetal hemoglobin has higher O2 affinity than adult hemoglobin; primarily due to much-reduced affinity to 2,3-bisphosphoglycerate .
The causes of shift to right can be remembered using the mnemonic, "CADET, face Right!" for CO2, Acid, 2,3-DPG,[Note 1] Exercise and Temperature.[2] Factors that move the oxygen dissociation curve to the right are those physiological states where tissues need more oxygen. For example, during exercise, muscles have a higher metabolic rate, and consequently need more oxygen, produce more carbon dioxide and lactic acid, and their temperature rises.
pH[edit]
A decrease in pH (increase in H+ ion concentration) shifts the standard curve to the right, while an increase shifts it to the left. This occurs because at greater H+ ion concentration, various amino acid residues, such as Histidine 146 exist predominantly in their protonated form allowing them to form ion pairs that stabilize deoxyhemoglobin in the T state.[3] The T state has a lower affinity for oxygen than the R state, so with increased acidity, the hemoglobin binds less O2 for a given PO2 (and more H+). This is known as the Bohr effect.[4] A reduction in the total binding capacity of hemoglobin to oxygen (i.e. shifting the curve down, not just to the right) due to reduced pH is called the root effect. This is seen in bony fish. The binding affinity of hemoglobin to O2 is greatest under a relatively high pH.
Carbon dioxide[edit]
Carbon dioxide affects the curve in two ways. First, CO2 accumulation causes carbamino compounds to be generated through chemical interactions, which bind to hemoglobin forming carbaminohemoglobin . CO2 is considered an Allosteric regulation as the inhibition happens not at the binding site of hemoglobin.[5] Second, it influences intracellular pH due to formation of bicarbonate ion. Formation of carbaminohemoglobin stabilizes T state hemoglobin by formation of ion pairs.[3] Only about 5–10% of the total CO2 content of blood is transported as carbamino compounds, whereas (80–90%) is transported as bicarbonate ions and a small amount is dissolved in the plasma.The formation of a bicarbonate ion will release a proton into the plasma, increasing acidity which also shifts the curve to the right as discussed above; low CO2 levels in the blood stream results in a high pH, and thus provides more optimal binding conditions for hemoglobin and O2. This is a physiologically favored mechanism, since hemoglobin will drop off more oxygen as the concentration of carbon dioxide increases dramatically where tissue respiration is happening rapidly and oxygen is in need. [6]
2,3-BPG[edit]
Main article: 2,3-bisphosphoglyceric acid
2,3-Bisphosphoglycerate or 2,3-BPG (formerly named 2,3-diphosphoglycerate or 2,3-DPG) is an organophosphate formed in erythrocytes during glycolysis and is the conjugate base of 2,3-bisphosphoglyceric acid. The production of 2,3-BPG is likely an important adaptive mechanism, because the production increases for several conditions in the presence of diminished peripheral tissue O2 availability, such as hypoxaemia, chronic lung disease, anaemia, and congestive heart failure, among others. High levels of 2,3-BPG shift the curve to the right (as in childhood), while low levels of 2,3-BPG cause a leftward shift, seen in states such as septic shock, and hypophosphataemia.[4] In the absence of 2,3-BPG, hemoglobin's affinity for oxygen increases. 2,3-BPG acts as a heteroallosteric effector of hemoglobin, lowering hemoglobin's affinity for oxygen by binding preferentially to deoxyhemoglobin. An increased concentration of BPG in red blood cells favours formation of the T, low-affinity state of hemoglobin and so the oxygen-binding curve will shift to the right.
Temperature[edit]
Increase in Θ {\displaystyle \Theta } shifts the ODC to the right. If Θ {\displaystyle \Theta } is increased keeping the [ O 2 ] {\displaystyle {\ce {[O2]}}} the same, then the oxygen saturation decreases because the bond between iron in the Hb {\displaystyle {\ce {Hb}}} and O 2 {\displaystyle {\ce {O2}}} gets denatured. Similarly, with increase in Θ {\displaystyle \Theta } , pO 2 {\displaystyle {\ce {pO2}}} also increases. So, one will have a lesser hemoglobin saturation percentage for the same [ O 2 ] {\displaystyle {\ce {[O2]}}} or a higher pO 2 {\displaystyle {\ce {pO2}}} . Thus, any point in the curve will shift rightwards (due to increased pO 2 {\displaystyle {\ce {pO2}}} ) and downwards (due to weakened Hb − O 2 {\displaystyle {\ce {Hb-O2}}} bond). Hence, the rightward shift of the curve.[7]
Carbon monoxide[edit]
Hemoglobin binds with carbon monoxide 200–250 times more readily than with oxygen.[4] Because of this higher affinity of hemoglobin for carbon monoxide than for oxygen, carbon monoxide is a highly successful competitor that will displace oxygen even at minuscule partial pressures. The reaction HbO2 + CO → HbCO + O2 almost irreversibly displaces the oxygen molecules forming carboxyhemoglobin; the binding of the carbon monoxide to the iron centre of hemoglobin is much stronger than that of oxygen, and the binding site remains blocked for the remainder of the life cycle of that effected red blood cell.[8] With an increased level of carbon monoxide, a person can suffer from severe tissue hypoxia while maintaining a normal pO2 because carboxyhaemoglobin does not carry oxygen to the tissues.
Effects of methemoglobinaemia[edit]
Methemoglobinaemia is a form of abnormal hemoglobin where the iron centre has been oxidised from the +2 oxidation state (the normal form) to the +3 state. This causes a leftward shift in the oxygen hemoglobin dissociation curve, as any residual heme with oxygenated ferrous iron (+2 state) is unable to unload its bound oxygen into tissues (because 3+ iron impairs hemoglobin's cooperativity), thereby increasing its affinity with oxygen. However, methemoglobin has increased rbc affinity for cyanide, and is therefore useful in the treatment of cyanide poisoning. In cases of accidental ingestion, administration of a nitrite (such as amyl nitrite) can be used to deliberately oxidise hemoglobin and raise methemoglobin levels, restoring the functioning of cytochrome oxidase. The nitrite also acts as a vasodilator, promoting the cellular supply of oxygen, and the addition of an iron salt provides for competitive binding of the free cyanide as the biochemically inert hexacyanoferrate(III) ion, [Fe(CN)6]3−. An alternative approach involves administering thiosulfate, thereby converting cyanide to thiocyanate, SCN−, which is excreted via the kidneys. Methemoglobin is also formed in small quantities when the dissociation of oxyhemoglobin results in the formation of methemoglobin and superoxide, O2−, instead of the usual products. Superoxide is a free radical and causes biochemical damage, but is neutralised by the action of the enzyme superoxide dismutase.
Effects of ITPP[edit]
Myo-inositol trispyrophosphate (ITPP), also known as OXY111A, is an inositol phosphate that causes a rightward shift in the oxygen hemoglobin dissociation curve through allosteric modulation of hemoglobin within red blood cells. It is an experimental drug intended to reduce tissue hypoxia. The effects appear to last roughly as long as the affected red blood cells remain in circulation.
Fetal hemoglobin[edit]
Fetal hemoglobin saturation curve
Fetal hemoglobin (HbF) is structurally different from normal adult hemoglobin (HbA), giving HbF a higher affinity for oxygen than HbA. HbF is composed of two alpha and two gamma chains whereas HbA is composed of two alpha and two beta chains. The fetal dissociation curve is shifted to the left relative to the curve for the normal adult because of these structural differences.
Typically, fetal arterial oxygen pressures are lower than adult arterial oxygen pressures. Hence higher affinity to bind oxygen is required at lower levels of partial pressure in the fetus to allow diffusion of oxygen across the placenta. At the placenta, there is a higher concentration of 2,3-BPG formed, and 2,3-BPG binds readily to beta chains rather than to alpha chains. As a result, 2,3-BPG binds more strongly to adult hemoglobin, causing HbA to release more oxygen for uptake by the fetus, whose HbF is unaffected by the 2,3-BPG.[9] HbF then delivers that bound oxygen to tissues that have even lower partial pressures where it can be released.
See also[edit]
Automated analyzer
Notes[edit]
Jump up ^ 2,3-DPG is an abbreviation of 2,3-DiPhosphoGlyceric acid, an obsolete name for 2,3-BPG
References[edit]
Jump up ^ Ahern, Kevin; Rajagopal, Indira; Tan, Taralyn (2017). Biochemistry Free For All (PDF) (1.2 ed.). NC: Creative Commons.
Jump up ^ "Medical mnemonics". LifeHugger. Retrieved 2009-12-19.
^ Jump up to: a b Lehninger. Principles of Biochemistry (6th ed.). p. 169.
^ Jump up to: a b c Jacquez, John (1979). Respiratory Physiology. McGraw-Hill. pp. 156–175.
Jump up ^ Ahern, Kevin; Rajagopal, Indira; Tan, Taralyn (5 August 2017). Biochemistry Free For All (1.2 ed.). NC-Creative Commons. p. 370. |access-date= requires |url= (help)
Jump up ^ Ahern, Kevin; Rajagopal, Indira; Tan, Taralyn (5 August 2017). Biochemistry Free For All (1.2 ed.). NC-Creative Commons. p. 134. |access-date= requires |url= (help)
Jump up ^ Schmidt-Nielsen (1997). Animal Physiology: Adaptation and Environment. Cambridge University Press. ISBN 0521570980.
Jump up ^ Kotz, John. Chemistry and Chemical Reactivity (8th ed.). Cengage Learning. p. 1032. ISBN 1133420079. Retrieved 2015-07-01.
Jump up ^ Lippincott's Illustrated Review: Biochemistry 4th edition. North America: Lippincott, Williams, and Wilkins. 2007. pp. 24–35. ISBN 978-0-7817-6960-0.
External links[edit]
Physiology: 4/4ch5/s4ch5_18 - Essentials of Human Physiology
The Interactive Oxyhemoglobin Dissociation Curve
[hide]
v
t
e
Respiratory physiology
Respiration
breath
inhalation
exhalation
respiratory rate
respirometer
pulmonary surfactant
compliance
elastic recoil
hysteresivity
airway resistance
bronchial
hyperresponsiveness
constriction
dilatation
mechanical ventilation
Control
pons
pneumotaxic center
apneustic center
medulla
dorsal respiratory group
ventral respiratory group
chemoreceptors
central
peripheral
pulmonary stretch receptors
Hering–Breuer reflex
Lung volumes
VC
FRC
Vt
dead space
CC
PEF
calculations
respiratory minute volume
FEV1/FVC ratio
Lung function tests
spirometry
body plethysmography
peak flow meter
nitrogen washout
Circulation
pulmonary circulation
hypoxic pulmonary vasoconstriction
pulmonary shunt
Interactions
ventilation (V)
Perfusion (Q)
Ventilation/perfusion ratio
V/Q scan
zones of the lung
gas exchange
pulmonary gas pressures
alveolar gas equation
alveolar–arterial gradient
hemoglobin
oxygen–haemoglobin dissociation curve (Oxygen saturation
2,3-BPG
Bohr effect
Haldane effect)
carbonic anhydrase (chloride shift)
oxyhemoglobin
respiratory quotient
arterial blood gas
diffusion capacity (DLCO)
Insufficiency
high altitude
oxygen toxicity
hypoxia
Retrieved from "https://en.wikipedia.org/w/index.php?title=Oxygen–hemoglobin_dissociation_curve&oldid=833805490"
Categories:
Respiratory physiology
Chemical pathology
Hematology
Oxygen
Hidden categories:
Pages using citations with accessdate and no URL
Articles needing additional references from March 2009
All articles needing additional references
Navigation menu
Personal tools
Not logged in
Talk
Contributions
Create account
Log in
Namespaces
Article
Talk
Variants
Views
Read
Edit
View history
More
Search
Navigation
Main page
Contents
Featured content
Current events
Random article
Donate to Wikipedia
Wikipedia store
Interaction
Help
About Wikipedia
Community portal
Recent changes
Contact page
Tools
What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Wikidata item
Cite this page
Print/export
Create a book
Download as PDF
Printable version
Languages
ไทย
Edit links
This page was last edited on 2 April 2018, at 14:34.
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Privacy policy
About Wikipedia
Disclaimers
Contact Wikipedia
Developers
Cookie statement
Mobile view
Enable previews

key: html

type: local

value: div

attrs: id class

values: mw-page-base noprint

values: mw-head-base noprint

value: a

attrs: id class lang

values: firstHeading firstHeading en

values: siteSub noprint

values: jump-to-nav mw-jump

value: img

attrs: alt src width height srcset data-file-width data-file-height

attrs: href class

value: td

attrs: href title

value: b

attrs: class href

values: Help:Introduction to referencing with Wiki Markup/1

value: span

value: i

value: small

value: tr

values: plainlinks metadata ambox ambox-content ambox-Refimprove

values: vertical-align: -2.171ex; width:15.92ex; height:5.509ex;

values:
/wiki/P50_(biochemistry)
mw-redirect
P50 (biochemistry)

values: Edit section: Factors that affect the standard dissociation curve

values:
/wiki/Allosteric_inhibitor
mw-redirect
Allosteric inhibitor

values:
/wiki/2,3-bisphosphoglyceric_acid
mw-redirect
2,3-bisphosphoglyceric acid

values:
/wiki/Conjugate_base
mw-redirect
Conjugate base

values: vertical-align: -0.338ex; width:1.808ex; height:2.176ex;

values: vertical-align: -1.005ex; width:4.156ex; height:3.009ex;

values: vertical-align: -0.338ex; width:3.036ex; height:2.176ex;

values: vertical-align: -1.005ex; width:2.862ex; height:2.843ex;

values: vertical-align: -1.005ex; width:4.155ex; height:2.843ex;

values: vertical-align: -1.005ex; width:7.706ex; height:2.843ex;

values: Edit section: Effects of methemoglobinaemia

values:
/wiki/Cytochrome_oxidase
mw-redirect
Cytochrome oxidase

values:
/wiki/Automated_analyzer
mw-redirect
Automated analyzer

values:
reflist mw-references-wrap
list-style-type: decimal;

values:
/wiki/Respiratory_physiology
mw-redirect
Respiratory physiology

values:
/wiki/Pulmonary_compliance
mw-redirect
Pulmonary compliance

values:
/wiki/Pneumotaxic_center
mw-redirect
Pneumotaxic center

values:
/wiki/Apneustic_center
mw-redirect
Apneustic center

values:
/wiki/Lung_function_test
mw-redirect
Lung function test

values:
/wiki/Body_plethysmography
mw-redirect
Body plethysmography

values:
/wiki/Peak_flow_meter
mw-redirect
Peak flow meter

values:
/wiki/Ventilation_(physiology)
mw-redirect
Ventilation (physiology)

values:
/wiki/Arterial_blood_gas
mw-redirect
Arterial blood gas

values:
/wiki/Diffusion_capacity
mw-redirect
Diffusion capacity

values: nowraplinks collapsible autocollapse navbox-inner

values: Category:Pages using citations with accessdate and no URL

values: Category:Articles needing additional references from March 2009

values: Category:All articles needing additional references

values: Discussion about edits from this IP address [ctrl-alt-n]

values: A list of edits made from this IP address [ctrl-alt-y]

values: You are encouraged to create an account and log in; however, it is not mandatory

values: You're encouraged to log in; however, it's not mandatory. [ctrl-alt-o]

values: Discussion about the content page [ctrl-alt-t]

values: p-namespaces navigation vectorTabs p-namespaces-label

values:
p-variants
navigation
vectorMenu emptyPortlet
p-variants-label

values: Past revisions of this page [ctrl-alt-h]

values: p-views navigation vectorTabs p-views-label

values:
p-cactions
navigation
vectorMenu emptyPortlet
p-cactions-label

values:
mw-wiki-logo
/wiki/Main_Page
Visit the main page

values:
/wiki/Main_Page
Visit the main page [ctrl-alt-z]
z

values: Featured content – the best of Wikipedia

values: Find background information on current events

values:
/wiki/Special:Random
Load a random article [ctrl-alt-x]
x

values: portal navigation p-navigation p-navigation-label

values: Guidance on how to use and edit Wikipedia

values: About the project, what you can do, where to find things

values: A list of recent changes in the wiki [ctrl-alt-r]

values: portal navigation p-interaction p-interaction-label

values: List of all English Wikipedia pages containing links to this page [ctrl-alt-j]

values: Recent changes in pages linked from this page [ctrl-alt-k]

values:
/wiki/Wikipedia:File_Upload_Wizard
Upload files [ctrl-alt-u]
u

values: A list of all special pages [ctrl-alt-q]

values: Permanent link to this revision of the page

values: Link to connected data repository item [ctrl-alt-g]

values: Printable version of this page [ctrl-alt-p]

values: กราฟการแตกตัวของออกซิเจนและเฮโมโกลบิน – Thai

values: /static/images/wikimedia-button-1.5x.png 1.5x, /static/images/wikimedia-button-2x.png 2x

values: /static/images/poweredby_mediawiki_132x47.png 1.5x, /static/images/poweredby_mediawiki_176x62.png 2x

values:
suggestions
display: none; font-size: 13px;

values: mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-Oxygen–hemoglobin_dissociation_curve rootpage-Oxygen–hemoglobin_dissociation_curve skin-vector action-view