The following is a paraphrased version of the excerpt from the medical textbook:

Metabolism occurs in the cytosol, and free ribosomes are responsible for protein synthesis. The cytoskeleton is involved in cell shape, movement, and intracellular transport. The nucleus contains the genome, which consists of 22 autosomes and 2 sex chromosomes, and is responsible for DNA and RNA synthesis. ATP synthesis through oxidative phosphorylation and calcium storage takes place in the mitochondria. The smooth endoplasmic reticulum is involved in lipid synthesis and calcium storage. Free ribosomes are responsible for translating mRNA into cytosolic proteins. The rough endoplasmic reticulum is responsible for translating mRNA into membrane-associated proteins or proteins that are secreted out of the cell. Lysosomes are involved in intracellular degradation, while endosomes are responsible for cellular uptake of cholesterol, removal of receptors from the plasma membrane, uptake of small molecules and water into the cell, and internalization of large particles like bacteria and cell debris. The Golgi apparatus is responsible for modifying, sorting, and packaging proteins and lipids for delivery to other organelles within the cell. The major lipids of the plasma membrane are phospholipids and phosphoglycerides. Phospholipids have an amphipathic nature, with hydrophobic fatty acyl chains forming the core of the bilayer and polar head groups exposed on the surface. Cholesterol and glycolipids are also present in the plasma membrane. The presence of unsaturated fatty acyl chains in phospholipids creates a "kink" that increases membrane fluidity.
CytosolMetabolism, protein synthesis (free ribosomes)CytoskeletonCell shape and movement, intracellular transportNucleusGenome (22 autosomes and 2 sex chromosomes), DNA and RNA synthesisMitochondriaATP synthesis by oxidative phosphorylation, Ca2+ storageSmooth endoplasmic reticulumSynthesis of lipids, Ca2+ storageFree ribosomesTranslation of mRNA into cytosolic proteinsRough endoplasmic reticulumTranslation of mRNA into membrane associated proteins or for secretion out of the cellLysosomeIntracellular degradationEndosomeCellular uptake of cholesterol, removal of receptors from the plasma membrane, uptake of small molecules and water into the cell, internalization of large particles (e.g., bacteria, cell debris)Golgi apparatusModification, sorting, and packaging of proteins and lipids for delivery to other organelles within
ATP, adenosine triphosphate; mRNA, messenger RNA.
inner or outer surfaces of the membrane, often by binding molecules that contain a charged (or polar) hydrophilic to the integral membrane proteins. head and two (nonpolar) hydrophobic fatty acyl chains (
Fig.
1.3 ). The amphipathic nature of the phospholipid molecule Membrane Lipids is critical for the formation of the bilayer: The hydrophobic The major lipids of the plasma membrane are phospholipids fatty acyl chains form the core of the bilayer, and the polar and phosphoglycerides. Phospholipids are amphipathic head groups are exposed on the surface.
• Fig. 1.2 Schematic diagram of the cell plasma membrane. Not shown are lipid rafts. See text for details. (Modified from Cooper GM. The Cell—A Molecular Approach. 2nd ed. Washington, DC: Sinauer; 2000, Fig. 12.3.)
Phospholipid Glycolipid (e.g., phosphatidylcholine) (e.g., galactosylceramide) Cholesterol
Sugar (e.g., galactose) • Fig. 1.3 Models of the major classes of plasma membrane lipids, depicting the hydrophilic and hydrophobic regions of the molecules. The molecules are arranged as they exist in one leaflet of the bilayer. The opposing leaflet is not shown. One of the fatty acyl chains in the phospholipid molecule is unsaturated. The presence of this double bond produces a “kink” in the fatty acyl chain, which prevents tight packing of membrane lipids and increases membrane fluidity. (Modified from Hansen JT, Koeppen BM: Netter’s Atlas of Human Physiology. Teterboro, NJ: Icon Learning Systems; 2002.)