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Cell structureComments

Cell structure

Most cells are between 10 and 100 micrometers. 1 micrometer is 10,000 angstrom units.

Structural features of all cells

ChromosomeThe chromosome is cDNA in prokaryotes. For eukaryotes, there are two categories: introns and exons. Introns are the noncoding regions of DNA. The chromosome is stored within the nucleus. The chromosome is divided into supercoiling domains (10-100 kb) and macrodomains (800-1000 kb). House-keeping genes essential for biosynthesis.
CytoplasmThe cytoplasm contains salt, sugar, RNA, DNA, amino acids, ribosomes, and protein. It is made of 75% Oxygen, 10% Carbon, 10% Hydrogen, 2% Nitrogen, .2% Sulfure, .3% Phosphorous, .3% Potassium, .1% Chlorine. In prokaryotes, there is not a nucleus; therefore, transcription and translation occur in the cytoplasm.
Cell membraneThe cytoplasmic Membrane is a permeable phospholipid bilayer. It is non-covalent, flexible, 8nm thick and as viscous as light-grade oil. To strengthen it are rigid planar molecules: sterols for eukaryotes and hopanoids for prokaryotes. It consists of glycerol, phosphate and fatty acids. Cations like Magnesium and Calcium stabilize the negatively charged phosphates. Primary function is to control movement of materials from one place to another. Hydrophobic bonds occur between nonpolar groups in water. The lipid Bilayer contains a strongly polar phosphate- or sugar-containing head of each molecule associating with water and nonpolar alkyl tails of the fatty acyl groups aggregating by hydrophobic interactions.
Membrane proteins

Membrane proteins are proteins embedded in the lipid bilayer.

Integral membrane proteins cannot be released from a membrane without breaking covalent bonds or disrupting the lipid bilayer. Some anchored to lipid bilayer by covalent linkage to a lipid, usually a fatty acyl group, prenyl, or a phospholipid.
Peripheral membrane proteins face either internally or externally, but not both. They are bound noncovalently to integral membrane components (such as lipids or proteins). They can be removed by treatments milder than required to remove integral membran proteins.
Transmembrane integral membrane proteins extend across the lipid bilayer. Most have α-helical 2° structure. Some transmembrane integral membrane proteins form ion channels across the membrane, some are active transport or facilitated diffusion carriers, and others are receptor for growth factors or hormones. Many have unknown function. They oftentimes have restricted mobility due to interaction with the cytoskeleton.

Structural features of all eukraryotes

Mitochondria
Nuclear envelope
Nucleolus
Nucleus
Smooth ER
Rough ER
Golgi complex
Secretory vesicles
Peroxisomes
Cytoskeleton(cytoskeletal fibers)
Cell wall

Structural features of all animal eukraryotes

Microvilli
Lysosomes

Structural features of all plant eukraryotes

Vacuole
Chloroplast