Chapter 4: PROTEIN SYNTHESIS

Chapter 5: BIOMEMBRANES & SUBCELLULAR ORGANIZATION

Biomembrane structure and function:

Phospholipids are the major constituents of biomembranes; phospholipids are comprised of a glycerol backbone, two fatty acyl chains, phosphate and an alcohol (5-27); the most common alcohols on phospholipids are choline, serine, ethanolamine and inositol (5-28); other constituents of biomembranes are sphingomyelin, glycolipids and cholesterol (5-27; 5-29); biomembranes are organized as bilayers with fatty acids in the middle and polar head groups facing the cytoplasm or exoplasm (outside of cell or lumen of organelle) (5-31).
The other major constituent of membranes are proteins, which can account for up to 76% of membrane mass; membrane proteins, glycolipids and phopholipids have asymmetric distributions on the inner and outer leaflet.
Lipids and proteins are laterally mobile; cell fusion experiment (5-35); FRAP experiment (5-36); fluidity depends on membrane composition (saturation, kinks, cholesterol) and temperature.
The plasma membrane functions to transport nutrients and waste products, prevent entry of unwanted material, maintain proper ionic composition/osmotic pressure, control cell-cell communication and form tissues.

Organelles of the eukaryotic cell (5-42):

Lysosomes; membrane bound organelle that degrades components that are obsolete or that have been taken into the cell via phagocytosis/pinocytosis; degrades nucleic acids, proteins and lipids; acidic pH of ~5 allows acid hydrolases to work in the lysosome; primary and secondary lysosomes (5-44).
Vacuoles; membrane bound organelle found primarily in plant cells; store water, ions and nutrients; produces high turgor pressure that allows elongation and growth.
Peroxisomes; contain oxidases that oxidize fatty acids and various toxic molecules that enter the bloodstream; oxidation produces peroxide that is removed by catalase.
Mitochondria; organelle containing an outer and inner membrane that occupies ~25% of the cytoplasm; Generates ATP through the aerobic degradation of glucose and fatty acids.
Chloroplasts; comprised of three membranes — inner, outer and thalakoid; contain chlorophyll and enzymes that absorb light and generate ATP during photosynthesis; converts CO2 to three-carbon intermediates that are converted to sugars.
Endoplasmic reticulum (ER); comprised of a series of interconnected membranes; smooth ER is where fatty acids and phospholipids are synthesized and hydrophobic chemicals are detoxified; rough ER is where secreted and membrane bound proteins are synthesized; bound ribosomes are what makes the rough ER look rough.
Golgi vesicles; receive vesicles containing secreted/membrane bound proteins from the rough ER; comprised of cis, medial and trans regions in which modification and targeting of proteins occurs.
Nucleus; surrounded by a double membrane; outer membrane usually continuous with the rough ER; membranes fuse at the nuclear pore, which function as channels that regulate movement in and out of the nucleus; contains the genomic DNA and the membrane bound nucleolus; lamins form shaeth inside the inner membrane which provides structure and shape.
Cytoplasm; contains 3 types of fibers that provide shape and enable transport within the cell; site of synthesis of proteins that are not secreted or membrane bound; stores glycogen and fatty acids; site of most cellular metabolism.