AP Biology Unit 2 Cheatsheet: Cells

Ribosomes: rRNA + protein; synthesize proteins from mRNA; found in all life forms (common ancestry).

Rough ER: membrane-bound ribosomes attached; protein synthesis; compartmentalization.

Smooth ER: detoxification; lipid synthesis; no ribosomes.

Golgi Complex: receives proteins from the rough ER, then chemically modifies (e.g., glycosylates), sorts, and packages them into vesicles for trafficking.

Mitochondria: double membrane; outer smooth, inner highly convoluted (cristae); site of aerobic respiration and ATP synthesis.

Lysosomes: membrane sacs with hydrolytic enzymes; digest material; role in apoptosis.

Vacuoles: Plant—large, maintains turgor pressure, stores nutrients/water. Animal—smaller, more numerous, store materials.

Chloroplasts: double membrane; photosynthesis in plants and algae.

Phospholipids: hydrophilic heads (polar phosphate) face aqueous environment; hydrophobic tails (nonpolar fatty acids) face interior.

Embedded Proteins: hydrophilic regions face the aqueous environments on either side of the membrane (cytosol or extracellular fluid) or line aqueous channels through the protein; hydrophobic regions interact with the fatty acid tails.

Fluid Mosaic Model: phospholipids, proteins, steroids (cholesterol), glycoproteins, and glycolipids move freely within the membrane.

Selective Permeability: hydrophobic interior prevents ions and large polar molecules from crossing freely.

Cell Wall: Bacteria (peptidoglycan), Archaea, Fungi (chitin), plants (cellulose); rigid but porous structural boundary that provides support and prevents osmotic lysis in hypotonic conditions — the plasma membrane, not the wall, is the selectively permeable barrier.