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AP Bio Unit 2: Cell Structure and Function Cheat Sheet (DRAFT) by

How cell structure and formation affect cell function

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Membrane Transport

Passive Transport: net movement of molecules from H to L concen­tration without ATP; used for import and export of materials
Facili­tated Diffusion: (1) Large quantities of water pass through aquaporins (2) Charged ions, (Na+ and K+), require channel proteins to move through membrane (3) Membranes may become polarized by movement of ions across the membrane
Active Transport: uses ATP to transport molecules and establ­ish­/ma­intain concen­tration gradients; requires membrane proteins
Exocyt­osis: internal vesicles fuse with plasma membrane and secrete large macrom­ole­cules out of cell
Endocy­tosis: cell takes in macrom­ole­cules and partic­ulate matter by forming new vesicles derived from plasma membrane

Selective Permea­bility

-Selective permea­bility is a direct conseq­uence of membrane structure
-Small, non polar molecules can pass through (N2, O2 and CO2)
-Hydro­philic substances (large polar molecules and ions) need embedded channels and transport proteins
-Polar uncharged molecules (H20) pass though in small amounts
-Allows for the formation of concen­tration gradients of solutes across the membrane

Surface Area to Volume Ratio

-Smaller cells typically have a higher SA:V for more efficient exchange of materials with enviro­nment
-As V increases, SA decreases, demand for internal resources increases
-Incre­asing cell size decreases SA:V
-Membrane folds can increase SA:V

Prokar­yotic vs. Eukaryotic

Typically have circular chromo­somes (plasmid)
Typically have multiple linear chromo­somes (can have plasmids too)
No membrane bound nucleus
Membrane bound nucleus
Rare: microt­ubules, cytosk­eleton; also chloro­phyll scattered in cell
Lysosomes, peroxi­somes, microt­ubules, ER, Mitoch­ondria, Cytosk­eleton, Vesicles, Golgi, Chloro­plasts
Smaller ribosomes, have vacuoles
Larger ribosomes, have vacuoles
Chemically complex cell wall
Chemically simple cell wall
Groups of genes (operons) are transc­ribed in a single mRNA molecule
Groups of genes may be influenced by the same transc­ription factors to coordi­nately regulate expression

Cell Compar­tme­nta­liz­ation

-Membr­ane­-bound organelles evolved from once free-l­iving prokar­yotic cells via endosy­mbiosis
-Proka­ryotes generally lack internal membrane- bound organelles but have internal regions with specia­lized structures and functions.
-Eukar­yotic cells maintain internal membranes that partition the cell into specia­lized regions

Cell Organelles

Comprise ribosomal RNA (rRNA) and protein; Synthesize protein according to mRNA sequence; Found in all forms of life (evidence of common ancestor)
Endopl­asmic Reticulum (ER)
Rough ER: compar­tme­nta­lizes the cell; Smooth ER: detoxi­fic­ation and lipid synthesis
Fold and chemically modify newly synthe­sized proteins; Packaging proteins for traffi­cking
Powerhouse of cell; Double membrane provides compar­tments for different metabolic reactions
Contain hydrolytic enzymes for intrac­ellular digestion, recycling of a cell’s organic materials, apoptosis
Storage and release of macrom­ole­cules and cellular waste products; In plants, aids in retention of water for turgor pressure


Water moves (by osmosis) from areas of H H20 potent­ial/L solute concen­tration to areas of L H2O potent­ial/H solute concen­tration