Membranes

Question 1

Integral Membrane Proteins

Answer 1

Majority of proteins in membranes

Large hydrophobic region allowing protein to be fully embedded in (PENETRATE) lipid bilayer

Always oriented the same way

Question 2

Peripheral membrane proteins

Answer 2

Some proteins on surface of membrane

Don’t have large hydrophobic regions

Question 3

Membranes: symmetric or asymmetric?

Answer 3

Asymmetric

Question 4

Fluorescence recovery after photo bleaching (FRAP)

Answer 4

Shows fluidity of membranes by bleaching previously dyed proteins

Unbleached proteins diffuse and fill in area

Question 5

Fluid mosaic model

Answer 5

Membrane amphipathy

Membrane asymmetry: lipids proteins and carbohydrates asymmetrically arranged

Membrane fluidity

Question 6

Cholesterol

Answer 6

Membrane antifreeze: less fluid at high temps, more fluid at low temps

≈ 25% of the lipids in our cell membranes

Embeds with phospholipid tails (non-polar)

OH groups associate with phospholipid heads (polar)

Question 7

Osmosis

Answer 7

Water flows from low (normal [solute] isotonic) to high [solute] (hypertonic)

Question 8

Evidence plasma membrane is selectively permeable

Answer 8

Plasma membrane is NOT permeable to ions or large, polar molecules

Plasma membrane IS permeable to small, uncharged molecules and non-polar molecules

Question 9

Small non-polar (permeability)

Answer 9

Can diffuse easily (examples O2 and CO2)

Question 10

Larger nonpolar (permeability)

Answer 10

Can diffuse easily (example benzene C6H6)

Question 11

Small polar uncharged </= 3Cs

Answer 11

Can pass through slowly (H2O, glycerol)

Question 12

Larger polar uncharged (permeability) >/= 4Cs

Answer 12

Cannot diffuse (glucose)

Question 13

ANYTHING ionized (permeability)

Answer 13

Cannot diffuse (Na+, Cl-, amino acids)

Question 14

Large hydrophobic molecules (solubility)

Answer 14

Can diffuse but will remain IN membrane UNLESS bound to carrier proteins

Question 15

Carrier proteins

Answer 15

Proteins with hydrophobic pockets that allow hydrophobic molecules to bind and be protected from polar surrounding

Question 16

Fatty acid membranes (how permeable)

Answer 16

Most permeable (most fluid!)

Question 17

Phospholipid membranes with some saturated and some unsaturated fatty acids (how permeable)

Answer 17

Moderately permeable (moderately solid/fluid)

Question 18

Phospholipid membranes with mostly saturated fatty acids (how pemeable)

Answer 18

Least permeable (most solid!