Cell Membranes And Transport (chapter 4)

Question 1

Phospholipid

Answer 1

Hydrophilic head
Hydrophobic tail

Question 2

Hydrophobic

Answer 2

Water hating - fat loving

Question 3

Hydrophilic

Answer 3

Water loving - fat hating

Question 4

Bilayer

Answer 4

Phospholipid bilayer

Question 5

Amphipathic

Answer 5

One end hydrophilic, other end hydrophobic

Question 6

Unsaturated hydrocarbon

Answer 6

Degree of Unsaturation (double bonds) in tail (more = more fluid)

Unsaturated hydrocarbons - tails with kinks

Question 7

Saturated hydrocarbon

Answer 7

Length of fatty acid tail (longer = more viscous)
Saturated hydrocarbon tails = no kinks, straight

Question 8

Desaturase

Answer 8

Desaturase enzyme makes double bonds (kink)

Question 9

Cholesterol

Answer 9

• Cholesterol is in the membrane of animal cells
• Cholesterol counters the effects of temperature extremes:
  • high temps, reduces membrane fluidity by restraining movement of lipids
  • low temps, increases membrane fluidity by preventing lipids from ordering

Question 10

Integral membrane (transmembrane) proteins

Answer 10

Contains hydrophobic domains that cross the bilayer

Question 11

Peripheral proteins

Answer 11

Sit on the surface and form non-covalent bonds with lipids and membrane proteins

Question 12

Passive transport

Answer 12

Transport from high to low concentration is driven by increase in entropy
1. Diffusion
2. Facilitated diffusion

Question 13

Active transport

Answer 13

Transport against the concentration gradient (from low to high concentration) requires energy
1. Primary - uses ATP
2. Secondary - uses electrochemical gradients

Question 14

Diffusion

Answer 14

Things move from high to low concentration “down their concentration gradient”
(Non-polar molecules) (small uncharged polar molecules)

Question 15

Osmosis

Answer 15

Movement of a solvent from high to low concentrations

Question 16

Hypotonic solution

Answer 16

Solution concentration < cell concentration
Volume increases (water moves into the cell)

Question 17

Hypertonic solution

Answer 17

Solution concentration > cell concentration
Volume decreases (water moves out of the cell)

Question 18

Isotonic solution

Answer 18

Solution concentration = cell concentration
Volume stays the same (stays the same)

Question 19

Simple diffusion

Answer 19

Small and uncharged molecules diffuse rapidly

Question 20

Facilitated diffusion - channel proteins

Answer 20

A. Channel protein
B. Gated channel protein
C. Carrier proteins

Question 21

Channel protein

Answer 21

From hydrophilic channels in the membrane through which water and ions can move

Question 22

Channel protein: Aquaporin

Answer 22

An aquaporin is a water channel. Water molecules move through channel by being handed off to a succession of hydrogen-bonding sites in the channel

Question 23

Gated channel proteins: K+ voltage-gated channel

Answer 23

Normal voltage across membrane, activation gate of K+ closed (no movement)

Response to voltage change across membrane, activation gate of K+ opens up for movement

Question 24

Carrier protein

Answer 24

1. In conformation so that binding site is exposed toward region of higher concentration
2. Solute molecule binds to carrier protein

Question 25

Primary active transport (example: sodium-potassium pump)

Answer 25

• moves sodium ions (NA+) out of cell
• moves potassium ions (K+) into cell
• the transporter uses ATP to do this

Both ions are moved against their concentration gradient so energy is needed

Question 26

Secondary active transport

Answer 26

• does not use ATP
• uses ion gradients (electrochemical) for energy
• energy is released as an ion moves with its concentration gradient is used to drive movement of a solute against its concentration gradient

Question 27

Symport

Answer 27

The transported solute moves in the same direction as the gradient of the driving ion

Question 28

Antiport

Answer 28

The transported solute moves in the direction opposite from the gradient of the driving ion

Question 29

Micelle

Answer 29

Micelle is water forms an aggregate with the hydrophilic “head” regions in contact with surrounding solvent. Hydrophobic single-tail regions in the centre on the micelle

Question 30

Selective permeability

Answer 30

Polymeric membrane that will allow certain molecules or ions to pass through by osmosis

Question 31

Uniport

Answer 31

Membrane transport protein that transports a single substrate across a cell membrane

Question 32

Electrochemical gradient

Answer 32

Gradient of electrochemical potential