B 2.1 Membranes

Question 1

phospholipid structure

Answer 1

amphipathic molecule
head = phosphate group + glycerol
2 tails = fatty acids

Question 2

be able to draw a phospholipid
+ phospholipid bilayer

Answer 2

circle for phosphate head + 2 tails for fatty acid tails
+ two rows of phospholipids, tails within the bilayer

Question 3

how does the lipid bilayer act as a barrier between (aq) solutions?

Answer 3

hydrophobic hydrocarbon chains that form at the center have low permeability to
- large molecules
- hydrophilic particles (ex.ions)

Question 4

simple diffusion
+ example

Answer 4

passive transport
high concentration → low concentration
+ O2 & CO2 exchange across alveoli (lungs) membrane

Question 5

integral proteins

Answer 5

• penetrate phospholipid bilayer
• hydrophobic center, hydrophilic top and bottom (to anchor protein)
  (glycoproteins, channels, protein pumps)

Question 6

peripheral proteins

Answer 6

• temporarily attached (electrostatic interactions) to one side of membrane
• hydrophilic
  (receptors, enzymes)

Question 7

osmosis

Answer 7

passive transport
low solute concentration → high solute concentration through semipermeable membrane
polar but small => passes through phospholipid bilayer
solutes = polar => not pass bilayer

Question 8

Facilitated diffusion example

Answer 8

Aquaporins!
integral channel proteins
faster than osmosis
increase membrane permeability to water

Question 9

Facilitated diffusion

Answer 9

the passive transport of molecules from a region of high concentration to a region of low concentration through channel proteins

Question 10

channel proteins

Answer 10

central pore: lined with hydrophilic R-groups allowing ONLY specific molecule
can be gated: only open in response to stimulus (ex. Na & K pumps in neuron)

Question 11

Active transport definition

Answer 11

movement of particles from a region of low concentration to a region of high concentration using protein pumps and ATP energy

Question 12

Active transport how?

Answer 12

1. A specific particle binds to a binding site on a specific protein pump.
2. ATP binds to the protein pump and performs hydrolysis
3. phosphate attached causes protein pump to change shape
4. particle moves against concentration gradient
5. phosphate released, protein back to original shape

Question 13

membrane selectivity & transport types

Answer 13

Facilitated diffusion = selective
Active transport = selective
Simple diffusion = not selective

Question 14

glycoproteins & glycolipids
(function)

Answer 14

carbohydrate chain attached to protein/lipid billayer
1. receptors (antigens)
2. cell to cell communication
3. immune response
4. cell to cell adhesion

Question 15

temp effects on membrane fluidity

Answer 15

high temp = more fluid
(+low viscosity, doesn’t hold shape, too permeable)
low temp = more solid
(+high viscosity, dense, rigid, not permeable)

Question 16

fatty acids and membrane fluidity

Answer 16

longer tail = more interaction between tails = less fluid
saturated = higher viscosity = high melting point (better 4 high temp)
unsaturated = lower viscosity = low melting point (better 4 low temp)

Question 17

membrane composition adaptations

Answer 17

chickpea = increases unsaturation of fatty acids at low temp

reindeer = different fatty acid compositions within organism
hooves → more unsaturated

Question 18

cholesterol in membrane (animal cells)

Answer 18

amphipathic
fluidity modulator
↑ temp → it stabilizes membrane
↓ temp → it prevents phospholipids from interfering

Question 19

membrane fluidity affected by:

Answer 19

• temperature
• fatty acid length
• fatty acid saturation
• presence of cholesterol

Question 20

formation of vesicles
+examples

Answer 20

exocytosis (out of cell)
+ macrophages engulf pathogens
endocytosis (into cell)
+ secretion of hormones (ex.insulin)

Question 21

missing?

Answer 21

B.2.1.14
B.2.1.15
B.2.1.16
B.2.1.17 (this one she didn’t miss but i dont understand it :(