Lecture 7

Question 1

What is the function of the cell membrane?

Answer 1

compartmentalize the cell and form a barrier between extracellular environment and cytoplasm

Question 2

What are membranes made of?

Answer 2

Lipids

Question 3

What are three properties of membranes?

Answer 3

• stable lipid bilayer which form spontaneously in water
• Stabilized by hydrophobic interactions
• low permeability

Question 4

4 characteristics of liposomes

Answer 4

• are most stable 50-500nm range
• Larger liposomes break up because of thermo-motion
• high salt concentrations stabilize liposomes
• carriers of hydrophilic molecules

Question 5

What two things form the membrane?

Answer 5

Lipids + cholesterol

Question 6

What does more structure mean within lipid movements

Answer 6

less structure = less movement

Question 7

What 3 things affects lipid fluidity

Answer 7

• temperature
  -unsaturated fatty acids
• cholesterol

Question 8

What does it mean for the membranes to be asymmetric?

Answer 8

It means the two bilayer are different

Question 9

What can easily pass though the membrane?

Answer 9

Small, non-charged molecules
O2, CO2, N2

Question 10

Can small uncharged polar molecules pass through the membrane?

Answer 10

The permeability of membranes is in part determined by lipid composition, water can move through but no very fast
h2O, ethanol, glycerol

Question 11

Can larger uncharged polar molecules pass through the cellular membrane?

Answer 11

They can, but very slow
Amino acids, glucose, and nucleotides

Question 12

Can ions pass through the membrane?

Answer 12

No
H+, Na+, K+, Ca2+

Question 13

What is osmolarity?

Answer 13

total concentration of all solute particles

Question 14

What has higher osmolarity, cytoplasm or extracellular space?

Answer 14

cytoplasm

Question 15

What causes turgor pressure?

Answer 15

Water pushing into the cell from the cytoplasm, having a higher osmolarity

Question 16

What allows for fast exchange of water?

Answer 16

aquaporins

Question 17

What keeps the plants “in shape”

Answer 17

Turgor pressure

Question 18

What stabilizes the plasma membrane of mammalian cells

Answer 18

cytoskeleton

Question 19

What is cytosol low in and high in

Answer 19

Low in Na+ and Ca2+
High in K+

Question 20

What is the concentration gradient?

Answer 20

Higher concentration of molecules on one side of the membrane compared to other side

Question 21

What is membrane potential?

Answer 21

Unequal charge distribution across the membrane

Question 22

Concentration gradient + membrane potential = ????

Answer 22

Electrochemical gradient

Question 23

What is electrochemical gradient?

Answer 23

determines which direction charge solutes will move

Question 24

What are two ways to transport molecules across membranes

Answer 24

1. transporter
2. Channels

Question 25

What are characteristics of transporters?

Answer 25

Contains a central binding site for the molecule/solute. The binding site chances accessibility from one side of the membrane to the other

Question 26

What are characteristics of channels?

Answer 26

Channels are selective pores Channels allow ions to pass membranes Electrochemical gradient determines the direction of flow

Question 27

What is passive transporter?

Answer 27

Follows the concentration gradient

Question 28

What is an active transporter?

Answer 28

Works against concentration gradient

Question 29

Describe the alternate access model of transporter function

Answer 29

- central binding pocket is accessible either from the outside or the cytosol - glucose transporters can function in both directions and thus follows concentration gradient

Question 30

What is hexokinase?

Answer 30

(Converting glucose to glucose-6-phosphate) drives the import forward. The transport across the membrane is passive, by the system uses energy to trap glucose which makes the glucose import an active transport system

Question 31

What drives the ion gradient?

Answer 31

ATP

Question 32

Amino acids can be imported or synthesized from what ...

Answer 32

glucose

Question 33

What are the jobs of ion channels?

Answer 33

The selectivity filter allows only specific ions to pass through (no water)

Question 34

Job of the gates in ion channels

Answer 34

signal open and close

Question 35

Where is the tetrametric protein complex found?

Answer 35

plasma membrane

Question 36

What is the function of the tetrametric protein?

Answer 36

pain receptor

Question 37

When is the tetrametric protein activated and what happens?

Answer 37

Activated by high temperature or chemicals which causes cations to flux

Question 38

What is a good example of ion channel?

Answer 38

neurons

Question 39

What is the job of the neuron?

Answer 39

Neurons receive information from other neurons on the dendrites, process the information, and send a signal down the axon to other neurons

Question 40

What are signals neurons use?

Answer 40

Changes in membrane potential

Question 41

Action potential = ???

Answer 41

a rapid and local change in membrane potential propagating along the membrane of neurons

Question 42

What is synapses?

Answer 42

Specialized areas of the neurons that make contact with other cells and deliver a signal to the postsynaptic cell

Question 43

What makes synapses unique?

Answer 43

Large number of vesicles present

Question 44

What occurs during step 1 of synaptic activity?

Answer 44

- the action potential from the axon ends up in synapses which include calcium channels - the calcium triggers the fusion of synaptic vesicles with the plasma membrane, which release a neurotransmitter

Question 45

What occurs during step 2 of synaptic activity?

Answer 45

- the neurotransmitter diffuses across the synaptic cleft and opens a cation channel in the postsynaptic neuron - the influx of cations produces an action potential in the postsynaptic neuron