Membrane Movement

Question 1

Main component of membrane

Answer 1

phospholipid bilayer
Hydrophilic head
Hydrophobic tail

Question 2

Cell membrane function

Answer 2

1. Physical Isolation
2. Regulation of exchange with the environment (what molecules can or can’t move in)
3. Communication between the cell and the environment (nervous system, endocrine system)
4. Support and structure (like skin, connect to cytoskeletal system)

Question 3

What is the four ring structure found in a cell membrane?

Answer 3

Cholesterol (also a lipid)

Question 4

What does cholesterol do in the membrane?

Answer 4

1. fill the gap between two phospholipids
2. Make it more flexible or more rigid

Question 5

Why does the birth control patch work?

Answer 5

Because it is a cholesterol based molecule (steroid hormone) and therefore can go through the lipid bilayer

Question 6

Membrane proteins

Answer 6

1. Transporters: help molecules that need to go through cell membrane
   -important for long distance
2. Structural:
   -connect to the cytoskeleton system
   - make cell change the structure and move
3. Receptors: can pick up signals and trigger response
   -cascade effect
4. Enzymes: Helps reactions move forward

Question 7

Movement across membrane depends on?

Answer 7

lipid solubility: if molecules are lipid soluble it can easily go through membrane
Size: small molecules go through membrane easily
Uncharged/polar: non charged molecules can easily go through and non polar

Question 8

What energy does passive transport use?

Answer 8

Concentration gradient

Question 9

What helps glucose go through the membrane?

Answer 9

Glucose carrier through facilitated diffusion.

Question 10

Which are the two glucose carriers?

Answer 10

-GLUT2
-GLUT4: insulin triggers more of this glucose carrier to lower blood sugar levels

Facilitated diffusion brings glucose into the cell down its concentration gradient.
Carriers go through conformational change

Question 11

What is G6P?

Answer 11

glucose can be converted into G6P so that glucose can keep coming in and diffusion doesn’t reach equilibrium.

Question 12

Do carriers get saturated?

Answer 12

yes

Question 13

Do channels get saturated?

Answer 13

NO

Question 14

What affects diffusion rate?

Answer 14

1. Temperature- higher temp, faster
2. Size- smaller, faster
3. distance- shorter, faster
4. Surface area- larger surface area, more diffusion

Question 15

Channel carrier

Answer 15

Open channels create a water-filled pore

Question 16

Do ion channels stay open?

Answer 16

No, if you leave the channel open for too long the ions will keep moving in and can create charge (not good) most are kept closed.

Question 17

Types of channels

Answer 17

1. voltage gated: cells voltage change and gate opens
2. Mechanically gated: mechanical force to open
3. Ligand gated: something binds to channel and it opens

Question 18

What energy does active transport use?

Answer 18

ATP (works against concentration gradient)

Question 19

Characteristics of mediated transport

Answer 19

1. Specificity: binding sites are specific (ex. Na+ and K+)
2. Competition: have limited seats so you will have competition with molecules)
3. Saturation: how many molecules can be transported per time

Question 20

Secondary active transport (indirect active transport)

Answer 20

1. active transporter of X molecule moves from [low] to [high] to set up gradient for X
2. X binds to secondary active transporter for Y against gradient
3. pump stops working –> transport stops

no ATP

Question 21

Symporter

Answer 21

Move in the same direction

Question 22

Antiporter

Answer 22

move in opposite direction