Membrane Proteins

Question 1

Give two membrane proteins by which ions and molecules can progress through a membrane.

Answer 1

Channel Proteins

Transporter Proteins

Question 2

Describe the two types of channel proteins.

Answer 2

Ligand-gated: signal molecules bind to channels causing a conformational change, opening the channel and allowing ions/molecules to pass through.

Voltage-gated: change in ion concentrations causes a conformational change, opening the channel and allowing ions/molecules to pass through.

Question 3

Describe transporter proteins

Answer 3

Ions/molecules bind to transporter protein, this causes a conformational change and the protein passes the molecules through to membrane.

Question 4

State the definition of the term ‘facilitated diffusion’

Answer 4

The process of passive movement across a membrane through specific membrane proteins.

Question 5

What is signal transduction?

Answer 5

Extracellular hydrophobic signal molecules bind to receptor proteins, triggering a signal-transduction pathway. This causes a specific intracellular response, involving cascades occur to amplify the signal.

This can change the uptake or secretion of molecules or rearrange the cytoskeleton.

Question 6

What is the role of the Sodium Potassium pump?

Answer 6

Moving sodium ions out of the cell and moving potassium ions into the cell to generate a new ion gradient.

Question 7

Describe 4 reasons the Na/K pump is important.

Answer 7

Maintains osmotic balance in animal cells -low ion concentration increases water concentration

Generation of sodium ion gradient for glucose symport

Generation of sodium ion gradient in kidney tubules - gradient created between lumen of tubule to cell

Maintain ion gradient for resting potential.

Question 8

State the two stable conformational states of the Na/K pump

Answer 8

Open towards inside of cell with high affinity for Na+ ions

Open towards outside of cell with high affinity for K+ ions

Question 9

Describe the 6 stages of how the Na/K pump works

Answer 9

1. 3 Na+ ions bind
2. ATP hydrolyses, phosphorylation occurs, conformational change occurs.
3. Na+ ions released
4. 2 K+ ions bind, triggering dephosphorylation
5. Conformational change occurs to original state
6. K+ ions are released

Question 10

Explain what the resting potential of a cell is.

Answer 10

Imbalance in electrical charge in a cell. K channels allow K+ to leak back out pf the cell causing a net positive charge outside of cell

Question 11

How does a nerve impulse pass along a neuron?

Answer 11

As a wave of depolarisation

Question 12

Describe the 5 stages of triggering a nerve impulse.

Answer 12

1. Neurotransmitter binds to ligand gates channel
2. Channel opens to allow Na+ to diffuse into neuron
3. Na+ movement causes depolarisation
4. Depolarisation reaches critical level
5. Voltage gated channel opens to allow Na+ to diffuse into cell, creating a domino effect

Question 13

Describe the 5 stages of resetting the resting potential

Answer 13

1. Voltage gated channel opens to allow Na+ to pass through
2. Voltage builds up so Na+ channel closes and K+ channel opens
3. K+ diffuses out of neuron to reverse depolarisation
4. Resting potential is restored so K+ channel closes
5. Na/K pump resets ion gradient

Question 14

Describe the term ‘coupled transport’

Answer 14

movement of one material down a concentration gradient, causing another material to move up against the concentration gradient

Question 15

Describe active transport.

Answer 15

The protein conformational change requires the binding of ATP

Question 16

State 3 examples of specific transmembrane proteins

Answer 16

Sodium Channels

Glucose Transporters

Proton Pumps

Question 17

Explain what an aquaporin is.

Answer 17

Specific channel protein that allows polar water molecules pass through the pore.