U1: KA3 - Membrane proteins

Question 1

Describe the structure of the plasma membrane.

Answer 1

Fluid mosiac model
composed of phospholipids and proteins

Question 2

Describe phospholipids.

Answer 2

Charged head that is hydrophillic
Uncharged non-polar tail which is hydrophobic

Question 3

What gives the membrane its fluid quality?

Answer 3

Phospholipids constantly changing position.

Question 4

The membrane is embedded with proteins which forms what?

Answer 4

A patchy mosaic.

Question 5

What functions can proteins in the membrane have?

Answer 5

Active transport proteins
Channel forming proteins
Enzymes
Receptors
Attachment proteins for the cell cytoskeleton

Question 6

What are the 2 types of protein in the plasma membrane?

Answer 6

Integral protein
Peripheral protein

Question 7

What are integral proteins?

Answer 7

Found within the membrane.
Transmembrane, meaning they span entire width of membrane
Interact with the hydrophobic region of membrane - phospholipids. Allowing hydrophobic interactions holding integral membrane proteins within the bilayer.

Question 8

What are peripheral proteins?

Answer 8

Found on the surface of the membrane have hydrophilic R groups bound to surface of membrane mainly by ionic and hydrogen bond interaction.
Many interact with the surfaces of integral membrane proteins.

Question 8

What is facilitated diffusion?

Answer 8

Passive transport of substances across the membrane through specific transmembrane proteins.

Question 9

Why are some channel proteins gated?

Answer 9

change conformation to allow or prevent diffusion
they respond to stimulus which causes them to open or close.

Question 9

What are channel proteins?

Answer 9

Multi-subunit proteins with subunits arranged to form water-filled pores that extend across the membrane. Most channel proteins are highly selective.

Question 10

What do ligand gated channels do?

Answer 10

Control binding of signal molecules. When the correct signal molecule binds the gate opens allowing ions to flow through.

Question 11

How do voltage gated channels work?

Answer 11

Controlled by change in ion concentration

Question 11

How do transporter proteins work?

Answer 11

Bind to specific substance to be to be transported and undergo a conformational change to transfer the solute across the membrane.

Question 12

Why do transporters alternative between two conformations?

Answer 12

So binding site for a solute is sequentially exposed on one side of the bilayer, then the other side.

Question 13

How do protein pumps work?

Answer 13

Active transport uses them to transfer substances across the membrane against the concentration gradient.

Question 14

Pumps that mediate active transport are what?

Answer 14

Transporter proteins coupled to an energy source

Question 17

What is the concentration gradient?

Answer 17

Difference in concentration of a solute across the plasma membrane.

Question 17

What is the Electrical potential difference?

Answer 17

Membrane potential - difference in electrical charge on the two sides of the membrane.

Question 17

The sodium-potassium pump transports ions ….. a steep concentration gradient.

Answer 17

Against

Question 18

How many ions are actively transported out of the cell and how many are in?

Answer 18

3 Sodium ions out
2 Potassium ions in

Question 18

What combines to form the electrochemical gradient and what does it determine?

Answer 18

Concentration gradient and the electrical potential difference.
Determines the transport of the solute.

Question 19

Ion pumps use what to establish and maintain ion gradients?

Answer 19

Energy from hydrolysis of ATP.

Question 20

What drives the active transport of glucose in intestinal epithelial cells?

Answer 20

The sodium potassium pump generates a sodium ion gradient across the plasma membrane.

Question 21

Glucose symport does what?

Answer 21

Transports sodium ions and glucose at the same time in the same direction.

Question 21

The sodium potassium pump accounts for a high proportion of what?

Answer 21

Basal metabolic rate

Question 22

How does the glucose symporter work?

Answer 22

Sodium ions enter the cell down the concentration gradient and the simultaneous transport of glucose pumps glucose into the cell against concentration gradient.