Membrane Proteins 1.3

Question 1

what is the cell membrane composed of?

Answer 1

proteins and phospholipids

Question 2

what is the function of the cell membrane

Answer 2

controls entry and exit of materials into and out of the cell

Question 3

what do regions of hydrophobic R groups allow?

Answer 3

strong hydrophobic interactions that hold integral membrane proteins within the phospholipid layer

Question 4

what can integral proteins be?

Answer 4

transmembrane proteins

Question 5

what do peripheral proteins have?

Answer 5

hydrophilic R group on they surface and are bound to the surface membranes mainly by ionic and hydrogen bonds

Question 6

what do many peripheral membrane proteins interact with?

Answer 6

the surfaces of integral membrane proteins

Question 7

what is the phospholipid bilayer?

Answer 7

barrier to ions and most uncharged polar molecules

Question 8

what molecules can pass through the bilayer by simple diffusion?

Answer 8

oxygen and carbon dioxide

Question 9

what is facilitated diffusion?

Answer 9

passive transport of substances across the membrane through specific transmembrane proteins

Question 10

why do different cell types have different channel and transporter proteins?

Answer 10

to perform specialised functions

Question 11

most channel proteins in animal and plant cells are what?

Answer 11

highly selective

Question 12

why are some channel proteins gated and change conformation?

Answer 12

to allow or prevent diffusion

Question 13

what are ligand-gated channels controlled by?

Answer 13

binding of signal molecules

Question 14

what are voltage-gated channels controlled by?

Answer 14

changes in ion concentration

Question 15

why do transporter proteins bind to specific substance?

Answer 15

to be transported and undergo a conformational change to transfer the solute across the membrane

Question 16

what does active transport use?

Answer 16

pump proteins that transfer substances across the membrane against their concentration gradient

Question 17

what is required for active transport?

Answer 17

a source of metabolic energy

Question 18

what determines the transport of a solute carrying a net charge?

Answer 18

the concentration gradient and the electrical potential difference combine to form the electrochemical gradient

Question 19

what energy does the sodium-potassium pump use?

Answer 19

energy from the hydrolysis of ATP to establish and maintain ion gradients

Question 20

describe the transportation of ions in the sodium-potassium pump

Answer 20

it transports ions against a steep concentration gradient using energy directly from ATP hydrolysis

Question 21

what does the sodium-potassium pump transport?

Answer 21

actively transports 3 sodium ions out of the cell and 2 potassium ions into the cell

Question 22

where is the sodium-potassium pump found?

Answer 22

in most animal cells - accounting for a high proportion of the basal metabolic rate in mainly organisms

Question 23

what does the sodium-potassium pump drive in the small intestine?

Answer 23

transport of glucose

Question 24

what is the glucose transporter responsible for?

Answer 24

glucose symport transports sodium ions and glucose at the same time and in the same direction

Question 25

describe the generation of an ion gradient

Answer 25

• the pump has high affinity for sodium ions inside the cell
• binding occurs-
  phosphorylation by ATP
• conformation changes
• affinity for sodium ion decreases
• sodium ions released outside of the cell
• potassium ions bind outside the cell - dephosphorylaton
• conformation changes -> potassium ions taken into cell
• affinity returns to start

Question 26

what do some active transport proteins do?

Answer 26

they hydrolyse ATP directly to provide the energy for the conformational change require to move substances across the membrane