Membrane Transport & Cell Receptors

Question 1

What two criteria are transport processes classified into?

Answer 1

• non-carrier medicated

• carrier mediated (passive/active)

Question 2

Describe non-carrier mediated transport;

Answer 2

• diffusion through the lipid bilayer

-diffusion through membrane channels

Question 3

Describe carrier mediated transport;

Answer 3

Required a transporter protein

Facilitated diffusion- substance uses it’s own kinetic energy to move down a concentration gradient

Active diffusion-a substance uses energy from another substance to move up a concentration gradient

Question 4

What factors is the rate of diffusion (net flux) across plasma membranes id influenced by?

Answer 4

Diffusion distance

Steepness of concentration gradient

Surface area

Temperature

Size/mass of diffusing molecule

Type of molecule & membrane

Question 5

What is osmosis?

Answer 5

Net movement of water through a selectively permeable membrane, from an area of higher concentration to an area of lower concentration across the membrane

Question 6

What % of cells are water by weight?

Answer 6

70%

Question 7

Describe uncharged molecules in passive transport;

Answer 7

Direction of transport determined by concentration gradient

Question 8

Describe charged molecules in passive transport;

Answer 8

Membrane potential exerts a force on molecule that carries an electrical charge

Question 9

Describe ion channels;

Answer 9

Bulk of cell’s channels facilitate passage of select inorganic ions

Highly selective

Not continuously open

Question 10

Describe the 3 transmembrane pumps associated with active transport;

Answer 10

• coupled pump
• ATP-driven pump
• light driven pump

Question 11

What is the function of the coupled pump?

Answer 11

Links uphill transport of one solute across a membrane to the downhill transport of another

Question 12

What is the function of the ATP-driven pump?

Answer 12

Hydrolyses ATP to drive uphill transport

Question 13

What is the function of the light driven pump?

Answer 13

Energy from sunlight to drive uphill transport (bacterial cells)

Question 14

Energy derived from ATP changes…

Answer 14

The shape of a transporter protein, which pumps a substrate across a plasma membrane against the gradient

Question 15

The energy stored in the form of a sodium or a hydrogen ion concentration gradient is used…

Answer 15

To drive other substances against their own concentration gradients

Question 16

Describe ion channel coupled receptors;

Answer 16

Opens/closes in response to bonding of signalling molecule

Allows flow of ions across membrane

Changed membrane potential and produces an electrical current

Question 17

Describe enzyme coupled receptors;

Answer 17

Receptor binds signalling molecule - enzyme activity is switched on inside cell

Reception has own enzyme activity, or associated with enzymes

Activate variety of intracellular signalling pathways

Question 18

What is phosphorylation?

Answer 18

Enzyme that modifies other proteins by chemically adding phosphate groups to them

Question 19

What does phosphorylation result in?

Answer 19

Functional change of the target protein by changing enzyme activity, cellular location or association with other proteins

Question 20

What do serine, threonine and tyrosine all have in common? (Amino acids)

Answer 20

They all have OH groups that can be phosphorylated by enzymes called kinases

Question 21

Describe G-protein-couples receptors (GPCR)

Answer 21

Receptor binds signalling molecule

Activated receptor signals GTP binding protein on inside of plasma memebrane

Either switches on/off enzyme or ion channel