3: Membrane transport

Question 1

What are the two main factors determining whether or not a particle can cross the plasma membrane without assistance?

Answer 1

It’s lipid solubility (is it polar or nonpolar?)

Size of the particle

Question 2

Does passive transport require energy?

Answer 2

No

Question 3

Active transport requires energy. What is the energy derived from?

Answer 3

ATP

Question 4

Name two types of unassisted passive transport which occur across the plasma membrane.

Answer 4

Diffusion

Movement along electrochemical gradient (i.e opposites attract)

Osmosis

Question 5

According to Fick’s Law of Diffusion, what are some factors influencing diffusion across a plasma membrane?

Answer 5

1. Magnitude of concentration gradient

2. Surface area of membrane

3. Lipid solubility

4. Size of particle

5. Thickness of membrane

Question 6

What do you get when you combine a concentration gradient (diffusion) with an electrical gradient (opposites attract)?

Answer 6

Electrochemical gradient

Question 7

What is osmosis?

Answer 7

Diffusion of water down its concentration gradient through a selectively permeable membrane

Question 8

What kind of plasma protein channel do water molecules pass through by osmosis?

Answer 8

Aquaporins

Question 9

During osmosis, water moves from a ___ water concentration to a ___ water concentration.

Answer 9

higher

lower

Question 10

During osmosis, water moves from a ___ solute concentration to a ___ solute concentration.

Answer 10

lower

higher

Question 11

What is osmolarity?

Answer 11

The concentration of osmotically active particles in a solution

Question 12

What is the unit of measurement for osmolarity?

Answer 12

Osmoles per litre (Osm/L)

Question 13

What is tonicity?

Answer 13

The effect that a solution has on cell volume

Question 14

Water moves from ___ osmolarity to ___ osmolarity.

Answer 14

low , high

Question 15

How many sodium ions are transported by NaKATPase?

In which direction?

Answer 15

3

Out of the cell

Question 16

How many potassium ions are transported by NaKATPase?

In which direction?

Answer 16

2

Into the cell

Question 17

What is secondary active transport?

Answer 17

Movement of X is paired with transport of another ion

Question 18

Which ion is usually involved in secondary active transport?

Answer 18

Na⁺

Question 19

In terms of secondary active transport, describe symport and antiport.

Answer 19

Symport - X and Na⁺ are transported in the same direction

Antiport - X and Na⁺ are transported in different directions

Question 20

Is vesicular transport active or passive?

Answer 20

Active

Question 21

Name two types of vesicular transport.

Answer 21

Endocytosis

Exocytosis

Question 22

What is endocytosis?

Answer 22

Movement of material into a cell via a vesicle

Question 23

What is exocytosis?

Answer 23

Movement of material out of a cell via a vesicle