Membrane Transport - Lecture 3

Question 1

What are the two properties that influence if a particle can permeate the plasma membrane without assistance?

Answer 1

Lipid solubility

Size

Question 2

What are the two types of Driving forces ?

Answer 2

Passive - (leak channels)

Active - (Requires the use of ATP to produce movement)

Question 3

In unassisted membrane transport what are the two forces that passively drive a particle across the membrane?

Answer 3

Electrical Concentration

Concentration Gradient

Question 4

What is dynamic equilibrium ?

Answer 4

This is were the concentration gradient no longer exists

Question 5

What is diffusion?

Answer 5

Diffusion is the net movement of molecules into or out of a cell down their concentration gradient

Question 6

What causes molecules to move from a high concentration gradient to a low

Answer 6

More collisions in the area with the higher concentration, as there are more particles
This causes particles to move from high to low

Question 7

What are the factors affecting Diffusion?

Answer 7

The magnitude of the concentration gradient
The surface area
The solubility of the substrate
The size of the substance/molecular weight
The Distance though which diffusion must take place

Question 8

What is fick’s law equation?

Answer 8

Q = Delta C x A x P

Q= rate of diffusion
delta C = Concentration gradient
A = Area of surface
P = Permeability

Question 9

What is osmosis?

Answer 9

Osmosis is the net diffusion of water down it own concentration gradient

Question 10

What are the channels through which water moves through called?

Answer 10

Aquaporins

Question 11

What is Osmolarity?

Answer 11

Osmolarity is the concentration of osmotically active particles present in a solution

(e.g. if the concentration of NaCl is 150 osm there would be 150 Na and 150 Cl - meaning there are 300 osmotically active substance

Osmolarity = No. Particles X Molar Concentration

Question 12

What is an isotonic solution?

Answer 12

An isotonic solution is one that has the same osmolarity as blood

Question 13

What is a hypotonic solution?

Answer 13

A hypotonic solution is one that has a lesser osmolarity than blood

Question 14

What is a hypertonic solution?

Answer 14

A hypertonic solution has a higher osmolarity than blood

Question 15

How does Carrier Mediated Transport occur?

Answer 15

Substance binds onto a specific carrier which undergoes a conformational change which transports the substance

Question 16

What are the characteristics that determine material transfer by carrier mediated transport?

Answer 16

Specific to the transporter

Saturation point has not been reached

Competition with the transporter

Question 17

What form of diffusion allows more substrate to enter the cell?

Answer 17

Facilitated Diffusion

Question 18

What are the forms of active transport?

Answer 18

Primary Active Transport

Secondary Active Transport

Question 19

What is Primary Active Transport?

Answer 19

Requires the direct use of energy to move a substance against its concentration gradient

Question 20

What is secondary Active Transport?

Answer 20

Required energy but does not utilise ATP

Utilises secondary energy stores in the form of ion concentration gradients

Question 21

What is the purpose of the Sodium Potassium pump ?

Answer 21

Sodium is transported into of cells

Potassium is transported out of cells

Question 22

How much sodium is transport into cells for Potassium exported?

Answer 22

3 Na+ for 2 K+

Question 23

What is the purpose of the Sodium Potassium Pump?

Answer 23

Establishes concentrations of Na+ and K+ across the plasma membrane

Helps regulate cell volume

Energy used to drive the pump indirectly serves as the energy source for secondary active
transport

Question 24

What is a Symport protein transporter?

Answer 24

Used for Secondary Active transport

The Solute and the ion move in the same direction

Question 25

What is a Antiport protein transporter?

Answer 25

Used for secondary active transport

The solute and ion move in opposite directions ( Ion into, solute out of the cell).

Question 26

What is Endocytosis?

Answer 26

This is the pinching off of membrane to engulf substance

Question 27

What is Exoctyosis?

Answer 27

A vesicle fuses with the plasma membrane releasing it contents to the ECF

Question 28

What is tonicity?

Answer 28

Tonicity is the effect a solution has on cell volume

Question 29

What occurs at the Transport Maximum of a protein (Tmax) ?

Answer 29

Each carrier can only absorb certain number of molecules per unit time
- This is the Saturation Point