W1- Lecture 3- Transport Across Membrane

Question 1

Is the concentration higher in or outside off the cell ?

1. Na+
2. K+
3. Cl-
4. Anions

Answer 1

1. Higher outside
2. Higher inside
3. higher outside
4. higher inside

Question 2

When does diffusion stop ?

Answer 2

Until equilibrium is reached

Question 3

What types of molecules can pass the bilayer through passive diffusion ?

Answer 3

Very small non polar molecules
E.g O2 and CO2
In the lungs conc in air greater then the in RBC so the O2 is taken up by the TBC in released where the conc is lower in body tissues

Question 4

What determines the maximum rate of facilitated diffusion ?

Answer 4

The maximum capacity of the carrier protein

If this is saturated it is at its max speed

Question 5

Which protein is required to let glucose pass the plasma membrane via facilitated diffusion ?

Answer 5

GLUT1

Question 6

What type of proteins are transport proteins

E.g lipid anchored

Answer 6

Integral

Question 7

What happens to a carrier protein when a solute molucule?

So that it can transport this

Answer 7

A conformational change to

Question 8

Name the three types of carriers proteins ?

-based on number of solutes transported

Answer 8

Uniport
Symport
Antiport

Question 9

Describe

Uniport
Symport
Antiport

Answer 9

Uniport- single solute

Symport-2 solutes simultaneously

Antiport-2 solutes opposite directions

Question 10

Outline the steps of facilitated diffusion of glucose by GLUT1 in red blood cell membrane

Answer 10

Glucose bind to GLUT1(transporter protein) that have its binding site open to the extra cellular space (T1)

This binding causes GLUT1 to shift to it’s T2 conformation with the binding site now open two the inside of the cell

Glucose is released into the cell initiating another conformational change back to its original conformation (binding site open to the extra cellular space )

Question 11

Name three types of Chanel proteins

Answer 11

Ion channels

Porins- large pores in mitochodria

Aquaporins- large pores for water transport

Question 12

Name 4 common ions that pass through a ion Channel

Answer 12

Sodium
Potassium
Calcium
Chloride

Question 13

Name three ways how ion channels are gates

Answer 13

Voltage (membrane potential )

Ligand (specific molecule binding )

Mechanic-sensitive (mechanic forces )
E.g Stretching of tissues

Question 14

Describe the process of an action potential

+ draw + label

Answer 14

Change in stimulus

1 (rising phase )voltage gated sodium channels open

2 (peak)Na+ channels close & K+ channels open

3(hyperpolorisation ) Na+K+ATPase restores resting potential

Question 15

Name three functions of active transport

Answer 15

Uptake to nutrients

Waste products removal

Maintaining restoration of intracellular concentrations of ions and resting membrane potential

Question 16

Explain the maintenance of the electrochemical gradient via primary active transport system

Answer 16

Enzyme in membrane Na+K+ATPase
Hydrolysis of ATP provide energy
K+ pumped against conc grad (inside )
Na+ pumped conc grad (outside )

Question 17

Explain the intake of glucose to gut epithelial cells via secondary active transport
After the sodium potassium pump takes place

Answer 17

Glucose transporter SGLT1

Uses lector chemical gradient of Na+ to carry the glucose against its conc grad

Indirect use of ATP (which is used to maintain the conc grad of Na+)

Question 18

Name 3 functions of vesticles

Answer 18

Delivery
Recycling
Turnover of membrane proteins

Via exo + endocytosis

Question 19

Describe exocytosis

Answer 19

Vesicle fuses with plasma membrane e
Causing a rupture of the pm

Which releases the contents outside of the cell
Vesicle membrane become integrated into the pm

Question 20

What kinds of substances are released via exocytosis ?

5

Answer 20

Peptide 
Protein hormones
Enzymes 
Neurotransmitters 
Water soluble hormones

Question 21

What is endocytosis ?

Answer 21

Process by which external materials are internalised by cells (

Question 22

What processes is endocytosis important in ?

Answer 22

Ingestion of nutrients

Defence against microorganisms by white blood cell

Signalling to nucleus and recycling/disposal of membrane components

Question 23

Explain the process of endocytosis

Answer 23

Membrane invaginate forming a pocket with materials from the exterior

Pockets begins to pinch off and form vesicle

vesicle separates from the membrane

Question 24

Name 4 types of endocytosis

+ vesticle sizes

Answer 24

Clathrin-mediated- 100 nm diameter

Caveolae- 50 nm diameter Enriched in cholesterol (rafts mentioned )

Pinocytosis-500 nm – 5 micrometer diameter
allows cells to ‘drink’, take up extracellular fluid.

Phagocytosis- up to 0.75 mm diameter
Parts of dead cells

Question 25

Phagocytosis
In vagination also known as ?

Wheat does it form ?

Answer 25

Pseudopodium

A phagosome

Question 26

Receptor mediated endocytosis

Key features

Answer 26

Coated pit (clathrin in cultured fibroblasts )

+receptors