Membrane transport: Active transport

Question 1

Define Active transport

Answer 1

The process at which molecules move up the concentration gradient, they move from an area of lower concentration to an area of higher concentration.
Requires energy (ATP)

Question 2

How is the energy for Active transport found?

Answer 2

Through different ways such as ATP hydrolysis and light

Question 3

What are the features in Na/K ATPase; Mammals which maintains membrane potential?

Answer 3

1) Pumps 3Na for every 2K (electrogenic)
2) Inhibited by vanadate and digoxin
3) ATP gives energy to a molecule by phosphorylating protein

Question 4

What happens in the E1 conformation for the Catalytic cycle of Na/K ATPase?

Answer 4

Faces inwards
High Na Affinity (Low Km) 
Low K affinity (High Km)
Preferentially release K and bind Na
Triggers ATP hydrolysis
Phosphate group (Pi) binds enzyme
Triggers E1 to E2 switch
Sodium ions moved out

Question 5

What happens in the E2 conformation for the Catalytic cycle of Na/K ATPase?

Answer 5

Faces out
High K+ affinity (Low Km)
Low Na+ affinity (high km)
E2 favours Na+ release and K+ binding
K+ binding triggers P1 cleavage
Resulting in E2 to E1 switch
K ions are taken into the cell
Inhibited by vanadate or digoxin

Question 6

What are the types of active transport?

Answer 6

Co-transport, antiport, symport or secondary active transports are active transports

Question 7

Define secondary active transport

Answer 7

Energetically unfavourable transport of a particle against its electrochemical gradient is facilitated by co-transport of a favourable one down its gradient
Transport linked to another molecules concentration gradient
Energy is taken from downhill ion movement to drive uphill glucose transport

Question 8

Secondary active transport has the need for an energy source, define charge imbalance?

Answer 8

Membranes have electrical potential ion, which moves in response to membrane potential
Ion moves to the side of the membrane with an opposite charge even against the concentration gradient

Question 9

Secondary active transport has the need for an energy source, define pH balance?

Answer 9

Exists across membrane (Acid-base gradient)

Acid/base moves to neutralise gradient, Acid to basic side, vice versa

Question 10

There are two types of secondary active transport: What is a symporter?

Answer 10

Sodium-dependent glucose transporters
Transport glucose into the cell against the concentration gradient (un-favourable).

Na^+ transported along with it, into the cell which is a favourable transport

Found in the small intestine

SGLT1 co-transports sodium ions and glucose across the luminal membrane of epithelial cells, so it absorbed into the bloodstream

Different to GLUT-1 = sodium independent uniport carrier that facilitates passive diffusion

Secondary co-transporters and many other are dependent on the primary Na,K-ATPase ultimately generates the NA^+ and K^+ gradients

Question 11

There are two types of secondary active transport: What is a Antiporter?

Answer 11

Na^+/Ca^2+ antiporter

Found in the heart to transport Ca2+ out of the cell against a steel concentration gradient and electrical gradient

While 3na^+ imported into the cell to balance the unfavourable Ca2+ transport

Secondary co-transports and many others, dependent on the primary Na,K-ATPase that ultimately generates the Na+ and K+ gradients, generated membrane potential works like battery being charged