Question

1:

a) How is active transport different from facilitated diffusion?

b) Describe the Na-K pump and the role of active transport within this pump.

Answer 1

a) ACTIVE TRANSPORT: Active Transport is defined as the movement of ions or molecules across a cell membane from region of lower concentration into a region of higher concentration against concentration gradient assisted by enzymes and requires energy to perform the movement.It is of two types:1.Primary Active Transport and 2.Secondary Active Transport

• It is a Active mechanism which requires energy to achieve the movement where in Primary active transport it requires ATP and in Secondary Active Transport it uses the Electrochemical Gradient.
• It is against the concentration Gradient(Higher to Lower Concentration)
• ATPases(Example:Sodium Potassium Pump) is example for Active Transport enzymes
• Examples of Active Transport:
  1. Sodium Potassium Pump to maintain cell potential by moving 3 sodium ions outside and 2 potassium ions inside.
  2. Sodium Calcium Exchanger/Antiporter which allows 3 sodium ions inside the cell and 1 calcium outside the cell

FACILITATED DIFFUSION: Facilitated Diffusion is defined as the transport of molecules or ions across a cell membrane from area of higher concentration to the area of lower concentration by means of carrier molecule which may be transmembrane integral proteins.

• It is passive mechanism which do not require any energy to perform the movement
• It is along/towards the concentration gradient(Lower to Higher Concentration)
• Permeases,Binding Proteins are examples of carrier molecules
• Example of Facilitated Diffusion: Exchange of gases like Oxygen and Carbondioxide in respiratory tissues and cells.

b)Sodium-Potassium pump helps in maintaining the resting potential by moving sodium and potassium ions in and out of the cell.

1. The pump open when three sodium ions bind to it,after binding they act as trigger for breakdown of ATP.
2. The ATP breaksdown into ADP and a phosphate group where the phosphate group is attached to the Sodium potassium pump which leads to change of shape of pump and makes it open to outside.
3. This releases 3 sodium ions outside and this changed shape of pump allows two Potassium ions bind to it with release of phophate group attached to it.
4. This release of phosphate group causes the pump to change its shape and makes it open to inside i.e., into cytoplasm of the cell.
5. This cycle continues to maintain resting potential and Cell osmolarity.
6. This is the process how active transport act within the sodium potassium pump by adding and removal of  phosphate group to pump leading to change in its shape and its ability to bind sodium when phospate added and ability to bind potassium when phospate is removed.