Active transport

Question 1

What is Active transport, and what types are present?

Answer 1

Use of ATP to move molecules across the cell membrane, and against the concentration gradient

Primary active transport directly uses the breakdown of ATP as an energy source

Secondary active transport indirectly uses ATP, through using energy stored in ion concentration gradients created by primary

Question 2

What is the Na+ - K+ pump in Primary active transport?

Answer 2

1. The sodium-potassium pump bind three sodium molecules and one ATP molecule (sodium promotes hydrolysis of ATP)
2. Hydrolysis of ATP causes phosphorylation, changing the shape of the channel and driving sodium ions through the channel
3. The sodium ions are then released into the ECF, and two potassium ions bind to the channel (this causes phosphates to be released)
4. The channel returns to its normal shape from dephosphorylating, and ATP binds to the channel again, causing a release of potassium into the ICF
5. The receptors are ready for sodium, and the cycle repeats

Question 3

What is an example of all modes of active transport being used?

Answer 3

Intestinal cells

1. Na+ is pumped out of the cell to reduce the concentration (primary)
2. Glucose is pumped against its concentration gradient as sodium rushes in along its concentration gradient (secondary)
3. Glucose can then travel down its concentration gradient to get into the bloodstream (facilitated diffusion through a carrier)

Question 4

What is Vesicular transport, and what does it involve?

Answer 4

A transfer of materials between the ECF and ICF within vesicles (requires energy from ATP)

Two types of this transport include Endocytosis (transport into the cell) and Exocytosis (transport out of the cell)

Question 5

What are the three types of Endocytosis?

Answer 5

1. Receptor mediated endocytosis: uptake triggered when target molecule binds to receptors on the plasma membrane
2. Pinocytosis: uptake of ECF (cell drinking)
3. Phagocytosis: uptake of solid objects such as bacteria and cellular debris (cell eating)

Question 6

What is Exocytosis in more detail?

Answer 6

The reverse of Endocytosis

Secretory vesicles are released form the Golgi apparatus, bind to the cell membrane and release their contents