Miss Lee - Active Transport

Question 1

What is active transport

Answer 1

Active Transport involves the movement of molecules across a membrane using proteins in the Bilayer similar to Carrier Proteins. These use energy in the form
of ATP to ‘pump’ molecules in one direction across a membrane.

Question 2

Example of substances moved by Active Transport

Answer 2

Sodium/potassium ions. NeuroneK+ in Na+ out
Potassium ions Guard cell (to open the stomata) In
Sodium ion Cells in loop of henle (kidney) Out
Calcium ion Muscle cell Into sarcoplasmic reticulum
Calcium ions Presynaptic knob out
Hydrogen ions In cells, respiring aerobically/photosynthesisin g cells For chemiosmosis

Question 3

How do molecules move by active transport?

Answer 3

• 1) The molecule or ion binds to receptors (complementary shape) on the carrier protein on the outside of the cell.
• 2) ATP binds to the carrier protein on the inside of the cell. It is hydrolysed to ADP + P with the release of energy. Phosphate molecule remains bound to the protein (phosphorylating it).
• 3) This provides the energy required for the carrier protein to change shape.
• 4) The molecule or ion is released to the inside of the cell.
• 5) The phosphate is released from the carrier protein and
recombines with ADP to form ATP.
• 6) The carrier protein returns to it’s original shape.

Question 4

What is bulk transport

Answer 4

• Bulk transport is another form of active transport.
• This type of transport moves substances e.g. enzymes & bacteria, hormones that are too large to move through channel or carrier proteins.

Question 5

How many types of bulk transport are there and what do they do?

Answer 5

• There are 2 types:
• Exocytosis: the bulk transport of material out of a cell using a vesicle (usually formed from the golgi apparatus) which fuses with the cell surface membrane & the contents are released.
• Endocytosis: the bulk transport of material into a cell by the fusing of a vesicle with the cell surface membrane. There are two types; Phagocytosis (movement of solids), and pinocytosis (movement of liquids)

Question 6

What is the process of exocytosis?

Answer 6

1. The self forms a versicle around material that needs to be expelled from the cell.
2. The bicycle is transported to the cell membrane.
3. The physical membrane fuses with the cell membrane and releases the contents from the cell.

Question 7

Why does bulk transport require energy

Answer 7

1. To transport vehicles to and from the cell-surface membrane along the cytoskeleton.
   2.Fusing the visit go to the membrane.
   Both of these processes require ATP energy