OUTSIDE CELL & co transport

OUTSIDE CELL

Receptor

Phosphate

1. Sodium binds:

The sodium potassium pump is open to the inside of the cell.

shape of the sodium potassium pump allows three sodium ions to bind with the carrier protein.

2: ATP action: phophaste

shape,

leave

con grad

phosphate groups binds with the sodium potassium pump leaving ADP.

changes shape of the sodium potassium pump allowing the sodium ions to leave the carrier protein on the other side of the membrane

. They have been moved against their concentration gradient.

3. Potassium ions:

right shape

fit how many in car

The shape of the sodium potassium pump is now the right shape to fit in two potassium ions which bind with the carrier.

Release of phosphate:

binding of

cause cha

rel potass on other si

con

binding with potassium ions cause the phosphate group to be released from the receptor.

causes the sodium potassium pump to change shape again

releasing the potassium ions on the other side of the membrane against their concentration gradient.

How co-transport works:

Co-transport moves two substances at the same time. It uses carrier proteins that do not in themselves require metabolic energy to carry the substances across the membrane. One of the substances moves down its concentration gradient. When the substance binds with the carrier protein it changes shape moving the original molecule and something else against its concentration gradient across the membrane. A good example is the mechanism used to absorb glucose into the walls of the small intestine. Glucose is transported against its concentration gradient at the same time as sodium ions are moved down their concentration gradient.

Where energy is required:

Co transport will not work if both substances are moving against their concentration gradient. Energy is needed to maintain the concentration gradient. For example, in order to move glucose against its concentration gradient, sodium ions must be at higher concentration outside of the ileum cells than inside. This concentration gradient is maintained by the sodium potassium pump which does require energy from ATP.