Question

• What active transport protein (ATPase) is found on the membranes of all of our cells, is constantly active, and uses 10% of our energy when we are at rest? (Hint: with every cycle this protein pumps 2 ions into the cell and 3 ions out of the cell). •Give 4 types of passive transport and explain each. How do filtration and osmosis differ? •How can you determine whether it is possible for a molecule to enter of leave a cell via simple diffusion? List some molecules that can cross the cell membrane by simple diffusion.

Answer 1

1) sodium potassium pump.

(Na+/K+ pump)

It pumps 3 Na+ out of the cell and take 2 K+ into the cell.

It moves these ions against their concentration and hence uses energy. Therefore it is called an active transport.

2) passive transport are those which move the ions according to their gradient difference inside and outside the cell.

They do not require energy.

The four main kinds of passive transport are simple diffusion, facilitated diffusion, filtration, and osmosis.

Diffusion is the net movement of material from an area of high concentration to an area with lower concentration.

Facilitated diffusion is the movement of molecules across the cell membrane via special transport proteins that are embedded within the cellular membrane.

Filtration is movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system.

Osmosis is the movement of water molecules across a selectively permeable membrane from a solution of high water potential to an area of low water potential.

Osmosis is much like simple diffusion but it specifically describes the movement of water (not the solute) across a selectively permeable membrane until there is an equal concentration of water and solute on both sides of the membrane.

3) Small and nonpolar(hydrophobic) molecules can freely pass through the membrane via simple diffusion. In the cell, examples of molecules that can use simple diffusion to travel in and out of the cell membrane are water, oxygen, carbon dioxide, ethanol and urea.