Active Transport

Active Transport:
Active Transport is the movement of molecules or ions in or out of a cell against a concentration gradient using energy and carrier molecules.
Active transport requires ATP, to directly move molecules, as opposed to relying on their kinetic energy like in passive transport. It also requires a concentration gradient; otherwise the molecule will not move from an area of low concentration to high.
1) State one similarity and one difference between active and passive transport: Active transport requires ATP whereas passive does not. Both active transport and passive involve getting molecules or ions in or out of cells.
2) The presence of mitochondria in cells that carry out active transport is necessary, because the mitochondria produce ATP, which is energy, and energy is required in active transport, as molecule need to be moved directly, and not by their own kinetic energy. So cells that use this process, would therefore need lot of mitochondria as they need lots of energy.

Absorption in the Small Intestine:
The villi and microvilli increase the surface area, and an increased surface area is a factor that increases the rate of diffusion. They are very thin walled, which makes a shorter diffusion distance, which also increases the rate of diffusion; they are well supplied with blood vessels so they can transport absorbed materials away.
The products or carbohydrate digestion are absorbed in the small intestine… As they are being digested constantly, there is normally a greater concentration of glucose in the small intestine then in the blood. There is therefore, a concentration gradient, which glucose diffuses from the small intestine to the blood. The blood is always being circulated by the heat, and so the glucose is removed by the cells on it’s way round, and this helps to maintain the concentration gradient.
Sodium ions are actively transported out by a sodium potassium pump, into the blood and the potassium comes in. There is then a higher concentration of Sodium in the lumen of the gut then in the epithelial cells, which creates a concentration gradient. They pass into the epithelial cells through co-transport proteins, and couple with a glucose molecule on the way. The glucose then goes into the blood via facilitated diffusion.

1) A glucose concentration gradient is maintained, as carbohydrates are constantly being digested, and this means there will always be a high concentration of glucose in the lumen of the small intestine. The heart is also always circulating blood, which means that the blood rich with glucose will be being pumped round and the glucose will be getting used in cells for respiration, keeping the concentration of it in the blood low.
2) Co-transport is used to describe the transport of glucose into cells as it relies on the Sodium ions going from the lumen of the gut to the cell for it to be able to pass into the cell, it wouldn’t do it on its own.
3) Sodium moving out of the epithelial cell is active. Sodium moving into the cell is passive. Glucose moving into the cell is passive.