Transport Across Cell Membranes(BIOLOGY) (Chapter 4)
What is the main function of active transport?
To move molecules against their concentration gradient
Which ion is pumped out of the cell using the sodium/potassium pump?
Sodium
How many sodium ions are pumped out of the cell for every two potassium ions pumped in?
3
Where does the energy for the sodium/potassium pump come from?
ATP hydrolysis
In which direction does the sodium/potassium pump transport sodium and potassium ions?
Sodium out, potassium in
Which type of active transport is the sodium/potassium pump an example of?
Primary active transport
What is the enzyme responsible for the hydrolysis of ATP in the sodium/potassium pump?
ATPase
What is a characteristic of the sodium/potassium pump?
Allows passive diffusion of ions
What is the net charge of the sodium/potassium pump after one complete cycle?
Positive
What is a common location for the sodium/potassium pump in cells?
Cell membrane
What is the function of the villi in the small intestine?
To generate ATP
What nutrient is primarily absorbed by the villi in the small intestine?
Glucose
How do villi increase the absorption rate of glucose?
Increasing the surface area
What is the role of the microvilli in the absorption process?
Absorb nutrients
What part of the intestine contains villi?
Small intestine
How does the structure of the villi contribute to its function?
It increases its surface area
What type of cells are found in the villi of the small intestine?
Epithelial
What do the villi do in the small intestine?
Produce digestive enzymes
What happens to glucose absorbed by the villi?
Transported to the liver
What is the main function of the ileum in the co-transport and absorption of glucose?
Absorption of glucose into the bloodstream
Which transport mechanism is involved in the absorption of glucose in the ileum?
Facilitated diffusion
What is the role of the sodium ions in the co-transport of glucose in the ileum?
They create a concentration gradient to drive glucose absorption
What is the primary energy source used for glucose absorption in the ileum?
ATP
How is glucose transported across the cellular membrane in the ileum?
Facilitated diffusion
What happens to the glucose concentration of glucose in the ileum during absorption?
Increases
What is a characteristic of the co-transport process in the ileum?
It requires energy
What is the role of the ileum in the overall digestion and absorption of glucose?
It is the site of active glucose absorption
What can affect the rate of glucose absorption in the ileum?
Presence of other nutrients
Define simple diffusion
The net movement of molecules or ions from a region of higher concentration to a region of lower concentration.
Describe facilitated diffusion
The assisted transport of large, polar ions across the membrane using carrier proteins and channel proteins.
Describe what a protein channel does
Allows water-soluble ions to pass through. If the ion is not present, the channel remains closed.
Describe what a carrier protein does
When a molecule that is specific to the protein is present, it binds with the protein.
Define osmosis
The transport of water from an area of more negative water potential to an area of less negative water potential through a selectively permeable membrane.
Define active transport
The movement of molecules or ions out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.
Describe the steps involved in the sodium/potassium pump(4 steps)
1) Sodium ions are actively transported out of epithelial cells, by the pump, into the blood. This occurs in a protein-carrier molecule in the membrane of the epithelial cells.
2) This maintains a much higher concentration of sodium ions in the lumen of the intestine than inside the epithelial cells.
3) Sodium ions diffuse into the epithelial cells down this concentration gradient through a co-transport protein in the cell-surface membrane. As the sodium ions diffuse, they can carry either amino acids or glucose molecules into the cell with them.
4) The glucose/amino acids then pass into the blood plasma by facilitated diffusion.