Active Transport & Glucose transport Flashcards
What is active transport?
• The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.
What is the purpose of ATP in active transport?
- Directly move molecules
- Individually move molecules using a concentration gradient which has already been set up by active transport ( Co-transport ).
What does Active Transport require?
Energy ( ATP ).
What are the main differences between active transport and facilitated diffusion?
- Active transport moves solutes usually from a low to high concentration, facilitated diffusion they move from high concentration to low concentrations.
- Active transport requires energy, facilitated diffusion does not.
- Carrier proteins molecules which act as pumps are involved.
- Process is highly selective, only specific substances are transported.
How is ATP produced?
Respiration
How does ATP provide energy?
- ATP undergoes a hydrolysis reaction, splitting into ADP and Pi ( inorganic phosphate ).
- This splitting releases energy so that the solutes can be transported.
What is the process of a single molecule being transported?
- Carrier proteins span the plasma membrane, and bind to the molecule/ion that is to be transported, on one side of it.
- Molecule or ion binds to the receptor sites on the carrier protein.
- On the inside of the cell/organelle, the ATP binds to the protein resulting in the ATP splitting into ADP and a phosphate molecule, and thus the protein molecule changes shape and opens to the opposite side of the membrane.
- The molecule or ion is then released to the other side of the membrane.
- The phosphate molecule is released from the protein which results in the protein reverting to its original shape, ready for the process to be repeated.
- The phosphate molecule recombines with the ADP to form ATP during respiration.
What is the sodium-potassium pump process?
• Potassium ions are actively taken in from the surroundings whilst sodium ions are actively removed
How do co-transporters work?
- They bind two molecules at a time
- The concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient.
What is an example of how co transporters work?
- Sodium ions move into a cell against down their concentration gradient.
- Glucose will also be moved into the cell against its concentration gradient.
What is the purpose of micro-villi?
• They provide a larger surface area for the insertion of carrier proteins through which diffusion and active transport can take place.
Where are micro-villi found?
Epithelial cells lining the ileum.
How can transport across membranes be increased?
- Increasing the number of micro-villi.
* Increase the number of protein channels and carrier proteins in any given area of membrane, a larger density.
Why is there are a greater concentration of glucose within the ileum?
Carbohydrates are being continuously digested.
Why is glucose being continuously removed from the ileum?
- The blood is down a concentration gradient to the blood, thus the glucose can move via facilitated diffusion from inside the ileum into the blood.
- Blood is being constantly circulated by the heart, so glucose is absorbed is continuously being removed by cells as they use it up during respiration.
- This also helps maintain the concentration gradient between the inside of the ileum and blood
How does glucose enter the ileum epithelium?
- Sodium ions are actively transported out of the ileum epithelial cells, into the blood, by the sodium potassium pump. This will create a concentration gradient - there is now a higher concentration of sodium ions in the lumen of the ileum than inside the cell.
- This causes sodium ions to diffuse from the lumen of the ileum into the epithelial cell, down the concentration gradient ( done via the sodium-glucose co transporter proteins ).
- Co transporter carries glucose into the cell with the sodium. The concentration of glucose inside the cell increases.
- Glucose diffuses out of the cell, into the blood, down the concentration gradient through a protein channel by facilitated diffusion.
What factors affect rate of active transport?
- Speed of individual carrier proteins, faster they work, faster the rate of active transport.
- Number of carrier proteins present, the more proteins, the faster the rate of active transport.
- Rate of respiration, and availability of ATP, if respiration is inhibited, active transport can’t take place.
