chapeter 4.4 Flashcards
In active transport ATP is used to:
- directly move molecules
- individually moves molecules using a concentration gradient which has already been set up by active transport, this is known as co-transport and is further explained later.
How does active transport differ from passive forms of transport?
- Metabolic energy is in the form of ATP is needed
- Substances are moved against a concentration gradient, that is from a lower to a higher concentration
- Carrier protein molecules which act as ‘pumps’ are involved
- The process is very selective, with specific substance being transported
Describe direct active transport of a single molecule or ion
- The molecule or ion bind to receptor sites on the carrier protein
- On the inside of the cell/organelle, ATP binds to the protein causing it to split into ADP and a phosphate molecule. As a result, 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 causes the protein to revert to its original shape, ready for the process to be repeated. The phosphate molecule then recombines with the ADP to form ATP during respiration.
does faciliated diffusion and active tranport difffer from
Facilitated diffusion and active transport both use carrier proteins but facilitated diffusion occurs down a concentration gradient, while active transport occurs against a concentration gradient. This means that facilitated diffusion does not require metabolic energy, while active transport does. The metabolic energy is provided in the form of ATP. h
How does facilitated diffusion and active transport differ from each other:
- Facilitated diffusion and active transport both use carrier proteins but facilitated diffusion occurs down a concentration gradient
- Active transport occurs against a concentration gradient.
- Facilitated diffusion does not require metabolic energy
- Active transport does require active metabolic energy is provided in the form of ATP
What are some examples of active transport
- uptake of glucose and amino acids in the small intestine
- absorption of mineral ions (nutrients and salts) by plant roots
- excretion of hydrogen used by the kidneys and blood stream
- exchange of sodium and potassium ions in neurones and muscle cells
Cells that undertake active transport on a large scale have many mitochondria, for example, muscle cells do.
Can more than one molecule or ion be moved in the same direction at the same time by active transport?
Sometimes more than one molecule or ion may be moved in the same direction at the same time by active transport.
What are sodium-potassium pumps?
- Sodium-potassium pumps is when a molecule or ion is moved into a cell/organelle at the same time as a different one is being removed from it.
- Sodium ions are actively removed from the cell/organelle while potassium ions are actively taken in from the surroundings.
- This process is essential to a number of important processes in the organism, including the creation of a nerve impulse.
How many Na (sodium) ions are transported out of the cell to how many k (potassium) molecules are taken into the cell?
3 sodium ions are released and 2 potassium ions are taken into the cell
What is the process of a sodium-potassium pump?
- Binding of cytoplasmic Na+ to the protein stimulate phosphorylation by ATP
- Phosphorylation causes the protein to change its conformation
- The conformational changes expel Na+ to the outside, and extracellular K+ binds
- K+ binding triggers release of a phosphate group
- Loss of a phosphate group restores original conformation
- K+ is released and Na+ sites are receptive again, the cycle repeats
Energy is needed to push sodium ion into the lumen. It is not needed when the K ion comes into the cytoplasm.
When is energy needed in a sodium-potassium pump?
Energy is needed to push sodium ion into the lumen. It is not needed when the K ion comes into the cytoplasm.
When is energy not needed in a sodium potassium pump?
It is not needed when the K ion comes into the cytoplasm.
Why are there three sodium’s for every two potassium ions.
This is needed for co-transport to get the circumstances right (concentration of sodium is too high on the side where the concentration of glucose for example is too low)
What is bulk transport
Bulk transport is where extremely large substances are needed to be moved across a membrane.
What are the two types of bulk transport
- endocytosis: is the bulk transport of material into the cell e.g. in phagocytosis
- exocytosis: is the bulk transport of material out of the cell
