Topic 1 Module 3
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What are the 2 types of active transport?
- 1. Require cellular membrane proteins + energy
- Primary active transport: uses energy expenditure to directly transport a molecule
- Secondary active transport: indirectly depends on energy expenditure; depends on electrochemical gradients created byt Primary Active Transport of ion across the cell membrane to then move the other substance
- 2. Bulk transport processes that use membrane vesicles (endo, exo, phagocytosis)
What are the 2 proteins used for active transport?
- Channel proteins: transmembrane integral proteins. Aqueous pores allowing substrate through
- Carrier proteins: Inner/outer integral membrane proteins. Bind substrate on one side of the membrane and then undergo a conformational change which results in the transport of the substrate across the membrane
What are the 3 types of primary active transport systems?
- Ion pumps (ATPase ion pumpms: transports ions
- ABC system (ATP binding cassette): involves ATP and 3 proteins to bind, transport and release the transported molecule
- Group translocation: a sequence of molecules involved and the transported substance is chemically modified.
What are ion pumps?
- 3 classes: P, V, F ATPase Ion pumps
- All three have one or more ATP binding sites on the cytosolic face of the membrane
- All use the same basic mechanism: conformational change in proteins as they are reversibly phosphorylated by ATP.
- All are reversible If the pumped ions are allowed to diffuse back through the membrane complex, ATP can be synthesized from ADP and inorganic phosphate.
Describe the Na+/K+-ATPase pump
- A large protein consisting of 2 subunits
- Crucial for all organs esp nerve cells
- The hydrolysis (break down) of ATP drives 3 Na+ out and 2K+ in
Describe the P class ion pumps
- The simplest of the ion pumps
- Consist of 4 transmembrane subunits: 2 ∂ and 2 ß polypeptides
- eg. Ca++ ATPase pumps in the membrane of the sarcoplasmic reticulum of muscles which is used to isolate Ca++ (SR is the muscle equivalent of the endoplasmic reticulum found in other cells)
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