Transport across Membranes Flashcards
What does “passive” mean in terms of diffusion?
Does not require energy
Is simple diffusion passive or active?
Passive
Which molecules can simply diffuse across membranes?
Small, non polar molecules
What is facilitated diffusion?
Diffusion but with the assistance of protein molecules.
Is facilitated diffusion an active or passive process?
Passive
Which proteins allow facilitated diffusion to occur?
Channel and Carrier proteins
What are protein channels?
Water-filled hydrophilic channels
How do protein channels work?
- Allow specific water-soluble ions to pass through.
- Selective as they only open in presence of certain ions.
- These ions bind to the protein so that one side closes but the other opens.
What do carrier proteins do?
- Molecules which are specific to the protein bind to it.
- This causes it to change shape in a way that the molecule is released to the inside of the membrane.
Is osmosis a passive or active process?
Passive
What does active transport use?
ATP and carrier proteins
What does it mean if active transport works against the concentration gradient?
Low to high concentration
How do carrier proteins work in active transport?
- Molecule binds to receptor sites on the carrier protein.
- Inside the cell/organelle, ATP binds to the protein and splits into ADP + Pi to release energy.
- This causes the protein to change shape allowing the molecule to release to the other side of the membrane.
- Pi releases from the protein, reverting the shape back to its original shape and the Pi joins with ADP again to form ATP during respiration.
How does a sodium-potassium pump work?
- Uses active transport and two carrier proteins, allowing Na2+ ions to move in but K2- ions to move out of the organelle.
- Uses ATP
