LEC02 Flashcards
Transport
What two types of proteins are used in facilitated diffusion?
Carrier and channel proteins.
Aquaporin Channel
A channel protein that opens for water so it can move through the membrane.
Ion Channel
A channel protein that opens for ions so it can move through the membrane. Forms pores for ions to pass through.
What does active transport require?
Energy, usually ATP.
How do hydrophilic substances cross the membrane, and why do they need help?
By types of carrier proteins. They need the help as they cannot pass the hydrophobic lipids.
What is the sodium-potassium pump?
An enzyme that moves sodium ions out of the cell, whilst moving potassium ions into the cell.
Why is the sodium-potassium important?
Ensures osmotic equilibrium and maintains membrane potential, also balancing the two types of ions both outside and inside the cell.
What is the proton pump?
A protein which actively carries protons (hydrogen ions) out of the cell.
What is cotransport?
Where the active transport of one solute indirectly drives the transport of another solute.
What is an example of how plant cells use cotransport?
Hydrogen ions generated by the proton pumps to drive active transport of nutrients into the cell.
What is an example of how animal cells use cotransport?
The sodium glucose cotransporter to drive glucose uptake against its concentration gradient.
What is the definition of bulk transport?
The process of moving large quantities of food or material across the membrane.
What are the two main categories of bulk transport?
Endocytosis and Exocytosis.
What are the three sub-categories of endocytosis?
- Phagocytosis - engulfing debris and other particles and internalising it.
- Pinocytosis - engulfing fluid and like fat and internalising it.
- Receptor-mediated endocytosis - Absorbing proteins, hormones, metabolites and internalising it.
What is the difference between endocytosis and exocytosis?
Endocytosis internalises external material, while exocytosis expels internal material.
