Membrane Proteins and Membrane Transport Flashcards
Week 8 (24 cards)
Why are the structures of membrane proteins different to proteins that are in the cytosol?
Because of the amphipathic nature of the phospholipid bilayer
What are the four methods of membrane transport?
Passive transport, active transport, secondary active transport and bulk transport
What are the basic principles of passive membrane transport?
Molecules move down their concentration gradient, this is spontaneous and does not require energy input
What are the basic principles of active membrane transport?
Ions move against their concentration/charge gradients, this is not spontaneous and requires energy input
What are the basic principles of secondary active membrane transport?
An ion gradient set up by an active transport protein is used to energise the transport of another ion or solute. Similar to energy coupling
What are the basic principles of bulk membrane transport?
The movement of large molecules contained in vesicles to fuse with the membrane through exocytosis and endocytosis
What is the term for molecules moving through the bilayer itself during passive membrane transport?
Simple diffusion
What is the term for molecules moving through transport proteins during passive membrane transport?
Facilitated diffusion
What are the two kinds of proteins involved in facilitated diffusion?
Channel proteins and carrier proteins
What are aquaporins?
Transport protein channels for water
What is turgor/turgidity?
An internal hydrostatic pressure which enables plant cells to resist swelling and avoid bursting. This helps plants remain upright
Facilitated diffusion carriers are uniporters, what does this mean?
They move just one solute across the membrane at a time
Do protein channels or protein carriers have a higher transport rate?
Protein channels (around 1 billion/second), compared to carriers (100,000 - 1 million/second)
What is the carrier protein responsible for moving glucose into cells?
GLUT4
What is GLUT4 controlled by and how?
Insulin, which is released and binds to a receptor which stimulates GLUT4 to be incorporated into the membrane
What is the difference between Type 1 Diabetes and Type 2 Diabetes?
With type 1 insulin is not produced, and with type 2 the insulin receptor is not active
How many of each ion does the Na+/K+ pump transport at a time?
3 sodium ions and 2 potassium ions
Briefly describe facilitated diffusion carrier’s process
Physical binding to the solute, in which the shape of the carrier changes so the binding site faces the other side of the membrane in order to transport
Explain the membrane potential of nerve cells
The charge gradient at which the movement of positive charge out of the cell opposes further movement of K+ down their concentration gradient
What are action potentials responsible for?
Nerve impulses
How does the action potential move along the axon?
The opening and closing of Na+ and K+ channels lead to Na+ and K+ movements across the membrane, and the channels are distributed along the axon of the nerve cell
Explain synaptic transmission
At the synapse there are voltage gated calcium channels which open, and the influx of calcium stimulates the release of neurotransmitters across the synapse, they then bind to ligand gated ion channels in the target cell to open and allow movement of ions through
What is a symporter?
Secondary active transport in which both products are moving in the same direction
What is an antiporter?
Secondary active transport in which products are moving in opposite directions
