Key Area 3: Membrane Protiens Flashcards
Which two molecules can diffuse directly across the phospholipid bilayer?
Oxygen and carbon dioxide
Which molecules does the bilayer act as a barrier to?
Molecules that are too large or too polar
What are three types of transmembrane proteins?
- channel
- transporter
- receptor
What does a channel protein do?
Allows the passive transport of molecules down concentration gradients
What does a transporter protein do?
Actively moves molecules across membranes against concentration gradients
What does a receptor protein do?
Receives signals and brings about responses
How do different cells perform specialised functions?
Different cell types and compartments must contain different channel and transporter proteins as the proteins expressed in the membrane are what the specialised function depends on
What protein is involved in the passive transport of water?
Aquaporin
How does a gated channel work?
Responds to signal molecules or electrical impulses and is open or closed to prevent or allow transcription
What is a ligand-gated channel?
Channel is opened or closed following binding of a ligand
What is a voltage-gated channel?
Responds to changes in ion concentration
What is facilitated transport?
A passive process which involves a conformational change in the protein
Does facilitated transport require energy?
No
What is active transport?
A process that requires energy to bring about the necessary conformational change of the transporter protein
Does active transport require energy?
Yes, it comes from hydrolysis of ATP
What is the difference between intercellular and extracellular?
Intercellular occurs inside a cell and extracellular occurs outside a cell
How is a signal passed?
Through a signal transduction pathway
What are four potential responses of a cell to a signal molecules?
- activation of special enzymes or G-proteins
- changes in molecule uptake or release
- rearrangement of cytoskeleton
- activation of proteins that regulate gene expression
How are ions pumped in Na/KATPase?
Against a steep concentration
How do Na/NATPase work?
Three sodium ions bind and phosphate group form ATP binds to the pump then affinity changed back to potassium and sodium is released outside the cell, one potassium ion binds and the phosphate group is released
What are four functions of Na/KATPase?
- maintenance of osmotic balance in animal cells
- generation of ion gradients for glucose symport in small intestine
- generation and long terms maintenance of ion gradient for resting potential in neurone
- generation of ion gradient in kidney tubule
What is depolarisation of a neutron?
When the charge across the membrane becomes les negative
What is nerve transmission?
A wave of depolarisation occurring when membrane potential changes
How is nerve transmission initiated?
The binding of a neurotransmitter which opens ligand gated channels in the neutron membrane
