Membrane Proteins Flashcards
Describe the mosiac model.
Proteins are scattered in a mosiac pattern and phopholipids create a fluid and dynamic barrier around the cell.
Describe the nature of an internal protein.
Hydrophobic R-groups and many create channels for diffusion. Interact with hydrophobic region of phospholipid bilayer.
Describe the nature of a peripheral protein.
Loosely bound to hydrophilic surface (usually by hydrogen and ionic bonds). Tend to be hydrophilic.
What passes through the cell membrane by simple diffusion>
Carbon dioxide and oxygen.
Describe the structure of a channel protein (4).
- Hydrophilic transmembrane channel that creates a ‘pore’.
- Multi-subunit
- Often highly selective
- E.g Aquaporin which only allows the transport of water.
Discuss facilitated diffusion. (3)
- Molecules bind to transporter proteins.
- Transporter proteins change conformation, so binding site is on intracellular face.
- To perform specialised functions, different cell types have different transporter proteins.
What are the two types of gated channels.
Ligand and voltage.
Describe voltage gated channel.
Controlled by changes in ion concentration.
Describe ligand gated channel.
Controlled by binding of signal molecules.
Describe the generation of an action potential (3).
- Initial influx of Na+ depolarises the membrane.
- This causes voltage gated channels to open, thus a further influx of Na+
- Rapid depolarisation spreads to further channels, generating an action potential.
What protein maintains the resting potential?
The Na+/K+ pump.
What proteins are used in active transport?
Pump proteins.
Whats is required in order for active transport to occur.
A source of metabolic energy.
What is an electrochemical gradient.
The combination of a concentration gradient and electrical potential.
What determines the transport of a solute.
The electrochemical gradient.
