The Cell Surface Flashcards
4 major phospholipids
- Phosphatidylethanolamine
- Phosphatidylserine
- Phosphatidylcholine
- Sphingomyelin
What does cholesterol do?
- Increases rigidity
- Decreases permeability to small molecules
What do intracellular signal transduction lipids do?
- Bind specifically to certain regions of proteins
- Cause conformational, localization and/or activity change(s)
What does fluidity of membranes allow?
- Signalling lipids and membrane proteins to rapidly diffuse laterally
- Membrane to be shared equally by daughter cells
- Membranes to fuse with other membranes
Integral and peripheral membrane proteins
- Single-pass
- Multi-pass
- Beta-barrel
- Lipid-linked
- Peripheral membrane
Functions of membrane proteins
- Transport
- Enzymatic activity
- Signal transduction
- Cell-cell recognition
- Intercellular joining
- Attachment to cytoskeleton and extracellular matrix
Factors affecting ability of solute to simply diffuse across a membrane
- Concentration gradient
- Hydrophobicity/charge
- Size
2 classes of membrane proteins involved in facilitated diffusion
- Channels
- Uniporter carrier proteins
What do channel proteins form in the membrane?
Hydrophilic pores
Speed of channel proteins
10^7 ions per second
How do uniporter carrier proteins work?
Solute binds to the binding site
Speed of uniporter carrier proteins
<1000 molecules per second
Why do cells maintain electrochemical gradients?
- Drive transport
- Maintain osmotic balance
- Electrical forces inside and out must be balanced
What protein is used to maintain Na+ electrochemical gradient?
Na+/K+ ATPase
Why is Na+/K+ ATPase both a carrier and enzyme?
Also hydrolyses ATP to ADP
Na+/K+ ATPase mechanism of action
- 3x Na+ bind and pump is phosphorylated by hydrolysing ATP
- Conformational change transfers Na+ and it is released
- 2x K+ bind and pump dephosphorylated
- Conformational return transfers K+ and releases them
3 ways active transport happens
- ATP-driven pumps
- Coupled transporters
- Light-driven pumps
How do ATP-driven pumps work?
Transport of solute coupled with hydrolysis of ATP (primary AT)
How do coupled transporters work?
Transport of one solute down gradient with to another against gradient (secondary AT)
Types of coupled transporters
- Symport (both solutes same way)
- Antiport (solutes in opposite directions)
How do light-driven pumps work?
Transport of solute coupled with input of energy from light
