Membranes & Receptors Flashcards
What are the 5 general functions of biological membranes?
- Highly selective permeable barrier
- Control of enclosed chemical environment
- Communication
- Recognition of signalling molecules
- Signal generation in response to stimuli
What % of a hydrated membrane is water?
20%
What are membranes comprised of? And in what proportions?
Dehydrated
- 40% Lipid
- 60% Protein
- 1-10% Carbohydrate
What characteristic of phospholipids allows them to form structures in water?
Amphipathic
What 2 structures can phospholipids form in water?
Micelles and Bilayers
What do phospholipids consist of?
- Glycerol
- 2 Fatty Acids
- Phosphate head group
What is unique about Sphingomyelin?
Only phospholipid not based on glycerol
What is the difference between Cerebrosides and Gangliosides?
Cerebrosides contain sugar monomers whereas Gangliosides contain oligosaccharide sugars
What is an unsaturated phospholipid?
One in the Cis conformation where double bonds form between fatty acids creating a kink
What effect do unsaturated phospholipids have on membrane fluidity?
Increased Fluidity
What are the 4 modes of phospholipid mobility in the bilayer?
- Flexion
- Rotation
- Lateral Diffusion
- Flip Flop
What is the effect on membrane fluidity due to cholesterol at high temperatures?
Reduced fluidity due to formation of hydrogen bonds
What are membrane proteins required for?
- Facilitated Diffusion
- Ion Gradient
- Specificity Of Cell Response
What proof is there of membrane proteins?
- Membrane Fractionation and SDS PAGE Electrophoresis
- Freeze Fracture
What are the 2 types of membrane protein and what is the main difference between them?
- Peripheral are on the surface
- Integral are deeply embedded
Why is orientation of membrane proteins important?
- For function as the recognition site must be on the correct side of the membrane
Name the 3 modes of motion for membrane proteins
- Conformational Change
- Rotation
- Lateral
Name 3 things that restrict membrane protein mobility
- Lipid mediated effects
- Membrane protein associations
- Extramembranous protein association
Name the 2 components of the cytoskeleton
- Spectrin
- Actin
What does an antiparallel Spectrin heterodimer consist of?
-An alpha and beta Spectrin rod wound together
What is the function of adapter proteins in the cytoskeleton?
- Attach the Spectrin-Actin network to the membrane proteins
What is Hereditary Spherocytosis and what is the consequence?
- Spectrin depletes by 40-50%
- Erythrocytes round up
- Prone to lysis
- Haemolytic Anaemia
What is the function of the stop transfer sequence?
- Causes the ribosome to detach
- Spans the bilayer forming transmembranous region
