Lecture 11: The Structure, Organisation and Properties of Membranes Flashcards
What are the functions of membranes ?
- Enclosure
- Transport
- Signals
- Enzyme catalysis
- Interactions with other cells
- Anchoring the cytoskeletons
What is enclosure ?
A surrounding barrier function
What is transport ?
Membranes represent permeability barriers
What is signals?
Reception of extracellular signals and trasfer to interior
What are membranes composed of ?
Largely proteins and lipids some carbohydrates
What is the major phospholipid of animal cells ?
Phosphocholine
What is the major phospholipid in bacteria ?
Phosphoethanolamine
What is not present in mitochodrial or bacterial membranes ?
Shingomyeline
What is a membrane ?
A continuous bilayer of amphipathic lipids
What do fluidity membranes exist in ?
Liquid crysatl state
What are membranes characterised by ?
An asymetry in lipid and protein composition
Why do bacteria not lyse when put in distilled water ?
Rigid exoskeleton
What did Gorter and Grendal conclude ?
Lipids must be arranged as a bilayer
What did the Danielli and Davson model conclude ?
Polar head groups interacted with protein layers
What were the problems with Danielli and Davson model ?
- Assumed membranes had the same structure
- The arrangement of proteins
What is the idea behind the fluid mosaic model ?
Proteins can be embedded in bilayer, and can sometimes protrude and be associated with one surface or leaflet
What did studies of tyrpsin on membrane show ?
Proteins distributed on both sides of the membrane
What is different when proteases has access to both sides of the membrane ?
The pattern of proteins susceptible of digestion
Where are proteins mobile ?
Surface bilayer
What does FRAP stand for ?
Fluorescence recovery andfter photobleeching
Where is ptd-inositol found ?
Inner leaflet
Where are glycolipids found ?
Outer leaflet
Where are lipids symetrically distributed ?
Endoplasmic reticulum
Where are lipids asymetrically distributed ?
Golgi, endosomal and plasma membrane of eukaryptoes
