Membrane Structure Flashcards
What are the general functions of the cell membrane?
Transport, cell recognition, cellular communication and metabolic regulation
What three molecules make up the sphingolipids group?
Ceramide, glycolipids, sphingomyelin
What could the polar head groups in a phospholipid be made up of?
Choline, serine, ethanolamine, inositol
Are substance evenly spread between the cytosolic and exoplasmic membrane?
No, some prefer being on one side
Where does synthesis of a membrane take place, and give the steps
On the cytoplasmic side of the membrane
- newly synthesised phospholipid
- one side of the membrane is enlarged (it curves)
- the newly synthesised phospholipid is transferred to the luminal side
What is an ATP-binding cassette transporter and what enzymes does it use?
ABC transporters allow for movement of phospholipids from one side of the membrane to the other
Flippase- outer to inner leaflet
Floppase- inner to outer leaflet
Scramblase- bidirectional movement
What does amphipathic mean?
The have a hydrophilic and a hydrophobic part
What are the three major lipids in the membrane?
Phospholipids, glycolipids and cholesterol
Which of lateral movement and transverse movement is the fast and which is the slow?
Lateral is fast and transverse is slow
How does temperature affect membrane fluidity?
High temp -> more energy ->more fluidity
How does chain length affect membrane fluidity?
Higher chain length
How does the degree and extent of saturation affect membrane fluidity?
More saturated means molecules closer together so less fluidity
How does cholesterol content affect membrane fluidity?
At a low temperature membrane fluidity increases. At a high temperature membrane fluidity decreases
What causes spur cell anaemia
Cholesterol content is increased by 25-65% leading to decreased membrane fluidity
Give some functions of proteins in the cell membrane
Flexible, self-sealing, selectively permeable, defines boundaries and divide the internal spaces
Give some functions of the integral membrane proteins
Strong non-covalent bonds (hard to separate), transmembrane domain often an alpha helix (Rgroups are hydrophobic)
Can be predicted from sequence
Mainly hydrophobic relationship with the lipids
Single or multi pass (can go through the membrane more than once)
Give some structural features of the peripheral membrane proteins
Located on both the extra cellular and cytosolic membranes
Associated by non-covalent bonds
Easier to remove than protons
What are lipid anchored membrane proteins
Covalently linked to a lipid molecule such as glycosylphosphatidylinositol or associated with a fatty acid
Give some structural features of membrane carbohydrates
- Associated with both membrane lipids and proteins
- forms 2-8% of the membrane weight
- the majority of glycolipids and glycoproteins are externally facing
- often involved in cell-cell interactions or cellular recognition
How are membrane carbohydrates important to RBCs?
- Blood group antigens are glycolipids
- In RBCs, 8% of the weight is carbohydrate
