M&R 1.1 - The Membrane Bilayer Flashcards
What are the functions of the bilayer? (5)
- Continuous and selective permeable barrier
- Control chemical environment inside
- Communication
- Recognition
- Signal generation in response to stimuli
What is the dehydrated composition of the membrane?
- 40% Lipid
- 60% Protein
- 1-10% Carbohydrate
How does the hydrated composition of the membrane differ from the dehydrated composition?
Hydrated is 20% water
What is the significance of water in the Bilayer?
- Bonds to Bilayer with hydrogen bonds
- Facilitates hydrophilic interactions
Which 3 lipids are involved in the membrane?
- Phospholipids
- Glycolipids
- Cholesterol
Describe the head of a phospholipid molecule
- Hydrophilic
- Polar
- Negative
Describe the fatty acid chains of a phospholipid molecule
- Hydrophobic
- Uncharged
- Non-polar
- Cis double bond causes a kink
What is the advantage of phospholipids in the bilayer?
Increases the fluidity therefore allowing it to be ever-changing
How do Glycolipids differ from phospholipids?
The phosphocholine moiety is replaced with a sugar group
What is a Glycolipid with a sugar monomer called?
Cerebroside
What is a Glycolipid with an oligosaccharide chain called?
Ganglioside
What is the advantage of the similarity between phospholipids and Glycolipids?
Creates a constant environment for membrane proteins
Describe the head group of a cholesterol molecule
- Polar
- Hydrophilic
- Hydroxyl
Describe the tail group of a cholesterol molecule
- Aliphatic
- Non-polar
Describe the conjugated ring structure of a cholesterol molecule
- Planar
- Single bonds that are rigid
What is the significance of cholesterol molecules in the bilayer?
- Form hydrogen bonds with phospholipids
- Increases stability of the environment
- Decreases movement therefore decreasing fluidity
- Controls fluidity of bilayer
How are micelles and the lipid Bilayer formed?
Spontaneously in water
What are the 4 movements in the dynamics of the lipid bilayer?
- Flexion
- Rotation
- Lateral Diffusion
- Flip-flop
Describe Flexion in relation to the membrane
Fatty acids are able to move left or right
Describe rotation in relation to the membrane
Fatty acids can rotate around
Describe lateral diffusion in relation to the membrane
Fatty acids are able to swap places (common)
Describe flip-flop in relation to the membrane
- Lipids move from one side to the other
- One for one exchange
- Rare as not thermodynamically stable
