Membrane Bilayers and Membrane Proteins Flashcards
Name the two main types of lipids
- Phospholipid
- Glycolipid
Describe the structure and characteristics of a fatty acid
- Hydrocarbon chain of varying length
- Can be straight and saturated with single bonds (trans)
- Can be bent and non-saturated by presence of a double bond (cis)
Why is a lipid amphipathic?
It has a hydrophilic head and a hydrophobic tail
How are lipid bilayers formed?
- Lipid membrane is polar
- There is interaction between hydrophilic heads and hydrophobic tails
What are the four types of motion that can occur in the lipid bilayer?
- Flexion
- Rotation
- Flip Flop
- Lateral Diffusion
Name 3 functions of biological membranes
- Selectively permeable barrier
- Chemical environment control
- Communication
- Recognition
- Signal Generation
- Secretion
- Transport
What is the most abundant component of membrane bilayers (dry weight)
Protein (60%)
What influence do unsaturated fatty acids have on membrane fluidity?
The double bond creates greater room for movement between lipids and prevents crystallisation
What are the 3 main elements of a cholesterol molecule?
- Polar Head
- Rigid Steroid Ring
- Non-Polar Hydrocarbon Tail
Which part of the cholesterol molecule restricts movement?
Rigid Steroid ring
Which part of the cholesterol molecule allows movement in the lipid bilayer?
Hydrocarbon tail
How does the cholesterol molecule connect to phospholipids?
It forms a hydrogen bond
What is the role of cholesterol in the lipid membrane?
- Stabilises the membrane
- Counteracts temperature changes
Name 2 positions proteins are integrated into the membrane and what forces are they under?
Peripherally - bound to surface by electrostatic or hydrogen bonds
Integrally - interact with hydrophobic domains
How are integral proteins are inserted into the membrane and what are they not removed by?
- Inserted by interacting with hydrophobic domains of lipid bilayer
- Cannot be removed by pH or ionic changes
- Only removed by detergents/solvents
What is membrane asymmetry?
Opposite sides of the membrane have different compositions
Give 3 pieces of evidence for the presence of membrane proteins
- Facilitated Diffusion
- Ion Gradients
- Freeze Fracture
- Cell Response Specificity
Name the 3 ways membrane proteins associate with the lipid bilayer
- Peripheral
- Integral
- Transmembrane
How can membrane proteins move?
- Conformational Change
- Rotational
- Lateral
How do membrane proteins contribute to the cytoskeleton? Give an example of this
- Attachment proteins bind the cytoskeleton to the membrane
- Erythrocyte Cytoskeleton - Spectrin lattice joined end to end
Name 3 mechanisms that restrict membrane protein mobility
- Lipid mediated effects
- Protein association
- Cytoskeleton association
What ‘locks’ proteins into the membrane?
Hydrophobic nature of amino acid chain
What makes proteins inside a eukaryotic cell?
- RNA
- Ribosomes
What pauses protein synthesis and what restarts it?
- Signal Recognition Particle pauses protein synthesis
- Docking Protein restarts protein synthesis
What is the role of a Docking Protein?
It brings the new protein and ER nearer the membrane so it can be fed through the bilayer
What feeds the protein through the bilayer?
Signal Sequence Receptor
How is the correct orientation of membrane proteins achieved?
Through membrane synthesis where the protein is directly inserted into the membrane and locked in by the hydrophobic amino acid chain
