ML1-2: Lipids and membranes Flashcards
What are the general principles of biological membranes?
- They surround every cell and some organelles within cells, e.g. mitochondria
- They form a highly selective barrier
- They are important in regulating cell function
What are the general principles of lipids?
- Structurally diverse
- Generally insoluble in water (hydrophobic)
- Most only contain C, H, O (phospholipids contain P, N)
What is the most simple type of lipid?
Fatty acid
What is the general formula for a fatty acid?
CH3(CH2)nCOOH
How many carbons can be present in a fatty acid?
Between 16 and 20
Which part of the general formula for fatty acids represents the hydrocarbon tail?
CH3(CH2)nCOOH
What is an amphipathic molecule?
One with hydrophobic and hydrophilic properties
Name one saturated and one unsaturated fatty acid.
Saturated: palmitate
Unsaturated: oleate
What effect on the properties of a fatty acid does a double bond have?
Melting point will be lower due to steric hindrance
What are the three types of lipids in biological membranes?
- Phospholipids
- Glycolipids
- Cholesterol
What is the general structure of a phospholipid?
What bond connects the fatty acid chains to the glycerol of a phospholipid?
Ester linkages
Name four phospholipids commonly found in membranes. Are they (overall) hydrophobic, amphipathic, or hydrophilic?
- Phosphatidylserine
- Phosphatidylcholine
- Phosphatidylethanolamine
- Phosphatidylinositol
Overall amphipathic
Are glycolipids (overall) hydrophobic, amphipathic, or hydrophilic?
Amphipathic
What is the role of cholesterol in eukaryotes? Is it present in prokaryotes?
- Keeps membrane fluid
- Important in signalling
- Not usually present in prokaryotic membranes
Which parts of the cholesterol molecule are hydrophilic and hydrophobic?
Is it (overall) hydrophobic, amphipathic, or hydrophilic?
All hydrophobic except the –OH group
What type of structure is cholesterol?
Steroid-based rings
What is the general shorthand form for membrane lipids?
Name six properties of biological membranes.
- Membrane lipids are all amphipathic molecules that spontaneously form bilayers in water
- Membranes are composed of sheets of lipids only two molecules thick
- Membranes are composed of lipids and proteins. Carbohydrates can be attached to these molecules
- Membranes are held together by non-covalent interactions
- Membranes are fluid structures. Lipids and protiens can diffuse readily in the plane of the membrane
- The two faces of a biological membrane are different – they are asymmetric
Describe hydrophobic interactions.
Hydrophobic (non-polar) molecules do not interact with water and cluster together to exclude it