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CB Lecture 5-6 A
Lipids, Membranes, and Membrane Transport
| Question | Answer |
|---|---|
| True or false: The fatty acid attached to C2 is often saturated? | FALSE: often unsaturated |
| All biological membranes are composed of what? | Lipids |
| True or false: Membrane compositions are the same | FALSE: Membrane composition varies. Ex. Phospholipids are made of 60 red blood cell while cholesterol is made of 23 |
| Are lipids soluble in water? | NO |
| Micelles | 50-100 lipid molecules in circle with polar heads facing out |
| What doesmulsifying agents do? | segregate hydrophobic compounds in micelle interior, allowing them to be dispersed in water as an emulsion |
| Describe a Bilayer Membrane? | polar heads face water and nonpolar hydrocarbon tails entwining together |
| How does lipid bilayers behave like? | two-dimensional fluids |
| Why are lipids highly mobile? | They rotate rapidly about lipid axis; diffuse rapidly in the membrane's plane; 3) Flip flow slowly |
| Flippase | enzyme that insert the lipid into the faces of the membranes. |
| Why is membrane fluidity important? | vital for cellular functions; such as endocytosis, exocytosis |
| At normal temperatures, cells membranes are fluid r solid? | Fluid! |
| Why is cooling cells to 0-4 C bad? | because the cell crystalize so no fluidity in the membrane. Many cellular functions slows or halt. |
| What three strategies are use to regulate membrane fluidity | 1) Alter length of lipid tails (all) 2) Alter saturation of lipid tails (all) 3)cholesterol (animals) |
| As the fatty acid length increases, does it fluidity increase or decrease? | Decrease |
| Which have more fluid, short fatty acid or long fatty acid? | SHORT - the have lower melting point. |
| Which have more fluid, saturated or unsaturated fatty acids? | Unsaturated - they have lower melting points. |
| What does cholesterol do to membrane? | make it less fluid and less permeable, keep the membrane more fluid at lower temp. |
| Are lipids distributed symmetrically in membranes? | No, they are assymetrically distributed |
| How much percent of protein does cellular membrane contain? | As much as 70% |
| Name the kinds of protein in the membrane? | Peripheral membrane protein; Integral membrane proteins |
| Peripheral membrane proteins | weakly anchor into the membrane |
| Integral membrane proteins | Strongly anchored to the membrane |
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