Lecture 18 Flashcards
What is good and bad about compartmentation?
Compartmentation is done by membranes and these allow for seperation of functions (e.g by specialising environment) but can make it more difficult to exchange molecules.
What is the structure of hydrocarbon tails?
Hydrocarbon tails (fatty acids) can be saturated (no double bonds) or unsaturated (with double bonds). A double bond will add kinks to the hydrocarbon tail, making them not straight. They will always be an even number of carbons and will be between 16-22 carbons long.
What are aphipathic molecules and what do they do?
phospholipid bilayers are made up of amphipathic (non polar (hydrophobic) and polar part (hydrophilic) ) molecules known as phospolipids, it naturally leads to formation of bilayers as the tail (hydrophobic) trys to avoid water while the head (hydrophilic) trys to be with the water.
What is the general structure of fatty acids.
The typical structure of each fatty acid is made from glycerol and one group of the three carbon branches (third) has a phosphate group while the other two have a lipid chains (non polar part) with varying groups with could be saturated or unsaturated, most will also have another R group (lots of possibilities) after the phosphate (typically polar).
What are two other types of membrane lipid?
sphingolipids are based on sphingosines (amino alcohols) instead of glycerol (particularly abundant in myelin sheath), glycolipids are sid chains attached by glycosidic (sugar like) linkage (common in plants).
What factors affect membrane fluidity? What is it supposed to be like?
Membrane fluidity is affected by temperature (higher heat means more fluidity, the more strongly lipids are held together the less this will have an effect due to the greater energy required, this strength increases with carbon atoms in the lipids due to more hydrophobic bonding (meaning less fluid with more carbons)), the type of fatty acid (increased by unsaturated due to the kinks weakening the hydrophobic interactions (and hence lowering melting point) because of extra distance), presence of cholesterol. It needs to be strong enough to maintain structure but not to strong that stuff can’t move within it.
What happens to an organism’s lipids with changing temperature?
An organisms lipids will become more unsaturated if environmental temperature is lower, this makes the membrane more fluid. If the temperature is higher the lipids become more saturated.
