Lipid Organism 1 (% of membrane composition) Organism 2 (% of membrane compositi
ID: 35276 • Letter: L
Question
Lipid
Organism 1
(% of membrane composition)
Organism 2
(% of membrane composition)
16:0
60
10
20:00
10
60
18:3
20
10
Cholesterol
10
20
These are the membrane characteristics of 2 different organisms
A. Which organism has the higher Tm? Briefly explain your answer
B. What impact would the different lipid content have on the: (1) thickness of the cell membrane; and (2) the structure (in particular, the length) of integral membrane proteins?
C. Suppose that each organism is moved to a temperature that
Lipid
Organism 1
(% of membrane composition)
Organism 2
(% of membrane composition)
16:0
60
10
20:00
10
60
18:3
20
10
Cholesterol
10
20
Explanation / Answer
A. Organism 2 contains highest Tm (melting temperature) than organism 1 because it contains high amount of cholesterol. Cholesterol stabilises (effers rigidity) the cell membrane and increases melting point at high temperatures.
B. (1) Thickness of the cell membrane depends on the acyl chain length and unsaturation of the fatty acids. Cell membranes having long chain unsaturated fatty acids have high thickness than the cell membranes with saturated short chain fatty acids.
B. (2) Integral membrane proteins are the proteins those that are embedded within the lipid bilayer of membrane. They are not rigid structures; they often change their structure to ensure good hydrophobic matching to the lipid layer surrounding them. The structure of the lipid head group region is defines the structure of a membrane protein located in that lipid head group region.
C. Organism 2 maintains its membrane fluidity at higher temperatures. because it contains high amount of cholesterol. Cholesterol stabilises (effers rigidity) the cell membrane at higher temperatures and decreases membrane fluidity.
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