Fats, Lipids and Cell Membranes

Question 1

What is a glycerophospholipid made up of?

Answer 1

1 phosphate group
1 glycerol
2 fatty acid chains - usually different in nature

Question 2

What are triglycerides?

Answer 2

they are triesters of glycerol

- contain 3 glycerols each with their own fatty chain

Question 3

What is saponification? What is its products?

Answer 3

saponification is a process that produces soap from fatty acids
- involves the base hydrolysis of esters
= requires sodium hydroxide, water and heat

forms glycerols and salts of fatty acids

Question 4

What features do fatty acids derived from the saponification of fats share?

Answer 4

always contain an even number of carbon atoms
- claisen condensation adds carbon atoms in groups of two

may be saturated or unsaturated
- variable number of bonds

if they are unsaturated then the stereochemistry is always Z (cis)

the fatty acids derived from hydrolysis are not usually identical
- due to different fatty acids having different ester linkages

Question 5

How does the length of the hydrocarbon affect the melting point of lipids?

Answer 5

as the length of the hydrocarbon increases, the melting point increases
- as chain length increases, there is larger surface area for intermolecular forces
= as a result intermolecular bonds are stronger and melting point goes up

Question 6

How does the degree of unsaturation affect the melting point of lipids?

Answer 6

as the degree of unsaturation increases, the melting point decreases
- as the number of double bonds increases, you get discontinuities in the packing of the molecules
= this weakens the intermolecular forces (Van der Waals attractive forces) and decreases melting point

Question 7

Why does the amphiphilic nature of glycerophospholipids makes them ideal for the lipid bilayer in cell membranes?

Answer 7

they have a polar ionic head and a non-polar hydrocarbon tail
- the polar ionic head can point into and out of the bilayer with the lipophilic tail in the middle (form a monolayer)
= allows for the solvation in aqueous medium as well as a lipophilic membrane.

Question 8

How can drugs moves across the plasma membrane?

Answer 8

direct diffusion through the lipid

diffusion through the aqueous pores
- are too small for most drugs

use of carrier proteins

pinocytosis
- encapsulated by inward folding of the cell membrane
= form a vesicle

Question 9

What is the role or cholesterol?

Answer 9

Cholesterol intercalates with the phospholipids and decreases the flexibility or increases the rigidity of the membrane