Biochemistry Lipids and Membranes 3

Question 1

Sphingolipids differ from glycerophospholipids in that their backbone is:

Accepted Answer

Sphingosine

Answer

Sphingolipids are built on a sphingosine backbone (an amino alcohol) rather than glycerol, with a fatty acid attached via an amide bond to form ceramide.

Question 2

Lipid rafts in cell membranes are enriched in which components?

Accepted Answer

Cholesterol and sphingolipids

Answer

Lipid rafts are dynamic microdomains enriched in cholesterol and sphingolipids that form a more ordered (liquid-ordered) phase and serve as platforms for signaling proteins.

Question 3

The saponification number (saponification value) of a fat is a measure of:

Accepted Answer

The average molecular weight of fatty acids

Answer

The saponification value reflects the amount of alkali required to saponify a fat; higher values indicate shorter-chain fatty acids, since more moles (and thus more alkali) are needed per gram.

Question 4

Which phospholipase cleaves the fatty acid at the sn-2 position of glycerophospholipids to release arachidonic acid?

Accepted Answer

Phospholipase A2

Answer

Phospholipase A2 cleaves the ester bond at the sn-2 position, releasing arachidonic acid (or other fatty acids) and a lysophospholipid.

Question 5

Familial hypercholesterolemia is caused by a defect in:

Accepted Answer

LDL receptor function

Answer

Familial hypercholesterolemia is typically caused by loss-of-function mutations in the LDL receptor gene, impairing LDL uptake and causing elevated plasma LDL cholesterol.

Biochemistry Practice Test

Biochemistry Practice Test

Biochemistry Lipids and Membranes 3