Question 1

Which of the following best describes the association of lipid-linked membrane proteins with the membrane?

Accepted Answer

They are reversibly and relatively weakly associated with the membrane compared to integral proteins.

Question 2

Which type of lipid-linked membrane protein is most likely to be found exclusively on the exterior side of the plasma membrane?

Accepted Answer

Glycosylphosphatidylinositol (GPI)-anchored proteins

Question 3

Which lipid anchor modification is readily reversible with the help of thioesterases?

Accepted Answer

Palmitoylation

Question 4

A protein is found to be covalently attached to a farnesyl group. Which class of lipid-linked membrane protein does this describe?

Accepted Answer

Prenylated protein

Question 5

Which of the following is a characteristic of myristoylated proteins?

Accepted Answer

They contain amide linkages to single-chain fatty acids.

Question 6

Which equation best represents the covalent attachment of a palmitoyl group to a protein via a thioester bond?

Accepted Answer

$$\mathrm{Protein{-}SH} + \mathrm{Palmitoyl{-}CoA} \rightarrow \mathrm{Protein{-}S{-}Palmitoyl} + \mathrm{CoA{-}SH}$$

Question 7

Which of the following statements about GPI-anchored proteins is TRUE?

Accepted Answer

They are primarily found on the extracellular surface of the plasma membrane.

Question 8

A mutation prevents the addition of a myristoyl group to a protein. Which of the following is most likely affected?

Accepted Answer

The protein's ability to associate with the membrane via an amide linkage to a fatty acid.

Question 9

Which of the following lipid-linked proteins is most likely to be involved in cell signaling due to its reversible membrane association?

Accepted Answer

Palmitoylated proteins

Question 10

Which of the following best explains why prenylated proteins are important in cancer biology?

Accepted Answer

Prenylation allows proteins such as Ras to anchor to the membrane, facilitating signal transduction pathways involved in cell growth.

Question 11

Which of the following is NOT a typical lipid group used for covalent attachment to membrane proteins?

Accepted Answer

Cholesterol

Question 12

A researcher discovers a protein with a thioether linkage to a prenyl group. Which process is most likely responsible for this modification?

Accepted Answer

Prenylation

Question 13

Which of the following best describes the linkage between a protein and a myristoyl group?

Accepted Answer

Amide bond

Question 14

Which of the following modifications is most likely to be irreversible under physiological conditions?

Accepted Answer

Myristoylation

Question 15

Which of the following best describes the role of thioesterases in membrane protein modification?

Accepted Answer

They catalyze the removal of palmitoyl groups from proteins.

Question 16

Which of the following is a correct sequence for the addition of a GPI anchor to a protein?

Accepted Answer

$$\mathrm{Protein{-}COOH} + \mathrm{GPI} \rightarrow \mathrm{Protein{-}GPI}$$

Question 17

Which of the following lipid modifications is most likely to target a protein to the cytosolic side of the membrane?

Accepted Answer

Prenylation

Question 18

Which of the following is a common misconception about palmitoylated proteins?

Accepted Answer

They are always irreversibly attached to the membrane.

Question 19

Which of the following best describes the difference between myristoylation and palmitoylation?

Accepted Answer

Myristoylation forms an amide bond, while palmitoylation forms a thioester bond.

Question 20

Which of the following is most likely to be found on the extracellular surface of the membrane and involved in immune recognition?

Accepted Answer

GPI-anchored proteins

Lipid-Linked Membrane Proteins: Structure, Types, and Functions

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