Question 1

Which of the following statements best describes the role of cholesterol in biological membranes?

Accepted Answer

Cholesterol prevents crystallization and phase shifts in the membrane, making it less deformable.

Question 2

Which amino acid contains a sulfhydryl group in its side chain and is important for forming disulfide bridges in proteins?

Accepted Answer

Cysteine

Question 3

A protein is found to consist of multiple polypeptide chains, each with its own tertiary structure. What is the term for the overall structure formed by these chains?

Accepted Answer

Quaternary structure

Question 4

Which of the following best explains why unsaturated fatty acids have lower melting points than saturated fatty acids?

Accepted Answer

Double bonds in unsaturated fatty acids create kinks, preventing close packing.

Question 5

Which equation represents the formation of a peptide bond between two amino acids?

Accepted Answer

$$\mathrm{R_1${-}CH(NH_2$)COOH} + \mathrm{R_2${-}CH(NH_2$)COOH} \rightarrow \mathrm{R_1${-}CH(NH_2$)CONH{-}CH(R_2$)COOH} + \mathrm{H_2O}$$

Question 6

Which property is shared by all zwitterions of amino acids at physiological pH?

Accepted Answer

The amino group is protonated and the carboxyl group is deprotonated.

Question 7

Which of the following is a correct description of the secondary structure of proteins?

Accepted Answer

It consists of repeating structures stabilized by hydrogen bonds between amide hydrogens and carbonyl oxygens.

Question 8

Which of the following amino acids is aromatic and can absorb UV light, making it useful in protein quantification assays?

Accepted Answer

Tryptophan

Question 9

What is the main reason enzymes are able to increase the rate of biochemical reactions?

Accepted Answer

They lower the activation energy required for the reaction.

Question 10

Which of the following bonds is NOT typically involved in stabilizing the tertiary structure of proteins?

Accepted Answer

Peptide bonds

Question 11

A mutation changes a glutamic acid (Glu, E) residue to valine (Val, V) in the primary structure of hemoglobin. What is the most likely effect on the protein?

Accepted Answer

The protein will lose a negative charge and gain a non-polar side chain, potentially affecting its solubility and function.

Question 12

Which of the following is a function of HDL (High Density Lipoprotein) in the body?

Accepted Answer

HDL builds and maintains cell membranes and is important for absorption of lipid-soluble vitamins.

Question 13

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

Phospholipids have both hydrophilic heads and hydrophobic tails.

Question 14

Which process converts fats and oils into soap molecules by hydrolyzing esters of fatty acids under basic conditions?

Accepted Answer

Saponification

Question 15

Which of the following is true about the structure of collagen?

Accepted Answer

Collagen is a fibrous protein with a rope-like structure reinforced by disulfide bonds.

Question 16

Which of the following statements about the quaternary structure of hemoglobin is correct?

Accepted Answer

Hemoglobin is composed of four globular polypeptides, each binding a heme group.

Question 17

Which of the following is a correct statement about the physical properties of amides in proteins?

Accepted Answer

The hydrogen on the nitrogen and the lone pair of electrons on the oxygen allow amides to participate in hydrogen bonding.

Question 18

Which of the following best explains the difference between cis and trans unsaturated fatty acids?

Accepted Answer

Cis fatty acids have bent chains due to double bonds on the same side, while trans fatty acids have straight chains due to double bonds on opposite sides.

Question 19

Which of the following is NOT a function of proteins listed in the study materials?

Accepted Answer

Storage of genetic information

Amino Acids, Proteins, Enzymes, and Lipids: Core Concepts in Biochemistry

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