Question 1

Which of the following statements best explains why sucrose does NOT give a positive result in Benedict’s or Tollen’s test?

Accepted Answer

Because both anomeric carbons are involved in a glycosidic bond, leaving no free hemiacetal group.

Question 2

A carbohydrate has the molecular formula $$C_6H_{12}O_6$. It contains a carbonyl group at C2 and rotates plane-polarized light. Which of the following best describes this molecule?

Accepted Answer

It is a ketohexose and is optically active.

Question 3

How many possible stereoisomers exist for an aldohexose sugar?

Accepted Answer

$$2^4 = 16$

Question 4

Which of the following best describes the difference between D- and L-glucose?

Accepted Answer

D-glucose has the -OH group on the right at the chiral carbon furthest from the carbonyl; L-glucose has it on the left.

Question 5

Which of the following statements about the structure and function of glycosaminoglycans (GAGs) in cartilage is CORRECT?

Accepted Answer

GAGs are long, highly charged polysaccharides that attract water, providing lubrication and shock absorption.

Question 6

Which of the following best explains why most natural unsaturated fatty acids are liquids at room temperature?

Accepted Answer

They contain cis double bonds that introduce kinks, preventing tight packing of the molecules.

Question 7

Which of the following is TRUE regarding the hydrolysis of a triacylglycerol (TAG) with a strong base?

Accepted Answer

It produces glycerol and the sodium salts of fatty acids (soap) in a process called saponification.

Question 8

Which of the following best describes the difference between passive and active transport across a cell membrane?

Accepted Answer

Passive transport moves molecules down their concentration gradient without energy; active transport moves molecules against their gradient using energy.

Question 9

Which of the following is a correct statement about the structure and biological role of cholesterol?

Accepted Answer

Cholesterol is a precursor for all steroid hormones and helps modulate membrane fluidity.

Question 10

Which of the following best describes the mechanism of action for peptide (water-soluble) hormones?

Accepted Answer

They bind to transmembrane receptors, activating second messenger systems such as cAMP.

Question 11

Which of the following is the correct sequence of events in the G-protein-coupled receptor (GPCR) mechanism for hormone signaling?

Accepted Answer

Hormone binds receptor → G-protein exchanges GDP for GTP → G-protein activates adenylate cyclase → ATP is converted to cAMP.

Question 12

Which of the following statements about the structure and function of cellulose is CORRECT?

Accepted Answer

Cellulose is composed of β-D-glucose units linked by β(1→4) glycosidic bonds and provides structural support in plants.

Question 13

Which of the following best explains why trans fatty acids are considered unhealthy compared to cis fatty acids?

Accepted Answer

Trans fatty acids pack tightly like saturated fats, raising melting points and increasing cardiovascular risk.

Question 14

Which of the following is TRUE regarding the difference between steroid and peptide hormone signaling?

Accepted Answer

Steroid hormones diffuse through the membrane and bind to cytosolic/nuclear receptors; peptide hormones bind to cell surface receptors.

Question 15

Which of the following is the precursor for all eicosanoid signaling molecules?

Accepted Answer

Arachidonic acid

Question 16

Which of the following best describes the effect of aspirin on inflammation?

Accepted Answer

Aspirin inhibits the enzyme cyclooxygenase (COX), reducing prostaglandin synthesis.

Question 17

Which of the following best describes the role of ligand-gated ion channels in nerve signaling?

Accepted Answer

They open in response to neurotransmitter binding, initiating a local change in membrane potential.

Question 18

Which of the following statements about glycoproteins is CORRECT?

Accepted Answer

Glycoproteins are proteins with carbohydrate chains attached, often functioning as cell surface ID tags.

Question 19

Which of the following best describes the difference between amylose and glycogen?

Accepted Answer

Amylose is a linear polymer with α(1→4) linkages; glycogen is highly branched with α(1→4) and α(1→6) linkages.

Chemistry Study Guide: Carbohydrates, Lipids, and Chemical Messengers

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