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

Both anomeric carbons in sucrose are involved in a glycosidic bond, so there is no free hemiacetal group.

Question 2

A carbohydrate has the molecular formula $$C_6H_{12}O_6$. It contains a carbonyl group at carbon 2 and forms a five-membered ring in solution. Which sugar is this most likely to be?

Accepted Answer

Fructose

Question 3

How many possible stereoisomers exist for an aldohexose?

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 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 glycosidic bonds is TRUE?

Accepted Answer

Once a glycosidic bond forms at the anomeric carbon, that carbon can no longer mutarotate or act as a reducing sugar.

Question 6

Which of the following best explains why cartilage is 'springy' and acts as a shock absorber in joints?

Accepted Answer

Cartilage contains glycosaminoglycans with high negative charge, causing electrostatic repulsion and water retention.

Question 7

Which of the following is a correct description of the structure and function of a wax found in nature?

Accepted Answer

A wax is an ester formed from a long-chain fatty acid and a long-chain alcohol, providing waterproofing for plants and animals.

Question 8

Which of the following statements about the hydrogenation of vegetable oils is CORRECT?

Accepted Answer

Hydrogenation converts cis double bonds to trans double bonds, increasing the melting point and making the fat more solid.

Question 9

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

Accepted Answer

Passive transport moves substances down their concentration gradient without energy input; active transport moves substances against their gradient and requires energy.

Question 10

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

Accepted Answer

Cholesterol is a steroid with a four-fused-ring structure that modulates membrane fluidity and is a precursor for bile salts and steroid hormones.

Question 11

A patient is prescribed a drug that acts as an antagonist at a specific cell-surface receptor. What is the most likely effect of this drug?

Accepted Answer

It will bind to the receptor and block the natural ligand, preventing the biological response.

Question 12

Which of the following best describes the mechanism of action for steroid hormones?

Accepted Answer

Steroid hormones diffuse through the cell membrane and bind to cytosolic or nuclear receptors, directly regulating gene expression.

Question 13

Which of the following is the precursor for all eicosanoid signaling molecules such as prostaglandins and leukotrienes?

Accepted Answer

Arachidonic acid

Question 14

Which of the following best explains how aspirin reduces inflammation?

Accepted Answer

Aspirin inhibits cyclooxygenase (COX), preventing the synthesis of prostaglandins from arachidonic acid.

Question 15

Which of the following is TRUE regarding the saponification of a triglyceride?

Accepted Answer

It produces glycerol and the sodium salts of fatty acids (soap) when reacted with a strong base.

Question 16

Which of the following best describes the difference between cellulose and starch?

Accepted Answer

Cellulose is composed of β(1→4) linked D-glucose units, while starch contains α(1→4) linkages.

Question 17

Which of the following best describes the role of glycolipids in the cell membrane?

Accepted Answer

They are lipids with carbohydrate chains that serve as cell recognition markers on the extracellular surface.

Question 18

Which of the following best describes the process of mutarotation in sugars?

Accepted Answer

It is the interconversion between α and β anomers via the open-chain form in aqueous solution.

Question 19

Which of the following is a correct description of the action of peptide (water-soluble) hormones?

Accepted Answer

They bind to transmembrane receptors and activate second messenger systems such as cAMP.

Chem 1120 Study Guide: Carbohydrates, Lipids, and Chemical Messengers

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