Question 1

Which property of carbon most directly explains its ability to form large, complex, and diverse biological molecules?

Accepted Answer

Its versatility in forming four covalent bonds with other atoms.

Question 2

Which of the following best describes the difference between cis and trans isomers?

Accepted Answer

Cis isomers have functional groups on the same side of a double bond, while trans isomers have them on opposite sides.

Question 3

L-dopa and D-dopa are enantiomers. Which statement best explains why only L-dopa is effective in treating Parkinson's disease?

Accepted Answer

Only L-dopa fits the active site of the enzyme involved in dopamine synthesis due to its specific three-dimensional arrangement.

Question 4

Which of the following functional groups is characteristic of alcohols and is found in sugars?

Accepted Answer

Hydroxyl group $$(-\mathrm{OH})$$

Question 5

A dehydration reaction is essential in the formation of which biological molecule?

Accepted Answer

A triglyceride from glycerol and fatty acids

Question 6

Which of the following best explains why saturated fatty acids are solid at room temperature, while unsaturated fatty acids are liquid?

Accepted Answer

Saturated fatty acids lack double bonds, allowing them to pack tightly together.

Question 7

Which of the following statements about polysaccharides is correct?

Accepted Answer

Polysaccharides can serve as structural components in plant cell walls.

Question 8

Which chemical group is responsible for the acidic properties of amino acids?

Accepted Answer

Carboxyl group $$(-\mathrm{COOH})$$

Question 9

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

Accepted Answer

Starch contains $$\alpha-1$$,4 glycosidic linkages, while cellulose contains $$\beta-1$$,4 glycosidic linkages.

Question 10

A patient has a genetic mutation that prevents the formation of phospholipids. Which cellular structure would be most directly affected?

Accepted Answer

The cell membrane

Question 11

Which of the following is a real-life consequence of the difference in biological activity between enantiomers?

Accepted Answer

Only D-glucose can be metabolized by human cells, not L-glucose.

Question 12

Which of the following best explains why cholesterol is important in animal cell membranes?

Accepted Answer

It increases membrane fluidity at high temperatures and decreases it at low temperatures.

Question 13

Which of the following reactions is an example of a condensation (dehydration) reaction?

Accepted Answer

Formation of a peptide bond between two amino acids, releasing $$\mathrm{H}_2\mathrm{O}$$

Question 14

Which of the following best describes the role of monosaccharides in cells?

Accepted Answer

They serve as an immediate energy source and as building blocks for larger molecules.

Question 15

Which of the following statements about the ring and linear forms of glucose is correct?

Accepted Answer

Glucose can interconvert between linear and ring forms in solution.

Question 16

Testosterone and estradiol are both derived from cholesterol but have very different effects in the body. What accounts for their different biological activities?

Accepted Answer

They have different functional groups attached to the same carbon skeleton.

Question 17

Which of the following best explains why atherosclerotic plaques form in blood vessels?

Accepted Answer

Accumulation of cholesterol and fats in the arterial wall leads to plaque formation.

Question 18

Which of the following best describes the process by which two monosaccharides are joined to form a disaccharide?

Accepted Answer

A dehydration reaction removes a water molecule, forming a glycosidic bond.

Question 19

Which of the following is a correct statement about the structure of triglycerides?

Accepted Answer

They are composed of three fatty acids attached to a glycerol backbone via ester bonds.

Question 20

Which of the following best explains why structural isomers have different chemical properties?

Accepted Answer

They have the same molecular formula but different covalent arrangements of their atoms.

Lec 3: Carbon and the Molecules of Life: Structure, Isomerism, and Biological Macromolecules

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