Question 1

Which property of carbon makes it uniquely suited to form the backbone of large, complex biological molecules?

Accepted Answer

Carbon has four valence electrons, allowing it to form four covalent bonds with a variety of atoms.

Question 2

A molecule of ethene (C2H4) has a double bond between its carbon atoms. What is the spatial arrangement of the atoms attached to the carbons?

Accepted Answer

The atoms attached to the carbons are in the same plane as the carbons.

Question 3

Which of the following best describes a structural isomer?

Accepted Answer

Compounds with the same molecular formula but different covalent arrangements of their atoms.

Question 4

Cis-trans isomers differ in their spatial arrangement due to the inflexibility of double bonds. Which real-life scenario illustrates the importance of this difference?

Accepted Answer

The activity of vision-related molecules in the eye, where a cis-trans isomerization triggers a nerve impulse.

Question 5

Enantiomers are isomers that are mirror images of each other. Why is only one enantiomer usually biologically active?

Accepted Answer

Biological molecules are often chiral, so only one enantiomer fits the active site of enzymes or receptors.

Question 6

Which functional group is most likely to act as an acid in biological molecules?

Accepted Answer

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

Question 7

ATP is a critical molecule in cellular energy transfer. What happens when ATP reacts with water?

Accepted Answer

ATP is converted to ADP, inorganic phosphate, and energy is released: $$\mathrm{ATP + H_2O \rightarrow ADP + P_i + Energy}$$

Question 8

Which process is responsible for joining monomers to form polymers in cells?

Accepted Answer

Dehydration reaction (dehydration synthesis)

Question 9

A patient is diagnosed with sickle-cell disease. Which change at the molecular level is responsible for this condition?

Accepted Answer

A single amino acid substitution in the primary structure of hemoglobin.

Question 10

Which of the following statements about cellulose is correct?

Accepted Answer

Cellulose is a structural polysaccharide in plants, composed of glucose monomers in the beta ($$\beta) $$conformation.

Question 11

Which of the following best explains why lipids are hydrophobic?

Accepted Answer

Lipids consist mostly of hydrocarbons, which form nonpolar covalent bonds.

Question 12

What is the major structural difference between saturated and unsaturated fatty acids?

Accepted Answer

Saturated fatty acids have no double bonds, while unsaturated fatty acids have one or more double bonds.

Question 13

Phospholipids are essential for cell membranes. What happens when phospholipids are added to water?

Accepted Answer

They self-assemble into a bilayer, with hydrophobic tails pointing inward and hydrophilic heads facing outward.

Question 14

Which of the following is NOT a function of proteins in living organisms?

Accepted Answer

Energy storage

Question 15

Which level of protein structure is directly determined by the sequence of amino acids?

Accepted Answer

Primary structure

Question 16

A protein is exposed to high heat and extreme pH. What is most likely to happen?

Accepted Answer

The protein will denature, losing its native structure and function.

Question 17

Which of the following statements about nucleic acids is correct?

Accepted Answer

DNA contains deoxyribose, while RNA contains ribose as the sugar component.

Question 18

Which type of bond joins adjacent nucleotides in a polynucleotide chain?

Accepted Answer

Phosphodiester linkage

Question 19

In the DNA double helix, what is the significance of antiparallel arrangement?

Accepted Answer

It allows the two strands to form hydrogen bonds between complementary bases.

Chapter 3: Carbon and the Molecular Diversity of Life – Study Notes

Study Guide - Practice Questions

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