Question 1

Which of the following statements best explains why carbon is considered the backbone of biological molecules?

Accepted Answer

Carbon can form up to four covalent bonds, allowing for a diversity of stable, complex structures.

Question 2

The Urey-Miller experiment demonstrated that:

Accepted Answer

Organic molecules can be synthesized abiotically under conditions thought to resemble those of early Earth.

Question 3

Which of the following best describes a hydrocarbon?

Accepted Answer

A molecule containing only carbon and hydrogen atoms.

Question 4

Which of the following is NOT a type of isomer?

Accepted Answer

Hydrocarbon isomer

Question 5

A molecule with the formula $$C_5H_{12}$$ can have different covalent arrangements of its carbon skeleton. These molecules are called:

Accepted Answer

Structural isomers

Question 6

Which functional group is present in all amino acids and acts as a base?

Accepted Answer

Amino group ($$—NH_2$)

Question 7

Which of the following best explains why enantiomers of a drug can have different effects in the human body?

Accepted Answer

Enantiomers have different spatial arrangements, so only one form may fit the biological receptor.

Question 8

Which functional group is a characteristic of alcohols and increases the solubility of organic molecules in water?

Accepted Answer

Hydroxyl group ($$—OH)$$

Question 9

A fat molecule contains long hydrocarbon chains. What property do these chains impart to fats?

Accepted Answer

They store large amounts of energy due to their nonpolar bonds.

Question 10

Which of the following molecules contains a carbonyl group?

Accepted Answer

Acetone ($$CH_3COCH_3)$$

Question 11

Which of the following best describes the difference between estradiol and testosterone?

Accepted Answer

They have the same carbon skeleton but differ in the functional groups attached.

Question 12

Which functional group is responsible for the acidic properties of acetic acid?

Accepted Answer

Carboxyl group ($$—COOH)$$

Question 13

Which of the following statements about cis-trans isomers is correct?

Accepted Answer

They have the same covalent bonds but differ in spatial arrangement around a double bond.

Question 14

A molecule with the formula $$C_6H_{12}O_6$ can exist as glucose or fructose. These two molecules are:

Accepted Answer

Structural isomers

Question 15

Which functional group is found in the amino acid cysteine and is important for forming disulfide bonds in proteins?

Accepted Answer

Sulfhydryl group ($$—SH)$$

Question 16

Which of the following best describes the role of phosphate groups in biological molecules?

Accepted Answer

They are involved in energy transfer, such as in ATP.

Question 17

Which of the following is a correct statement about the valence of carbon?

Accepted Answer

Carbon has a valence of 4, allowing it to form four covalent bonds.

Question 18

Which of the following functional groups is nonpolar and often acts as a tag on biological molecules?

Accepted Answer

Methyl group ($$—CH_3$)

Question 19

A molecule with the formula $$CO(NH_2$)_2 is $$known as:

Accepted Answer

Urea

Question 20

Which of the following best explains why organisms are sensitive to even subtle variations in molecular structure?

Accepted Answer

Small changes in structure can lead to large differences in biological activity, as seen with enantiomers.

Carbon and the Molecular Diversity of Life

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