Question 1

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice create a lattice structure that spaces water molecules farther apart, lowering its density.

Question 2

Which of the following is NOT an emergent property of water that is crucial for life?

Accepted Answer

High compressibility

Question 3

Which chemical bond is the strongest in biological systems and why?

Accepted Answer

Covalent bond, because it involves sharing of electron pairs between atoms.

Question 4

If you add HCl (a strong acid) to pure water, what happens to the pH and why? Use the formula $$\mathrm{pH} = -\log_{10}[\mathrm{H}^+] to $$support your answer.

Accepted Answer

The pH decreases because the concentration of $$\mathrm{H}^+$$ ions increases.

Question 5

Which of the following best describes a structural isomer?

Accepted Answer

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

Question 6

Glucose is an aldehyde sugar and fructose is a ketone sugar. Both have the molecular formula $$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6. $$Which statement best explains their difference?

Accepted Answer

Glucose has a carbonyl group at the end of the carbon chain (aldehyde), while fructose has it within the chain (ketone).

Question 7

Which of the following is a real-world example of a cis-trans isomer?

Accepted Answer

Unsaturated fatty acids, such as oleic acid (cis) and elaidic acid (trans)

Question 8

Which property of water allows insects to walk on its surface?

Accepted Answer

Cohesion due to hydrogen bonding

Question 9

What is the main difference between a saturated and an unsaturated fatty acid?

Accepted Answer

Saturated fatty acids have no double bonds between carbon atoms; unsaturated have one or more double bonds.

Question 10

Which of the following best describes how a phospholipid reacts with water?

Accepted Answer

The hydrophilic head interacts with water, while the hydrophobic tail avoids water.

Question 11

Which of the following is NOT a component of an amino acid?

Accepted Answer

A phosphate group ($$-\mathrm{PO}_4)$$

Question 12

Which level of protein structure is primarily stabilized by hydrogen bonds between backbone atoms?

Accepted Answer

Secondary structure

Question 13

Which of the following best explains why carbon can form so many different molecules?

Accepted Answer

Carbon can form up to four covalent bonds with other atoms.

Question 14

Which chemical reaction is responsible for breaking down polymers into monomers?

Accepted Answer

Hydrolysis

Question 15

Which of the following is a correct example of a dehydration synthesis reaction?

Accepted Answer

Forming a disaccharide from two monosaccharides by removing water

Question 16

Which property of water helps moderate Earth's climate?

Accepted Answer

High specific heat

Question 17

Which of the following best describes the tertiary structure of a protein?

Accepted Answer

The folding of a polypeptide due to interactions between R groups.

Question 18

Which of the following is a correct formula for calculating the pH of a solution?

Accepted Answer

$$\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$$

Question 19

Which of the following is a correct description of a peptide bond?

Accepted Answer

A bond formed between two amino acids by a dehydration reaction.

General Biology: Chemical Bonds, Water Properties, and Biomolecules Study Guide

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