Question 1

Which property of water is MOST critical for its role as a solvent in biological systems?

Accepted Answer

Its ability to form hydrogen bonds due to its polar structure.

Question 2

Which of the following molecules contains atoms arranged in a plane and is important in biological systems?

Accepted Answer

Carbon dioxide ($$O=C=O)$$

Question 3

Which of the following best explains why spontaneous chemical reactions are important for the origin of life?

Accepted Answer

They release energy and can form complex molecules without external input.

Question 4

Which four elements make up approximately 96% of the mass of living organisms?

Accepted Answer

Carbon, Hydrogen, Oxygen, Nitrogen

Question 5

A molecule of water ($$H_2O) is $$described as polar because:

Accepted Answer

Oxygen pulls electrons closer, creating partial charges.

Question 6

Which equation correctly represents the dissociation of water and is important in acid-base chemistry?

Accepted Answer

$$H_2O \rightarrow H^+ + OH^-$$

Question 7

Which of the following statements about ionic bonds is TRUE?

Accepted Answer

Ionic bonds form due to electrical attraction between oppositely charged ions.

Question 8

If a molecule has a positive charge after losing an electron, it is called:

Accepted Answer

Cation

Question 9

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a hydrogen atom and an electronegative atom like oxygen.

Question 10

Which property of water allows it to moderate temperature changes in living organisms?

Accepted Answer

High specific heat

Question 11

Which of the following is a correct statement about acid-base reactions in biological systems?

Accepted Answer

Acid-base reactions can change the charge and shape of proteins.

Question 12

Given the following equation for pH: $$pH = -\log[H^+]$$, what is the pH of a solution with $$[H^+] = 1 	imes 10$$^{-4}$$ M?

Accepted Answer

pH = 4

Question 13

Which of the following molecules is hydrophilic?

Accepted Answer

Glucose ($$C_6H_{12}O_6$)

Question 14

Which of the following best explains why carbon is central to biological molecules?

Accepted Answer

Carbon can form up to four covalent bonds, allowing for complex structures.

Question 15

Which of the following is the correct order of electronegativity for the four most abundant elements in biological molecules?

Accepted Answer

$$O \u003e N \u003e C \approx H$$

Question 16

A solution has a pH of 2. What is the concentration of hydrogen ions $$[H^+] in $$the solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-2}$$ M

Question 17

Which of the following is a consequence of water's ability to form hydrogen bonds?

Accepted Answer

Water has a high boiling point compared to similar-sized molecules.

Question 18

Which of the following statements about covalent bonds is TRUE?

Accepted Answer

Covalent bonds involve the sharing of electrons between atoms.

Question 19

Which of the following is a real-world example of an acid-base reaction important in human physiology?

Accepted Answer

Buffering of blood pH by bicarbonate: $$HCO_3^- + H$$^+ \rightarrow H_2CO_3$$

Question 20

Which of the following best describes the difference between hydrophobic and hydrophilic molecules?

Accepted Answer

Hydrophilic molecules dissolve in water due to their polarity, while hydrophobic molecules do not.

Water, Carbon, and the Chemical Basis of Life

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