Q: A solution has a pH of 5. What is the hydrogen ion concentration $$[H^+] in $$this solution?

$$[H^+] = 1 \times 10$$^{-5}$$ M

Question 1

Which of the following best describes why water is considered an ideal medium for biochemical reactions in living organisms?

Accepted Answer

Water has two hydrogen bond donor sites, two acceptor sites, a permanent dipole, high heat capacity, and a density greater in liquid form.

Question 2

A patient is found to have a blood pH of 7.2. Based on the physiological pH range, how would you classify this condition, and what could be a possible consequence for enzyme activity?

Accepted Answer

The patient is in an acidic state (acidosis); enzyme activity may decrease due to altered molecular charge.

Question 3

Which of the following correctly matches a biological macromolecule with its monomer and the type of linkage that joins the monomers?

Accepted Answer

Polysaccharide – Monosaccharide – Glycosidic (ether) bond

Question 4

Which of the following elements is NOT considered one of the four most abundant elements in living systems?

Accepted Answer

Sulfur (S)

Question 5

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-6}$$ M. What is the pH of this solution?

Accepted Answer

$$pH = 6$$

Question 6

Which of the following statements about amphipathic molecules is correct?

Accepted Answer

They contain both hydrophilic and hydrophobic regions, allowing them to form micelles and bilayers in water.

Question 7

Which of the following best explains why the density of water is greater in the liquid state than in the solid state?

Accepted Answer

Hydrogen bonds in ice form a lattice structure with more open space, making ice less dense.

Question 8

Which of the following is a correct application of the Brønsted-Lowry definition in a biochemical context?

Accepted Answer

An acid donates a proton to water, forming a hydronium ion ($$H_3O^+).$$

Question 9

Which of the following ions is essential for life and plays a key role in nerve impulse transmission?

Accepted Answer

$$Na^+$$

Question 10

A researcher is studying a macromolecule composed of amino acids linked by peptide bonds. Which class of biological macromolecule is being studied, and what is the primary function of this class?

Accepted Answer

Proteins; catalysis, structure, and regulation

Question 11

Which of the following best describes the relationship between pH and the charge of biomolecules such as proteins?

Accepted Answer

As pH changes, the ionization state of functional groups changes, altering the overall charge of the molecule.

Question 12

Which of the following is NOT a function of lipids in biological systems?

Accepted Answer

Catalyzing biochemical reactions

Question 13

A solution has a pH of 5. What is the hydrogen ion concentration $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-5}$$ M

Question 14

Which of the following best explains why phospholipids spontaneously form bilayers in aqueous environments?

Accepted Answer

Their amphipathic nature causes hydrophobic tails to avoid water and hydrophilic heads to interact with water, forming a bilayer.

Question 15

Which of the following is a correct statement about the physiological pH range?

Accepted Answer

Most biological reactions occur between pH 6.5 and 8.0.

Question 16

Which of the following is a correct pairing of a macromolecule and its linkage type?

Accepted Answer

Nucleic acid – Phosphodiester bond

Question 17

Which of the following best describes the role of magnesium ions ($$Mg^{2+}) in $$living systems?

Accepted Answer

They act as essential cofactors for many enzymes.

Question 18

Which of the following statements about the structure of water is FALSE?

Accepted Answer

Water has a low heat capacity compared to other solvents.

Question 19

Which of the following best explains why strong acids dissociate almost completely in water?

Accepted Answer

Strong acids readily donate protons to water, forming hydronium ions and their conjugate bases.

Introduction to Biochemistry: Chemical Foundations and Biological Macromolecules

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