$$\text{pH} = -\log_{10}([H^+])$$

Question 1

Which of the following statements best explains why water is considered the 'universal solvent' in biological systems?

Accepted Answer

Water's polarity allows it to surround and stabilize ionic and polar solutes, keeping them in solution.

Question 2

A patient presents with a blood pH of 7.28. Which acid-base disorder is most likely present, and what is the physiological consequence?

Accepted Answer

Acidosis; impaired protein structure and function.

Question 3

Which equation correctly represents the relationship between pH and hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$	ext{pH} = -\log_{10}([H^+])$$

Question 4

Which of the following best describes the composition of the plasma membrane?

Accepted Answer

Lipids (phospholipids and cholesterol), proteins, and carbohydrates.

Question 5

Amino acids act as buffers in solution. Which property allows them to resist changes in pH?

Accepted Answer

They contain both an amino group and a carboxyl group that can accept or donate $$H^+$$ ions.

Question 6

Which of the following is the major intracellular cation and what is its significance?

Accepted Answer

Potassium ($$K^+$$); essential for maintaining cell membrane potential.

Question 7

Which of the following best describes a zwitterion?

Accepted Answer

A molecule with both positive and negative charges, but overall neutral.

Question 8

A protein is exposed to high temperature and strong acid. Which structural levels are most likely disrupted, and which remain intact?

Accepted Answer

Secondary, tertiary, and quaternary structures are disrupted; primary structure remains intact.

Question 9

Which of the following is NOT a function of proteins in the human body?

Accepted Answer

Storage and transmission of genetic information.

Question 10

Which process describes the joining of two amino acids to form a peptide bond?

Accepted Answer

Condensation (dehydration synthesis), removing a molecule of water.

Question 11

A patient with phenylketonuria (PKU) has a mutation in the phenylalanine hydroxylase enzyme. What is the biochemical consequence?

Accepted Answer

Phenylalanine cannot be converted to tyrosine, leading to phenylalanine accumulation.

Question 12

Which of the following best explains why changes in body temperature and pH can be detrimental to protein function?

Accepted Answer

They disrupt non-covalent interactions, leading to denaturation and loss of protein function.

Question 13

Which of the following is a correct statement about the stereochemistry of amino acids in proteins?

Accepted Answer

Proteins in humans are composed of L-amino acids.

Question 14

Which of the following is a major function of water in the human body?

Accepted Answer

Lubrication and cushioning of tissues.

Question 15

Which of the following best describes the effect of pH on the net charge of an amino acid?

Accepted Answer

At $$	ext{pH} = 	ext{pI}$$, the amino acid is neutral (zwitterion).

Question 16

Which of the following is NOT a property shared by all biomolecules?

Accepted Answer

They exist only as geometric isomers.

Question 17

Which buffer system is most important for maintaining plasma pH in the human body?

Accepted Answer

Bicarbonate buffer system.

Question 18

Which of the following best describes the difference between essential and non-essential amino acids?

Accepted Answer

Essential amino acids must be obtained from the diet; non-essential can be synthesized by the body.

Question 19

Which of the following is a real-life example of how protein structure determines function?

Accepted Answer

A single amino acid substitution in haemoglobin causes sickle-cell anaemia.

Question 20

Which of the following best describes the process of protein hydrolysis?

Accepted Answer

Addition of water breaks peptide bonds, separating the protein into amino acids.

Foundations of Biochemistry: Body Fluids, pH, and Protein Structure

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