Q: A solution has a pH of 4. What is the concentration of hydrogen ions $[H^+]$ in this solution?

$[H^+] = 1 \times 10^{-4} \ \mathrm{M}$

Question 1

Which of the following statements best describes the difference between an ion and an isotope?

Accepted Answer

An ion has an unequal number of protons and electrons, resulting in a charge, while an isotope has the same number of protons but a different number of neutrons.

Question 2

A solution has a pH of 4. What is the concentration of hydrogen ions $[H^+]$ in this solution?

Accepted Answer

$[H^+] = 1 	imes 10^{-4} \ \mathrm{M}$

Question 3

Which of the following best explains why water is an excellent solvent for polar substances?

Accepted Answer

Water molecules form hydrogen bonds with polar substances due to their polar covalent bonds.

Question 4

Which of the following functional groups is found in all amino acids and is responsible for their acidic properties?

Accepted Answer

Carboxyl group ($-COOH$)

Question 5

A triglyceride is formed by the combination of which of the following components?

Accepted Answer

Three fatty acids and one glycerol molecule

Question 6

Which type of chemical bond is primarily responsible for the secondary structure of proteins, such as alpha-helices and beta-pleated sheets?

Accepted Answer

Hydrogen bonds

Question 7

A patient’s blood pH drops from 7.4 to 7.1. By what factor has the hydrogen ion concentration increased?

Accepted Answer

By a factor of 2^{(7.4-7.1)} = 10^{0.3} \approx 2$

Question 8

Which of the following best describes the difference between saturated and unsaturated fatty acids?

Accepted Answer

Saturated fatty acids contain only single bonds between carbon atoms, while unsaturated fatty acids contain one or more double bonds.

Question 9

Which of the following statements about phospholipids is correct?

Accepted Answer

Phospholipids are amphipathic, containing both hydrophilic and hydrophobic regions.

Question 10

Which of the following best explains why enzymes are important in biological systems?

Accepted Answer

Enzymes decrease the activation energy required for chemical reactions, increasing reaction rates.

Question 11

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

Accepted Answer

A bond formed between two monosaccharides by dehydration synthesis.

Question 12

Which of the following is true regarding the structure of DNA and RNA?

Accepted Answer

DNA is double-stranded and contains thymine, while RNA is single-stranded and contains uracil.

Question 13

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers stabilize pH by absorbing or releasing $H^+$ ions.

Question 14

Which of the following is a real-life example of an exergonic reaction in cells?

Accepted Answer

The breakdown of glucose during cellular respiration, releasing ATP.

Question 15

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

Accepted Answer

The association of two or more polypeptide chains to form a functional protein complex.

Question 16

Which of the following best explains why mutations in DNA can have devastating effects on protein function?

Accepted Answer

Mutations can alter the primary structure of a protein, which affects all higher-order structures and function.

Question 17

Which of the following is a property of amphipathic molecules?

Accepted Answer

They have both hydrophilic and hydrophobic regions.

Question 18

Which of the following best describes the role of ATP in cells?

Accepted Answer

ATP is a ribonucleotide that serves as the main energy currency of the cell.

Question 19

Which of the following statements about van der Waals interactions is correct?

Accepted Answer

They are weak attractions due to temporary dipoles, but collectively can stabilize large molecules.

Question 20

A solution is made by dissolving 9 grams of NaCl in 1 liter of water. What is the percent (weight/volume) concentration of NaCl in this solution?

Accepted Answer

0.9%

Biochemistry Basics for Microbiology: Atoms, Elements, and the Periodic Table

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