Chapter 1 Self-test questions

. It is believed that life evolved with RNA as the genetic material, but RNA has been replaced by DNA in all current cellular life. Which feature of DNA probably accounts for this?

DNA can direct its own replication while RNA cannot.

DNA is a nucleic acid while RNA is not.

DNA is more stable than RNA.

Only DNA can form the genetic material of viruses.

. Which of the following statements correctly describes the energy content of the universe, as captured by the first law of thermodynamics?

The total energy content of the universe remains constant.

The total energy content of the universe is in a state of continual flux, increasing at some times, and decreasing at others.

The total energy content of the universe is gradually increasing with time.

The total energy content of the universe is gradually decreasing with time.

. Which of the following statements correctly describes the entropy of the universe, as captured by the second law of thermodynamics?

The total entropy of the universe fluctuates between being high and being low.

The total entropy of the universe remains constant.

The total entropy of the universe is continually decreasing.

The total entropy of the universe is continually increasing.

. ATP (adenosine triphosphate) can be termed the universal energy currency in life because it:

enables cells to disobey the first law of thermodynamics.

enables cells to disobey the second law of thermodynamics.

releases energy as heat when it undergoes hydrolysis.

traps energy released from the oxidation of different classes of food molecules.

. Atoms are at their most stable when which of the following statements apply?

When their valence shells are completely empty.

When their valence shells are half-full.

The degree of filling of valence shells has no impact on the stability of an atom, so it doesn't matter how full (or empty) they are.

When their valence shells are completely full.

. Which of the following groups of elements represent the most common elements in biological systems?

Carbon, nitrogen, sodium, and hydrogen.

Carbon, sodium, potassium, and nitrogen.

Carbon, sodium, hydrogen, and oxygen.

Carbon, nitrogen, oxygen, and hydrogen.

. Which of the following is a covalent bond?

co-ordinate bond.

ionic bond.

hydrogen bond.

van der Waals interaction.

. Water constitutes about 70% of a typical cell. Water is able to form hydrogen bonds, which are:

covalent bonds between hydrogen atoms.

covalent bonds between hydrogen and oxygen atoms.

strong electrostatic bonds between positive hydrogen ions and negative oxygen ions.

weak electrostatic bonds between partially charged hydrogen and oxygen atoms.

. The synthesis of proteins involves polymerisation of:

amino acids.

glucose.

monosaccharides.

nucleotides.

. A ribozyme is:

a class of RNA molecule that can catalyse chemical reactions.

a monomeric subunit of RNA.

a particle composed of RNA and protein that is involved in the synthesis of proteins.

a protein enzyme that catalyses the synthesis of RNA.

. How many different amino acids are found in naturally-occurring proteins?

16

20

24

64

. Which of the following statements about acids and bases is correct?

At pH values below its pK_a, more than 50% of a weak acid will be present in the dissociated state (as the conjugate base).

At pH values above its pK_a, more than 50% of a weak acid will be present in the dissociated state (as the conjugate base).

The pH value of a 0.001 M solution of hydrochloric acid (HCl) is 4.

Acetic (ethanoic) acid (pK_a 4.76) is a good physiological buffer in blood.

. Carbonic acid and sodium bicarbonate (sodium hydrogen carbonate) act as buffers in the blood. When a small amount of acid is added to this buffer, the H+ ions are used up as they combine with the bicarbonate ions. What happens as a result?

The pH of the blood increases.

The pH of the blood decreases

The reaction is irreversible.

The pH of the blood does not change

Chapter 1 Self-test questions

Quiz Content