Deck 1: Biochemistry: an Evolving Science

Question 1

What is the [H⁺] concentration in a urine sample that has a pH of 6?

A) 10^-6 M
B) 10^-8 M
C) 10⁶ M
D) 10^-14 M
E) 6 M

Answer 1

A

Question 2

What gives proteins such a dominant role in biochemistry?

A) the rigidity of the peptide backbone
B) the ability to act as a blueprint
C) the ability to self-replicate
D) the ability to spontaneously fold into complex three-dimensional structures
E) All of the answers are correct.

Answer 2

D

Question 3

Which is the correct order of decreasing bond strengths?

A) hydrogen bonds, covalent bonds, van der Waals interactions
B) hydrogen bonds, electrostatic interactions, covalent bonds
C) van der Waals interactions, covalent bonds, hydrogen bonds
D) covalent bonds, hydrogen bonds, van der Waals interactions
E) hydrophobic interactions, hydrogen bonds, electrostatic interactions

Answer 3

D

Question 4

If the whole chain is used in a nonoverlapping frame, how many amino acids are defined by this DNA sequence: ATGTTTGGACTA?

A) two
B) three
C) four
D) six
E) twelve

Question 5

The fundamental groups of organisms include Eukarya, Bacteria, and _____.

A) Plantae
B) Animalia
C) Protista
D) Archaea
E) Fungi

Question 6

The DNA backbone is made from repeating _____.

A) monosaccharide units
B) amino acid units
C) sugar-phosphate units
D) fatty acid
E) None of the answers is correct.

Question 7

The matter within a defined region of space is referred to as the _____.

A) universe
B) system
C) outer space
D) wormhole
E) None of the answers is correct.

Question 8

The number of hydrogen bonds formed between G and C is _____.

A) 1
B) 2
C) 3
D) 4
E) 2 if in RNA, 3 if in DNA

Question 9

Which of the following is a hydrogen bond donor?

A) the N in N-H D
B) the H in S-H
C) the O in P-O
D) the H in O-H
E) None of the answers is correct.

Question 10

DNA is made from the building blocks adenine, guanine, cytosine and _____.

A) uridine
B) thymine
C) inosine
D) ribose
E) None of the answers is correct.

Question 11

What did Watson and Crick suggest to be significant about the base pairing found in the helix?

A) It allowed the DNA to twist in a helix.
B) The DNA could be circular.
C) It was a mechanism for copying.
D) All of the answers are correct.
E) None of the answers is correct.

Question 12

The energies for hydrogen bonds are approximately

A) 400 kJ mol^-1.
B) 100-240 kJ mol^-1.
C) 4-20 kJ mol^-1.
D) 200 kJ mol^-1.
E) None of the answers is correct.

Question 13

The structure of DNA described by Watson and Crick included

A) a double helix.
B) the sugar phosphate backbone aligned in the center of the helix.
C) the base pairs that are stacked on the inside of the double helix.
D) both a double helix and the sugar phosphate backbone aligned in the center of the helix
E) a double helix and the base pairs that are stacked on the inside of the double helix

Question 14

The number of hydrogen bonds formed between A and T is _____.

A) 1
B) 2
C) 3
D) 4
E) 2 if in DNA, 3 if in RNA

Question 15

For a spontaneous reaction, the $\Delta$ G must be _____.

A) positive
B) negative
C) greater than 1
D) between 1 and 0
E) 0

Question 16

Which of the following describes the relationship between the strengths of hydrogen and covalent bonds?

A) Hydrogen bonds are always stronger than covalent bonds.
B) Hydrogen bonds and covalent bonds have equivalent strength.
C) Hydrogen bonds are always weaker than covalent bonds.
D) With a few exceptions, most hydrogen bonds are stronger than covalent bonds.
E) With a few exceptions, most covalent bonds are stronger than hydrogen bonds.

Question 17

The term _____ is used to indicate Gibbs free energy.

A) $\Delta$ H
B) $\Delta$ E
C) $\Delta$ S
D) $\Delta$ G
E) $\Delta$ T

Question 18

Approximately what percentage of the human genome encodes proteins?

A) 50%
B) 90%
C) 20%
D) 3%
E) None of the answers is correct.

Question 19

Which of the following is considered a metabolite, a substance that is chemically transformed in a biochemical process?

A) deoxyribonucleic acid
B) glycerol
C) protein
D) ribonucleic acid
E) polysaccharide

Question 20

Which of the following are the strongest bonds in molecules?

A) covalent bonds
B) ionic bonds
C) hydrogen bonds
D) metallic bonds
E) None of the answers is correct.

Question 21

The Second Law of Thermodynamics states

A) the total entropy of a system and its surroundings always increases for a spontaneous process.
B) temperatures will always decrease in a spontaneous process.
C) the total energy of a system and its surroundings is constant.
D) diversity is the result of gradual evolution.
E) None of the answers is correct.

Question 22

How is water able to be a solvent for so many biological molecules?

Question 23

Using the Henderson-Hasselbalch equation, calculate the pH of a buffer solution made from 0.20 M CH₃COOH and 0.050 M CH₃COO^- that has pK_a= 4.7.

A) 5.3
B) 4.1
C) 2.5
D) 0.4
E) None of the answers is correct.

Question 24

What two properties of water are important for biological interactions?

A) the polarity of water
B) the density of water
C) the cohesive properties of water
D) the polarity of water and the cohesive properties of water
E) the density of water and the cohesive properties of water

Question 25

What happens to nonpolar molecules in water?

A) They dissolve independently.
B) They aggregate together.
C) They precipitate.
D) All of the answers are correct.
E) None of the answers is correct.

Question 26

Typical van der Waals energies are about

A) 4-20 kJ mol^-1.
B) 2-4 kJ mol^-1.
C) 200 kJ mol^-1.
D) 500-1000 kJ mol^-1.
E) None of the answers is correct.

Question 27

Entropy is defined as

A) a spontaneous reaction.
B) the enthalpy of the system.
C) the measure of randomness of a system.
D) the amount of heat exchanged.
E) None of the answers is correct.

Question 28

The First Law of Thermodynamics states

A) diversity is the result of gradual evolution.
B) the total entropy of a system and its surroundings always increases for a spontaneous process.
C) the total energy of a system and its surroundings is constant.
D) light is both particle and wave.
E) None of the answers is correct.

Question 29

What is the [A^-]/[HA] ratio when a weak acid is in a solution one pH unit below its pK_a?

A) 1:1
B) 1:10
C) 10:1
D) 2:1
E) None of the answers is correct.

Question 30

If most proteins are found surrounded by water in the cell, what type of functional groups would you expect to find on the surface of a water-soluble protein?

Question 31

Which of the following atoms commonly found in biological molecules are often hydrogen-bond acceptors?

A) carbon
B) oxygen
C) nitrogen
D) All of the answers are correct.
E) oxygen and nitrogen

Question 32

If a particular reaction has a negative $\Delta$ G, is it likely to occur?

A) Not unless energy is added to the system
B) Yes, if it is coupled to another reaction
C) Yes, it is spontaneous.
D) No, it is not spontaneous.
E) Yes, as long as the temperature increases

Question 33

What is the net effect of many van der Waals interactions?

Question 34

What are some of the medical implications of the human genome project?

Question 35

Describe resonance structures.

Question 36

What is significant about the fact that metabolic processes are common to many organisms?

Question 37

What are the primary chemical components present in a phosphate buffer at pH 7.4?

A) H₃PO₄ and PO₄^3-
B) H₂PO₄^- and PO₄^3-
C) HPO₄^2- and PO₄^3-
D) H₂PO₄^- and HPO₄^2-
E) H₃PO₄ and HPO₄^2-

Question 38

Why does DNA denature when the pH is raised above 9?

A) Protons dissociate from guanine bases disrupting the hydrogen bonding to the other strand.
B) Protons bind to guanine residues giving them additional positive charges which disrupt the hydrogen bonding to the other strand.
C) Protons bind to functional groups that serve as hydrogen-bond acceptors, thus disrupting the hydrogen bonding to the other strand.
D) Protons dissociate from the phosphate groups in the backbone, which disrupts the hydrogen-bonding pattern between strands.
E) None of the answers is correct.

Question 39

What is the significance of hydrogen bonding in biochemical structures such as DNA?

Question 40

The simplest way to depict stereochemistry is to use

A) ball-and-stick models.
B) ribbon diagrams.
C) space-filling models.
D) Fisher projections.
E) None of the answers is correct.

Question 41

What is the significance of using $\Delta$ G in biochemistry?

Question 42

What thermodynamic and free-energy changes participate in protein folding?

Question 43

Provide a simple example of a process in which the entropy of a system changes.

Question 44

When solutions containing complementary single strands of DNA are mixed, a loss of entropy occurs. How is it that the Second Law of Thermodynamics is not violated?

Question 45

How do hydrophobic interactions aid in protein folding?

Question 46

Describe the shape of methane.

Question 47

How can a cell exist if the Second Law of Thermodynamics is true?

Question 48

How are electrostatic forces used in protein folding?

Question 49

What are the enthalpy and entropy changes that accompany the formation of DNA double helices from complementary single strands of DNA?

Question 50

If the First Law of Thermodynamics is true, how can biological processes be carried out?