Deck 1: Chemical Foundations

Question 1

How do phospholipids interact with water molecules?

A)The polar heads interact with water;the nonpolar tails do not.
B)Phospholipids don't interact with water because water is polar and lipids are nonpolar.
C)The polar heads avoid water;the nonpolar tails attract water (because water is polar and opposites attract).
D)Phospholipids dissolve in water.

Answer 1

A

Question 2

You discover that you suffer from a deficiency in the amino acid tryptophan.At the pharmacy,you find both d-tryptophan and l-tryptophan supplements.Which do you purchase? Why?

Answer 2

You should choose l-tryptophan.All amino acids can exist as one of two stereoisomers (d or l)because of asymmetry around the α carbon.Proteins consist of the l form of amino acids,and as these stereoisomers possess distinct biological properties and are not readily interconverted,you should choose the form that is normally utilized by cells.

Question 3

Which of the following is the BEST explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?

A)Vegetable oil has fewer double bonds than animal fats.
B)Animal fats have no amphipathic character.
C)Vegetable oil has longer fatty-acid tails than do animal fats.
D)Vegetable oil has more double bonds than do animal fats.

Answer 3

A

Question 4

Which of the following is the weakest interaction?

A)hydrogen bond
B)ionic bond
C)phosphoanhydride bond
D)van der Waals interaction

Question 5

Which of the following is a noncovalent interaction?

A)hydrophobic effect
B)ionic interactions
C)van der Waals interactions
D)all of the above

Question 6

Which of the following is/are a hydrophilic amino acid?

A)aspartate
B)serine
C)tryptophan
D)aspartate and serine

Question 7

Which of the following is NOT one of the ways RNA differs from DNA?

A)Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
B)Ribonucleotides can have enzymatic activity.
C)Ribonucleotides contain a phosphate group.
D)Ribonucleotides can contain the base uracil.

Question 8

Covalent bonds between which of the following pairs of atoms are nonpolar?

A)C-C
B)C-H
C)O-H
D)a and b

Question 9

Based on what you know about hydrophobic interactions,which of the following is/are composed of a bilayer?

A)a cell's membrane
B)spontaneously aggregated phospholipids surrounding an aqueous interior
C)lipid vesicles that have budded off the cell's membrane
D)all of the above

Question 10

Adenosine is a:

A)component of RNA.
B)nucleoside.
C)pyrimidine.
D)a and b

Question 11

Triacylglycerol and cholesterol esters are nonpolar;in contrast,phospholipids are amphipathic molecules.Biomembranes are based on phospholipids rather than on triacylglycerols.Why?

Question 12

What produces the dipole of a water molecule?

Question 13

Cysteine often plays an important role in stabilizing protein structure.Explain how this works.

Question 14

A nucleotide can vary in _____.

A)the base
B)the sugar
C)the phosphate group
D)the sugar and the base

Question 15

What is the major structural difference between starch and cellulose?

A)the types of monosaccharide subunits in the molecules
B)the amount of branching that occurs in the molecule
C)that humans can only ingest starch
D)the type of glycosidic linkages in the molecule

Question 16

Which of the following is a negatively charged amino acid?

A)alanine
B)aspartate
C)glutamine
D)histidine

Question 17

Which of the following is a monosaccharide?

A)fructose
B)galactose
C)glucose
D)all of the above

Question 18

Which of the following is the strongest interaction?

A)hydrogen bond
B)ionic bond
C)phosphoanhydride bond
D)van der Waals interaction

Question 19

The interactions between two proteins such as an antibody and an antigen or a hormone and its receptor are quite strong despite the fact that these interactions consist of relatively weak noncovalent bonds.How can this be?

Question 20

When two atoms differing in electronegativity are joined in a covalent bond,then the:

A)electrons are shared equally between the atoms.
B)bond is nonpolar.
C)resulting compound is devoid of any dipole moment.
D)atom with the greater electronegativity attracts the bonded electrons more strongly.

Question 21

The pKₐ of the weak base NH₃ is 9.25.When present in lysosomes,a subcellular organelle-ammonia-is almost totally protonated.Which of the pH values listed below is most likely to be that of the lysosome lumen?

A)1
B)5
C)8
D)14

Question 22

If the equilibrium constant for the reaction A→ B is 0.5 and the initial concentration of A is 25 mM and of B is 12.5 mM,then the reaction:

A)will proceed in the direction it is written,producing a net increase in the concentration of B.
B)will produce energy,which can be used to drive ATP synthesis.
C)will proceed in the reverse direction,producing a net increase in the concentration of A.
D)is at equilibrium.

Question 23

A solution of 8 M urea is sometimes used in the isolation of protein molecules.When the solution is prepared by dissolving urea in water at room temperature,it becomes cold.How should the ΔG for this process change if you tried to dissolve urea in the cold room,rather than at room temperature?

Question 24

Phosphoglucomutase converts glucose 1-phosphate,the product of the reaction catalyzed by glycogen phosphorylase,into glucose 6-phosphate.The Kₑq for this reaction is 19 under standard conditions.What is the ΔG°´ for the reaction?

Question 25

A 1-mL solution of 0.1 M NaOH is diluted to 1 L at 25°C.What is the pH of the resulting solution?

A)1
B)7
C)10
D)13

Question 26

A reaction with a positive ΔG value can be made energetically favorable by increasing the:

A)ΔG°´.
B)starting concentration of products.
C)starting concentration of reactants.
D)The first two answers are correct.

Question 27

In the reaction NAD⁺ + H⁺ + 2e−→ NADH,NAD⁺ becomes:

A)dehydrated.
B)hydrolyzed.
C)oxidized.
D)reduced.

Question 28

Under what conditions is the ΔG for a reaction different from the ΔG°´?

Question 29

In a biochemical reaction in which ΔH < 0 and ΔS > 0:

A)the reaction is spontaneous.
B)the reaction is endothermic.
C)the reaction is endergonic.
D)ΔG is positive.

Question 30

What is the effect of an enzyme on the end equilibrium concentration of reactants and products?

Question 31

A 1-mL solution of 0.05 M H₂SO₄ is diluted to 100 mL at 25°C.What is the pH of the resulting solution?

A)1
B)2
C)3
D)4

Question 32

The ultimate source of chemical energy for all cells is:

A)electricity.
B)heat.
C)light.
D)magnetism.

Question 33

An Archaea cell living in an abandoned mine is found to contain a very high concentration of protons.It is likely that this cell:

A)has a high ph and is acidic.
B)has a high ph and is alkaline.
C)has low ph and is acidic.
D)has a low pH and is alkaline.

Question 34

The enzyme alcohol dehydrogenase is capable of catalyzing the oxidation of a number of different substances,including ethanol,ethylene glycol,and methanol,to an aldehyde.The metabolic products of both ethylene glycol and methanol are highly toxic to humans.A standard medical treatment for prevention of ethylene glycol or methanol poisoning is the administration of a dose of ethanol.Why is this treatment effective?

Question 35

NAD⁺ and FAD are often referred to as:

A)redox proteins.
B)polymers.
C)reduced dinucleotides.
D)electron-carrying coenzymes.

Question 36

Photosynthesis by plants and certain microbes traps the energy in light and uses it to:

A)reduce glucose into carbon dioxide.
B)synthesize ATP from ADP and inorganic phosphate.
C)generate ATP from the oxidation of reduced inorganic compounds.
D)none of the above

Question 37

For the binding reaction A + B→ AB,the dissociation constant is equal to:

A)([AB] / [A])+[B].
B)([A] + [B])/[AB].
C)Kₑq
D)The first and third answers are correct.

Question 38

What is [P]/[R] when ΔG =ΔG°´?

A)-1
B)0
C)1
D)2.3

Question 39

How do cells maintain a relatively constant pH despite the fact that many metabolic processes produce acids?

Question 40

Hydrolysis of ATP:

A)is endothermic.
B)has a positive ΔG value.
C)must be coupled to an energetically favorable reaction.
D)none of the above

Question 41

The amount of free energy released when bonds are broken during a reaction is higher when the molecule has more electronegative atoms.

Question 42

Which of the following is true about an observed change in free energy (ΔG)?

A)Free energy was created when the Big Bang occurred.
B)It can be calculated from the total change in energy,temperature,and change in entropy.
C)If a reaction's free energy is greater than zero,it is likely to happen spontaneously.
D)Free energy is comparable to unusable energy.