Biochem Test 1

Front 1

carboxyl

Back 1

What is the name of this functional group

Front 2

amido

Back 2

what is the name of this functional group

Front 3

carboxyl

Back 3

What is the class of functional group shown

Front 4

A hydronium ion:

Back 4

is a hydrated proton.
is a hydrated hydrogen ion
has the structure H3O+.
is the usual form of one of the dissociation products of water in solution.

Front 5

The pH of a sample of blood is 7.4. The pH of a sample of gastric juice is 1.4. The blood sample has:

Back 5

a million times lower [H+] than the gastric juice.

Front 6

The aqueous solution with the lowest pH is:
0.1 M HCl.
0.1 M acetic acid (pKa = 4.86).
0.1 M formic acid (pKa = 3.75).
10-13 M NaOH.

Back 6

0.1 M HCl.

Front 7

The four covalent bonds in methane (CH4) are arranged around carbon to give what geometry?

Back 7

tetrahedral

Front 8

What is true of hydrogen bonds?

Back 8

Hydrogen bonds form readily in aqueous solutions
Individual hydrogen bonds are much weaker than covalent bonds.
Hydrogen bonds account for the anomalously high boiling point of water.
In liquid water, the average water molecule forms hydrogen bonds with three to four other water molecules.

Front 9

Hydrophobic interactions:

Back 9

are the driving force in the formation of micelles of amphipathic compounds in water.

Front 10

Which of the following statements about buffers is true?
a. The pH of a buffered solution remains constant no matter how much acid or base is added to the solution.

b. The strongest buffers are those composed of strong acids and strong bases.

c. A buffer composed of a weak acid of pKa = 5 is stronger at pH 4 than at pH 6.

d. When pH = pKa, the weak acid and salt concentrations in a buffer are equal.

Back 10

d. When pH = pKa, the weak acid and salt concentrations in a buffer are equal.

Front 11

The Henderson-Hasselbalch equation:

Back 11

a. relates the pH of a solution to the pKa and the concentrations of acid and salt.

Front 12

What two properties of water are important for biological interactions?

Back 12

the polarity of water and the cohesive properties of water

Front 13

Consider an acetate buffer, initially at the same pH as its pKa (4.76). When sodium hydroxide (NaOH) is mixed with this buffer, the:

Back 13

ratio of acetic acid to sodium acetate in the buffer falls.

Front 14

At a pH of 12, what charged group(s) are present in glycine?

Back 14

COO–

Front 15

The angles of rotation about the peptide bond are called

Back 15

phi and psi.

Front 16

Name three amino acids that are positively charged at a neutral pH.

Back 16

lys, arg, and his

Front 17

The spatial arrangement of protein subunits is called

Back 17

quaternary structure.

Front 18

Why is the peptide bond planar?

Back 18

It contains partial double bond character, preventing rotation.

Front 19

The side chains of nonpolar amino acids are best categorized as:

Back 19

uncharged.

Front 20

In a highly basic solution, pH = 13, the dominant form of glycine is:

Back 20

NH2–CH2–COO-.

Front 21

The peptide alanylglutamylglycylalanylleucine has:

Back 21

four peptide bonds.

Front 22

Which of the following refers to particularly stable arrangements of amino acid residues in a protein that give rise to recurring patterns?

Back 22

secondary structure

Front 23

Which of the following describes the overall three-dimensional folding of a polypeptide?

Back 23

tertiary structure

Front 24

All of the following are considered "weak" interactions in proteins except:
a. van der Waals forces.
b. hydrogen bonds.
c. ionic bonds.
d. peptide bonds.

e. hydrophobic interactions.

Back 24

d. peptide bonds.

Front 25

In the alpha helix the hydrogen bonds:

Back 25

occur mainly between electronegative atoms of the backbone.

Front 26

In an alpha helix, the R groups on the amino acid residues:

Back 26

are found on the outside of the helix spiral.

Front 27

Proteins often have regions that show specific, coherent patterns of folding or function. These regions are called:

Back 27

domains.

Front 28

oligomeric proteins:

Back 28

Some subunits may have nonprotein prosthetic groups.
A subunit may be very similar to other proteins.
Some oligomeric proteins can further associate into large fibers.
Many have regulatory roles.

Front 29

how do enzymes stabilize a transition state?

Back 29

covalent catalysis
using binding energy
general acid-base catalysis
catalysis by approximation

Front 30

A prosthetic group of a protein is a non-protein structure that is:

Back 30

permanently associated with the protein.

Front 31

Enzymes are potent catalysts. They:

Back 31

lower the activation energy for the reactions they catalyze.

Front 32

What is true of enzyme catalysts?

Back 32

They lower the activation energy for conversion of substrate to product.

Front 33

The role of an enzyme in an enzyme-catalyzed reaction is to:

Back 33

increase the rate at which substrate is converted into product.

Front 34

Which of the following statements is false?
a. A reaction may not occur at a detectable rate even though it has a favorable equilibrium
b. At the end of an enzyme-catalyzed reaction, the functional enzyme becomes available to catalyze the reaction again.
c. Substrate binds to an enzyme's active site.
d. For S goes to P, a catalyst shifts the reaction equilibrium to the right.
e. Lowering the temperature of a reaction will lower the reaction rate.

Back 34

d. For S goes to P, a catalyst shifts the reaction equilibrium to the right.

Front 35

Which of the following parameters remains the same for S to P, whether the reaction is enzyme-catalyzed or uncatalyzed?

Back 35

Keq'

Front 36

Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows Michaelis-Menten kinetics is false?
a. Km is the [S] at which V0 = 1/2 Vmax.
b. The shape of the curve is a hyperbola.
c. The y-axis is a rate term with units of mmol/min.
d. As [S] increases, the initial velocity of reaction, V0, also increases.
e. At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km.

Back 36

e. At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km.

Front 37

The Lineweaver-Burk plot is used to:

Back 37

solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration.

Front 38

The double-reciprocal transformation of the Michaelis-Menten equation, also called the Lineweaver-Burk plot, is given by

1/V0 = Km /(Vmax[S]) + 1/Vmax.

To determine Km from a double-reciprocal plot, you would:

Back 38

multiply the reciprocal of the x-axis intercept by -1.

Front 39

The number of substrate molecules converted to product in a given unit of time by a single enzyme molecule at saturation is referred to as the:

Back 39

turnover number.

Front 40

In a plot of l/V against 1/[S] for an enzyme-catalyzed reaction, the presence of a competitive inhibitor will alter the:

Back 40

intercept on the l/[S] axis

Front 41

Which of these statements about enzyme-catalyzed reactions is false?
a. At saturating levels of substrate, the rate of an enzyme-catalyzed reaction is proportional to the enzyme concentration.
b. The Michaelis-Menten constant Km equals the [S] at which V = 1/2 Vmax.
c. If enough substrate is added, the normal Vmax of a reaction can be attained even in the presence of a competitive inhibitor.
d. The rate of a reaction decreases steadily with time as substrate is depleted.
e. The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction.

Back 41

e. The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction.

Front 42

Vmax for an enzyme-catalyzed reaction:

Back 42

is twice the rate observed when the concentration of substrate is equal to the Km.

Front 43

Enzymes differ from other catalysts in that enzymes:

Back 43

usually display specificity toward a single reactant.