Exam 1

Question 1

What types of atoms in biological molecules are commonly found as hydrogen bond acceptors?

Answer 1

Nitrogen and Oxygen - highly electronegative with a lone pair of electrons

Question 2

What is the approximate distance of a van der waals interaction?

Answer 2

1 A

Question 3

What functional groups would increase the solubility of a molecule in water?

Answer 3

Any polar molecule.

- Ester, amine, phosphate, hydroxyl are all true

Question 4

What is the concentration of protons in a solution with a pH of 7.4?

Answer 4

4.00 x 10^-8 M

Question 5

Aspirin is a weak acid with a pKa of 3.52. If aspirin is dissolved in water and the pH of the solution adjusted to 4, what is the ratio of the conjugate base to the acid in the solution?

Answer 5

30.2 :1

Question 6

Alpha-ketoglutarate has two carboxylic acid groups with pKa values of 2.47 and 4.68. What would be the charge on an alpha-ketoglutarate molecule in the cytoplasm of the cell where the pH is approximately 7.2?

Answer 6

-2

Question 7

A mixture of a weak acid (pKa 6.4) would have a good buffer around which pH values?

Answer 7

5.4-7.4 +- 1

Question 8

Which of the amino acids does not contain a chiral carbon atom?

Answer 8

Glycine, the simplest amino acid

Question 9

The isomer of amino acids that is found in proteins in living organisms is:

Answer 9

The L isomer only

Question 10

Which of the following amino acids does no contain a hydroxyl group?

Answer 10

Cysteine

Question 11

What would be the overall charge on the amino acid histidine at pH 5.0?

Answer 11

+1

Question 12

When a peptide bond is formed between two amino acids, what molecule is lost?

Answer 12

H20 (always)

Question 13

Why is the peptide bond planar?

Answer 13

It exhibits partial double-bond character which prevents rotation (sp2 hybridization)

Question 14

Name the 2 examples of protein secondary structure

Answer 14

Alpha helices and beta sheets

Question 15

Enzymes accelerate the rate of a chemical reaction by

Answer 15

Lowering the free energy of activation

Question 16

An enzyme will specifically bind its substrate because of

Answer 16

A large number of weak interactions at the active site

Question 17

The conversion of g6p to f6p is catalyze by an isomerase enzyme. If the value of Keq for the reaction is 0.50, what can be said about the value of delta g?

Answer 17

It must be positive

Question 18

The Km value for an enzyme is

Answer 18

Equal to the substrate concentration when the reaction rate is half it maximal value

Question 19

Addition of a non competitive inhibitor to an enzyme catalyzed reaction will have what effect on Km for the substrate?

Answer 19

The Km will not change

Question 20

Hexokinase and glucokinase are different variation of an enzyme and catalyze the same reaction. THis would be an example of what type of regulation?

Answer 20

Isozyme regulation

Question 21

Phosphorylation is an example of a covalent, reversible modification. One of the amino aicd residues that can udnergo phosphorylation is tyrosine. Which feature of tyrosine makes it an acceptable substrate for phosphorylation?

Answer 21

The presence of a Hydroxyl group

Question 22

In competetive inhibition, an inhibitor

Answer 22

Binds reversibly at the active site

Question 23

The concept of induced fit refers to the fact that

Answer 23

substrate binding may induce a conformational change in the enzyme, which facilitates catalysis

Question 24

Which of the following best describes a stem and loop structure?

Answer 24

A common example of secondary structure in RNA

Question 25

What is the average bond dissociation energy associated with a covalent bond?

Answer 25

350 kJ/mol

Question 26

Which of the following characteristics of water contributes to the polarity of water molecules?

Answer 26

- the polarity of hydrogen-oxygen bonds - the tetrahedral electron domain geometry of water - the bent molecular geometry of water

Question 27

If the pH of a solution changes by 3, (5-8) how does the H+ concentration in the solution change?

Answer 27

The H+ decreases by a factor of 1000

Question 28

Spontaneous association of nonpolar molecules in a water is driven by the ____- which is facilitated by a ______

Answer 28

- hydrophobic effect | - increase in the entropy of the water molecules

Question 29

Which amino acid would you predict to most likely find on the interior of a protein?

Answer 29

Hydrophobic | - Leucine

Question 30

Which amino acid contains a thiol group?

Answer 30

Cysteine

Question 31

What would be the overall charge on the amino acid tyrosine at pH = 12?

Answer 31

-2

Question 32

A ramachandran plot shows regions of allowed combinations of what bond angles in the primary structure?

Answer 32

Phi and psi | - no rotation about peptide bond

Question 33

If the value of the Gibbs free energy change for a reaction is negative, the reaction is

Answer 33

spontaneous

Question 34

Enzymes accelerate the rate of a chemical reaction by

Answer 34

Lowering the free energy of activation

Question 35

What does noncompetetive inhibition do?

Answer 35

Lowers the V max

Question 36

Hemoglobin contains the tightly bound, iron containing protoporphyrin heme. Heme would best be classified as a

Answer 36

Prosthetic group - tightly bound

Question 37

Enzyme activity is often regulated via phosphorylation. Which amino acid residue would you expect to be a site of phosphorylation in a protein?

Answer 37

Serine

Question 38

Two enzymes catalyze the same reaction. The enzymes are located in different cell types in the body, have 2 different values of Km. and are regulated via different mechanisms. These two enzymes would be an example of

Answer 38

regulation via isozymes | enzymes that catalyze the same reaction

Question 39

Which types of bonds contribute to the stability of nucleic acid primary structure?

Answer 39

Covalent bonds

Question 40

An example of nucleic acid quaternary structure would be

Answer 40

Interaction of DNA with histone proteins

Question 41

During the condensation of mono nucleotides to form an oligonucleotide a molecule of ____ is lost

Answer 41

water

Question 42

The bond dissociation energy for a van der Waals interaction is approximately

Answer 42

2-4 kJ/mol

Question 43

The bond dissocation energy of a hydrogen bond is

Answer 43

4-13 kJ/mol

Question 44

The bond dissociate energy of electrostatic bonds is:

Answer 44

5.9 kJ/mol