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Biochemistry > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

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

A

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

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2
Q

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

A

1 A

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3
Q

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

A

Any polar molecule.

- Ester, amine, phosphate, hydroxyl are all true

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4
Q

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

A

4.00 x 10^-8 M

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5
Q

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?

A

30.2 :1

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6
Q

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?

A

-2

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7
Q

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

A

5.4-7.4 +- 1

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8
Q

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

A

Glycine, the simplest amino acid

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9
Q

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

A

The L isomer only

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10
Q

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

A

Cysteine

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11
Q

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

A

+1

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12
Q

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

A

H20 (always)

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13
Q

Why is the peptide bond planar?

A

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

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14
Q

Name the 2 examples of protein secondary structure

A

Alpha helices and beta sheets

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15
Q

Enzymes accelerate the rate of a chemical reaction by

A

Lowering the free energy of activation

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16
Q

An enzyme will specifically bind its substrate because of

A

A large number of weak interactions at the active site

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17
Q

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?

A

It must be positive

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18
Q

The Km value for an enzyme is

A

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

19
Q

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

A

The Km will not change

20
Q

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

A

Isozyme regulation

21
Q

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?

A

The presence of a Hydroxyl group

22
Q

In competetive inhibition, an inhibitor

A

Binds reversibly at the active site

23
Q

The concept of induced fit refers to the fact that

A

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

24
Q

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

A

A common example of secondary structure in RNA

25
Q

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

A

350 kJ/mol

26
Q

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

A
  • the polarity of hydrogen-oxygen bonds
  • the tetrahedral electron domain geometry of water
  • the bent molecular geometry of water
27
Q

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

A

The H+ decreases by a factor of 1000

28
Q

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

A
  • hydrophobic effect

- increase in the entropy of the water molecules

29
Q

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

A

Hydrophobic

- Leucine

30
Q

Which amino acid contains a thiol group?

A

Cysteine

31
Q

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

A

-2

32
Q

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

A

Phi and psi

- no rotation about peptide bond

33
Q

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

A

spontaneous

34
Q

Enzymes accelerate the rate of a chemical reaction by

A

Lowering the free energy of activation

35
Q

What does noncompetetive inhibition do?

A

Lowers the V max

36
Q

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

A

Prosthetic group - tightly bound

37
Q

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

A

Serine

38
Q

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

A

regulation via isozymes

enzymes that catalyze the same reaction

39
Q

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

A

Covalent bonds

40
Q

An example of nucleic acid quaternary structure would be

A

Interaction of DNA with histone proteins

41
Q

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

A

water

42
Q

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

A

2-4 kJ/mol

43
Q

The bond dissocation energy of a hydrogen bond is

A

4-13 kJ/mol

44
Q

The bond dissociate energy of electrostatic bonds is:

A

5.9 kJ/mol

Biochemistry (7 decks)

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