Download Practice Exam I

Name_______________
Biology 211
Molecular and Cell Biology
Fall 2001
Practice Exam I
(100 pts.)
Multiple choice (4 points each). For each select the one best answer.
1.
a.
b.
c.
d.
e.
Carbon is well suited to be the backbone of organic molecules because
it can form covalent bonds.
it can bond to up to four other types of atoms.
it can form ionic bonds.
both a and b are correct.
all of the above.
2.
32
P, a radioactive isotope of phosphorus, has
15
a.
b.
c.
d.
e.
an atomic number of 32
an atomic mass of 15
an atomic mass of 47
32 electrons
17 neutrons
3.
a.
b.
c.
d.
Fats are made of
steroids and glycerol
amino acids
fatty acids and glycerol
long polymers of fatty acids
4. If an enzyme is saturated with substrate, the best way to obtain an even faster yield of
products would be to
a. add more of the enzyme
b. heat the solution to 90C
c. add more substrate
d. add a non-competitive inhibitor
e. lower the pH to 2
5.
a.
b.
c.
d.
The chemical formula for glucose is
C6H12O12
C6H12O6
C3H6O3
C5H10O5
6. Of the following elements, which is likely to form the least polar covalent bonds with
hydrogen
a. nitrogen
b. oxygen
c. carbon
d. phosphorus
7. For a reaction with a free energy change G = +0.7 kcal/mole, which of the following
statements is true?
a. the reaction is exergonic
b. the reaction could never take place
c. the reaction is endergonic
d. the reaction has reached equilibrium
8.
a.
b.
c.
d.
The cellular role of phospholipids is to
store energy
catalyze reactions
contain hereditary information
make up membranes
9.
a.
b.
c.
d.
e.
Acids
release hydrogen ions
have a pH value above 7
release hydroxide ions
increase the number of water molecules
both a and b are correct
10. A short sequence of amino acids linked with covalent bonds is a
a. monosaccharide
b. peptide
c. protein
d. lipid
11. ATP
a. is an amino acid
b. is a component of deoxyribonucleic acid
c. is a high energy molecule that can be broken down to ADP and phosphate
d. is more energetic when in the ADP state
12. The difference between one amino acid and another is found in the
a. amino group
b. carboxyl group
c. R group
d. peptide bond
e. carbon atoms
13. Which of the following is an example of hydrolysis?
a. amino acid + amino acid  dipeptide + H20
b. dipeptide + H20  amino acid + amino acid
c. denaturation of a polypeptide
d. two single strands of DNA  DNA double helix
14. The active site of an enzyme
a. is similar to that of any other enzyme
b. is the part of the enzyme where the substrate can fit
c. is only used once
d. is usually not affected by pH or temperature
15. All the chemical reactions that occur in the cell
a. metabolism
b. free energy
c. kinetic energy
d. catabolism
16. (12 points) List the four levels of protein structure and give a brief description of
each.
17. (12 points) Compare the two enzymes pepsin and trypsin whose pH optima are
shown in the graph below.
a. Which one would work better in a slightly alkaline environment?
b. Assuming that the side chains of amino acids that make up the active site are
important for the activity of each of the enzymes, which of the following side chains is
important for the activity of pepsin?
A. -COOH
B. -NH2
C. -CH3
D. -carbonyl
c. List and briefly discuss two other factors that can influence the activity of enzymes.
18. (16 points) In the laboratory, you used the biuret test to identify proteins and peptides.
A purple compound is produced in the presence of proteins. A pink compound is
produced in the presence of peptides. Assume you have three unlabeled tubes containing
solutions. One contains a glucose solution, one contains the enzyme acid phosphatase
and one contains a protein that has been treated with the proteolytic enzyme pepsin in
dilute HCl solution. Design an experiment to distinguish between the three tubes. Be
sure to give the predicted results.