Exam 1 Sample Questions
Cell Biology
Fall 2001 Lantz
Multiple choice. Circle the letter next to the best answer.
1. Digestive enzymes (e.g. proteases) located within the _________________ are optimally
active in the acidic conditions (pH ~5) maintained within this organelle.
A.
B.
C.
D.
E.
lysosome
mitochondrium
peroxisome
Golgi apparatus
endoplasmic reticulum
2. Which of the following statements is false?
A.
B.
C.
D.
All eubacteria contain ribosomes.
Some procaryotic cells (e.g. archaebacteria) contain a nucleus.
All procaryotic cells lack lysosomes.
All procaryotic cells lack mitochondria.
3. The tertiary structure or overall conformation of a protein is influenced by all of the
following except:
A.
B.
C.
D.
E.
hydrogen bonds
disulfide bonds (S-S bonds)
hydrophobic interactions
interactions between amino acid side chains
all of the above influence the tertiary structure
4. Triglycerides (triacylglycerols):
A.
B.
C.
D.
are hydrophilic molecules that are soluble in water.
do not form hydrogen-bonds with water.
contain C, O, N, and H
are major components of cell membranes.
5. Nucleotides are covalently linked to form nucleic acids by the formation of a
_____________ between the phosphate on the 5'C of one pentose and the 3'-OH on another.
A.
B.
C.
D.
phosphoanhydride bond
pyrophosphate bond.
phosphodiester bond.
acyl phosphate bond.
Name ____________________________
6. All plant and animal cells obtain their energy by _________________ organic molecules
(e.g. sugars, proteins, fats).
A.
B.
C.
D.
phosphorylating
hydrating
oxidizing
reducing
7. Which of the following statements is true?
A. RNA usually occurs in the cell as a double-stranded molecule composed of two
polynucleotide chains
B. RNA contains a pyrimidine not present in DNA
C. RNA lacks a hydroxyl group at the 2 carbon of its pentose sugar
D. none of the above statements are true.
8. An enzyme accelerates a metabolic reaction by:
A.
B.
C.
D.
9.
altering the overall free-energy change for the reaction
making an endergonic reaction occur spontaneously
lowering the activation energy
pushing the reaction away from equilibrium
In the branched metabolic pathway diagramed below, a dotted arrow with a minus sign
symbolizes inhibition of a metabolic step by an end-product. Which reaction would prevail
if both Q and S arepresent in the cell in high concentrations?
_
A.
B.
C.
D.
E.
LM
MO
LN
OP
RS
_
Q
P
M
L
O
R
N
_
S
10. Among solutions with the following pH values, the one that has the greatest
concentration of protons (H+) is the one with a pH value of:
A.
B.
C.
E.
3
7
10
12
Name ____________________________
For questions 11-14, fill in the blanks
11. _______________________________ is the process whereby a relatively unspecialized cell
(e.g. fertilized egg cell) undergoes a change becoming a more specialized cell (e.g. nerve
cell)
12. _______________________________ reactions involve the degradation of larger molecules
to smaller molecules with production of useful energy.
13. _______________________________ are polymers constructed by covalently linking small
organic molecules (e.g. nucleotides, amino acids, or polysaccharides) into long chains.
14. _______________________________ are small molecules that frequently associate with the
active site of an enzyme and assist with its catalytic function.
For question 15, fill in the blanks with the correct word or phrase selected from the list below.
Use each word or phrase only once.
15. a.
____________________________ assist in the proper folding and assembly of proteins
into their correct conformation.
b.
Chemical bond energy derived from exergonic reactions (e.g. the catabolic breakdown
of food) is often temporarily stored in molecules called
_______________________________.
c.
The process where plants and animals obtain energy by the oxidation of
organic molecules is called ________________________________.
d.
The study of how organisms manage their energy resources is called
___________________________________.
e.
The nucleotide ________________________________ is abbreviated dTTP.
f.
For any chemical reaction to proceed spontaneously, the G must be
_______________________________.
catalysts; bioenergetics; enzyme kinetics; cellular physiology; deoxythymine triphosphate;
activated carriers; deoxyribothymine triphosphate; chaperones; cofactors; deoxythymidine
triphosphate; positive; negative; zero; cellular respiration; photosynthesis; reduction
16. In biology, questions about the present are inescapably linked to questions about the past.
Which one of the three tenets of the cell theory best clarifies this statement?
Name ____________________________
17. Describe how cells use coupled reactions to obtain chemical energy in a useful form (i.e.
describe energy coupling).
18. Describe one mechanism that enzymes use to speed up the reactions they catalyze (i.e. how
do enzymes specifically alter/interact with their substrate so that product formation is likely
to occur?)
19. Denaturation typically destroys a protein's binding site, a region of the protein that
associates with a ligand. What does this indicate about the arrangement of amino acids that
make up the binding site (i.e. their relative positions along the polypeptide chain)?
Name ____________________________
20. Protein structure can be described at several levels of organization. Name and briefly
describe the four levels of protein organization. You may use simple illustrations as part of
your answer
21. Use the model of the protein below to answer the following questions.
a. name the type of secondary
structure indicated by the arrow.
b. what types of bond is involved
in forming this type of secondary
structure?
c. Explain at a molecular level why
elements of secondary structure
are common folding patterns in proteins.
Name ____________________________
22. Use the structure below to answer the following questions.
a. What is the name of the bond that links
these glucose monomers together?
b. If a larger polymer were made by
linking glucose together in a similar way,
could this polymer be used by animal or
plants cells as a source of energy? Briefly
explain.
23. Use the photograph to the right to answer the
following questions.
ribosomes
a. what is the name of the organelle to which
the ribosomes are attached?
b. what type of microscope was used to generate
this image? Be very specific.
24. As diagramed below, a protein can be modified by the attachment (reaction X) or removal
(reaction Y) of a phosphate group. Use the diagram below to answer the following questions.
a. name the type of enzyme which catalyzes
reaction X.
b. name the type of enzyme which catalyzes
reaction Y.
X
c. in addition to serine, what other amino
acid(s) can be modified by phosphate addition?
Y
d. describe in one sentence how reaction X or Y
changes a protein's function.
Name ____________________________
25. You are interested in determining the effect of molecule X on the kinetics of an enzyme
reaction. You first determined the rate at which the enzyme catalyzes a reaction by
measuring the amount of product formed in a series of incubation mixtures that contained
the same amount of enzyme but an increasing concentration of substrate. You then
performed a similar experiment that included a fixed concentration of molecule X in the
incubation mixtures. The results are plotted below.
without molecule X
Answer the following questions.
b. If molecule X binds noncovalently to the
enzyme, what type of inhibitor is molecule
X? Be very specific.
c. The region on the enzyme to which
molecule X binds is called the
_______________________________.
12
Initial rate of reaction
a. What is the Vmax of the enzymatic reaction
in the presence of molecule X?
10
8
6
4
2
with molecule X
0
0
2
4
6
8 10 12
Concentration of substrate (M)
26. Draw the complete structure of a dipeptide (two amino acids linked by a peptide bond) that
has methionne (-CH2-CH2-S-CH3) at its N-terminus, and alanine (-CH3) at its C-terminus.
The amino acid side chains are shown in parentheses. Use an arrow to indicate the exact
location of the peptide bond.