HOMEWORK #12
CHEM 121, section 1 Winter 2010
Printed Name:
Background for the Chapter. 21. Enzymes and Vitamins.
Homework Feb XX, 2010 by 12:15 PM!
Group Name:
1. How a catalyst does speeds up a chemical reaction?
2. Draw energy diagrams for uncatalyzed and catalyzed reactions.
3. List some characteristics of enzymes.
4. Answers following about the cofactors and coenzymes
a. Explain the difference between the cofactor and coenzyme.
b. Describe the relationships of the following parts of a typical enzyme: cofactor, enzyme,
coenzyme, vitamin, protein.
5. Answers following about the enzymes
a. Explain what is meant by the lock and key theory of enzyme action.
Include: active site, substrate, enzyme.
b. Explain the Induced Fit Model of enzyme action and contrast with the lock and key model.
a. List four factors which may effect how well an enzyme works.
b. From the above factors, list two non-specific enzyme inhibitors. Explain how they inhibit enzyme
action.
c. What happens to the active site and the molecular geometry of the enzyme as it is denatured?
d. Excess of either acid or base causes denaturing of protein. What type of bonds are disrupted by
this action?
e.
Name some other denaturing methods to inhibit or destroy enzyme activity.
f. If an enzyme has been denatured, is it likely that its enzyme activity can be restored? Is the
inhibition reversible or irreversible? Explain.
Ques 7. Briefly define and explain the actions of the following enzyme inhibitors. Give some
examples:
a. reversible competitive inhibitor
b. reversible noncompetitive inhibitor
c. irreversible inhibitor
d. allosteric inhibitor
e. feedback inhibitor
QUES. 8: If the concentration of inhibitor is less than that of the substrate and the substrate has a
higher affinity for the active site, is the enzyme inhibited a lot, or a little?
Ques. 9. MSG (monosodium glutamate) is used for a meat flavoring agent. Only the L optical isomer
is effective. After drawing the mirror image, explain why the D isomer apparently is unable to react
with taste receptor sites on the tongue.
O
+
Na
NH2
H2
C
C
O
C
C
H2
OH
C
H
O
Ethanol is metabolized in the body by oxidation to acetaldehyde, which is in turn further oxidized to
acetic acid by aldehyde oxidase enzymes. Normally, the second reaction is rapid so that
acetaldehyde does not accumulate in the body.
Ques. 10: CH3CH2OH + (0) 
+ (0) 
A drug, disulfiram (Antabuse) inhibits the aldehyde oxidase which causes the accumulation of
acetaldehyde with subsequent unpleasant side-effects of nausea and vomiting. This drug is
sometimes used to help people overcome the drinking habit.
H3 C
CH3
H2C
S
N
C
C
H2C
CH2
S
S
N
CH2
S
H3 C
CH3
QUES. 11: Which part of the disulfiram molecule probably interacts with the active site of aldehyde
oxidase.? Hint: Look for something similar to the -C=O group.
Methanol poisoning occurs because methanol is oxidized to formaldehyde and formic acid which
attack the optic nerve causing blindness. Ethanol is given as an antidote for methanol poisoning
because ethanol competitively inhibits the oxidation of methanol. Ethanol is oxidized in preference to
methanol and consequently, the oxidation of methanol is slowed down so that the toxic by-products
do not have a chance to accumulate.
QUES. 12: Ethylene glycol, if ingested, can be poisonous. Ethylene glycol is oxidized by the same
enzymes used in the previous examples by ethanol and methanol. Describe how ethanol can be
used as an antidote.
H2
C
HO
C
H2
dehydrogenase
OH
ethylene glycol
aldehyde
HO
oxidase
H2
C
O
C
H
O
OH
2-hydroxyethanal
C
O
C
OH
oxalic acid
Ques. 13. In the digestion of food, what do the following enzymes do? Give the substance acted upon
and the final products in words. (Need to look in the index or chap 23 and 25)
amylase,
maltase
lactase
sucrase
lipase
pepsinogen
pepsin
trysin
chymotrypsin
Ques. 14. Enzymes are used for diagnostic testing of health conditions: List 5 enzymes and the
conditions that are measured if elevated.
1. Characterize the function of a catalyst in a chemical reaction.
2. List some characteristics of enzymes.
3. Draw energy diagrams for uncatalyzed and catalyzed reactions.
4. Distinguish between absolute, relative, and stereochemical specificity.
5. Explain the function of cofactors and coenzymes in enzyme catalysis.
6. Distinguish between the six classes of enzymes.
7. Identify the class of an enzyme given the chemical reaction it catalyzes.
8. Interpret a systematic enzyme name.
9. Distinguish between the lock-and-key model and the induced-fit model of
enzyme catalysis.
10. Describe several mechanisms of catalysis.
11. Explain why enzyme assays can be diagnostically useful. Give some
examples.
12. Predict the effects of an increase in the concentration of substrate or enzyme
on the rate of an enzyme catalyzed reaction.
13. Describe the effects of temperature and pH on an enzyme catalyzed reaction.
14. Characterize several modes of enzyme regulation.
15. Distinguish between a positive allosteric regulator and a negative allosteric
regulator.
16. Explain the role of zymogens in enzyme regulation.
17. Distinguish between a competitive enzyme inhibitor and a non-competitive
enzyme inhibitor. Give some examples.
18. Explain the role of genetics in the regulation of enzymatic activity.
19. Explain the connection between enzyme activity and nutrition (specifically
minerals and vitamins).
i. The substrate (S) and enzyme structure (E) come into contact and interact
over a small region of the enzyme surface (active site).
ii. An enzyme-substrate complex (ES) forms when the substrate “bonds” to the
active site via temporary non-covalent interactions or covalent interactions
(less frequent).
iii. The substrate is destabilized in the ES complex lowering the Ea of the
reaction.
iv. The product (P) is released from the enzyme structure and the original form
of the enzyme is regenerated (and ready for another catalytic adventure!).
1. Draw a diagram illustrating the process below. Be sure to include the active site in your
enzyme. Be creative!!
1) E + S ES E + P
2) Give the names of names of pentose sugars written in Fisher projections (linear
form) below.
3) Give the names of names of pentose sugars written in Haworth projections
(cyclic hemiacetal form) below. (Label the carbon atoms)
4) Give the names of names of bases and identify them as purines and pyrimidines
(Label the atoms in the ring)
5) a) What is phosphate and phosphate mono/di-esters?
b) What is a nucleotide?
b)
Draw the structure of dAMP and GMP
6) (3 pts) Draw the following
a) Backbone of a nucleic acid
b) DNA sequence 5'-TGA CGG TAC CC-3'
7) What is the difference between DNA and RNA?
DNA
RNA
number of strands
sugar used
bases used
base pairs
possible locations
full name
8) Write the type of RNA used for each of the following functions:
a) makes up part of the ribosome
b) delivers amino acid to the ribosomes
c) codes for proteins
9) Fill in the table:
Name of process
copying DNA
making RNA from DNA
making protein from RNA
Location
8. What is the name given to the short (610 bp) sequence of bases in the RNA prior to
the start of transcription to which the RNA polymerase binds?
9.
(a) How many nucleotides make up a codon?
(b) How mant different codons are there?
(c) How many different amino acids are there?
10. Write the RNA sequence transcribed from the following DNA sequence. Then
write the amino acid sequence of the protein translated from that RNA.
5'-TGA TTT CGG TAC GAT TAA CAA CCT CGA ATT CC-3'
11. What causes the variation in traits that is the basis for evolution?
12. Why are frequently-dividing cells more prone to mutation?
13.
(a) What is gene expression?
(b) Why is gene expression regulated?
14. For each of the following mutations in the DNA sequence bloiw, show then explain
the effect that the mutation will have on the RNA and protein sequence and, if
applicable, on the protein in general. (The numbers for each mutation below
correspond to the arrows above the sequence.)
5'-TGA TTT CGG TAC GAT TAA CAA CCT CGA ATT CC-3'
1. T in GAT is replaced by C
2. T in TAA is replaced by C
3. first A in TAA is replaced by G
4. C in CAA is replaced by A
5. delete CAA
1. delete T in GAT
Hydrophobic amino acids: glycine, alanine, valine, leucine, isoleucine, phenylalanine,
tryptophan
All others are polar
15. Questions from articles:
(a) The founder of TIGR (The Institute of Genomic Research) is also the founder of
Celera, the private company that last year completed sequencing the human genome
(along with a government group). What is his name?
(b) What organism has the smallest genome known?
(c) How many genes does this bacteria have?:
(d) How many of these genes were found to be necessary for the organism to still be
alive?
(e) What did the bioethicists say about this "minimal genome" research? (What do you
think?)
(f) How many amino acid altering mutations occur in each generation of humans?