Chemistry 30B_Spring 2009
Note to students: The answers to these questions are detailed as this is
considered an open book assignment. Use this key as a worksheet for final
exam and you can simplify the answers in your own words, if you need to!
Generation of Biochemical Energy and Krebs cycle:
1. Distinguish between cyclic vs spiral metabolic pathways?
A metabolic pathway in which a molecule is progressively built up/broken by repeated
interaction with the same set of enzymes is a spiral pathway.
A metabolic pathway in which a series of steps, each using different enzymes,
regenerates one of the early reactants, is a cyclic pathway.
2. Which sequence illustrates the order of the steps from food to biochemically useful
energy?
A) digestion, citric acid cycle, ATP production, acetyl-ScoA production
B) digestion, citric acid cycle, acetyl-ScoA production, ATP production
C) citric acid cycle, digestion, acetyl-ScoA production, ATP production
D) digestion, acetyl-ScoA production, citric acid cycle, ATP production
E) digestion, acetyl-ScoA production, ATP production, citric acid cycle
3. Why is ATP is so useful as a biochemical energy transport molecule?
The text is not real explicit on this, but it is the one molecule that can be used by all
cells in the body. Other texts use the term "universal energy currency " for cells.
ATP is only hydrolyzed slowly in the absence of the correct enzymes. This means it is a
stable energy storage molecule and the release of its energy can be carefully
controlled.
4. The reaction in which ATP is converted to ADP with release of 7.3 kcal is a(an)
Hydrolysis reaction. Exergonic. (Use text to draw an exergonic curve. Use arrows to
show Eact and G on the graph)
5. Below are two sets of molecules? Circle the one that has higher energy.
ADP, CO2, NAD+, FAD
ATP, acetyl-SCoA, NADH, FADH2
Citic Acid Cycle:
1. In the Citric Acid (Krebs) cycle, which enzyme catalyzes a hydration reaction?
Fumarase
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Chemistry 30B_Spring 2009
2. In the Citric Acid cycle the carbon-carbon bond formation reaction is catalyzed
by: citrate synthase (Lyase)
3. How many ATP molecules are generated per turn of the Krebs cycle? What
other type of energy molecules and chemical waste are also generated?
1 ATP per turn
4 Reduced Coenzymes
2 CO2
4. Match the left and the right hand side:
Catabolism (D)
anabolism (B)
ADP(A)
Digestion (C)
ATP (E)
citric acid cycle (H)
acetyl-ScoA(G)
A) a molecule which can be phosphorylated as
a means of temporarily storing energy
B) metabolic processes which consume
energy in order to build molecules
C) the stage of catabolism in which complex
food molecules are broken down into
simpler substances for transport and/or
further reaction
D) metabolic processes that break down large
molecules, thereby releasing energy
E) the universal energy currency of the cell; a
molecule used to transfer energy
F) the stage of catabolism in which the energy
stored in reduced coenzymes is converted
to ATP
G) the molecule produced from digestion
products in the second stage of catabolism
H) the stage of catabolism in which acetyleSCoA is oxidized to produce ATP, reduced
coenzymes, and CO2
electron transport chain (F)
5. State the reactants and the products for the citric acid cycle (you need not mention
any intermediate substarte names)
The reactants for the citric acid cycle for 1 acetyl group: 3 NAD+, 1 FAD, 1 ADP, and 1
Pi (inorganic phosphates are often shown as this notation). Products are HS-CoA, 3
NADH, 1FADH2, 1 ATP.
(the intermediates are not listed as the reactants)
Note: 2 acetyl-SCoA molecules are produced from each glucose molecule, so two
cycles are required per glucose molecule.
6. State the total number of NADH and FADH2 produced for each acetyl-CoA that enters
the citric acid cycle.
Products of one turn of the cycle are: one GTP (or ATP), three NADH, one FADH2.
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Chemistry 30B_Spring 2009
Glycolysis:
*1. What are the reactants and products of Glycolysis?
The reactants of glycolysis are glucose , 2 NAD+, 2 ADP, and 2 inorganic phosphates
(also written as 2Pi in textbooks).
The products of glycolysis are 2 pyruvate , 2 NADH, 2 H+, and 2 net ATP. 2H2O also
produced.
2. Which molecule/s is most likely to be used in a reaction coupled with the reaction
shown below?
glucose  glucose-6-phosphate
ATP (this is a phosphorylation reaction)
3. What is the total number and the net number of ATP produced by during glycolysis.?
A total of 4 ATP are produced by phosphorylation during glycolysis, but since 2 ATP
were used in steps 1 and 3, the net total is 2 ATP.
4. Why is Glycolysis considered a catabolic pathway? Because it is a set of reactions that
breaks food down into biochemical energy
5. Conversion of dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate is a(n)
isomerization reaction
Fatty Acid Metabolism:
1. What is a beta-oxidation?
the catabolic reaction in which fatty acids are broken down two carbons at a time
2. Where in the cell does beta-oxidation of fatty acids (i.e energy generation) occur?
MitoChondria
3. What is meant by the activation of fatty acids before beta-oxidation begins?
Conversion of Fatty Acid to Fatty Acid-Acyl-Co-A (esterification of an acid)
4. Which has greater "energy density," carbohydrates or fats. Explain your answer in
terms of molecular structure and net energy production.
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Chemistry 30B_Spring 2009
Fats have a greater energy density than carbohydrates. Fats provide nine Calories
energy per gram, and carbohydrates only four Calories per gram. One reason for this
is that one gram of fat contains more molecules of fat than a gram of carbohydrates
because the molecules fit together more closely and because the carbohydrates are
hydrophilic and may include some water in their overall structure. In addition, in
considering a carbohydrate and a fat of similar molecular mass, the fat contains more
carbon atoms and those carbon atoms are more highly reduced (and therefore of
higher energy) than the carbon atoms in the carbohydrate.
5. Calculate the energy released for oxidation of Lauric acid (12 Carbon acid)?
[Assume each NADH produces app 2.5 ATP’s and each FADH2 produces 1.5 ATP, Assume
2 ATP’s needed for the first activation step]
A. First, calculate the number of acetyl-Sco-A that can be produced from Lauric Acid.
(We do this by taking the number of carbon atoms in the acid and divide by 2.)
This is 6 Acetyl-Sco-A’s
B. Then each Acetyl-Sco-A will produce 1 ATP, 3NADH, and 1 FADH2 (Citirc A. cycle)
Using the info provided this is 10 ATP’s from 1 Acetyl Sco-A
So total number of ATP’ s now is 60 (from 6 acetyl-sco-A)
C. Then, recall that for Lauric Acid there are 5 turns of beta-oxdn. This is 20 ATP’s.
D. Total: [60 ATP + 20 ATP] produced – 2 ATP (used in first step of activation) = 78
ATP’s NET
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