Download Chapter 15 Review Worksheet and Key

Chapter 15 Review Worksheet and Key
NOTE: You can view the key in the back of the document
1.
Define the term metabolic pathway.
2.
Explain how it is possible that the initial reactant in glycolysis (glucose) has six
carbons, but the product (acetyl-CoA) has three carbons.
3.
What effect will an enzyme have on the value of ΔG for the reaction?
4.
What provides the energy used to produce ATP from ADP and Pi, anabolism or
catabolism?
5.
Define the term reduction and explain how it applies to the difference in the
structures of NAD+ and NADH.
6.
How does anabolism differ from catabolism in terms of the relative size of the
reactants that enter a particular pathway and the products that leave it?
7.
Write a reaction equation for the hydrolysis of ATP to produce Pi.
1
8.
Where (in the mouth, the stomach, and/or the small intestine) does digestion of
each take place?
a. polysaccharides
b. triglycerides
.
c. proteins
9.
How do the structures of amylose and amylopectin, the two homopolysaccharides
that make up starch, differ?
10.
What is the role of glycolysis?
11.
What compound acts as an inhibitor of glycolysis?
12.
a. What products are formed when pyruvate undergoes alcoholic fermentation?
13.
a. Is the conversion of pyruvate to lactate an oxidation or a reduction?
b. When this reaction takes place in a cell, what is the oxidizing agent?
c. What is the reducing agent?
14.
Is the conversion of pyruvate into acetyl-CoA an oxidation or a reduction?
2
15.
Glycolysis can be described as a process in which energy is invested “up front”
in exchange for a greater return of energy later on. Which steps in glycolysis
involve investment of energy?
16.
Which three steps in glycolysis cannot be directly reversed during
gluconeogenesis?
17.
In the citric acid cycle, is the alcohol group in isocitrate oxidized, or reduced?
Explain.
18.
What is the net change in ATP, NADH, and FADH2 from the passage of two
acetyl-CoA through the citric acid cycle?
19.
a. Which two compounds donate their electrons to electron transport chain?
b. Which molecule is the final electron acceptor of the electron transport chain?
20.
H+ moves from the intermembrane space, through ATP synthase, and into the
mitochondrial matrix. Which term best describes this process: facilitated
diffusion or active transport?
21.
Oxidative phosphorylation typically generates how many ATP from 1 NADH?
22.
Account for the 30-32 ATPs generated when one glucose molecule is catabolized
by glycolysis and the citric acid cycle.
23.
Describe how fatty acid salts are activated in order to undergo β oxidation.
24.
In one pass through the β oxidation spiral a fatty acyl-CoA is shortened by two
carbon atoms. What other products are formed?
3
25.
Calculate the net number of ATPs produced when one 18-carbon fatty acid salt is
activated, enters the mitochondrion, and undergoes complete β oxidation.
Include the ATP formed from acetyl-CoA in the citric acid cycle, and ATP from
all of the reduced coenzymes that are produced.
26.
a. Name the three ketone bodies.
b. Are they all ketones?
27.
What is the source of NH4+ produced during amino acid catabolism?
38.
Oxidative deamination of glutamate produces which compound besides NH4+?
4
Chapter 15 Review Worksheet KEY
1.
Define the term metabolic pathway.
A metabolic pathway is a series of biochemical reactions.
2.
Explain how it is possible that the initial reactant in glycolysis (glucose) has six
carbons, but the product (pyruvate) has three carbons.
Because glucose is split into two 3-carbon compound in steps 4 and 5 of
glycolysis. Ultimately, two pyruvate ions are formed.
3.
What effect will the enzyme have on the value of ΔG for the reaction?
No effect. An enzyme increases the rate of a reaction, but it has no effect on ΔG.
4.
What provides the energy used to produce ATP from ADP and Pi, anabolism or
catabolism?
Catabolism
5.
Define the term reduction and explain how it applies to the difference in the
structures of NAD+ and NADH.
Reduction is the gain of electrons. In organic and biochemical molecules, a gain
of hydrogen and /or a loss of oxygen is indication that reduction has taken place.
NADH, the reduced form of the coenzyme, has one more hydrogen atom than
NAD+, the oxidized form of the coenzyme.
6.
How does anabolism differ from catabolism in terms of the relative size of the
reactants that enter a particular pathway and the products that leave it?
During anabolism small molecules are combined to make larger ones. In
catabolism larger molecules are broken down into smaller ones.
7.
Write a reaction equation for the hydrolysis of ATP to produce Pi.
ATP + H2O à ADP + Pi + H+
8.
Where in the body does digestion of each take place?
d. polysaccharides
Mouth and small intestine.
5
e. triglycerides
Stomach, but mostly in the small intestine.
f. proteins
Stomach and small intestine.
9.
How do the structures of amylose and amylopectin, the two homopolysaccharides
that make up starch, differ?
Amylopectin contains α-(1 → 6) glycosidic bonds. Amylose does not.
10.
What is the role of glycolysis?
Glycolysis converts a glucose molecule into 2 pyruvate ions with accompanying
production of 2 ATP and 2 NADH.
11.
What compound acts as an inhibitor of glycolysis?
ATP
12.
a. What products are formed when pyruvate undergoes alcoholic fermentation?
Ethanol and CO2.
13.
a. Is the conversion of pyruvate to lactate an oxidation or a reduction?
In Figure 15.9, the conversion of pyruvate to lactate shows a ketone being
converted to an alcohol by addition of hydrogen. This indicates reduction has
occurred.
Reduction
b. When this reaction takes place in a cell, what is the oxidizing agent?
The oxidizing agent in a reaction is the substance that is reduced. Therefore,
pyruvate is the oxidizing agent.
Pyruvate
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c. What is the reducing agent?
The NADH is losing hydrogen and an electron. In doing so, it reduces the
pyruvate and it is therefore the reducing agent.
NADH
14.
Is the conversion of pyruvate into acetyl-CoA an oxidation or a reduction?
Oxidation: Organic oxidation is observed as the loss of hydrogen or the gain of
oxygen. The conversion of pyruvate to acetyl-CoA results in the pyruvate losing
hydrogen and an electron to NAD+. Therefore the pyruvate is oxidized.
15.
Glycolysis can be described as a process in which energy is invested “up front”
in exchange for a greater return of energy later on. Which steps in glycolysis
involve investment of energy?
Steps 1 and 3 involve “investment” or input of energy through coupling of the
reaction with ATP hydrolysis.
16.
Which three steps in glycolysis cannot be directly reversed during
gluconeogenesis?
Steps 1, 3, and 10.
17.
In the citric acid cycle, is the alcohol group in isocitrate oxidized, or reduced?
The alcohol is oxidized; it loses hydrogens.
18.
What is the net change in ATP, NADH, and FADH2 from the passage of two
acetyl-CoA through the citric acid cycle?
The passage of two acetyl-CoA through the citric cycle creates 2 ATP, 6
NADH, and 2 FADH2.
19.
a. Which two compounds donate their electrons to electron transport chain?
NADH and FADH2
b. Which molecule is the final electron acceptor of the electron transport chain?
The O2 molecule.
7
20.
H+ moves from the intermembrane space, through ATP synthase, and into the
mitochondrial matrix. Which term best describes this process: facilitated
diffusion or active transport?
Facilitated diffusion is the process of ions or molecules moving through a
membrane assisted by a protein. The hydrogens move through this enzyme
because of the concentration gradient. No additional external energy is required.
Facilitated diffusion
21.
Oxidative phosphorylation typically generates how many ATP from 1 NADH?
2.5 ATP
22.
Account for the 30-32 ATPs generated when one glucose molecule is catabolized
by glycolysis and the citric acid cycle.
In glycolysis, one glucose molecule yields 2 pyruvates, 2 ATP and 2 NADH.
Depending on the system used to shuttle the electrons from NADH into
mitochondria, these 2 NADH become 2 NADH or 2 FADH2. Converting the 2
pyruvates into 2 acetyl-CoA’s produces 2 NADH.
Two passes through the citric acid cycle starting with acetyl-CoA produces
2 ATP, 2 FADH2, and 6 NADH.
In the electron transport chain, each FADH2 generates 1.5 ATP and each NADH
generates 2.5 ATP.
23.
Describe how fatty acid salts are activated in order to undergo β oxidation.
Fatty acid salts are activated by the attachment of a coenzyme A (CoA) residue to
produce fatty acyl-CoA.
24.
In one pass through the β oxidation spiral a fatty acyl-CoA is shortened by two
carbon atoms. What other products are formed?
One acetyl-CoA, one FADH2, and one NADH
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25.
Calculate the net number of ATPs produced when one 18-carbon fatty acid salt is
activated, enters the mitochondrion, and undergoes complete β oxidation.
Include the ATP formed from acetyl-CoA in the citric acid cycle, and ATP from
all of the reduced coenzymes that are produced.
Activation in the first step consumes on ATP. Each step in the spiral produces
one FADH2 , one NADH and one acetyl-CoA. The number of passes = (number
of carbons – 2)/2 so for an 18-carbon fatty acid salt there are (18-2)/2 = 8. The
NADH and FADH2 produced in these passes produces ATP as follows:
.
FADH2
8 x 1.5 = 12 ATP
NADH
8 x 2.5 = 20 ATP
Total from β oxidation reactions = 32 ATP
Then, since two ATPs are generated in the final cycle, a total of 9 acetyl-CoA
enter the citric cycle.
The ATP produced as these 9 acetyl-CoA undergo the reactions of the citric acid
cycle is calculated as follows:
9 Acetyl-CoA (1 ATP per citric acid cycle) = 9 ATP
NADH
(9 x 3) x 2.5 = 67.5 ATP
FADH2
9 x 1.5 = 13.5 ATP
Total ATP produced from acetyl CoA = (9 + 67.5 + 13.5) = 90 ATP
Total ATP for reaction =
Total from β oxidation reactions + Total of citric cycle - Activation
= 32 ATP + 90 ATP – 1 ATP
= 121 ATP
Total ATPs produced = 121
26.
a. Name the three ketone bodies.
Acetoacetate, 3-hydroxybutyrate, and acetone
b. Are they all ketones?
No. 3-Hydroxybutyrate contains does not contain the ketone bonding
pattern.
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27.
What is the source of NH4+ produced during amino acid catabolism?
The release of NH4+ from amino acids commonly requires two reactions. The first
is transamination, wherein an amino group from an amino acid is transferred to an
α-keto acid. The second is oxidative deamination, wherein the amino group is
replaced by a carbonyl group. The amino group is released as NH4+.
Oxidative deamination
38.
Oxidative deamination of glutamate produces which compound besides NH4+?
α-ketoglutarate
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