Exam (elaborations)
CHEM 301 Biochem Final Exam Practice Questions and Answers
CHEM 301 Biochem Final Exam Practice
Questions and Answers
For metabolism in multicellular organisms to proceed efficiently, it is important that the final products
be gases, water, or both. Why? - ANSWER-To maintain metabolism in a steady state, there must be
no possibility of a build-up of fi...
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CHEM 301 Biochem Final Exam Practice
Questions and Answers
For metabolism in multicellular organisms to proceed efficiently, it is important that the final products
be gases, water, or both. Why? - ANSWER✔✔-To maintain metabolism in a steady state, there must be
no possibility of a build-up of final products. The easiest disposal products are the multicellular
organism's universal solvent, gases, or both.
Compare the tendency of NADH to donate electrons and the tendency of oxygen to accept them. If
NADH and oxygen are mixed, will the electrons stay with NADH or go to oxygen? - ANSWER✔✔-If NADH
and oxygen are mixed, electrons will be transferred from NADH to oxygen with the release of
considerable energy:
NADH + ADH + ½ O2 + H+ ↔ NAD+ + H2O εo′ = 1.13 V
What structural feature do the "high-energy" compounds ATP, FADH2, and NADH share with acetyl-CoA?
- ANSWER✔✔-The "high-energy" compounds share an ADP unit or, in the case of acetyl-CoA, a closely
related derivative.
What is an anabolic process? - ANSWER✔✔-a biochemical reaction that synthesizes larger molecules
from smaller molecules. They are reductive in nature.
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What is a catabolic process? - ANSWER✔✔-An oxidative process. A larger molecule is broken down into
smaller ones. They are the primary energy source for heterotrophic organisms.
Reductive processes require... - ANSWER✔✔-electron sources such as NADPH, NADH, or FADH2
Oxidative processes require... - ANSWER✔✔-electron carriers such as NAD+, NADP+, or FAD
Glycolysis is controlled by... - ANSWER✔✔--how fast glucose flows into the cell
-how quickly pyruvate can be used up
-whether any of the ten "products" are diverted to other reactions
-the concentration of catalysts that control the ten reactions
-feedback loops in which products of the ten reactions regulate preceding reactions
3 categories of organic reactions that occur in vivo - ANSWER✔✔--oxidative and reductive
-elimination, isomerization, and rearrangement reactions
-group transfer reactions
What makes a high energy compound? - ANSWER✔✔-The magnitude of ΔGo′ of hydrolysis and the
redox potential
The more negative ΔGo′... - ANSWER✔✔-The greater the energy release and therefore the greater
energy in the original bond
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The energy released comes from 3 sources: - ANSWER✔✔--resonance: more structures for products
-electrostatic repulsion: lower in products than reactants
-entropy: greater for products
The greater the gain in resonance stabilization... - ANSWER✔✔-the greater relief from electrostatic
repulsion and the greater gain in entropy produced by a chemical change, the greater the energy
released.
What does εo′ represent? - ANSWER✔✔-The redox potential of compounds in a standard state.
Glycolysis is inhibited by iodoacetic acid through inactivation of the enzyme glyceraldehyde-3-phosphate
dehydrogenase (GAPDH). As a result, there is an accumulation of fructose-1,6-biphosphate. Why is this
product more prevalent than glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, the
products that form immediately preceding GAPDH? - ANSWER✔✔-The reaction that converts fructose
1,6-bisphosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate is near equilibrium in
vivo (i.e., ΔG near zero), while the preceding reaction producing fructose 1,6-bisphosphate is not.
Therefore it is F1,6BP that will accumulate, not glyceraldehyde-3-phosphate and dihydroxyacetone
phosphate.
The "Pasteur effect" is the dramatic decrease in glucose consumption when oxygen is introduced to an
anaerobic fermentation broth. Why do the yeast cells use less glucose after oxygen is introduced? How
much less glucose do they use after oxygen is introduced? - ANSWER✔✔-The introduction of oxygen
allows yeast to convert from anaerobic to aerobic metabolism. Since aerobic metabolism provides more
ATP, the amount of glucose that must be used to nourish the yeast is much less. Approximately 6% of the
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glucose metabolized anaerobically is needed to provide the same amount of energy under aerobic
conditions.
Why do you get hot when you exercise? - ANSWER✔✔-PEP (phosphoenolpyruvate) is a very high-energy
compound. The reaction that converts PEP to pyruvate is so highly energetically favourable (very
negative ΔG) that there is almost enough energy in PEP to stimulate production of a second ATP through
substrate level phosphorylation, but it is not used. The excess energy is lost as heat.
What are the three enzymes that are regulated in glycolysis? How does AMP affect glycolysis? -
ANSWER✔✔-The three enzymes that are regulated in glycolysis are: hexokinase, phosphofructokinase
(PFK), and pyruvate kinase. High amounts of AMP activate PFK and pyruvate kinase, which stimulate
glycolysis because ATP is needed.
List the possible uses of pyruvate. - ANSWER✔✔-The possible uses of pyruvate are:
- ATP production and NAD+ regeneration through TCA cycle and electron transport
- glucose synthesis by gluconeogenesis
- ATP production and NAD+ generation and lactate or ethanol production by fermentation
- alanine synthesis
- oxaloacetate synthesis
What does the liver do with the lactate that is produced during heavy exercise? - ANSWER✔✔-During
heavy exercise, the body needs ATP and generates lactate through anaerobic respiration faster than the
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