Exam 3 W23

Question 1

The reaction that converts the molecule shown below into its ketose isomer is catalyzed by
1. Glycerol 3-phosphate dehydrogenase
2. GAPDH
3. aldolase
4. triose phosphate isomerase
5. glycerol kinase

Answer 1

4. triose phosphate isomerase

Question 2

The enzyme in beta-oxidation that is localized in the inner mitochondrial membrane uses which of the following cofactors?
NAD(P)H
fatty acyl-CoA
CoA-SH
FAD
NAD+

Answer 2

FAD

Question 3

Which of the following is NOT an appropriate response to insulin secretion?
1. Decrease in blood glucose levels
2. Increase in glycolysis
3. Phosphorylation of enzymes involved in glucose metabolism
3. Activation of glycogen synthesis
4. Increase in the oxidative phase of the pentose phosphate pathway

Answer 3

Phosphorylation of enzymes involved in glucose metabolism

Question 4

In the metabolism of poly-unsaturated fatty acids, the first double bond is handled, metabolically speaking, similar to the oxidation of mono-unsaturated fatty acids. However, the handling of the second double bond encountered in poly-unsaturated fatty acids requires the investment of
1. Acetyl-CoA
2. reducing equivalents (electrons)
3. ATP
4. NAD(P)+

Answer 4

2. reducing equivalents (electrons)

Question 5

The fumarase-catalyzed reaction in the citric acid cycle is part of a sequence of three chemical steps also seen in another pathway. In the other pathway, what type of enzyme catalyzes the equivalent of the fumarase-catalyzed reaction?
hydratase
lactonase
enolase
aconitase
aldolase

Answer 5

hydratase

Question 6

An example of a substrate-level phosphorylation reaction that occurs efficiently only under aerobic conditions is catalyzed by the enzyme
Citrate synthase
Hexokinase
phosphoglycerate kinase
pyruvate kinase
succinyl CoA synthetase

Answer 6

succinyl CoA synthetase

Question 7

Oxidation of what specific type of fatty acids involves a unique free radical-based mechanism? Fatty acids containing
1. mono-unsaturated even-numbered carbons
2. odd-numbered carbons
3. fully saturated, even-numbered carbons
4. poly-unsaturated, even-numbered
5. carbons long-chains

Answer 7

odd number carbons

Question 8

The glyoxylate cycle allows the use of acetyl CoA for gluconeogenesis via the formation of the following citric acid intermediates
alpha ketoglutarate
citrate
glycolate
isocitrate
succinate

Answer 8

succinate

Question 9

What is FALSE about glycogen synthesis?
1. it happens in the skeletal muscles
2. It can be regulated by insulin AND glucagon
3. Two glucose-UDP molecules react to form an α1–>4 linkage using the enzyme glycogen synthase
4.It involves glycogenin
5. It happens in the liver

Answer 9

Two glucose-UDP molecules react to form an α1–>4 linkage using the enzyme glycogen synthase

Question 10

The principle behind using PET scans (with a radiolabeled glucose analog) to diagnose cancer metastasis is as follows:
1. the pentose phosphate pathway is slower in cancer cells compared to normal cells
2. cancer cells take in more glucose from the blood compared to normal cells
3. cancer cells have a greater affinity for radioactive compounds compared to normal cells
4. glycolytic enzymes are expressed less in cancer cells than normal cells
5. tissue density of the tumor is different than that of the surrounding normal tissue

Answer 10

cancer cells take in more glucose from the blood compared to normal cells

Question 11

Select the TRUE statement
1.In fermentation, pyruvate is oxidized to lactate.
2. Dehydrogenase enzymes remove both two electrons and two hydrogen atoms from the same molecule.
3.Reduction of a compound involves the removal of hydride ions from it.
4.Oxidation of a compound involves addition of electrons to it.
5.In a redox reaction, there is a transfer of electrons from one molecule/atom/ion to another.

Answer 11

In a redox reaction, there is a transfer of electrons from one molecule/atom/ion to another.

Question 12

Glycolysis fails to occur under conditions lacking inorganic phosphate. The failure of which enzyme under these conditions is responsible for the failure of glycolysis?
Hexokinase
Glyceraldehyde 3-phosphate
dehydrogenase pyruvate kinase
phosphoglycerate
kinase PFK-1

Answer 12

Glyceraldehyde 3-phosphate

Question 13

What is FALSE about the lipoate involved in the pyruvate dehydrogenase complex?
1. It is covalently bonded to a lysine residue on an enzyme
2. It can participate in redox catalysis
3. It helps catalyze the decarboxylation of pyruvate to acetaldehyde
4. It can participate in acetyl group transfer
5. It can participate in thioester bond formation

Answer 13

3. It helps catalyze the decarboxylation of pyruvate to acetaldehyde

Question 14

Gluconeogenesis in animals
1. requires the action of pyruvate kinase 2. cannot convert amino acids to glucose.
3. cannot be achieved starting from fatty acids.
4. is increased after a sugary meal.
5. is inactivated by the hormone glucagon

Answer 14

3. cannot be achieved starting from fatty acids.

Question 15

Which one is NOT a defining feature of a committed step of a pathway
1. It is the only irreversible reaction in the pathway
2. It is a highly regulated step in the pathway
3. The reaction has a free energy change in the cell that is negative
4. Most feed-in metabolites enter the pathway before this step
5. It must be a spontaneous reaction under the conditions of the ce

Answer 15

1. It is the only irreversible reaction in the pathway

Question 16

What monosaccharide products do you expect from a mixture of a 5-carbon and a 4-carbon-containing sugar-phosphate substrate in the presence of a transketolase enzyme?
6 and 5 carbon containing sugar phosphate
4 and 3 carbon containing sugar phosphate
7 and 2 carbon containing sugar phosphates
6 and 3 carbon containing sugar phosphates
One 9 carbon containing sugar phosphate

Answer 16

6 and 3 carbon containing sugar phosphates

Question 17

The primary purpose of the oxidative phase of the pentose phosphate pathway is to:
1. provide intermediates for the citric acid cycle.
2. convert 6 ribose phosphates to 5 hexose phosphates
3. oxidize glucose 6P, reduce NAD+, and as a result help generate energy (ATP)
4. facilitate the Cori cycle.
5. generate pentoses for the synthesis of nucleotides and nucleic acids

Answer 17

5. generate pentoses for the synthesis of nucleotides and nucleic acids

Question 18

What is the primary function of serum albumin in mobilizing triacyl glycerol for energy?

1. it is the protein component of the chylomicron, which helps solubilize lipids when transferring them from intestinal cells into the bloodstream
2. It is a lipase, which is an enzyme that breaks down lipids into fatty acids
3. it is an enzyme that helps “charge” fatty acids by converting them to fatty acyl CoA in order to oxidize them for energy
   4.It helps solubilize fatty acids so as to transfer them from the adipose cells to the adjacent muscle cells via blood when glucose levels are low
   5.It is phosphorylated when glucose levels are high

Answer 18

It helps solubilize fatty acids so as to transfer them from the adipose cells to the adjacent muscle cells via blood when glucose levels are low

Question 19

Thioesters are often used to transfer which of the following groups from one molecule to another?
aryl
oxidized form of lipoate
acyl
phosphoryl
alkyl

Answer 19

acyl

Question 20

Based on the table: Which of the reactions will NOT be spontaneous (assume that there is an enzyme to do each of the reactions in the choices below) under standard conditions.
1. PEP + AMP → pyruvate + ADP
2. Acetyl CoA + water → acetate + CoA-SH
3. PEP + ADP → pyruvate + ATP
4. Glucose 3-phosphate + AMP → Glucose + ADP
5. ADP + glycerol → glycerol 3-phosphate + AMP

Answer 20

Glucose 3-phosphate + AMP → Glucose + ADP

Question 21

Including malate as an intermediate is beneficial for gluconeogenesis because:

1. it helps carry electrons (reducing equivalents) from the mitochondria to the cytosol to facilitate the reduction of an intermediate of gluconeogenesis
2. it is the only way in which gluconeogenesis can occur in the liver
3. it is the only way to do gluconeogenesis as part of the Cori cycle.
4. It couples with a highly irreversible step to make the overall pathway irreversible
5. It allows stimulation of glycolysis and inhibition of gluconeogenesis at the same time, serving as an example of coordinated regulation of reverse pathways.

Answer 21

1. it helps carry electrons (reducing equivalents) from the mitochondria to the cytosol to facilitate the reduction of an intermediate of gluconeogenesis

Question 22

Fructose 2,6-bisphosphate
Fructose 1,6-bisphosphate
PFK-2
Glucose
Fructose 6-phosphate

Answer 22

Fructose 6-phosphate

Question 23

The ΔGo of the reaction is +111 kJoule/mole, what is true about this reaction at standard conditions?
1. will occur irreversibly.
2. will occur with a large Km
3. will not be spontaneous
4. More information is needed to answer the question.
5. will occur with a small kcat

Answer 23

3. will not be spontaneous

Question 24

The symptoms of lactose intolerance can be relieved by the ingestion of
1. glucose transporters to increase the uptake of lactose in the intestinal cells
2.antacid
3. glycolytic enzymes to break down lactose and galactose (a monosaccharide)
4. the enzyme that would breakdown a specific disaccharide into two monosaccharides
5. lactate dehydrogenase

Answer 24

4. the enzyme that would breakdown a specific disaccharide into two monosaccharides

Question 25

An enzyme involved in glycogen breakdown
1. uses TPP as a prosthetic group is glycogen synthase.
2. is a protein called Glycogenin, which contains a catalytic tyrosine residue
3. is called the branching enzyme
4. is activated when it is acted upon by a kinase enzyme

Answer 25

4. is activated when it is acted upon by a kinase enzyme

Question 26

Acetyl CoA → acetic acid + CoA-SH, change in free energy (kJ/mol) = –54
Ethyl acetate → acetic acid + Ethanol, change in free energy (kJ/mol) = –18
What is the overall change in free energy in (kJ/mol) for the following reaction? Acetyl CoA + Ethanol → Ethyl acetate + CoA- SH?

Answer 26

-36

Question 27

Answer 27

0

Question 28

What is the full ATP potential (i.e., taking into consideration ATP from NTP, NADH, and FADH2) of the oxidation of 3 glucose molecules to 6 acetyl CoA molecules and 6 CO2 molecules using aerobic oxidation?

Answer 28

36

Question 29

The Citric acid cycle takes the carbons from acetyl CoA and oxidizes them to CO2. How many net carbons from acetyl CoA still remain in the intermediate shown below.

Answer 29

0

Question 30

Answer 30

206

Question 31

When a polyunsaturated fatty acid of chemical formula 26:2 Δ9,12 is oxidized using the beta-oxidation pathway, the number of FADH2 produced will be

Answer 31

11

Question 32

For beta-oxidation of long-chain fatty acids:
1. NADPH serves as an electron carrier that feeds electrons into the electron transport chain for ATP synthesis.

2. All the enzymes required for beta-oxidation are present in the mitochrondria
3. Some products of β-oxidation can directly enter stage III of aerobic respiration.
4. Oxidation of a 15-carbon fatty acid produces at least one propionyl-CoA.
5. Oxidation of an 18-carbon fully saturated fatty acid involves 9 cycles, each of which produces 1 acetyl Co-A.
6. Carbon atoms are removed from the acyl chain one at a time

Answer 32

2. All the enzymes required for beta-oxidation are present in the mitochrondria
3. Some products of β-oxidation can directly enter stage III of aerobic respiration.
4. Oxidation of a 15-carbon fatty acid produces at least one propionyl-CoA.

Question 33

1. The allosteric regulator fructose 2,6-bisphosphate allows for the reciprocal regulation of glycolysis and gluconeogenesis
2. When blood glucose levels are low, the liver is forced to do both gluconeogenesis (to provide brain with glucose) and glycolysis (to meet the liver’s own energy needs) in the same cells (hepatocytes) at the same time.
3. Glycogen phosphorylase acts as a substrate for a phosphatase enzyme (PP1)
4. Tyrosine is not part of a glycogen polymer
5. Fructose 6P inhibits hexokinase IV
6. A new pathway is discovered that converts two glucose molecules into a five-carbon and seven-carbon molecule. You would expect that phosphorylation of the enzymes on this pathway will activate them.

Answer 33

1. The allosteric regulator fructose 2,6-bisphosphate allows for the reciprocal regulation of glycolysis and gluconeogenesis
2. Glycogen phosphorylase acts as a substrate for a phosphatase enzyme (PP1)
3. Fructose 6P inhibits hexokinase IV

Question 34

FAD
NADP+
Lipoyllysine
Coenzyme A
Thiamine pyrophosphate (TPP)
NAD+

Answer 34

FAD
Lipoyllysine
NAD+