exam 3 22F

Question 1

Match the following process with their respective functions
Catabolism of glucose
catabolism of FA
Oxidation of Acetyl CoA
Synthesis of glucose from three-carbon substrates
Production of NADPH and ribose for anabolic reactions
Incorporation of CO2 into sugars

Answer 1

Glycolysis: catabolism of glucose
beta oxidation: catabolism of FA
CAC: oxidation of Acetyl CoA
Calvin Cycle: Incorporation of CO2 into sugars
PPP: production of NADPH and RIbose for anabolic reactions
Gluconeogenesis: synthesis of glucose from 3 carbon substrates

Question 2

One reason that fa!y acids make an excellent source of fuel is that they carry more energy per carbon atom than do carbohydrates. This is because:
1. The carbons in fatty acids are more polar than the carbons in carbohydrates.
2. The carbons in fatty acids are lighter than carbons in carbohydrates.
3. The carbons in fatty acids are more hydrophobic than the carbons in carbohydrates.
The carbons in fatty acids are more oxidized than the carbons in carbohydrates.
The carbons in fatty acids are more reduced than the carbons in carbohydrates.

Answer 2

The carbons in fatty acids are more reduced than the carbons in carbohydrates.

Question 3

When a free glucose molecule first enters a cell (via the glucose transporter), the most likely first reaction catalyzed is:
1. Phosphorylation of the C6 carbon using ATP
2. Dehydrogenation generating NADH
3. Phosphorylation of the C1 carbon using ATP
4. Isomerization into fructose
5. Dehydration generarating fructose

Answer 3

1. Phosphorylation of the C6 carbon using ATP

Question 4

Under anaerobic conditions mammals utilize a process termed the “Cori Cycle” in which glucose is fermented to lactic acid in the muscle, and lactic acid is transported to the liver where it is converted back to glucose. During these processes, the net gain/loss of other metabolites is (consider all NTPs to be equivalent):
+2 ATP in muscle, -4 ATP in liver
+32 ATP in muscle
+2 ATP and +1 NADH in muscle, -6 ATP in liver and -1 NADH in liver
+2 ATP in muscle, -6 ATP in liver
+2 ATP and +1 NADH in muscle, -4 ATP in liver and -1 NADH in liver

Answer 4

+2 ATP in muscle, -6 ATP in liver

Question 5

Suppose you had a very specific inhibitor of the Citric Acid Cycle (CAC) enzyme Isocitrate Dehydrogenase. If this inhibitor is added to actively metabolizing cells, you would expect the CAC intermediate _______________.

alpha-Ketoglutarate
Oxaloacetate
Acetyl-CoA
Citrate
Isocitrate

Answer 5

citrate

Question 6

A kinase reaction typically utilizes _______ as a phosphate donor while using ___________ as a cofactor.
Glucose 6-phosphate, H2O
ATP, Mg2+
PEP, Mg2+
ATP, NAD+
Inorganic phosphate, NAD+

Answer 6

ATP, Mg2+

Question 7

In the non-oxidative reactions of the Pentose Phosphate Pathway:

Six pentoses (5C) can be used to make five hexoses (6C)

A pentose (5C) and a tetrose (4C) can be used to make a hexose (6C) and a triose (3C)

A septose (7C) and a triose (3C) can be used to make a hexose (6C) and a tretose (4C)

Two pentoses (5C) can be used to make one septose (7C) and one triose (3C).

All of these combinations are possible

Answer 7

All of these combinations are possible

Question 8

The reaction in Glycolysis with the highest energy barrier under standard conditions is:

Transfer of a phosphoryl group to a 6-carbon sugar
Cleavage of a 6-carbon sugar to two 3-carbon sugars
Incorpora”on of an inorganic phosphate

Transfer of a phosphoryl group to ADP yielding ATP.
Conversion of an aldose to a ketose

Answer 8

Cleavage of a 6-carbon sugar to two 3-carbon sugars

Question 9

PFK-1 is a logical step for regulation of Glycolysis because:

It has a large positive G value and is the second committed step in Glycolysis.

It acts before the merging point where a number of feeder pathways enter Glycolysis.

It has a large negative G and generates ATP as a product.

It acts after the merging point where a number of feeder pathways enter Glycolysis.

It has a large positive G value and is the first committed step in Glycolysis.

Answer 9

It acts after the merging point where a number of feeder pathways enter Glycolysis.

Question 10

The reaction catalyzed by GAPDH starts with a deprotonated Cys residue in the active site, due to a pKa shift for this cysteine. The presence of which amino acids or other substrates could facilitate this pKa shift?
None of the other choices
All of these (His, Arg, NAD+)
The binding of NAD+ in the ac”ve site A conserved Histadine residue
A conserved Arginine residue

Answer 10

All of these (His, Arg, NAD+)

Question 11

The conversion of
DHAP GAP is an important reaction in glycolysis. This reaction has a
deltaG’o of 7.5 in normal cellular conditions this reaction can proceed in the forward direction provided that
1. The substrate is kept at a low concentration.
2. The temperature is raised sufficiently high, thus increasing the entropy of the products.
An enzyme catalyzing the reac”on is present.
This reac”on will not proceed under normal cellular condi”ons.
The product is consumed immediately thus keeping product concentra”ons low..

Answer 11

the product is consumed immediately thus keeping product concentrations low..

Question 12

During one complete round of glycolysis, for every Glucose molecule which enters: (Choose the BEST answer.)
Two ATPs are consumed during the preparatory phase and four ATPs are produced in the payoff phase.

Two ATPs are consumed during the preparatory phase and four ATPs and two NADHs are produced in the payoff phase.

Two ATPs are consumed during the preparatory phase and two ATPs, two GTPs and two NADPHs are produced in the payoff phase.

One ATP is consumed during the preparatory phase and two ATPs are produced in the payoff phase.

One ATP is consumed during the preparatory phase and two ATPs and one NADH are produced in the payoff phase.

Answer 12

Two ATPs are consumed during the preparatory phase and four ATPs and two NADHs are produced in the payoff phase.

Question 13

Prior to beta-oxidation, long chain fatty acids must be activated in the cytosol then transported to the mitochondria for beta-oxidation.
Which answer best describes the activation step? (Choose the best answer from the choices below.)

A free fatty acid is transferred to CoA utilizing a phosphorylated intermediate at the cost of one ATP equivalent.

A free fatty acid is transferred to carnitine utilizing an adenylylated intermediate at the cost of one ATP equivalent.

A free fatty acid is transferred to carnitine utilizing an adenylylated intermediate at the cost of two ATP equivalents.

A free fatty acid is transferred to CoA utilizing an adenylylated intermediate at the cost of two ATP equivalents.

A free fatty acid is transferred to CoA utilizing a phosphorylated intermediate at the cost of two ATP equivalents.

Answer 13

A free fatty acid is transferred to CoA utilizing an adenylylated intermediate at the cost of two ATP equivalents.

Question 14

The regenerative phase of the Calvin Cycle is most similar in strategy to:
beta-oxidation of fatty acids
The citric acid cycle
The oxidative reactions of the Pentose Phosphate Pathway
The preparative phase of glycolysis
The non-oxidative reactions of the Pentose Phosphate Pathway

Answer 14

The non-oxidative reactions of the Pentose Phosphate Pathway

Question 15

The incorpora”on of CO2 into Ribulose 1,5-bisphosphate requires:
energy provided by the hydrolysis of ATP electrons provided by oxidizing NADPH electrons provided by oxidizing FADH2 none of these are required

Answer 15

none of these are required

Question 16

Entry of acetyl-CoA into the citric acid cycle is decreased when:
the ratio of [NAD+]/[NADH] is high.

the ratio of [ATP]/[ADP] or [ATP]/AMP] is high.

NADH is rapidly oxidized through the respiratory chain.
the ratio of [ATP]/[ADP] or [ATP]/[AMP] is low

[AMP] is high.

Answer 16

the ratio of [ATP]/[ADP] or [ATP]/AMP] is high

Question 17

The oxidative steps of the Pentose Phosphate Pathway (PPP) convert a 6-carbon substrate to a 5-carbon product while undergoing two oxidation reactions for a total of 4 electrons lost. These 5-carbon products can be used to regenerate the 6-carbon starting material for the PPP. How do we account for the electrons lost in the oxidative steps when regenerating the 6-carbon sugar?
1. The electrons are added back by use of acid/base catalysis.

2. Since there is a hydrolysis step in the PPP, no carbon atoms actually changed their oxidation status. The electrons came instead from water.
3. The electrons are added back from the consumption of ATP.
4. We don’t need to add any electrons back as the PPP also releases a fully oxidized carbon in the form of CO₂, and the remaining carbons did not change their oxidation states.
5. The electrons are added back during the regenerative process by consuming NADPH.

Answer 17

4. We don’t need to add any electrons back as the PPP also releases a fully oxidized carbon in the form of CO₂, and the remaining carbons did not change their oxidation states.

Question 18

The reaction shown below is catalyzed by GAPDH. Which statement is FALSE about the reaction shown below (choose the BEST answer):
This reaction is part of the payoff phase of glycolysis.
This reaction incorporates an inorganic phosphate.
This reaction consumes one ATP.
This reaction has a positive value for G’o. This reaction generates one NADH + H+.

Answer 18

This reaction consumes one ATP.
- this is false, actually what happens is that the reaction uses an inorganic phosphate (Pi) and generates NADH.

Question 19

The first reaction of Gluconeogenesis (Pyruvate carboxylase) utilizes ATP. During this reaction, the phosphoryl group from ATP is:
not present in the final product
transferred to an active site his”dine residue transferred to the C3 carbon of pyruvate
transferred to the C2 carbon of pyruvate transferred to the C1 carbon of pyruvate

Answer 19

not present in the final product

Question 20

The interconversion of a 4-carbon sugar and a 5-carbon sugar to produce a 6-carbon and 3-carbon sugar likely uses a _________________ which requires ________________. (Choose the best answer to fill in the blanks.)
transaldolase, no cofactors
transaldolase, a TPP cofactor
aldolase, no cofactors
transketolase, a TPP cofactor
transketolase, a lipoate cofactor

Answer 20

transketolase, a TPP cofactor

Question 21

After cleavage and incorporation of CO2 into Ribulose 1,5-bisphosphate to generate two 3-carbon molecules, the CO2 carbon atom is now the:

C1 atom of 3-phosphoglycerate
C3 atom of 3-phosphoglycerate
C3 atom of glyceraldehyde-3-phosphate C1 atom of 2-phosphoglycolate
C1 atom of glyceraldehyde-3-phosphate

Answer 21

C1 atom of 3-phosphoglycerate

Question 22

Enzymes which utilize a Biotin prosthe”c group are present in multiple metabolic pathways. These enzymes catalyze a ________________ reaction using ____________ as substrates.
Oxida”on; FAD
carboxylase; bicarbonate and ATP hydrogena”on; NADH thioesterase; Coenzyme A oxida”ve decarboxyla”on; NAD+

Answer 22

carboxylase; bicarbonate and ATP

Question 23

In mammalian tissues, if the citric acid cycle (CAC) intermediates have been diverted for amino acid synthesis, they can be replenished by:
Inhibi”on of -Ketoglutarate dehydrogenase.

Use of the glyoxylate cycle to generate succinate from two Acetyl-CoA molecules.

Entry of pyruvate into the CAC by way of pyruvate carboxylase

Entry of pyruvate into the CAC by way of pyruvate dehydrogenase

Answer 23

Entry of pyruvate into the CAC by way of pyruvate carboxylase

Question 24

Suppose you had a very specific inhibitor of the Citric Acid Cycle (CAC) enzyme Citrate synthase. If this inhibitor is added to actively metabolizing cells, you would expect the metabolic intermediates _______________ and _____________ to accumulate.
alpha-Ketoglutarate, malate
Oxaloacate, Malate
Malate, Acetyl-CoA
Oxaloacetate, Acetyl-CoA
Citrate, Acetyl-CoA

Answer 24

Malate, Acetyl-CoA

Question 25

When beta oxidation is run to completion for the a 14:1( delta 9) expected net yield of ATP is:

Answer 25

90.5

Question 26

Place the following steps from the PAYOFF phase of Glycolysis in the correct order (Note: some steps my not be part of the process).
Incorporation of a phosphate with oxidation
Phosphoryl group transfer from the C1 position
Conversion of a C3-phosphorylated compound
Dehydration of a 3-carbon intermediate
Phosphoryl group transfer from the C2 position

Answer 26

1. Incorporation of a phosphate with oxidation
2. Phosphoryl group transfer from the C1 position
3. Conversion of a C3-phosphorylated compound
4. Dehydration of a 3-carbon intermediate
5. Phosphoryl group transfer from the C2 position

Question 27

Answer 27

D,B,C,A

Question 28

Match the cofactors/coenzymes in pyruvate dehydrogenase complex with their functional roles in the reaction cycle.
1. Carries no oxidized two carbon intermediates
2. carries two carbon intermediate and is involved in electron transfer
3. acceptor of oxidized two carbon product
4. electron carrying prosthetic group (only)

Answer 28

1. Acetyl CoA
2. Lipoate
3. NAD+
4. FAD

Question 29

This reaction requires activation by ATP.
This reaction uses a Mg²⁺ cofactor.
This reaction uses a cobalt-containing prosthetic group.
This reaction uses a thiamine pyrophosphate (TPP) prosthetic group. The product of this reaction goes directly into the citric acid cycle.
This reaction is part of the catabolism of odd-numbered fatty acids
This reaction has a free-radical intermediate
This reaction is part of catabolism of even-numbered fa!y-acids.

Answer 29

This reaction uses a cobalt-containing prosthetic group.

The product of this reaction goes directly into the citric acid cycle

This reaction is part of the catabolism of odd-numbered fatty acids.

Question 30

Glucose 6-phosphate (G6P) has many possible fates in cells. For each of the following pathways, indicate what is the FIRST reaction which acts on G6P.
Mutase, Isomerase, Dehydrogenase, phosphorolysis
Glycogen synthesis
glycolysis
PPP
Export from cell

Answer 30

Glycolysis= Isomerase
PPP= Dehydrogenation
Glycogen synthesis= mutase
export from the cell= hydrolysis

Question 31

This reaction uses a biotin cofactor.
This reaction occurs BOTH prior to the citric acid cycle and as part of the citric acid cycle (depending on the identity of the R group).
This reaction uses a lipoyl-lysine prosthetic group.
This reaction occurs prior to the citric acid cycle and in no other pathways. The final electron acceptor in this reaction is FAD.
The final electron acceptor in this reaction is NAD+.
This reaction occurs as part of the citric acid cycle and in no other pathways. This reaction uses a TPP cofactor.

Answer 31

This reaction occurs BOTH prior to the citric acid cycle and as part of the citric acid cycle (depending on the identity of the R group).
The final electron acceptor in this reac”on is NAD+
This reac”on uses a Lipoyllysine prosthe”c group
This reac”on uses a TPP cofactor