Bis 103- practice final 2

Which statement is NOT true of electron transport in the electron transport chain?
-Electrons flow from electron carriers with a higher reduction potential to carriers with a lower reduction potential.
-The electrochemical gradient across the inner membrane is established as electrons move through the chain.
-The electron transport chain oxidizes reduced cofactors.
- Cytochrome C has a higher reduction potential than FADH2.
- Electrons can enter the chain directly from Glycerol 3-phosphate dehydrogenase.

Which statement is NOT true of electron transport in the electron transport chain?
-Electrons flow from electron carriers with a higher reduction potential to carriers with a lower reduction potential.
-The electrochemical gradient across the inner membrane is established as electrons move through the chain.
-The electron transport chain oxidizes reduced cofactors.
- Cytochrome C has a higher reduction potential than FADH2.
- Electrons can enter the chain directly from Glycerol 3-phosphate dehydrogenase.

- Electrons flow from electron carriers with a higher reduction potential to carriers with a lower reduction potential.

Entry of acetyl CoA into the TCA cycle is decreased when

- the ratio of [ATP]/[ADP] is high
-the ratio of [NAD+]/[NADH] is high
- [AMP] is high
- [citrate] is low
- [NH4+] is high

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

After ingestion of a carbohydrate-rich meal, increased concentration of glucose in the blood is associated with many changes in the metabolism of humans. Which change would NOT be expected?

- a decrease in the secretion of glucagon from the pancreas
- an increase in glycogen phosphorylase activity
- an increase in the secretion of insulin from the pancreas
- increased synthesis of storage triacylglycerols in adipose cells
- increased glycolysis in the liver

an increase in glycogen phosphorylase activity

What is the closest value to the ∆G'° for the following reaction:
Dihydrolipoic acid + 1/2 O2 ---> lipoic acid + H2O


∆G'° = -nF∆E'°
E= E'°+ (0.026V/n)ln [electron acceptor]/[electron donor]
F= 96.5 kJ/V∙mol

A) 100 kJ/mol
B) 200 kJ/mol
C) -100 kJ/mol
D) -200 kJ/mol
E) need more information to calculate this

D) -200

How much water is produced by the electron transport chain when one NADH is used as a substrate by NADH dehydrogenase and one succinate is used as a substrate by Complex II?

- 1 H2O
- 2 H2O
- 3 H2O
- 4 H2O
- 10 H2O

2 H2O

A metabolic uncoupler like Dinitrophenol has an ionizable group and works by

- forming pores in the mitochondrial inner membrane
- intercepting electrons that are being passed between electron carriers in the electron transport chain
- diminishing the electrochemical gradient across the outer membrane of the mitochondria
- being small and hydrophobic enough to easily pass through biological membranes
- all of the above

being small and hydrophobic enough to easily pass through biological membranes

Which nitrogen-containing compounds cross the mitochondrial membrane as part of the urea cycle?
i. ornithine
ii. citrulline
iii. argininosuccinate
iv. aspartate
v. carbamoylphosphate

i, ii, iv

The isozyme of hexokinase that exists in the liver

- has a lower Km (i.e. [S] at ½ vmax) than the isozyme in muscle
- is saturated at lower substrate concentrations than the isozyme in muscle
- is not allosterically inhibited by glucose 6 phosphate
- doesn't catalyze the same reaction as the isozyme of hexokinase in muscle
- all of the above

is not allosterically inhibited by glucose 6 phosphate

Which of the statements about the metabolism of glucose, amino acids, and fatty acids in mammals is true?

-Blood sugar levels impact the metabolism of all three types of molecules.
-The metabolism of all three are affected by the hormone glucagon.
- All three are precursors for more complex molecules.
-The liver is capable of catabolizing all three types of molecules.
-All of the above are true.

all of the above are true

Which one of these statements describes an aspect of how ATP synthase works?

-The beta subunits may all be in the empty conformation at the same time.
- The term "Conformational change" refers to the change in the shape of ADP when it is converted to ATP.
- The movement of protons through the F0 subunit induces rotation of the c subunits.
- The gamma subunit contains an active site which binds ADP and Pi.
- All of the above are true.

The movement of protons through the F0 subunit induces rotation of the c subunits.

How does aspartate enter the urea cycle?

- By forming a carbon-carbon bond with citrulline
- By displacing a phosphate group
- By displacing an adenylate group
- By condensing with carbamoyl phosphate
- By forming a carbon-nitrogen bond with ornithine

By displacing an adenylate group

Which of the following changes in enzyme activity is likely to happen by the release of insulin from the pancreas?

- decrease in glycogen phosphorylase activity
- increase in phosphofructokinase 1 activity
- decrease in PEP (phosphoenolpyruvate) carboxykinase
- increase in acetyl CoA carboxylase
- two or more of the above

two or more of the above

You have discovered a modified electron transport chain in the mitochondria in a new species of yeast that you are studying. You observe that this chain has an additional ETC complex, which you name Complex X. You find that Complex X has a single cytochrome with a standard reduction potential of 0.27 V. Which part of the ETC do you predict Complex X receives electrons from? The standard reduction potentials that are known for the respiratory chain components are listed below.

A) cytochrome c
B) cytochrome a
C) cytochrome b
D) cytochrome c1
E) ubiquinone

cytochrome c

What would likely be the consequence of a biochemical defect in which glucagon was secreted in excess?

-muscular fatigue due to lactic acidosis
-inhibited glycolysis in the liver and depleted glycogen stores
-lowered concentrations of ketone bodies circulating in the blood stream
- decreased rate of urea excretion
- increased accumulation of triacylglycerols in adipocytes

inhibited glycolysis in the liver and depleted glycogen stores

You discover a new protein that is activated by low energy conditions in the cell (i.e. [ADP] >> [ATP]). You name this protein MO, after your favorite biochem professor. Which of the following statements is true about MO?

i. You would expect glycogen synthesis to be increased by active MO
ii. You would expect glycogen synthesis to be decreased by active MO
iii. You would expect ATP-producing processes to be stimulated by MO
iv. You would expect ATP-producing processes to be inhibited by MO

ii, iii

After the ARC re-opens, you get so excited to work out, you go in there and immediately pick up the heaviest thing you can find and lift it over your head five times. Which molecule below is most likely to provide the extra ATP you suddenly need?

- ketone bodies
- phosphocreatine
- triglycerides
- fatty acids

phosphocreatine

The activity of phosphofructokinase 1 is inhibited by the binding of

- ATP
- citrate
- ADP
- acetyl CoA
- two or more of the above

two or more of the above

You decide to add a protein supplement (eg. a protein shake) to your breakfast and lunch in addition to what you normally eat. Which of the following biochemical responses would you expect to see in your body?

- decreased urea production
- decreased transcription of arginase
- increased levels of N-Acetylglutamate
- increased activity of carbamoyl phosphate synthetase I
- 2 or more of the above would occur

2 or more would occur

Which of the following correctly pairs the enzyme with the type of reaction it catalyzes in amino acid/nitrogen metabolism?

- phosphoglycerate dehydrogenase: transamination
- aspartate aminotransferase: hydrolysis
-nitrate reductase: isomerization
-branched chain alpha keto acid dehydrogenase complex: oxidative decarboxylation
- phosphoserine phosphatase: oxidation/reduction

branched chain alpha keto acid dehydrogenase complex: oxidative decarboxylation

Which of the following occur(s) in the movement of electrons through the respiratory chain?

-hydride ions are passed from one carrier to another
-direct transfer of electrons between ions
-electrons are moved as part of a hydrogen atom
- all of the above
- none of the above

all of the above

Which of the following molecules are substrates for an enzyme that uses Pyridoxal Phosphate (PLP) as a cofactor?

- glutamate and NAD+
- carbamoyl phosphate and ornithine
- alanine and alpha-ketoglutarate
- glutamate and ATP
- 3-phosphoglycerate and NAD+

alanine and alpha-ketoglutarate

Which of the following statements about mitochondrial respiration are TRUE?
1.Electrons that pass through the chain are eventually incorporated into water molecules.
2.Some complexes of the respiratory chain are located in the mitochondrial outer membrane.
3.Cristae surface area is positively correlated with mitochondrial respiration rates.
4.During electron transport, protons are pumped from the mitochondrial matrix to the intermembrane space.
5.Complex II catalyzes a reaction in the citric acid cycle.

1,3,4,5

Ketogenic amino acids are catabolized to form which of the following compounds?

- Acetyl-CoA and acetoacetyl-CoA
- Acetyl-CoA and pyruvate
- only acetyl-CoA
- pyruvate and oxaloacetate
- α-ketoglutarate

Acetyl-CoA and acetoacetyl-CoA

What is a correct statement regarding the purpose of amino acid catabolism?

- To provide energy sources, particularly during starvation
- To provide carbon skeletons for use in glucose production
- To breakdown amino acids into compounds such as fumarate, acetyl-CoA or acetoacetate
- To generate ATP from the oxidation of carbon skeletons into CO2 and H20
- All of the above describe a purpose of amino acid catabolism

All of the above describe a purpose of amino acid catabolism

The Nitrogen cycle describes

- various nitrogen containing compounds that are made within a single organism during metabolism
- the creation of nitrogen compounds in various oxidation states
- the use of nitrogen containing compounds for creation of carbohydrates
- the intersection of the urea cycle and the citric acid cycle
- reactions that take place only in the mitochondria

the creation of nitrogen compounds in various oxidation states

Glutamate is considered a "collection point" in amino acid catabolism because

- Glutamate is stored as an energy source to use in fasting or starvation conditions
- Glutamate is exported from extrahepatic tissue for further catabolism in the liver
- Catabolism of a variety of amino acids in the liver produces glutamate
- Glutamate is used as a substrate in the urea cycle to "collect" amino groups
- Skeletal muscle is broken down as fuel when needed and glutamate travels to the liver from the muscle for further catabolism

Catabolism of a variety of amino acids in the liver produces glutamate

Regulatory mechanisms in metabolic pathways do which of the following?

- allow for pathways like amino acid synthesis and amino acid catabolism to occur at the same time to the same degree
- allow an organism to use the right fuel at the right time
- use one or two methods to regulate enzymes to control the flux through a given metabolic pathway
- ensure there are more end products of biosynthetic pathways than needed
- all of the above

allow an organism to use the right fuel at the right time

You are studying a rare bacterium and find a new amino acid which you name BTS, after your favorite musical group. You determine that the final step of BTS synthesis is the following reaction. (preBTS stands for precursor of BTS)
preBTS + H+ ---> BTS + CO2
Which enzyme below would you predict catalyzes this reaction?

-BTS reductase
- preBTS aminotransferase
- preBTS decarboxylase
- BTS lyase
- preBTS oxidase

preBTS decarboxylase

If electron transfer in the mitochondrial electron transport chain is blocked at Complex III in the presence of oxygen, then

- ATP synthesis will continue but the rate will decrease slightly
- ATP production from ATP synthase will stop
- ATP synthesis will increase to compensate for the lack of Complex III function.
- Complex I and II will pump more protons across the inner membrane to compensate for the lack of Complex III function.
- Complex IV will pump more protons across the inner membrane to compensate for the lack of Complex III function.

ATP production from ATP synthase will stop

Which reaction associated with the urea cycle occurs in the cytosol?

- the synthesis of carbamoyl phosphate
- the synthesis of citrulline
- the synthesis of argininosuccinate
- the synthesis of both carbamoyl phosphate and citrulline
- the synthesis of both citrulline and argininosuccinate

the synthesis of argininosuccinate

Which of the following enzymes are most likely to be regulated in glycolysis?

- all enzymes in glycolysis are potential regulation points
- enzymes that catalyze reversible steps are most likely to be regulated
- hexokinase and pyruvate kinase
- the first three enzymes of the pathway, since regulation is most efficient if it occurs at the beginning of a pathway
- enzymes like aldolase, which catalyze big chemical changes like cleavage of C—C bonds

hexokinase and pyruvate kinase

Which of the following statements about Complex II of the respiratory chain is accurate?

- Complex II pumps 4 H+ into the intermembrane space for every 4 e- that pass through
- Complex II does not pass electrons directly to Complex III
- Complex II receives electrons from NADH
- Complex II is also an enzyme in the urea cycle.
- Two or more of the above are true

Complex II does not pass electrons directly to Complex III

Which of the following statements about oxidative phosphorylation in the mitochondria is FALSE?

- The majority of ATP made in the cell is made by oxidative phosphorylation.
- Reduction of molecular oxygen contributes to a proton gradient across the mitochondrial inner membrane.
- For oxidative phosphorylation to occur, it is essential to have a membrane that is impermeable to protons except through specific protein pores or complexes.
- Complex I accepts electrons from a flavoprotein.
- Oxidation of ubiquinol provides energy for proton pumping.

Complex I accepts electrons from a flavoprotein.

Tetrahydrofolate (THF) shuttle _____ between different substrates.

- electrons
- H+
- acyl groups
- one carbon units
- NH2 groups

one carbon units

Which of the following fuels are not directly used by the brain at any point during metabolism?

- glucose
- ketone bodies
- beta hydroxybutyrate
- fatty acids
- B and C

fatty acids

You discover a chemical that affects the function of ATP synthase. When exposed to this chemical, ATP synthase allows protons to travel through it to the matrix but the gamma subunit does not turn at all. What would be the effect of this chemical on a cellular level?

- more ATP will be made
- more oxygen will be used
- less electron transport through the electron transport chain will occur
- no change because catalysis will still occur in the beta subunits
- A and B

more oxygen will be used