final practice test 1

A patient has been exposed to a toxic compound that increases the permeability of the mitochondrial membranes to protons. Which of the following metabolic changes would be expected in this patient?

A patient has been exposed to a toxic compound that increases the permeability of the mitochondrial membranes to protons. Which of the following metabolic changes would be expected in this patient?

Increased oxygen utilization

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

Complex II is an enzyme that catalyzes a reaction in the citric acid cycle.

Which of the following describes the most direct source of energy used by ATP synthase to produce ATP?

- energy from the metabolism of amino acids
- energy from the conversion of glucose to pyruvate
- energy from the oxidation of pyruvate producing CO2 and H2O
- energy derived from the breakdown of NADH and FADH2
- energy from a proton gradient established in mitochondria

energy from a proton gradient established in mitochondria

Which coenzyme below can transfer a one carbon unit at multiple oxidation states?

- biotin
- S-adenosylmethionine
- tetrahydrofolate (THF)
- lipoic acid
- flavin adenine dinucleotide

tetrahydrofolate (THF)

Ornithine is an intermediate that

- is created in the same reaction that creates urea
- is a reactant of the first step of the urea cycle
- has amino groups that do not leave the urea cycle in the form of urea
- is recreated with every turn of the cycle, like oxaloacetate in the CAC
- all of the above

all of the above

Which of the following statements about the electron transport chain and ATP production in the mitochondria is false?

- Any drug that inhibits the ATP synthase will also inhibit the flow of electrons in the ETC.
- For oxidative phosphorylation to occur, it is essential to have a membrane that is impermeable to protons except through specific proteins pores or protein complexes
- The yield of ATP per mole of fuel depends on the type of molecule being catabolized.
- Some complexes of the respiratory chain pump protons into the matrix to create an electrochemical gradient.
- Exergonic electron transfer provides the energy for proton pumping.

Some complexes of the respiratory chain pump protons into the matrix to create an electrochemical gradient.

The term rotational catalysis refers to which of the following descriptions of ATP synthase activity?

- Protons rotate as they travel down their concentration gradients through a subunit of ATP Synthase
- Each ATP synthase has one ATP producing catalytic site in the gamma subunit which undergoes conformation change to produce ATP
- Catalytic sites of the c subunits rotate when protons travel down their concentration gradients through them
- The turning of c subunits also turns a gamma subunit, which induces conformational change in three beta subunits that can produce ATP
- None of the above occurs in ATP synthase

The turning of c subunits also turns a gamma subunit, which induces conformational change in three beta subunits that can produce ATP

Which of the following enzymes catalyzes this reaction?

glutamate dehydrogenase

Right after the exam, you walk outside and decide to relieve some stress by picking up the heaviest thing you can find and lifting it up 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
- glutamine

phosphocreatine

Proline is synthesized from Glu in a pathway that involves the following reaction:
Pyrroline 5 carboxylate + NAD(P)H + H+ ---> Proline + NAD(P)+
Which enzyme below catalyzes this reaction?

-Pyrroline 5 carboxylate -reductase
-Proline reductase
-Pyrroline 5 carboxylate dehydrogenase
-Proline isomerase
-Proline phosphatase

Pyrroline 5 carboxylate reductase

What is the closest value to the ∆G°' for the following reaction:
Malate + fumarate ---> oxaloacetate + succinate

T = 25 ºC (298 K) ∆G°' = -nF∆E°'
E= E°'+ (0.026V/n)ln [electron acceptor]/[electron donor]
R = 8.315 J / mol K F= 96.5 kJ/V∙mol

- (-38) kJ/mol
- (-20) kJ/mol
- 26 kJ/mol
- 40 kJ/mol
- need more information to calculate this

- 38 kj/mol

Considering the complete oxidation of 1 Glucose (going from glycolysis to oxidative phosphorylation),

- 1 ATP is made for every NADH made
- The NADH made from the pyruvate dehydrogenase complex step ultimately produces 5 ATP
- NADH formation, but not FADH2 formation, leads to ATP production
- a total of 15 ATP are made.
- all of the above

The NADH made from the pyruvate dehydrogenase complex step ultimately produces 5 ATP

Which of the following correctly matches an enzyme with its cofactor?

- alanine aminotransferase -- pyridoxal phosphate (PLP)
- nitrate reductase -- tetrahydrofolate (THF)
-branched chain alpha keto acid -dehydrogenase complex --
-thiamine pyrophosphate (TPP)
glutamate dehydrogenase - NAD(P)H/ NAD(P)+
-two or more of the above are correct

two or more are correst

Hexokinase I is the isozyme of hexokinase that is found in muscle. Which statement is true about HK I?

-Hexokinase I will have low phosphorylation activity unless substrate levels are high.
-It has a low affinity for its substrate as compared to Hexokinase IV.
-It has a lower Km ([S] at ½ maximum velocity) than Hexokinase IV.
-HK I is not inhibited by the product of the reaction it catalyzes.
-The activity of Hexokinase I is directly related to maintaining blood glucose levels.

It has a lower Km ([S] at ½ maximum velocity) than Hexokinase IV.

If a person did not eat for two weeks, which of the following compounds would be present at the highest concentration in this person's blood plasma?

- glucose
- acetone
- hydroxybutyrate
- fatty acids
- two of the above would be present at the same concentration

beta hydroxybutyrate

Oxidation of NADH to NAD+ is catalyzed by which complex of the Electron Transport Chain?

- ATP Synthase
- Complex IV
- Complex III
- Complex II
- Complex I

Complex I

All of the following are entry points for electrons into the mitochondrial electron transport chain except

- Complex I
- Complex II
- Complex III
- Fatty acyl CoA dehydrogenase
- Glycerol 3 phosphate dehydrogenase

complex III

The activity of phosphofructokinase 1 is increased by the binding of

- ATP
- ADP
- Citrate
- Acetyl CoA
- Two or more of the above

ADP

Which of the following six statements about mitochondrial respiration are true?

1.The complexes of the respiratory chain are present in the cytoplasm of the cell
2.The final electron acceptor is oxygen
3.The electron carriers are arranged in order of increasing reduction potential.
4.During electron transport, protons are pumped from the intermembrane space of the mitochondria to the matrix.
5.Ubiquinone and cytochrome C transport electrons between the respiratory chain complexes
6.Complex II may receive electrons from succinate or NADH.

2,3,5

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

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

branched chain alpha keto acid dehydrogenase complex: oxidative decarboxylation

Which of the following best describes the direct inputs into the mammalian urea cycle as discussed in class?

- uric acid and HCO3-
- serine and HCO3-
-carbamoyl phosphate and aspartate
-ammonia
-carbamoyl phosphate and alanine

carbamoyl phosphate and aspartate

Which of the following compounds are produced from catabolism of glucogenic amino acids?

- acetyl CoA and acetoacetyl CoA
- acetyl CoA and acetone
- oxaloacetate and fumarate
- only acetyl CoA
- phenylalanine and leucine

oxaloacetate and fumarate

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 activity
- increase in acetyl-CoA carboxylase activity
- two or more of the above

two or more of the above

A type of reaction found in the catabolism of most amino acids is a(an):

- decarboxylation requiring thiamine pyrophosphate (TPP)
-decarboxylation requiring pyridoxal phosphate (PLP)
-hydroxylation requiring NADPH and oxygen
-aminotransferase reaction requiring pyridoxal phosphate (PLP)
-none of the above

aminotransferase reaction requiring pyridoxal phosphate (PLP)

Right after a meal, which of the following things would be occurring metabolically?

- insulin release is triggered by low blood glucose
- ingested amino acids are either used to make proteins or broken down
- amino acids in skeletal muscle will be used to form intermediates of gluconeogenesis
- ketone bodies are exported from the liver for use in extrahepatic tissue, like the brain
- two or more of the above would occur

ingested amino acids are either used to make proteins or broken down

List the following in order of increasing tendency to accept electrons: (a) alpha-ketoglutarate + CO2 (yielding isocitrate); (b) oxaloacetate; (c) NADP+ ; (d) O2

a, c, b, d

Which of the following is true about electron carriers involved in cellular respiration?

- the value of reduction potentials for FMN and FAD depend on the enzyme they are associated with
- electron acceptors accept electrons primarily as hydride ions
- cytochromes contain Fe-S clusters that can accept and donate electrons
- ubiquinone is a relatively large integral membrane protein that is an electron carrier in the respiratory chain
- all of the above

the value of reduction potentials for FMN and FAD depend on the enzyme they are associated with

If a person's urine contains a higher than normal concentration of urea, which of the diets below have they probably been eating recently?

- very high carbohydrate, appropriate protein to meet daily requirement
- very low carbohydrate, higher protein than needed to meet daily requirement
- very high fat, appropriate protein to meet daily requirement
- very high fat, high carbohydrate, appropriate protein to meet daily requirement
- none of the above are likely to change urea levels in urine

very low carbohydrate, higher protein than needed to meet daily requirement

Which of the following is not a possible fate for glucose 6 phosphate in a liver cell?

- the urea cycle
- glycogen synthesis
- nucleotide synthesis
- complete oxidation to carbon dioxide and water
- all of the above are possible fates

the urea cycle

Which of the following is true about the regulation of the Citric Acid Cycle (CAC)?

- Every step is allosterically regulated to ensure tight control of this pathway.
- ATP and citrate are negative regulators (i.e. inhibitory regulators) of the CAC.
- NADH is an activating allosteric regulator of one or more of the early steps of the CAC.
- Only molecules that are products, reactants, or cofactors of the pathway are allosteric regulators of the CAC.
- All of the above are true.

ATP and citrate are negative regulators (i.e. inhibitory regulators) of the CAC.

Which of the following is an example of regulating enzyme activity by covalent modification?

- The mRNA encoding the E1 of PDC is degraded so a ribosome cannot use it for translation.
- ATP binds to the pyruvate dehydrogenase complex and inhibits its activity.
- Glycogen phosphorylase that has been tagged with ubiquitin is degraded by the proteasome
- A transcription factor binds to DNA and induces expression of the gene for the E1 of the PDC.
- Phosphorylation of glycogen phosphorylase by a kinase activates the phosphorylase.

Phosphorylation of glycogen phosphorylase by a kinase activates the phosphorylase.

A researcher observes that adding arginine to a test tube containing a culture of mammalian liver cells leads to an increase in the rate of carbamoyl-phosphate production. Which of the following is the most likely explanation for this observation?

- Arginine stimulates the production of aspartate which increases the flow of nitrogen through the urea cycle
- Arginine activates carbamoyl-phosphate synthetase I
- N-acetylglutamate synthase activity is increased
- The citric acid cycle is producing more CO2 to convert to HCO3-
- Arginine directly stimulates the phosphorylation of carbamate ions

N-acetylglutamate synthase activity is increased

ATP is required for which of the steps in the urea cycle?

- the production of ornithine by arginase
- hydrolysis of arginine to urea
- cleavage of argininosuccinate into arginine and fumarate
- the production of argininosuccinate from citrulline
- the production of citrulline from carbamoyl phosphate and ornithine

the production of argininosuccinate from citrulline

Why do we transport large amounts of alanine in the blood?

- all extrahepatic tissues that catabolize amino acids export amino groups to the liver in the form of alanine
- skeletal muscle will break down protein for fuel if needed and the ammonia produced during catabolism cannot travel to the liver on its own through the blood
- alanine can be taken in by most tissues and converted to pyruvate for use in gluconeogenesis
- to transport nitrogen from protein breakdown in liver to the muscle
- alanine is the only amino acid that can transport Nitrogen between extrahepatic tissue and the liver

skeletal muscle will break down protein for fuel if needed and the ammonia produced during catabolism cannot travel to the liver on its own through the blood

Regulatory mechanisms of metabolic pathways

- may involve changing the number of a certain type of enzyme present in a cell
- allow for biosynthetic pathways to continue even if there are enough products of that pathway present
- allow for opposite pathways (eg. Glycolysis and Gluconeogenesis) to occur at the same time
- will rarely the affect the flux through metabolic pathways
- do all of the above

may involve changing the number of a certain type of enzyme present in a cell

You have heard advice that it is most healthy to eat six small meals a day. You decide to try this out -- which of the following things would occur in your body?

- Your liver would be in a glucogenic state most of the time
- Glycogen phosphorylase would be upregulated or activated often throughout the day
- PEP carboxykinase would be activated often throughout the day
- Fatty acid synthesis in the liver will be inhibited
- None of the above would occur.

none of the abpve would occur