Biochem exam 4 (two)

Which molecule is a product of the urea cycle and an intermediate of the citric acid cycle?
argininosuccinate
oxaloacetate
citrulline
ornithine
fumarate

fumarate

Deoxyribonucleotides are:
A. made by the reduction of the ribose component of ribonucleotide phosphates
B. made by the attachment of te purine and pyrimidine bases to deoxyribose phosphates
C. synthesized in the same manner as ribonucleotides, except that 5-phosphodeoxyribosyl-1-pyrophosphate is used instead c 5-phosphoribosyl-1-pyrophosphate.
D. made only after RNA molecules are polymerized

made by the reduction of the ribose component of ribonucleotide phosphates

Fatty acid biosynthesis depends on the presence of CO2 to generate malony CoA from acetyl CoA. Consider an experiment in which a culture of cells is grown in the presence of C14-labeled bicarbonate. Which carbons of the newly synthesized fatty acids would be expected to be radiolabeled (contain C14)?

the odd-numbered carbons
all of the carbons
none of the carbons
the even-numbered carbons

none of the carbons

Mark all the molecules that are amino acid precursors.

pyruvate
succinate
3-phosphoglycerate

oxaloacetate
erythrose 4-phosphate
a-ketoglutarate
UDP-glucose
phosphoenolpyruvate

glucose-6-phosphate
ribose-5-phosphate

pyruvate
3-phosphoglycerate

oxaloacetate

erythrose 4-phosphate

phosphoenolpyruvate

ribose-5-phosphate

Identify all the amino acids required for de novo synthesis of purines

glutamine
serine
glycine
arginine
aspartate

glutamine

glycine

aspartate

If a person's urine contains unusually high concentralions oMtrea, which diet has he or she probably been eating recenty?

very very high fat, high carbohydrate, no protein
very low carbohydrate, very high protein
very high fat, very low protein
high carbohydrate, very low protein
very high carbohydrate, no protein, no fat

very low carbohydrate, very high protein

How many molecules of ATP must be hydrolyzed per N2 molecule fixed?
1
3
8
12
16

16

The final product of purine degradation is ____ high levels of it causes the disease ____.
ammonia; pancreatitis
uric acid; phenylketonuria
uric acid; gout
urea; diabetes

uric acid; gout

Which of the following is not a component of the pentose phosphate pathway?

Phosphoenolpyruvate
CO2
Ribose-5-phosphate
Erythrose 4-phosphate

Phosphoenolpyruvate

What are the sources of NADPH for fatty acid synthesis? Select all that apply.

citric acid cycle
pentose phosphate pathway

oxidative phosphorylation
oxidative decarboxylation of malate by malic enzyme in cytoplasm
lactic fermentation

pentose phosphate pathway

oxidative decarboxylation of malate by malic enzyme in cytoplasm

Red blood cells lack mitochondria. These cells process glucose to lactate, but they also generate CO2 . How can they generate COz if they lack mitochondria?

glycolysis coupled with the citric acid cycle
fatty acid oxidation coupled with the citric acid cycle.
the pentose phosphate pathway coupled with glycolysis
glycolysis coupled with ethanol fermentation

the pentose phosphate pathway coupled with glycolysis

Predict which product of phosphoglucomutase reaction predominates when insulin levels are high.

glucose-1-phosphate
glucose 1,6-bisphosphate
glucose 6-phosphate
glucose

glucose-1-phosphate

What is the donor of glycosyl units in autoglycosylation of glycogenin?

glycogenin
PRPP
UDP-glucose

glucose-1-phosphate
glucose

UDP-glucose

What enzyme catalyzes the committed step of the pentose phosphate pathway?

phosphopentose isomerase
lactonase
transketolase
phopshopfructokinase
glucose 6-phosphate dehydrogenase

glucose 6-phosphate dehydrogenase

Identify the enzymes that are required for the synthesis of a glycogen particle starting from glucose 6-phosphate.

glycogen phosphorylase
glycogen synthase
UDP-glucose pyrophosphorylase
branching eznzyme
glycogen synthase kinase

glycogen synthase

UDP-glucose pyrophosphorylase

branching eznzyme

The synthetic pathways leading to AMP and GMP are

branched at the lever of an intermediate that can be converted into either AMP or GMP.
linearly related with AMP being produced first and then converted to GMP.
linearly related with GMP being produced first and then converted to AMP.

branched at the lever of an intermediate that can be converted into either AMP or GMP.

Which metabolic process is INHIBITED by insulin?

synthesis of triacylglycerols in adipose tissue
entry of glucose into muscles and adipose cells
glycolysis in the liver
gluconeogenesis in the liver

glycogen synthesis in liver and muscle

gluconeogenesis in the liver

Which metabolic pathway is NOT a source of carbon skeletons for amino acid biosynthesis?

citric acid cycle
B-oxidation
pentose phosphate pathway
glycolysis

B-oxidation

The major consequence of loss of the gene encoding glycogenin would be

producing glucose polymers of 10-20 glucosyl units accumulation of glycogen
producing unbranched glycogen molecules
increased glycogen degradation
preventing the initiation of glycogen synthesis

reventing the initiation of glycogen synthesis

Common precursor for biosynthesis of Valine, Leucine, and Alanine

ribose 5-phosphate
Pyruvate
alpha-ketoglutarate
Oxaloacetate
3-phosphoglycerate

Pyruvate

the key regulatory enzyme in glycogen synthesis.

Glycogen synthase
Branching enzyme
Glycogen phosphorylase
Protein phosphatase 1 (PP1)
Glycogenin

Glycogen synthase

The major product of mammalian fatty acid synthesis is

cholesterol
palmitic acid
oleic acid
linoleic acid

palmitic acid

Choose the statement that sums up reciprocal regulation of gluconeogenesis and glycolysis.

When glucose is abundant, glycolysis will predominate.
When glucose is scarce, glycolysis will predominate.
When glucose is abundant, glycogenolysis will predominate.
When glucose is abundant, glycolysis will be stopped.
When glucose is abundant, gluconeogenesis will predominate.

When glucose is abundant, glycolysis will predominate.

Terrestrial vertebrates convert the NH4 to urea such that thl urea can be excreted. In the production of the urea, only one of nitrogens come from NH4. What is the source of the other nitrogen in urea?

carbamoyl phosphate
fumarate
aspartate
ornithine

aspartate

What kind of organisms convert nitrogen into NH4* through nitrogen fixation?

bacteria

Glucose 6-phosphate can be utilized by either the glycolytic or the pentose phosphate pathway. What is the major factor regulating the distribution of glucose 6-phosphate between these two pathways?

the relative levels of NADP+ and NADPH
the different location of the two pathways within the cell
allosteric inhibition of the glucose6-phosphate dehydrogenease enzyme by ATP
the ratio of ATP to AMP in the cell

the relative levels of NADP+ and NADPH

What happens when NADPH concentration is high?

The pentose phosphate pathway activates and glucose 6-phosphate converts to pentose phosphates.
The Pentose Phosphate Pathway is inhibited and Glucose-6-Phosphate enter glycolysis.
The nonoxidative phase of the pentose phosphate pathway halts and ribose 5-phosphate enters DNA synthesis.
The nonoxidative phase of the pentose phosphate pathway halts and ribose 5-phosphate enters gluconeogenesis.
The oxidative phase of the pentose phosphate pathway halts and glucose 6-phosphate converts to pentose phosphates.

The Pentose Phosphate Pathway is inhibited and Glucose-6-Phosphate enter glycolysis.

What precursors can be used to make glucose in gluconeogenesis? Select all that apply.

fatty acids
Acetyl CoA
glycerol
lactate
amino acids

glycerol
lactate
amino acids

Lactate produced in muscle tissue is converted to ____ by ____.

ATP; the citric acid cycle lactate; the Cori cycle
pyruvate; glycolysis
glucose; glycogen degradation
glucose; the Cori cycle

glucose; the Cori cycle

An a-1,6-glycosidic link in glycogen molecule is created by the

branching enzyme
glucose transterase
glycogen synthase
glycogen isomerase.

branching enzyme

The reactions of the urea cycle occur in two different cellular compartments. Which urea cycle intermediate(s) must be transported across the inner mitochondrial membrane?

Argininosuccinate and citrulline
Ornithine
Argininosuccinate
Citrulline and Ornithine
Citrulline

Citrulline and Ornithine

Acetyl groups to be used for fatty acid biosynthesis are transferred across the mitochondrial membrane in what form?

citrate
acetyl CoA
pyruvate
acetyl-carnitine complexes

citrate

The conversion of glucose 6-phosphate to glucose takes place where in the cell?

endoplasmic reticulum

The committed step in fatty acid synthesis is the formation of [a] in a reaction catalyzed by [b].

• citrate
citrate synthase
• malic enzyme
• malonyl CoA
• ATP-citrate lyase
• NADPH
acetyl CoA carboxylase
acetyl CoA

malonyl CoA; acetyl CoA carboxylase

Surplus amino acids are

stored in proteasomes.
used as metabolic fuel
stored in protein scaffolds
All of the above
None of the above

used as metabolic fuel

Fatty Acid Synthesis primarily takes place in the

cytoplasm

Match the precursor with the nucleotide derived from it

precursors: IMP, UMP, dUMP, UTP, ADP
nucleotides: UTP, СТР, GTP, dADP, TMP

inosinate (IMP) → GTP

uridylate (UMP) → UTP

dUMP → TMP

UTP → CTP

ADP → dADP

The Pentose Phosphate Pathway:

generates ATP
synthesize 5-Carbon sugars
synthesize 5-Carbon sugars and generates NADPH generates NADPH
synthesize 5-Carbon sugars and generates ATP

synthesize 5-Carbon sugars and generates NADPH generates NADPH

Avidin is a protein from egg white. It has very high affinity to biotin and because of that works as a highly specific inhibitor of biotin enzymes.
% Which of the following conversions would be blocked by the addition of avidin to a cell homogenate? Choose all that apply.

Malate -› oxaloacetate
Glucose -> pyruvate
Oxaloacetate -> glucose
Pyruvate -> glucose
Pyruvate -> oxaloacetate
glyceraldehyde 3-phosphate -> fructose 1,6-bisphosphate

Pyruvate -> glucose
Pyruvate -> oxaloacetate

Which compound can serve as a direct acceptor of an amino group derived from amino acid catabolism?

a-Ketoglutarate
Asparagine
Glycerol
Fumarate
Glutamine

a-Ketoglutarate