1
Which of the following compounds has an ester group?



















Choose one answer.
a. A
b. B
c. C
d. D
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Question 2
Which of the following compounds has a ketone group?










Choose one answer.
A. A
B. B
C. C
D. D
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Question 3

Below is the conversion of ubiquinone to ubiquinol. This reaction takes place in the inner mitochondrial membrane, and ubiquinone and ubiquinol are two forms of coenzyme Q in the electron transport chain. Please analyze the following reaction carefully, and choose the statement which describes it best.


 


Choose one answer.
A. This is an addition reaction, because electrons and protons are added to ubiquinone to form ubiquinol.
B. This is an addition reaction, because hydrogen atoms are added to ubiquinone to form ubiquinol.
C. This is a redox reaction, wherein ubiquinone is reduced to ubiquinol and ubiquinone is the oxidizing agent.
D. This is a redox reaction, wherein ubiquinone is reduced to ubiquinol and ubiquinone is the reducing agent.
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Question 4

The overall chemical reaction of aerobic respiration is:

C6H12O6+ 6 O2® 6 CO2+ 6 H2O + Energy

Please analyze this reaction carefully, and choose the description which describes it best.

Choose one answer.
A. This is a reduction, because oxygen is reduced to water.
B. This is an oxidation, because glucose is oxidized to carbon dioxide.
C. This is a redox reaction, wherein oxygen is the electron acceptor and carbon and hydrogen atoms are the electron donors.
D. This is oxidation, because oxygen atom can be found in at least one of the reactant molecules.
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Question 5

The following diagram depicts the tetrahedral active site intermediate formation during serine protease catalyzed peptide bond hydrolysis. Aspartate (Asp), histidine (His), and serine (Ser) are amino acids of the serine protease, which are close to each other and can interact to catalyze the breakdown of certain peptide bonds in proteins. The protein is R'NHCOR in the diagram below. You can see hydrogen bonds between the enzyme's Asp and His, and also the His is taking away a hydrogen from the Ser hydroxyl group. Which of the following statements best describes the Ser attack on the peptide bond?

Choose one answer.
A. Ser is a strong acid; this is why Ser gives His a proton. The result is a stable tetrahedral intermediate.
B. The hydrogen is a strong electrophile, and it attacks the peptide bond forming a negatively charged oxyanion.
C. The deprotonated Ser is a strong nucleophile, and it attacks the peptide bond forming a negatively charged oxyanion.
D. Ser is a strong base, and it attacks the peptide bond forming a negatively charged oxyanion.
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Question 6

The following diagram depicts lactase catalyzed cleavage of lactose. Glu-1749 is the side chain of the active site glutamate amino acid in the lactase enzyme. Lactose is a disaccharide; it is composed of a galactose and a glucose. Downregulated lactase expression results in lactose intolerance. Please analyze the following diagram carefully, and choose the statement which describes it best.



Choose one answer.
A. Glucose leaves after the Glu-1749 electrophile attack on the glycosidic carbon of the galactose, and galactose is freed after water reacts with the hemiacetal carbon.
B. Glucose leaves after the Glu-1749 electrophile attack on the glycosidic carbon of the galactose, and galactose is freed after water reacts with the acetal carbon.
C. The acetal carbon of the galactose receives two nucleophile attacks: the first nucleophile is Glu-1749 and the second one is water.
D. The hemiacetal carbon of the galactose receives two nucleophile attacks: the first nucleophile is Glu-1749 and the second one is water.
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Question 7

Fill in the blanks. Use the following structural formula to identify carbon 1 and 6. The oxidation state number of carbon atom 1 is ___, and the oxidation state number of carbon atom 6 is ____.

 

Choose one answer.
A. +1, -1
B. +4, +2
C. +3, 0
D. -2, -1
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.
Question 8
Use the following structural formula to calculate the oxidation state number of the carbon atom in urea.

 


Choose one answer.
A. +2
B. -2
C. +4
D. -4
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Question 9

Fill in the blanks. A simplified outline of the catabolism of proteins, polysaccharides, and fats can be seen below. Nutrients are ______ when they are converted to acetyl-CoA. The citric acid cycle produces the ______ form of nicotinamide adenine dinucleotide, which is _________ by the electron transport chain.

 

Choose one answer.
A. Reduced, oxidized, reduced
B. Reduced, oxidized, oxidized
C. Oxidized, oxidized, reduced
D. Oxidized, reduced, oxidized
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Question 10

Fill in the blank.The rearrangements that result in the common cyclic forms of D-glucose can be seen below. The cyclic form is a(n) ______.


Choose one answer.
A. Ether
B. Ester
C. Acetal
D. Hemiacetal
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Question 11

Fill in the blank. Sucrose, the common table sugar, is a disaccharide, which is formed from glucose and fructose monosaccharides. The structural formula of sucrose is shown below. The glycosidic linkage between glucose and fructose makes sucrose a(n) ______.

Choose one answer.
A. Ether
B. Ester
C. Acetal
D. Hemiacetal
.
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Question 12

Fill in the blank. Sucrose, the common table sugar, is a disaccharide, which is formed from glucose and fructose monosaccharides. The structural formula of sucrose is shown below. The formation of sucrose from glucose and fructose is a(n) _____ reaction.

Choose one answer.
A. Substitution
B. Elimination
C. Condensation
D. Redox
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Question 13

Glyceraldehyde-3-phosphate (G3P) is an intermediate of glycolysis. The formula of G3P is shown below. G3P is converted to the next intermediate in a redox reaction catalyzed by a dehydrogenase enzyme. What is the product of this reaction?

A.


Choose one answer.
A. A
B. B
C. C
D. D
.
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Question 14

Fill in the blank. The diagram of protein synthesis can be seen below. The addition of new amino acids during protein synthesis is a(n) _____ reaction.

Choose one answer.
A. Substitution
B. Elimination
C. Condensation
D. Redox
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Question 15

At the initial step of β-oxidation, acyl-CoA (the general structural formula is shown below) is converted in an elimination reaction. What is the product of this reaction?







Choose one answer.
A. A
B. B
C. C
D. D
.
.
Question 16

Fill in the blank. Glycolysis produces ATP via _____ .

Choose one answer.
A. Substrate level phosphorylation
B. Redox reaction
C. Oxidation
D. Isomerization
.
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Question 17



Choose one answer.
A. A coenzyme. Coenzymes are organic cofactors that are essential for the biological activity of certain enzymes.
B. A monosaccharide. Monosaccharides are the building blocks of polysaccharides.
C. Choline. Choline is linked to the phosphate group in phospholipids.
D. An amino acid. Amino acids are the building blocks of proteins.
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Question 18

18. What does the structural formula below show, and what is its function? 


 


Choose one answer.
A. A coenzyme. Coenzymes are organic cofactors that are essential for the biological activity of certain enzymes.
B. A monosaccharide. Monosaccharides are the building blocks of polysaccharides.
C. Choline. Choline is linked to the phosphate group in phospholipids.
D. An amino acid. Amino acids are the building blocks of proteins.
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Question 19

What does the structural formula below show, and what is its function?

 

Choose one answer.
A. N-acetylglucosamine. N-acetylglucosamine is a building block of bacterial cell wall.
B. A nucleotide. Nucleotides are the building blocks of nucleic acids.
C. An amino acid. Amino acids are the building blocks of proteins.
D. Uracyl. Uracyl is a building block of RNA.
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Question 20

What does the structural formula below show, and what is its function?

 

Choose one answer.
A. N-acetylmuramic acid. N-acetylmuramic acid is the building block of bacterial cell wall.
B. A nucleotide. Nucleotides are the building blocks of nucleic acids.
C. An amino acid. Amino acids are the building blocks of proteins.
D. Tryptophan. Tryptophan is a building block of proteins.
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Question 21

How many chiral carbon atoms can be found in the following organic molecule?


Choose one answer.
A. 2
B. 3
C. 4
D. 5
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Question 22

How many chiral carbon atoms can be found in the following organic molecule?


Choose one answer.
A. 2
B. 3
C. 4
D. 5
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.
Question 23

How many chiral carbon atoms can be found in the following organic molecule?

 

Choose one answer.
A. 1
B. 2
C. 3
D. None
.
.
Question 24

How many chiral carbon atoms can be found in the following organic molecule?

 

Choose one answer.
A. 1
B. 2
C. 3
D. None
.
.
Question 25

How many chiral carbon atoms can be found in the following organic molecule?

 

Choose one answer.
A. 1
B. 2
C. 3
D. 4
.
.
Question 26

How many chiral carbon atoms can be found in the following organic molecule?

 

Choose one answer.
A. 1
B. 3
C. 5
D. 6
.
.
Question 27

Fill in the blank. Triglycerides ______ chiral carbon atoms.

Choose one answer.
A. Always have 1
B. Always have 2
C. Always have 3
D. Do not always have
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Question 28

The following diagram depicts energy level changes during chemical reactions. One of the lines represents a reaction without a catalyst. What can be the relationship of the two energy profiles on the diagram?


Choose one answer.
A. The reaction without a catalyst must be the red line. The green line cannot be the same reaction catalyzed by an enzyme, because the energy levels of the green and red products are different.
B. The red line is the enzyme catalyzed reaction, because enzymes speed up reactions and produce higher energy level products. The green line is the reaction without a catalyst.
C. The red and green lines represent two different reactions; it is unclear if any of these reactions are enzyme catalyzed or not.
D. Both the red and green lines represent enzyme catalyzed reactions; the green and red energy peaks represent the breaking of the chemical bonds in the substrates.
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Question 29

The following diagram depicts energy level changes during chemical reactions. One of the lines represents a reaction without a catalyst. Could the other line be the energy profile of an enzyme catalyzed reaction?


Choose one answer.
A. The red and green lines represent two different reactions; it is unclear if any of these reactions are enzyme catalyzed or not.
B. Both the red and green lines represent enzyme catalyzed reactions; the green and red energy peaks represent the breaking of the chemical bonds in the substrates.
C. The green and the red lines may represent the same reaction; the red is without a catalyst, and the green is enzyme catalyzed.
D. The green and the red line represent different reactions, because the green and red activation energies are different.
.
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Question 30

The following diagram depicts energy level changes during chemical reactions. Which line represents an endergonic, and which one represents an exergonic reaction?


Choose one answer.
A. The green line represents an endergonic reaction; the red line represents an exergonic reaction.
B. The red line represents an endergonic reaction; the green line represents an exergonic reaction.
C. Both the green and the red lines represent endergonic reactions.
D. Both the green and the red lines represent exergonic reactions.
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Question 31

You are a scientist and you want to set up a protein phosphorylation reaction using PKA. You purchased PKA from a biotech company, and the datasheet tells you that PKA requires ATP, cAMP and Mg2+. What could be the role of these reaction mixture ingredients?

Choose one answer.
A. ATP and cAMP are coenzymes; Mg2+is a cofactor.
B. ATP is a substrate; cAMP and Mg2+ are cofactors.
C. ATP, cAMP, and Mg2+ are cofactors.
D. ATP is a substrate; cAMP is a coenzyme, and Mg2+ is a cofactor.
.
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Question 32

You are a scientist and you would like to set up a carbon fixation reaction in the test tube. You would like to make glyceraldehyde-3-phosphate [G3P] from carbon dioxide; you would like to mirror the Calvin-Benson cycle. What should you consider, when you design your experiment?

Choose one answer.
A. This will be an exergonic reaction, which will produce ATP and other possible high-energy molecules as well.
B. This will be an exergonic reaction; thus, cooling will be necessary if you would like to avoid the high-energy G3P-driven explosion.
C. This will be an endergonic reaction; thus, you will need an enzyme to catalyze it.
D. This will be an endergonic reaction; thus, you will need high energy compounds that can provide the energy, which will be stored in G3P.
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.
Question 33

Fill in the blank. Bile acids emulsify_____ and expose them for _______ in the small intestine.

Choose one answer.
A. Cholesterol, the pancreatic hydrolase
B. Chylomicrons, apolipoprotein B-100
C. LDL, LDL receptor
D. Triglycerides, the pancreatic lipase
.
.
Question 34

Fill in the blank. Bile acid can emulsify fats, because it is _____.

Choose one answer.
A. Hydrophilic
B. Amphipathic
C. Lipophilic
D. Hydrophobic
.
.
Question 35

Fill in the blank. Triglycerides combine with bile to form _____________ and enter the central lacteal of the villi.

Choose one answer.
A. Low density lipoproteins
B. High density lipoproteins
C. Chylomicrons
D. Very low density lipoproteins
.
.
Question 36

β-oxidation breaks down fatty acids to acetyl-CoA, but odd-numbered fatty acids cannot be fully converted into acetyl-CoA. How are odd-numbered fatty acids metabolized?

Choose one answer.
A. Odd-numbered fatty acids contribute to the regulation of the Szent-Györgyi-Krebs cycle's intermediates through giving rise to succinyl-CoA.
B. Odd-numbered fatty acids do not occur naturally, and there is no metabolic pathway to break them down fully. If industrially produced odd-numbered fatty acids are consumed, then the last three carbon atoms will be excreted as a waste in the form of propionic acid.
C. Eukaryotic cells cannot break down the last three carbon atoms containing propionyl-CoA, but bacteria in the gastrointestinal tract can. Bacteria will produce methane gas from propionyl-CoA, and this will result in gastrointestinal discomfort.
D. β-oxidation breaks down fatty acids to acetyl-CoA and propionyl-CoA. Both acetyl-CoA and propionyl-CoA can step into the Szent-Györgyi-Krebs cycle, and they can be used to generate NADH and FADH2 for the electron transport chain.
.
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Question 37

What is the contribution of fatty acids metabolism to the production of metabolites for biosynthesis and to energy production?

Choose one answer.
A. Metabolites for biosynthesis are produced by fatty acid catabolism; only anabolism makes energy.
B. Metabolites for biosynthesis are produced by fatty acid anabolism; only catabolism makes energy.
C. Metabolites for biosynthesis are produced by fatty acid catabolism and anabolism; only catabolism makes energy.
D. Metabolites for biosynthesis are produced by fatty acid catabolism; both anabolism and catabolism make energy.
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Question 38

Fill in the blank. The synthesis of__________ is the first step of fatty acid synthesis; this metabolite inhibits carnitine palmitoyltransferase, which controls fatty acid oxidation.

Choose one answer.
A. Malonyl-CoA
B. Acetyl-CoA
C. Citric acid
D. Succinyl-CoA
.
.
Question 39
Fill in the blanks. ___________ the end product of β-oxidation, which contributes to ___________ in the first step of the Szent-Györgyi-Krebs cycle. An increased level of the latter activates fatty acid synthesis through the activation of acetyl-CoA carboxylase.
Choose one answer.
A. Carbon dioxide is, NADH and FADH2
B. Acetyl-CoA is, oxaloacetic acid
C. Acetyl-CoA is, citric acid
D. Acetyl-CoA and glycerol are, ATP
.
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Question 40

Fill in the blank. Both fatty acid synthesis and catabolism takes place through a series of ___________ reactions.

Choose one answer.
A. Elimination
B. Dehydration synthesis
C. Substitution
D. Redox
.
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Question 41

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency affects 1 in 17000 people in the United States. Why should MCAD deficient people avoid prolonged fasting?

Choose one answer.
A. High glucagon level during fasting activates fatty acid oxidation, which cannot be completed due to MCAD deficiency. Fatty acids will be increasingly retained in the adipose tissue, and this will result in obesity.
B. High glucagon levels during fasting activate fatty acid oxidation, which in turn inhibits glucose oxidation. If glucose oxidation cannot be inhibited as the result of MCAD deficiency, then the brain will not get sufficient glucose.
C. This is a common misconception. MCAD deficient people are simple lucky, because they can eat fatty food. Most of the consumed fat is excreted in the form of medium chain fatty acids, and their adipose tissue cannot accumulate in excess.
D. MCAD deficient people do not have efficient fatty acid catabolism in their brain, because most of the fat energy is lost during the excretion of medium chain fatty acids.
.
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Question 42

Fill in the blanks. The transcription factor, __________, regulates both the synthesis and the cellular uptake of cholesterol. Thus, this transcription factor is directly involved in _________.

Choose one answer.
A. SCREBP, artherosclerotic plaque formation
B. SCREBP, development of high blood pressure
C. Sterol, risk level of cardiac arrest
D. Sterol, cardiovascular disease
.
.
Question 43

The simplified diagram of the sterol biosynthesis is shown below. What is the name of the growing red-blue structure in this pathway?

 

Choose one answer.
A. Mevalonate
B. Lanosterol
C. HMG-CoA
D. Isoprene
.
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Question 44

Which of the following is a five-carbon organic compound and is a precursor of terpenoid biosynthesis?

Choose one answer.
A. Mevalonate
B. Lanosterol
C. HMG-CoA
D. Isoprene
.
.
Question 45

Which of the following reactions produces mevalonate?


 



 



 



 

Choose one answer.
A. A
B. B
C. C
D. D
.
.
Question 46

The chemical structure of a free fatty acid is shown below. How would you characterize this fatty acid?


Choose one answer.
A. 18:4 ω-3
B. 18:3 ω-4
C. 18:3 ω-6
D. 18:4 ω-6
.
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Question 47

The chemical structure of a free fatty acid is shown below. How would you characterize this fatty acid?


Choose one answer.
A. 18:9 ω-2
B. 18:6 ω-9
C. 18:2 ω-6
D. 18:2 ω-6
.
.
Question 48

You can see the space-filling models of two fatty acids below (1 and 2). Which fatty acid is essential, and which one is non-essential for humans?


Choose one answer.
A. 1
B. 2
C. Both
D. None
.
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Question 49

Fill in the blank. Linoleic acid and linolenic acid cannot be synthesized in human tissues, because ____________.

Choose one answer.
A. Human cells can synthesize only mono-unsaturated fatty acids.
B. Humans are diploid organisms; only polyploid organisms have enough genes for the biosynthesis of theses fatty acids.
C. The corresponding biosynthetic pathway was lost during evolution.
D. Human cells cannot synthesize unsaturated fatty acids.
.
.
Question 50

The following diagram shows the catabolism of the three main nutrient groups, including carbohydrates. Which arrow represents a pathway that is utilized in every cell?

 

Choose one answer.
A. Monosaccharide -> Acetyl-CoA
B. Citric acid cycle
C. Oxidative phosphorylation
D. Polysaccharide -> monosaccharide
.
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Question 51

Why can termites digest cellulose?

Choose one answer.
A. Their digestive tract secretes β-glucosidase.
B. Bacteria in their digestive tract secrete β-glucosidase.
C. Their digestive tract secretes α-glucosidase.
D. Bacteria in their digestive tract secrete α-glucosidase.
.
.
Question 52

Which of the following structural formula show an α, and which one shows a β anomer?

1.  

2.  

Choose one answer.
A. 1 is an α anomer, and 2 is a β anomer.
B. 2 is an α anomer, and 1 is a β anomer.
C. Both are α anomers.
D. Both are β anomers.
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.
Question 53

Which enzyme is a key regulator of glycolysis?

 

Choose one answer.
A. Hexokinase
B. Glucose 6-phosphate
C. Phosphofructokinase
D. Pyruvate kinase
.
.
Question 54

Fill in the blank. ATP is required for the activity of phosphofructokinase, but high ATP level inhibits its activity. This is because ATP _____________.

Choose one answer.
A. Is both a substrate and an allosteric inhibitor of phosphofructokinase
B. Is both an allosteric activator and an allosteric inhibitor of phosphofructokinase
C. Is used only when there is plenty in the cell
D. Level decreases immediately in the presence of phosphofructokinase
.
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Question 55

Fill in the blank. Both ATP and citric acid are allosteric inhibitors of the phosphofructokinase enzyme. High levels of these compounds indicate that ________________. 

Choose one answer.
A. The cellular respiration is not going on efficiently, but the ATP level is sufficient
B. The cellular respiration is efficiently going on, and it is producing sufficient ATP
C. Phosphofructokinase expression is inhibited by ATP and citric acid
D. Phosphofructokinase is a subject of negative feedback inhibition as the first enzyme of the glycolytic pathway
.
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Question 56

Fill in the blank. Fermentation recycles ______, thus glycolysis can produce more ATP.

Choose one answer.
A. FADH2
B. NADP+
C. NAD+
D. AMP
.
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Question 57

What is the final electron acceptor during fermentation?

Choose one answer.
A. A coenzyme
B. NADH
C. ATP
D. An organic molecule
.
.
Question 58

58. Fill in the blanks. Louis Pasteur, a French chemist, was the first to determine that the presence of some microorganism results in ____fermentation, while other microorganisms produce _____.

Choose one answer.
A. Alcoholic, acid
B. Acidic, carbon dioxide
C. Alcoholic, carbon dioxide
D. Ethanol, lactic acid
.
.
Question 59

The following diagram shows an outline of cellular respiration. Why is the Citric Acid Cycle called a "cycle," but the glycolysis and the electron transport chain is not?

 

Choose one answer.
A. The two carbon atoms of the CoA linked acetyl group are catabolized in two consecutive steps.
B. The citric acid cycle requires the presence of a starter molecule (oxaloacetate) for the catabolism of the CoA linked acetyl group, and this starter molecule is recycled after the catabolism of the acetyl group.
C. It is a historical nomenclature; there is no particular reason to call a pathway "cycle."
D. It takes two rounds for the citric acid cycle to release the remaining carbon atoms of one glucose molecule in the form of carbon dioxide.
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Question 60

Fill in the blanks. The cyclic and the linear light reactions produce ATP, but only the ______ light reaction makes _______.

Choose one answer.
A. Cyclic, NADH
B. Cyclic, NADPH
C. Linear, NADPH
D. Linear, NADH
.
.
Question 61

The following diagram shows an outline of the Calvin-Benson Cycle. Why is this pathway called a “cycle?”

 

Choose one answer.
A. Glyceraldehyde 3-phosphate, the three carbon containing sugar, is built by three consecutive steps.
B. The Calvin-Benson cycle requires the presence of a starter molecule (ribulose 1,5-bisphosphate) for the carbon fixation, and this starter molecule is recycled after the synthesis of the three carbon sugar.
C. It is a historical nomenclature; there is no particular reason to call a pathway "cycle."
D. Because it takes three rounds for the Calvin-Benson cycle to synthesize one triose molecule from carbon dioxide.
.
.
Question 62

Fill in the blank. A eukaryotic cell that has insufficient amount of oxaloacetate _____.

Choose one answer.
A. Will complete the cellular respiration of glucose to carbon dioxide, because the involved pathways do not produce net oxaloacetate.
B. Will not be able to survive, because it cannot complete cellular respiration.
C. Will produce two ATP molecules per glucose, and it will recycle NAD+ with fermentation.
D. Will have increased carbon dioxide binding, thus it will be able to perform carbon fixation more efficiently.
.
.
Question 63

Fill in the blank. A eukaryotic cell that lacks ribulose 1,5-bisphosphate is a(n) _________.

Choose one answer.
A. Chemoautotroph
B. Photoheterotroph
C. Autotroph
D. Heterotroph
.
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Question 64

Fill in the blank. A eukaryotic cell which harvests light energy with only the cyclic light reaction _____________.

Choose one answer.
A. Will need a light reaction independent NADPH source to perform carbon fixation
B. Can fully support carbon fixation with the cyclic light reaction
C. Will employ an NADPH independent way of carbon fixation
D. Will become heterotroph
.
.
Question 65

Glycolysis and the pentose phosphate pathway are alternatives, but the pentose phosphate pathway is less efficient in ATP production. Is there a special need for the pentose phosphate pathway in the cell?

Choose one answer.
A. Glycolysis and the pentose phosphate pathway are completely interchangeable.
B. The pentose phosphate pathway produces metabolites for the synthesis of essential amino acids.
C. The pentose phosphate pathway is used, when the cell has high ATP levels, and it is not very important to extract as much energy as possible from one glucose molecule.
D. The pentose phosphate pathway produces essential metabolites for nucleotide synthesis and NADPH.
.
.
Question 66

What is similar in the Szent-Györgyi-Krebs and the Calvin-Benson cycles?

Choose one answer.
A. Both the Calvin-Benson and the Szent-Györgyi-Krebs cycles have key metabolites that are necessary to start the cycle: oxaloacetic acid for the Szent-Györgyi-Krebs cycle, and ribulose 1,5-bisphosphate for the Calvin-Benson cycle.
B. Both the Calvin-Benson and the Szent-Györgyi-Krebs cycles make ATP and other high energy molecules.
C. Both metabolic cycles result in the production of carbon dioxide.
D. The primary role of both pathways is the production of NADH and FADH2 for the electron transport chain.
.
.
Question 67
What is different in the Szent-Györgyi-Krebs and the Calvin-Benson cycles?
Choose one answer.
A. The Szent-Györgyi-Krebs cycle breaks down a triose to carbon dioxide; the Calvin-Benson cycle synthesizes a triose from carbon dioxide.
B. The Calvin-Benson cycle requires NADH, while the Szent-Györgyi-Krebs makes NADH.
C. The Szent-Györgyi-Krebs cycle breaks down an organic molecule to carbon dioxide; the Calvin-Benson cycle synthesizes an organic molecule from carbon dioxide.
D. The Szent-Györgyi-Krebs cycle requires high energy molecules for carbon dioxide production; the Calvin-Benson cycle produces high energy molecules as a byproduct of triose synthesis.
.
.
Question 68

Why are BRCAs not synthesized in human tissues?

Choose one answer.
A. Human cells can synthesize only polar amino acids.
B. Humans are diploid organisms; only polyploid organisms have enough genes for the biosynthesis of BRCAs.
C. The corresponding biosynthetic pathway was lost during evolution.
D. Human cells cannot synthesize apolar amino acids.
.
.
Question 69

Fill in the blank. Essential amino acids are those that cannot be produced by an organism, e.g. _____ has no essential amino acid, but all amino acids are essential for _______.

Choose one answer.
A. Escherichia coli, algae
B. Escherichia coli, Lactobacteria
C. Plants, humans
D. Lactobacteria, humans.
.
.
Question 70

Fill in the blanks. Metabolic diseases may render an otherwise nonessential amino acid to become essential. For example, the inherited metabolic disease _______, moves _______ to the essential amino acid category in affected individuals.

Choose one answer.
A. Phenylketonuria, phenylalanine
B. Maple syrup urine disease, branched chained amino acids
C. Alkaptonuria, tyrosine
D. Phenylketonuria, tyrosine
.
.
Question 71

How many amino acids are essential?

Choose one answer.
A. For some species all amino acids are essential, for others none are essential.
B. There are nine essential amino acids.
C. Plants and fungi have none; for every other species, 9 amino acids are essential.
D. There are 10 essential amino acids.
.
.
Question 72

Complete the sentence. Ornithine is essential in the urea cycle, because ______________.

Choose one answer.
A. It is converted to arginine, and arginine is used in protein synthesis
B. The urea cycle requires the presence of ornithine as a starter molecule, and it is being recycled as the nitrogen leaves the cycle in the form of urea
C. Ornithine delivers the nitrogen from amino acid catalysis into the cycle
D. Ornithine is cycling between the cytosol and the mitochondria during the cycle
.
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Question 73

What is a common way of regulating amino acid synthesis?

Choose one answer.
A. Many amino acids are allosteric inhibitors of an early step of their own anabolic pathway.
B. Many amino acids are competitive inhibitors of their own anabolic pathway.
C. Many amino acids are allosteric activators of an early step of their own anabolic pathway.
D. Most amino acids originate from the breakdown of proteins; the amino acid anabolic pathways are hardly used and are not regulated anymore.
.
.
Question 74

Which compound reacts with carbamoyl phosphate in the urea cycle?



 


 



 



Choose one answer.
A. A
B. B
C. C
D. D
.
.
Question 75

What is the biological function of the following pathway?


 

Choose one answer.
A. The biological role of this cycle is to fix nitrogen.
B. The biological role of this cycle is to synthesize arginine.
C. The biological role of this cycle is to eliminate nitrogen.
D. The biological role of this cycle is to synthesize ornithine.
.
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Question 76

What regulates the committed step of the urea cycle? 

Choose one answer.
A. The excess of glutamate
B. Low levels of urea
C. High levels of ornithine
D. The absence of citrulline
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Question 77

Which statement best describes the metabolism of amino acids?


Choose one answer.
A. Glutamate is involved in both amino acid synthesis and amino acid breakdown.
B. Glutamate is involved only in the deamination of other amino acids.
C. The amino acid catabolism and the amino acid synthesis pathways do not overlap.
D. Pyridoxal phosphate is a coenzyme for transamination reactions.
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Question 78

Which of the following best describes a transaminases catalyzed reaction?

Choose one answer.
A. It is an elimination reaction, because it results in the removal of the amino group from the amino acid.
B. It is a substitution reaction, because the amino group is exchanged to ketone group.
C. It is an oxidation, because the α-carbon is oxidized in the product.
D. It is a redox reaction, because the α-carbon is oxidized in the product.
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Question 79

Which enzymes are used during both the biosynthesis and the catabolism of amino acid?

Choose one answer.
A. Transaminases
B. Transcarbamilases
C. Phosphoenolpyrivate kinase and phosphatase
D. Dighydroxiacid dehydratases
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Question 80
What is the fate of the carbone skeleton during amino acid catabolism?
Choose one answer.
A. It can be stored in fats.
B. It can be stored in glucose.
C. It can be stored in fats and glucose.
D. It always released as carbon dioxide.
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Question 81

Which metabolic pathway has the intermediate which is used to start the biosynthesis of all branch chain amino acids?

Choose one answer.
A. Glycolysis
B. Calvin-Benson cycle
C. Szent-Györgyi-Krebs cycle
D. Alanine cycle
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Question 82

Fill in the blank. If the urea cycle does not work efficiently, the blood ____ levels will increase.

Choose one answer.
A. Amino acid
B. Ammonia
C. Glutamine
D. Glutamate
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Question 83

Fill in the blank. High ammonia levels _______.

Choose one answer.
A. Result from the breakdown of urea in the urea cycle.
B. Result in unnecessary amino acid production, and excessive protein synthesis.
C. Decrease glutamate levels, thus it interferes with neuronal signal transduction.
D. Result from the breakdown of carbamoyl phosphate at the end of the urea cycle.
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Question 84

Which metabolic pathway has the intermediate which is used to start the biosynthesis of all aromatic amino acids? 

Choose one answer.
A. Glycolysis
B. Calvin-Benson cycle
C. Szent-Györgyi-Krebs cycle
D. Alanine cycle
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Question 85

Which metabolic pathway has the intermediate which is used to start the biosynthesis of threonine and glutamate?

Choose one answer.
A. Glycolysis
B. Calvin-Benson cycle
C. Szent-Györgyi-Krebs cycle
D. Alanine cycle
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Question 86

Which metabolic pathway has the intermediate which is used to start the biosynthesis of histidine?

Choose one answer.
A. Pentose phosphate pathway
B. Calvin-Benson cycle
C. Szent-Györgyi-Krebs cycle
D. Alanine cycle
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Question 87

What is the heterocyclic intermediate of the purine nucleotide interconversion?

Choose one answer.
A. AMP
B. IMP
C. GMP
D. Uric acid
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Question 88

Which nucleotides are used as energy source by the cell?

Choose one answer.
A. ATP is the only nucleotide that is used as the source of energy in anabolic reactions.
B. ATP is the most commonly used, but GTP, CTP, and UTP are used as well.
C. GTP is used during protein synthesis, but every other anabolic pathway utilizes ATP.
D. ATP is the energy source in anabolic reactions, but catabolic reactions use GTP, CTP, and UTP.
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Question 89

Which metabolite is involved in both the salvage of adenine and the biosynthesis of adenosine-5'-monophosphate?

Choose one answer.
A. inosine-5'-monophosphate
B. Hypoxanthine
C. Ribose-5-phosphate
D. 5-phosphoribosyl-1-ribophosphate
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Question 90

The relative activity of kinases determines the nucleotide levels in the cell. Which nucleotides have the highest levels?

Choose one answer.
A. The NMP levels are highest, because the cell invests in NDP and NTP synthesis only as needed.
B. The NMP levels are highest, because the nucleoside kinases are the most active.
C. The NTP levels are highest, because the NDP kinases are the most active.
D. The NDP levels are highest, because the NMP kinases are the most active.
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Question 91

Fill in the blanks. ___________ is synthesized from glutamine for pyrimidine biosynthesis, but for amino acid catabolism, it is derived from ____________ bicarbonate.

Choose one answer.
A. α-ketoglutarate, carbamate or
B. α-ketoglutarate, ammonia and
C. Carbamoyl phosphate, carbamate or
D. Carbamoyl phosphate, ammonia and
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Question 92

Fill in the blanks. The __________cycle catabolizes AMP to ___________.

Choose one answer.
A. Calvin-Benson, glyceraldehyde-3-phosphate
B. Purine nucleotide, fumarate
C. Szent-Györgyi-Krebs, fumarate
D. Citric acid, oxaloacetic acid
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Question 93
The most common genetically inherited SCID affects the enzyme adenosine deaminase. This deficiency results in which of the following?
Choose one answer.
a. dATP accumulation and the general inhibition of dNTP synthesis from NTPs
b. dATP accumulation and the general inhibition of RNA synthesis
c. AMP accumulation and the selective inhibition of GMP synthesis
d. AMP accumulation and the selective inhibition of IMP synthesis
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Question 94
Fill in the blank. Glutamine and _____ are building blocks of pyrimidine base biosynthesis.
Choose one answer.
a. Aspartate
b. 10-formyl tetrahydrofolate
c. Glycine
d. 5-Phosphoribosil-1-phosphate
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Question 95

Fill in the blanks. Glutamine, aspartate, and _________ are building blocks of __________ base synthesis.

Choose one answer.
a. 10-formyl tetrahydrofolate, purine and pyrimidine
b. 10-formyl tetrahydrofolate, purine
c. Glycine, pyrimidine
d. 5-Phosphoribosil-1-phosphate, purine and pyrimidine
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Question 96

The end product of purine base metabolism is uric acid, and its accumulation may lead to gout formation. Which drug may be used to lower uric acid levels?

Choose one answer.
a. PRPP, which inhibits de novo IMP synthesis
b. Hypoxanthine, which inhibits xanthine oxidase
c. Allopurinol, which is an isomer of hypoxanthine
d. Oxypurinol, which is an isomer of hypoxanthine
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Question 97
Fill in the blank. The biosynthesis of purine and pyrimidine nucleosides utilize _____, which is an activated sugar.
Choose one answer.
a. Adenosine-5'-triphosphate
b. 5-Phosphoribosil-1-phosphate
c. 5-Phosphoribosil-1-pyrophosphate
d. Guanosine-5'-triphosphate
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Question 98
Fill in the blank. De novo nucleotide synthesis results in ____, which can be reduced to ______ as needed.
Choose one answer.
a. Ribonucleotides, deoxyribonucleotides
b. Deoxyribonucleotides, ribonucleotides
c. Inosine-5'-monophosphate, guanine-5'-monophosphate
d. Uric acid, adenosine-5'-monophosphate
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Question 99
Fill in the blank. Vitamin B12 deficiency inhibits DNA synthesis, because it ____.
Choose one answer.
a. Is the precursor of tetrahydrofolate
b. Interferes with dTMP synthesis
c. Interferes with dUMP synthesis
d. Activates glycine synthesis
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Question 100
What are the regulators of ribonucleotide reductase?
Choose one answer.
a. The active site of the enzyme is a complement only to the ribose part of the nucleotide, and its activity is allosterically regulated by the dGTP: GTP ratio.
b. ATP is an activator and dATP is an inhibitor of this enzyme, and all four dNTPs are produced simultaneously.
c. Each ribonucleotide reductase enzyme is specific to one NTP substrate, and its activity is negatively regulated by high levels of the corresponding dNTP.
d. ATP is an activator and dATP is an inhibitor of this enzyme. Furthermore, all four dNTPs adjust the specificity of this broad spectrum enzyme.
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