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WorksheetsMetabolic Biochemistry MCQ practice Quiz
Total questions: 65
Worksheet time: 33mins
Normal serum levels of ketone bodies can be defined as:
100 - 200 μM.
10 - 25 mM.
> 3.0 mM.
1.0 - 3.0 mM.
< 0.5 mM.
After 3 days of continuous fasting 3-β-hydroxybutyrate concentration for a typical healthy individual would be between:
0.5 - 2.0 mM.
2.0 - 5.0 mM.
5.00 - 10.0 mM.
10.0 - 15.0 mM.
15.0 - 20.0 mM.
Which of the following statements is INCORRECT?
Ketone bodies are produced by the liver and used peripherally as an energy source when glucose is not readily available.
Acetone is typically the least abundant ketone body.
Ketone production occurs in conditions of low circulating insulin.
In acute DKA, the ketone body ratio (3-β-hydroxybutyrate:AcAc) rises from normal (1:1) to as high as 10:1.
3-β-hydroxybutyrate is formed from the decarboxylation of AcAc in the mitochondria.
The correct sequence of ketolysis is:
3-β-hydroxybutyrate → AcAc → acetoacetyl CoA → acetyl CoA → oxaloacetate.
AcAc → 3-β-hydroxybutyrate → oxaloacetate → acetoacetyl CoA → acetyl CoA.
Oxaloacetate → AcAc → 3-β-hydroxybutyrate → acetoacetyl CoA → acetyl CoA.
3-β-hydroxybutyrate → acetyl CoA → acetoacetyl CoA → AcAc → oxaloacetate.
3-β-hydroxybutyrate → acetyl CoA → acetoacetyl CoA → oxaloacetate → AcAc.
Acetylcholinesterase (AchE) is an example of a (an):
aspartate synthase.
asparagine reductase.
serine phosphatase.
aspartate reductase.
serine esterase.
Which statement best describes the mode of action of 2-pralidoxime (2-PAM)?
It displaces acetylcholine from the anionic binding site at the active site of AchE.
It breaks the ester covalent bond between serine-200 (at the active site of AchE) and the phosphate group of the organophosphate agent, thereby regenerating serine-200.
It completely changes the conformation of AchE, reducing its biological activity further.
Both a) and c).
None of the above statements are correct.
Edrophonium is itself an example of a (an):
nerve agent.
anti-cholinesterase.
substrate which gives acetylcholine, following AchE catalysis.
inhibitor of ATP synthase.
HM-CoA reductase inhibitor.
With reference to the Luo et al. paper, the nerve agent VX has a lower EC50 value for inhibition of AchE, with respect to a similar agent, sarin. This means:
nothing – sarin and VX have entirely different modes of action and are therefore not comparable.
that sarin is a more potent inhibitor of AchE than VX.
that VX has insufficient potency to make it a viable nerve agent for military use.
that VX is more likely to be absorbed through the skin than sarin, based upon these data.
that VX is a more potent inhibitor of AchE than sarin.
Glycogen is:
a) a linear polymer of glucose residues joined together by α(1, 4) and α(1, 6) linkages.
b) a linear polymer of glucose residues joined together by α(1, 4) linkages.
c) a linear polymer of glucose residues joined together by α(1, 6) linkages.
d) a branched polymer of glucose residues joined together by α(1, 4) and α(1, 6) linkages.
e) the major store of energy (in terms of kJ) in the body.
Which of the following statements is CORRECT? Glycogen phosphorylase
is responsible for breaking α(1, 4) linkages in glycogen.
is responsible for breaking α(1, 6) linkages in glycogen.
is responsible for the synthesis of glycogen from excess cellular glucose.
is responsible for the synthesis of glycogen from excess cellular fructose.
is only expressed in muscle cells.
What is the function of the de-branching enzyme?
It breaks α(1, 4) linkages in glycogen.
It breaks α(1, 6) linkages in glycogen.
It is responsible for the transport of glucose into muscle tissue.
It is responsible for the inter-conversation of glucose-1-phosphate and glucose-6-phosphate.
It allows branched amino acids (e.g. valine, leucine) to be used for the biosynthesis of proteins.
von Gierke’s disease is caused by a deficiency of:
glycogen phosphorylase a.
glycogen phosphorylase b.
glycogen synthase.
lysosomal α(1, 4) glucosidase.
glucose-6-phosphatase.
Which enzyme is primarily responsible for the synthesis of glycogen from glucose?
Glycogen synthase
Glycogen phosphorylase
De-branching enzyme
Hexokinase
Glucose-6-phosphatase
What type of glycosidic bond creates the branches in glycogen structure?
α(1, 2) linkage
β(1, 6) linkage
α(1, 6) linkage
β(1, 4) linkage
α(1, 4) linkage
Which of the following is a function of glucose-6-phosphatase in glycogen metabolism?
It breaks α(1, 4) linkages in glycogen.
It converts glucose-6-phosphate to free glucose.
It forms branches in glycogen.
It synthesizes glycogen from glucose.
It transports glucose into cells.
G proteins are capable of hydrolysing high energy phosphates from which molecule?
GTP.
CTP.
ATP.
AMP.
cAMP.
Which second messenger signals the release of Ca²⁺ from the endoplasmic reticulum during Gq signalling?
Diacylglycerol.
IP3
PIP2.
Protein Kinase C.
cAMP.
Which of the following enzymes catalyses the cleavage of PIP2 into IP3 and diacylglycerol downstream of Gq signalling?
Phosphokinase C.
Phospholipase C.
Lipokinase C.
Phosphodiesterase C.
Protein Kinase C.
GTP analogues such as GTPγS that can bind to G proteins but cannot be hydrolysed to GDP have what effect on GPCR signalling?
Increases G protein signalling.
Decreases G protein signalling.
No effect on G protein signalling.
Degrades G proteins.
None of the above.
What is true regarding amino acids?
There are close to 300 types of amino acids in nature, only 20 of which serve as protein building blocks.
All amino acids behave as neurotransmitters and control, virtually, all cellular processes.
The chemical properties of the amino acids in proteins determine the biological activity of the protein.
They are a poor nitrogen source during the synthesis of nucleotides.
a and c are true.
Which amino acids are Helix-Helix breakers? Select the correct pair.
Leucine and alanine.
Proline and leucine.
Alanine and phenylalanine.
Proline and phenylalanine.
Proline and alanine.
During Protein degradation: Dipeptides are hydrolysed to amino acids in the membrane before entering the portal circulation.
Dipeptides are hydrolysed to amino acids in the membrane before entering the portal circulation.
after complete digestion, free amino acids and dipeptides are absorbed by the epithelial cells.
trypsin hydrolyses amino bonds between lysine and serine
passive transport is the only way in which of amino acids are taken up by epithelial cells.
the roles of carboxypeptidases A and B is to carry out post-translational modifications of amino acids
What is the number of ATP molecules produced during the glucose-alanine cycle?
14.
12.
10.
8.
6.
What is true during the urea cycle?
The enzyme ornithine transcarbamylase catalyses the reaction of citrulline with arginine to form arginosuccinate.
Ornithine transcarbamylase is located in the cytosol.
Citrulline is a by-product of serine metabolism.
Cleavage of arginosuccinate to form arginine and fumarate is carried out by argino-succinate lyase.
Carbamoyl phosphate synthetase 1 cleaves ornithine to give rise arginine.
What is the correct statement regarding urea cycle disorders?
The severity of the disorder is high regardless of which enzyme is affected.
In individuals with full enzyme deficiencies, the first recognised clinical episode may be delayed for several months.
These disorders are characterised by the accumulation of ammonia, with clinical manifestations appearing only in full-term infants with diabetes associated risk factors.
These disorders are characterised by the accumulation of ammonia and glutamine, with clinical manifestations appearing in full-term infants with mothers with no prior obstetric risk factors.
These disorders are characterised by the accumulation of ammonia, with clinical manifestations appearing in full-term infants with mothers with no prior obstetric risk factors.
Which of the following is a role or roles of the tricarboxylic acid (TCA) cycle?
A source of reduced coenzymes for the electron transport chain.
Final pathway for the complete oxidation of proteins, fats and carbohydrates to carbon dioxide.
Source of precursors for biosynthetic pathways.
Source of GTP for energy production.
All of the above.
The cellular locations of the TCA cycle and oxidative phosphorylation are:
The TCA cycle and oxidative phosphorylation occur in the mitochondrial matrix
The TCA cycle takes place in the mitochondrial matrix, and oxidative phosphorylation takes place across the inner mitochondrial membrane.
The TCA cycle takes place in the cytosol, and oxidative phosphorylation takes place in the mitochondria.
All but one stage (which involves succinate DH) of the TCA cycle occurs within the mitochondrial matrix, and oxidative phosphorylation takes place across the inner mitochondrial membrane.
The TCA cycle and oxidative phosphorylation take place across the inner mitochondrial membrane of the mitochondria.
NAD+ is reduced in reactions forming the following within the TCA cycle:
Alpha-ketoglutarate, succinyl-CoA, oxaloacetate.
Succinyl-CoA, fumarate, oxaloacetate.
Oxalosuccinate, succinyl-CoA, oxaloacetate.
Alpha-ketoglutarate, fumarate, oxaloacetate.
Oxalosuccinate, fumarate, oxaloacetate.
Malonate is added to a cell suspension. Which of the following is likely to occur initially?
Nothing, as it will be out competed by succinate.
Succinate dehydrogenase will be irreversibly inhibited.
Succinate levels will fall.
Succinate levels will increase.
None of the above.
ATPase catalyses the reaction between ADP and Pi to form ATP. Which of the following is the most accurate description of this process?
This takes place in the active sites within the Fo region of ATPase, catalysed by the energy released from the flow of hydrogen ions into the intermembrane space.
This takes place in the active sites within the F1 region of ATPase, as a result of the conformational changes catalysed by the energy released by the flow of hydrogen ions through the enzyme.
This takes place in the active sites within the F1 region of ATPase, catalysed by the energy released from the flow of hydrogen ions against the proton motive force.
This takes place in the active sites within the Fo region of ATPase, as a result of the conformational changes catalysed by the energy released by the flow of hydrogen ions through the enzyme.
This takes place in the active sites within the F1 region of ATPase, catalysed by the energy released from the flow of hydrogen ions into the intermembrane space.
How many reduced co-enzymes are produced in the redox reactions of the TCA cycle, for each glucose molecule that enters the glycolytic pathway:
2.
4.
6.
8.
10.
The inheritance pattern for medium-chain acyl-CoA dehydrogenase deficiency is __.
autosomal recessive.
autosomal dominant.
X-linked dominant.
X-linked recessive.
Mitochondrial.
Untreated medium-chain acyl-CoA dehydrogenase deficiency will most commonly result in which of the following signs?
Headaches.
Breathing difficulties.
Elevated liver transaminases.
Nausea.
Vomiting.
Medium-chain acyl-CoA dehydrogenase works in the ___________ to convert Acyl-CoA to trans-2-enoyl-CoA.
Cytosol
Outer mitochondrial membrane
Mitochondrial inner membrane space
Inner mitochondrial space.
Mitochondrial matrix
Please select the correct answer to complete the following sentence correctly:
Medium chain fatty acids have between _________ carbons
five and ten
six and twelve
three and nine
nine and twelve.
eight and sixteen.
Which enzyme in the TCA cycle is directly inhibited by malonate?
Isocitrate dehydrogenase
Succinate dehydrogenase
Citrate synthase
Alpha-ketoglutarate dehydrogenase
Fumarase
Which of the following amino acids is most likely to disrupt an alpha-helix structure in a protein?
Alanine
Leucine
Phenylalanine
Glycine
Proline
During the urea cycle, which compound is formed by the condensation of citrulline and aspartate?
Fumarate
Carbamoyl phosphate
Argininosuccinate
Ornithine
Arginine
What is the word used to describe a reaction in which free energy is released?
Exothermic.
Endothermic.
Exergonic.
Endergonic.
None of the above.
Which of the following reactions will have the largest increase in entropy?
GeO₂(s) + 4HCl(g) = GeCl₄(l) + 2H₂O(l)
2NH₃(g) = N₂(g) + 3H₂(g)
SO₄²⁻(aq) + H⁺(aq) = HSO₄⁻(aq)
H₂O(s) = H₂O(l)
Unfolded protein = folded protein
If a reaction goes to completion which of the following statements will be true for the reaction?
ΔG will be positive.
ΔG will be 0.
The value of K_eq will be very large and negative.
The value of K_eq will be very large and positive.
The value of K_eq will be zero.
The ΔG'° for this reaction is:
– 3280 J mol⁻¹ / – 3.28 kJ mol⁻¹
– 634 J mol⁻¹ / – 0.634 kJ mol⁻¹
– 275 J mol⁻¹ / 0.275 kJ mol⁻¹
– 7560 J mol⁻¹ / – 7.56 kJ mol⁻¹
– 8214 J mol⁻¹ / – 8.21 kJ mol⁻¹
The free energy for the hydrolysis of ATP to ADP and water at 25ºC is approx. –30 kJ mol⁻¹ while the free energy change for the oxidation of glucose to pyruvate via the glycolytic pathway is –150 kJ mol⁻¹. What percentage of the free energy released during glycolysis is captured in the form of ATP?
About 10%.
About 20%.
About 30%.
About 40%.
About 50%.
Which of the following statements about glycolysis is incorrect?
Glycolysis generates a total of four molecules ATP via substrate level phosphorylation per glucose molecule.
Glycolysis uses two molecules of ATP during the so called “preparatory phase”.
Glycolysis takes place in the mitochondria of eukaryotic cells.
Glycolysis does not require the presence of oxygen.
Some organisms can survive solely using glycolysis to make ATP.
Which of the following are all hydrophobic amino acids?
Serine, threonine and tyrosine.
Leucine, valine and isoleucine.
Proline, aspartic acid and glycine.
Histidine, arginine and lysine.
Phenylalanine, tyrosine and tryptophan.
Which of the following statements about proteins / or protein structure is incorrect?
The DNA sequence encoding a protein is more highly conserved than the corresponding amino acid sequence.
Protein structure is more highly conserved within a protein family than protein sequence.
A protein’s 3D structure largely determines its biological function.
Homologous proteins will have similar 3D structures.
A protein’s amino acid sequence specifies its 3D structure.
An enzyme obeys Michaelis-Menten kinetics and has a Vmax of 32 nmol/s and a Km of 7.6 mM for a particular substrate. What is the initial rate (v0) of the reaction as a percentage of Vmax when the substrate concentration is 11.9 mM?
31%
41%
51%
61%
71%
Examine the graph below and identify the type of inhibition taking place.
Competitive inhibition.
Uncompetitive inhibition.
Non-competitive inhibition.
Mixed inhibition.
Irreversible inhibition.
What is the value of Km for the following enzyme catalysed reaction? You may assume numerical value of the intercept on the y axis is 0.0781 and that on the x axis is –0.312.
1.42 mM
2.71 mM
3.21 mM
4.81 mM
5.76 mM
You are investigating the inhibitory effect of a range of molecules on the activity of a key enzyme involved in the DNA metabolism in an important human parasite. Based on this data, say which compound is the best inhibitor of the parasite enzyme.
Compound 1.
Compound 2.
Compound 3.
Compound 4.
Compound 5.
What is the correct notation for the following fatty acid using lipid numbers (i.e. CX:Y) and Δx notation?
C17.
C18:2 (cis-, cis-Δ9,12).
C18:3 (cis-, cis-, cis-Δ9,12,15).
C18:2 (cis-, cis-Δ8,11).
C17:2 (cis-, cis-Δ8,11).
What is the source of electrons used in fatty acid synthesis?
FADH₂.
NADP⁺.
NADH.
NADPH.
NAD⁺.
Why in chemical terms does the oxidation of a gram of fatty acid yield more energy than the oxidation of a gram of carbohydrate?
Fat is more oxidised to start with.
Fat is more hydrophobic.
Fatty acids contain very little oxygen compared to carbohydrates.
The enzymes in the β-oxidation pathway are more efficient than those in glycolysis.
The β-oxidation pathway takes place in the mitochondria in eukaryotes.
Kangaroo rats typically eat more than 1 kg of seeds per year. Assuming that 1 kg of fatty acids are released from lipids in the seed and that they are entirely palmitic acid (C16:0 with a molar mass of 256 g mol⁻¹), how much metabolic energy per year will this diet supply for each kangaroo rat?
-20703.1 kJ mol⁻¹
-1.246 x 10²⁸ kJ
-414.06 kJ mol⁻¹
-20703.1 kJ
-20703.1 J
Assuming that 1 kg of fatty acids are released from lipids in the seed and that they are entirely palmitic acid (C16:0 with a molar mass of 256 g mol⁻¹), what volume of water will each kangaroo rat gain from this diet?
1.6172 L
89.84 L
-1.6172 L
89.84 kg
3.906 L
How many transmembrane spanning domains do G-protein coupled receptors have?
One membrane spanning domain.
Three membrane-spanning domains.
Five membrane-spanning domains.
Seven membrane-spanning domains.
Nine membrane-spanning domains.
Which of the following statements about enzyme kinetics is correct?
Enzyme activity decreases as substrate concentration increases.
Km represents the maximum velocity of the enzyme.
Vmax is independent of enzyme concentration.
Vmax is reached when all enzyme active sites are occupied by substrate.
Km is always higher than the substrate concentration at Vmax.
Which molecule acts as the main electron donor in the electron transport chain during cellular respiration?
CO₂
FAD
ATP
Glucose
NADH
Which of the following best describes the role of allosteric regulation in enzyme activity?
It involves the binding of a molecule at the active site to increase enzyme activity.
It is a type of irreversible inhibition.
It involves the binding of a molecule at a site other than the active site, altering enzyme activity.
It always results in decreased enzyme activity.
It only occurs in enzymes involved in glycolysis.
Which enzyme catalyzes the conversion of pyruvate to oxaloacetate in gluconeogenesis?
Phosphoenolpyruvate carboxykinase
Pyruvate kinase
Malate dehydrogenase
Lactate dehydrogenase
Pyruvate carboxylase
Which of the following amino acids is most likely to be found in the interior of a globular protein due to its hydrophobic nature?
Serine
Glutamine
Arginine
Valine
Threonine
Which step in the TCA cycle directly produces GTP (or ATP)?
Conversion of fumarate to malate
Conversion of succinyl-CoA to succinate
Conversion of alpha-ketoglutarate to succinyl-CoA
Conversion of citrate to isocitrate
Conversion of malate to oxaloacetate
Which enzyme is responsible for catalyzing the conversion of pyruvate to oxaloacetate in gluconeogenesis?
Pyruvate kinase
Pyruvate carboxylase
Phosphoenolpyruvate carboxykinase
Lactate dehydrogenase
Malate dehydrogenase
Which of the following amino acids is most likely to disrupt an alpha-helix structure in a protein?
Leucine
Proline
Valine
Glycine
Alanine
Which of the following best describes the role of FAD in the TCA cycle?
It acts as a substrate for citrate synthase.
It is required for the conversion of malate to oxaloacetate.
It phosphorylates ADP to ATP.
It is reduced to FADH2 during the oxidation of succinate to fumarate.
It hydrolyzes acetyl-CoA.
