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Biochemistry Final Review

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3rd year undergraduate biochemistry final exam review - glycolysis to Cori cycle
Katja Marie
Quiz by Katja Marie, updated more than 1 year ago More Less
Kaitlyn Emily Bi
Created by Kaitlyn Emily Bi over 8 years ago
Katja Marie
Copied by Katja Marie over 6 years ago
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Question 1

Question
Which of the following statements about the role of the PPP pathway is correct?
Answer
  • a) The PPP produces ribose-5-P and NADPH
  • b) THE PPP pathway oxidizes NADPH to NADP+
  • c) The rate-limiting reaction of the PPP is catalyzed by transketolase
  • a) The PPP occurs in the mitochondria of most cells

Question 2

Question
Which of the following statements about the oxidative section of the PPP is correct
Answer
  • a) The PPP generates NADH
  • b) THE PPP pathway oxidizes NADPH to NADP+
  • c) The rate-limiting reaction of the PPP is catalyzed by G6P
  • d) The PPP supplies ribose-5-P and NADPH in the quantities the cells require

Question 3

Question
Which of the following statements about the non-oxidative section of the PPP is correct
Answer
  • a) The non-oxidative reactions of the PPP are not reversible
  • b) Transketolase is an enzyme that transfers three-carbon units in the PPP
  • c) Transaldolase is an enzyme that transfers two-carbon units in the PPP
  • d) Pentoses undergo isomerizations in the PPP

Question 4

Question
Which of the following statements about the PPP is not true:
Answer
  • a) The PPP relies on the availability of NADP+
  • b) The PPP has an irreversible oxidative section and a reversible non-oxidative section
  • c) The PPP enables excess ribose to be metabolized
  • d) The PPP relies on the availability of NADPH

Question 5

Question
Haemolytic anemia can be triggered in people deficient in glucose-6-phosphatatse by infections. What is the mechanism?
Answer
  • a) Infection leads to increased production of immunoglobulins which attack the erythrocyte
  • b) Infection is accomplished by generation of oxidants which destroy the erythrocyte membrane
  • c) Infection leads to weakening of erythrocyte cell membranes by the attachment of bacterial toxins
  • d) Infection compromises the immune system which is unable to protect the erythrocyte

Question 6

Question
What is an important function of the PPP
Answer
  • a) Generation of NADH for the production of ATP by the ETC
  • b) Generation of NADPH for fatty acid synthesis
  • c) Generation of NAD which is necessary for glycolysis
  • d) Generation of NADP needed in amino acid metabolism

Question 7

Question
Which of the following statements about the reactions of glycolysis is correct?
Answer
  • G6P is split into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
  • fructose-1,6-bisphosphate is split into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
  • fructose-6-phosphate is split into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
  • G6P is isomerized to fructose-1,6-bisphosphate

Question 8

Question
Which of the following statements about the glycolytic intermediate fructose-6-phosphate is correct?
Answer
  • fructose-6-phosphate is formed from G6P and is split by the aldol reaction into an aldehyde and a ketone
  • fructose-6-phosphate is an aldol so once phosphorylated to F-1,6-BP cannot be split by the aldol reaction into an aldehyde and a ketone
  • fructose-6-phosphate is converted to G6P and can then be split by the aldol reaction into an aldehyde and a ketone
  • fructose-6-phosphate is an aldol but is not itself split by the aldol reaction until phosphorylated to F-1,6-BP

Question 9

Question
Which of the following statements about the Citric Acid Cycle is correct?
Answer
  • Oxygen is used to oxidize the acetyl group carbons of acetyl-CoA
  • Three molecules of NADH and one molecule of FADH2 are produced in one turn of the ycle
  • Oxygen is not used in the CA cycle, so the cycle can occur in anaerobic conditions
  • The CA cycle produces the water that is formed during the complete oxidation of glucose

Question 10

Question
Which of the following statements about the Electron Transport Chain is correct?
Answer
  • The ETC is made up of a chain of electron carriers with decreasing electron affinity
  • The ETC is made up of a chain of electron carriers with increasing redox potential
  • The ETC is made up of a chain of electron carriers with decreasing oxidizing power
  • The electrons transferred from carrier to carier in the ETC gain energy

Question 11

Question
Glycogenolysis is inhibited by insulin
Answer
  • True
  • False

Question 12

Question
Glycogenolysis is inhibited by glucagon and epinephrine
Answer
  • True
  • False

Question 13

Question
Glycogenesis is the synthesis of glycogen from G6P
Answer
  • True
  • False

Question 14

Question
Insulin inhibits glycogenolysis
Answer
  • True
  • False

Question 15

Question
Insulin deactivates glycogenesis
Answer
  • True
  • False

Question 16

Question
Epinephrine release activates glycogenolysis
Answer
  • True
  • False

Question 17

Question
Epinephrine release inhibits glycogenesis
Answer
  • True
  • False

Question 18

Question
Glucagon inhibits glycogen breakdown
Answer
  • True
  • False

Question 19

Question
Glucagon activates liver gluconeogenesis
Answer
  • True
  • False

Question 20

Question
Insulin is secreted from the liver in response to an increase in blood glucose
Answer
  • True
  • False

Question 21

Question
Insulin's effect include:
Answer
  • Stimulation of lipid synthesis
  • Glycogen synthesis
  • Protein Synthesis
  • Glycolysis and inhibition of gluconeogenesis and lipid breakdown
  • All of the above
  • None of the above

Question 22

Question
Gluconeogenesis is the formation of new glucose molecules from precursors in the liver including:
Answer
  • Lactate
  • Pyruvate
  • Alpha-keto acids
  • All of the above
  • None of the above

Question 23

Question
What is the net yield of ATP per glucose molecule that passes through all of aerobic respiration (glucose --> CO2 + H2O)?
Answer
  • 2
  • 4
  • 6
  • 32, depending on the shuttle system used
  • None of the above

Question 24

Question
What do cyanide, azide, and carbon monoxide all have in common?
Answer
  • They are all products of combustion and contribute to smog
  • They are all nitrogenous compounds
  • They all inhibit the final step of electron transport
  • They all bind to hemoglobin irreversibly
  • All of the above

Question 25

Question
Uncouplers are compounds that inhibit the phosphorylation of ADP:
Answer
  • By enhancing the proton gradient across the outer mitochondrial membrane
  • By enhancing the proton gradient across the inner mitochondrial membrane
  • Because the are transmembrane proteins in the outer mitochondrial membrane
  • Without affecting electron transport

Question 26

Question
Coenzyme Q can act as an intermediate electron carrier, since the ketone group of the quinone structure is readily reduced to an alcohol
Answer
  • True
  • False

Question 27

Question
In Eukaryotes the enzymes of the citric acid cycle are found in the:
Answer
  • Nucleus
  • Mitochondria
  • Endoplasmic Reticulum
  • Cytosol

Question 28

Question
A cytochrome that can move freely in the mitochondrial membrane is:
Answer
  • Cytochrome a
  • Cytochrome b
  • Cytochrome c
  • Cytochrome c1

Question 29

Question
Which of the following enzymatic reactions are control points for glycolysis?
Answer
  • Aldolase
  • Glucose-6-phosphate isomerase
  • Both A and B
  • Neither A nor B

Question 30

Question
The Q cycle refers to flow of electrons from
Answer
  • NADH to coenzyme Q via Complex I
  • FADH2 to coenzyme Q via Complex II
  • Coenzyme Q to cytochrome c via Complex III
  • Coenzyme Q to NADH

Question 31

Question
The step in which acetyl-CoA enters the CA cycle is classified as what type of reaction?
Answer
  • Decarboxylation
  • Dehydrogenation
  • Condensation
  • substrate-level phosphorylation

Question 32

Question
The following enzyme(s) is/are unique to the glyoxylate cycle
Answer
  • malate synthase
  • malate dehydrogenase
  • isocitrate lyase
  • All of the above
  • A and C only

Question 33

Question
Which complex in the electron transport chain carries electrons from cytochrome c to molecular oxygen, reducing it to water?
Answer
  • I
  • II
  • III
  • IV
  • V

Question 34

Question
The terminal electron acceptor for complex III of the ETC is:
Answer
  • FAD
  • Q
  • Fe-S
  • Cytochrome c

Question 35

Question
The glyoxylate cycle leads from two-carbon compounds to glucose in each organism below, except:
Answer
  • Yeast
  • Animals
  • Bacteria
  • Plants
  • None of the above

Question 36

Question
Which is a component of Complex I?
Answer
  • Q
  • FMN
  • TPP
  • FAD

Question 37

Question
The glyoxylate cycle is:
Answer
  • A catabolic pathway in plants and some microorganisms
  • Regarded as a shunt within the citric acid cycle
  • An anabolic pathway in plants and some microorganisms
  • A and C only
  • B and C only

Question 38

Question
What feature of Cytochromes makes them valuable in electron transport systems?
Answer
  • The porphyrin ring
  • Aspartate residues in the active site
  • The Iron Ion
  • The multiple alpha-helices

Question 39

Question
Complex II in the electron transport chain supplies electrons as what to teh rest of the chain (Complexes III and IV)
Answer
  • QH2
  • FADH2
  • Fe-S
  • Succinate

Question 40

Question
Compare the pH of the mitochondrial matrix and the intermembrane space
Answer
  • The pH is lower in the intermembrane space
  • The pH in both regions is the same
  • The pH is lower in the matrix
  • The comparison of pH varies from moment to moment depending on energy needs of the cell

Question 41

Question
How many protons are translocated across the inner mitochondrial membrane by Complex III for each pair of electrons passing through the ETC
Answer
  • 0
  • 1
  • 2
  • 4

Question 42

Question
The P/O ratio refers to the number of moles of ATP produced for each moles of:
Answer
  • Oxygen atoms consumed in electron transport
  • Hydrogen molecules consumed in electron transport
  • NADH reoxidized in electron transport
  • FADH2 reoxidized in electron transport

Question 43

Question
During glycolysis, isomerization occurs during which of the following reactions?
Answer
  • Fructose-1,6-bisphosphate --> dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
  • Glucose --> glucose-6-phosphate
  • Fructose-6-phosphate --> fructose-1,6-bisphosphate
  • Glucose-6-phosphate --> fructose-6-phosphate

Question 44

Question
Iron sulfur clusters (Fe-S) that can accept or donate one electron are found in which complexes of the electron transport chain?
Answer
  • I, II, III, and IV
  • II and III
  • I
  • I, II, and III

Question 45

Question
The enzyme that catalyzes the conversion of pyruvate to lactate is:
Answer
  • Pyruvate kinase
  • Lactate dehydrogenase
  • Lactate reductase
  • Lactoenolpyruvate

Question 46

Question
The ultimate electron acceptor from complex II is:
Answer
  • Q
  • O2
  • QH2
  • FMN
  • cytochrome c

Question 47

Question
The proton motive force is a result of:
Answer
  • the flow of protons within the inner mitochondrial membrane
  • a combination of an electrical potential and a chemical potential
  • the flow of electrons from the matrix to the intermembrane space
  • all of the above

Question 48

Question
Which substance causes muscles to ache during strenuous exercise?
Answer
  • Pyruvic acid
  • Lactic acid
  • Lactate Ion
  • Lactose dehydrogenase

Question 49

Question
ATP synthase is located in what area of the mitochondrion?
Answer
  • matrix
  • intermembrane space
  • inner membrane
  • outer membrane

Question 50

Question
In the respiratory ETC electrons are passed from:
Answer
  • NADH and QH2 to O2
  • O2 to NAD+ and Q
  • ATP to O2
  • O2 to NADH

Question 51

Question
The citric acid cycle oxidizes pyruvate, and some of the pathway intermediates are starting materials for many biosynthetic pathways. This means the citric acid cycle is:
Answer
  • Anabolic
  • Catabolic
  • Amplifying
  • Amphibolic (catabolic and anabolic)

Question 52

Question
The inner mitochondrial membrane contributes to the formation of a proton gradient mainly because it:
Answer
  • contains ATP synthase complex
  • is not rich in proteins
  • is the location of specific transport proteins
  • is a barrier to protons
  • is rich in proteins

Question 53

Question
Oxidative phosphorylation requires all of the items listed below, except:
Answer
  • a terminal electron acceptor which is H2O in mitochondria
  • a matrix more positively charged than the intermembrane space
  • the flow of electrons from NADH and QH2 in the membrane
  • ATP synthase in the correct position in the membrane
  • enzyme complexes embedded in the membrane

Question 54

Question
Once inside a cell, glucose is rapidly phosphorylated to G6P. What is the main purpose of this phosphorylation?
Answer
  • to activate phosphofructokinase-1
  • to keep glucose inside the cell
  • to form a high-energy compound
  • to prevent mutarotation

Question 55

Question
In the mitochondria NADH and QH2 are essentially oxidized by ____________ since it is the terminal electron acceptor
Answer
  • Ozone
  • Hydrogen Peroxide
  • Carbon Dioxide
  • Oxygen

Question 56

Question
Heat can be generated in the brown adipose tissue of hibernating mammals due to _______________:
Answer
  • increased ATP production by ATP synthase
  • a greater pH gradient across the inner mitochondrial membrane by complex IV
  • uncoupling by thermogenin
  • insufficient NADH production during the citric acid cycle due to less active pyruvate translocases

Question 57

Question
How many protons are translocated across the inner mitochondrial membrane by complex IV for every pair of electrons passing the electron transport chain?
Answer
  • 0
  • 1
  • 2
  • 3
  • 4

Question 58

Question
Which enzyme catalyzes the conversion of citrate to isocitrate?
Answer
  • Aldolase
  • Citrate isomerase
  • Aconitase
  • Citrate synthase

Question 59

Question
Which step int he citric acid cycle is a rearrangement reaction?
Answer
  • citrate to isocitrate
  • succinyl-CoA to succinate
  • fumarate to L-malate
  • glucose-1,6-bisphosphate to fructose-1,6-bisphosphate

Question 60

Question
Which 5-carbon intermediate of the citric acid cycle is converted to a 4-carbon molecule with the release of Carbon dioxide
Answer
  • isocitrate
  • succinate
  • alpha-ketoglutarate
  • fumerase

Question 61

Question
Pyruvate passes through the outer mitochondrial membrane by _____________?
Answer
  • Porin proteins
  • simple diffusion through the lipid bilayer
  • pyruvate translocase
  • passive transport

Question 62

Question
What type of reaction is the conversion of fumarate to malate?
Answer
  • condensation
  • oxidative decarboxylation
  • dehydrogenation
  • hydration

Question 63

Question
Which cofactor is NOT used by the pyruvate dehydrogenase complex?
Answer
  • QH2
  • FAD
  • thiamine pyrophosphate
  • lipoamide

Question 64

Question
2,3-bisphosphoglycerate is:
Answer
  • essential for the efficient release of O2 from hemoglobin
  • a product of the enzyme phosphofructokinase
  • converted to 3-phosphoglycerate with formation of ATP
  • an essential component of glycolysis for ATP production

Question 65

Question
Which of the following elements is required for the enzymatic reaction that produces phosphoenolpyruvate?
Answer
  • Manganese
  • Potassium
  • Magnesium
  • Calcium

Question 66

Question
What two isomerization reactions occur in glycolysis? Why are these steps necessary
Answer
  • Glucose-6-phosphate is isomerized to fructose-6-phosphate, converting an aldose to a ketose, which then allows phosphorylation at the number 1 carbon
  • Later in the pathway, dihydroxyacetone is converted to glyceraldehyde-3-phosphate, utilizing both of the molecules formed from fructose-1,6-bisphosphate cleavage

Question 67

Question
How is glycolysis maintained under anaerobic conditions?
Answer
  • Pyruvate can be reduced to either lactate or ethanol, and this reaction is accompanied by the oxidation of NADH to regenerate NAD+
  • Fermentation reactions ^^ lactic or alcoholic fermentation

Question 68

Question
How does citrate influence glycolysis?
Answer
  • Phosphofructokinase is inhibited by citrate, which is an intermediate in the citric acid cycle
  • Thus, if citrate levels are high, the enzyme is inhibited, and fewer glucose molecules are metabolized
  • In this sense, citrate serves as a cell indicator
  • High levels of citrate in the cytoplasm means that biosynthetic precursors are abundant, and sot here is no need to degrade additional glucose for this purpose

Question 69

Question
Describe the two isoforms of lactate dehydrogenase
Answer
  • Two forms exist, called M and H, which predominate in the skeletal and heart muscle, respectively
  • The two forms are products of different genes, but are similar in structure, and can form tetramers in various H:M ratios
  • The two forms differ in their sensitivity to pyruvate
  • H+ functions primarily to oxidize lactate to pyruvate, which serves as a fuel for aerobic metabolism. In contrast, M4 produces lactate so that glycolysis can continue under anaerobic conditions

Question 70

Question
Why is it necessary that there be a mechanism to replenish oxaloacetate?
Answer
  • During periods of biosynthesis, oxaloacetate may be converted to amino acids for protein synthesis
  • Even if acetyl-CoA will operate at reduced levels until new oxaloacetate is formed

Question 71

Question
How is succinate dehydrogenase unique when compared to the other enzymes in the citric acid cycle
Answer
  • It is the only enzyme embedded in the mitochondrial membrane
  • It is directly associated with the electron transport chain
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