Which of the following statements about the role of the PPP pathway is correct?
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
Which of the following statements about the oxidative section of the PPP is correct
a) The PPP generates NADH
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
Which of the following statements about the non-oxidative section of the PPP is correct
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
Which of the following statements about the PPP is not true:
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
Haemolytic anemia can be triggered in people deficient in glucose-6-phosphatatse by infections. What is the mechanism?
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
What is an important function of the PPP
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
Which of the following statements about the reactions of glycolysis is correct?
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
Which of the following statements about the glycolytic intermediate fructose-6-phosphate is correct?
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
Which of the following statements about the Citric Acid Cycle is correct?
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
Which of the following statements about the Electron Transport Chain is correct?
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
Glycogenolysis is inhibited by insulin
Glycogenolysis is inhibited by glucagon and epinephrine
Glycogenesis is the synthesis of glycogen from G6P
Insulin inhibits glycogenolysis
Insulin deactivates glycogenesis
Epinephrine release activates glycogenolysis
Epinephrine release inhibits glycogenesis
Glucagon inhibits glycogen breakdown
Glucagon activates liver gluconeogenesis
Insulin is secreted from the liver in response to an increase in blood glucose
Insulin's effect include:
Stimulation of lipid synthesis
Glycogen synthesis
Protein Synthesis
Glycolysis and inhibition of gluconeogenesis and lipid breakdown
All of the above
None of the above
Gluconeogenesis is the formation of new glucose molecules from precursors in the liver including:
Lactate
Pyruvate
Alpha-keto acids
What is the net yield of ATP per glucose molecule that passes through all of aerobic respiration (glucose --> CO2 + H2O)?
2
4
6
32, depending on the shuttle system used
What do cyanide, azide, and carbon monoxide all have in common?
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
Uncouplers are compounds that inhibit the phosphorylation of ADP:
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
Coenzyme Q can act as an intermediate electron carrier, since the ketone group of the quinone structure is readily reduced to an alcohol
In Eukaryotes the enzymes of the citric acid cycle are found in the:
Nucleus
Mitochondria
Endoplasmic Reticulum
Cytosol
A cytochrome that can move freely in the mitochondrial membrane is:
Cytochrome a
Cytochrome b
Cytochrome c
Cytochrome c1
Which of the following enzymatic reactions are control points for glycolysis?
Aldolase
Glucose-6-phosphate isomerase
Both A and B
Neither A nor B
The Q cycle refers to flow of electrons from
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
The step in which acetyl-CoA enters the CA cycle is classified as what type of reaction?
Decarboxylation
Dehydrogenation
Condensation
substrate-level phosphorylation
The following enzyme(s) is/are unique to the glyoxylate cycle
malate synthase
malate dehydrogenase
isocitrate lyase
A and C only
Which complex in the electron transport chain carries electrons from cytochrome c to molecular oxygen, reducing it to water?
I
II
III
IV
V
The terminal electron acceptor for complex III of the ETC is:
FAD
Q
Fe-S
The glyoxylate cycle leads from two-carbon compounds to glucose in each organism below, except:
Yeast
Animals
Bacteria
Plants
Which is a component of Complex I?
FMN
TPP
The glyoxylate cycle is:
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
B and C only
What feature of Cytochromes makes them valuable in electron transport systems?
The porphyrin ring
Aspartate residues in the active site
The Iron Ion
The multiple alpha-helices
Complex II in the electron transport chain supplies electrons as what to teh rest of the chain (Complexes III and IV)
QH2
FADH2
Succinate
Compare the pH of the mitochondrial matrix and the intermembrane space
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
How many protons are translocated across the inner mitochondrial membrane by Complex III for each pair of electrons passing through the ETC
0
1
The P/O ratio refers to the number of moles of ATP produced for each moles of:
Oxygen atoms consumed in electron transport
Hydrogen molecules consumed in electron transport
NADH reoxidized in electron transport
FADH2 reoxidized in electron transport
During glycolysis, isomerization occurs during which of the following reactions?
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
Iron sulfur clusters (Fe-S) that can accept or donate one electron are found in which complexes of the electron transport chain?
I, II, III, and IV
II and III
I, II, and III
The enzyme that catalyzes the conversion of pyruvate to lactate is:
Pyruvate kinase
Lactate dehydrogenase
Lactate reductase
Lactoenolpyruvate
The ultimate electron acceptor from complex II is:
O2
cytochrome c
The proton motive force is a result of:
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
Which substance causes muscles to ache during strenuous exercise?
Pyruvic acid
Lactic acid
Lactate Ion
Lactose dehydrogenase
ATP synthase is located in what area of the mitochondrion?
matrix
intermembrane space
inner membrane
outer membrane
In the respiratory ETC electrons are passed from:
NADH and QH2 to O2
O2 to NAD+ and Q
ATP to O2
O2 to NADH
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:
Anabolic
Catabolic
Amplifying
Amphibolic (catabolic and anabolic)
The inner mitochondrial membrane contributes to the formation of a proton gradient mainly because it:
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
Oxidative phosphorylation requires all of the items listed below, except:
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
Once inside a cell, glucose is rapidly phosphorylated to G6P. What is the main purpose of this phosphorylation?
to activate phosphofructokinase-1
to keep glucose inside the cell
to form a high-energy compound
to prevent mutarotation
In the mitochondria NADH and QH2 are essentially oxidized by ____________ since it is the terminal electron acceptor
Ozone
Hydrogen Peroxide
Carbon Dioxide
Oxygen
Heat can be generated in the brown adipose tissue of hibernating mammals due to _______________:
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
How many protons are translocated across the inner mitochondrial membrane by complex IV for every pair of electrons passing the electron transport chain?
3
Which enzyme catalyzes the conversion of citrate to isocitrate?
Citrate isomerase
Aconitase
Citrate synthase
Which step int he citric acid cycle is a rearrangement reaction?
citrate to isocitrate
succinyl-CoA to succinate
fumarate to L-malate
glucose-1,6-bisphosphate to fructose-1,6-bisphosphate
Which 5-carbon intermediate of the citric acid cycle is converted to a 4-carbon molecule with the release of Carbon dioxide
isocitrate
succinate
alpha-ketoglutarate
fumerase
Pyruvate passes through the outer mitochondrial membrane by _____________?
Porin proteins
simple diffusion through the lipid bilayer
pyruvate translocase
passive transport
What type of reaction is the conversion of fumarate to malate?
condensation
oxidative decarboxylation
dehydrogenation
hydration
Which cofactor is NOT used by the pyruvate dehydrogenase complex?
thiamine pyrophosphate
lipoamide
2,3-bisphosphoglycerate is:
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
Which of the following elements is required for the enzymatic reaction that produces phosphoenolpyruvate?
Manganese
Potassium
Magnesium
Calcium
What two isomerization reactions occur in glycolysis? Why are these steps necessary
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
How is glycolysis maintained under anaerobic conditions?
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
How does citrate influence glycolysis?
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
Describe the two isoforms of lactate dehydrogenase
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
Why is it necessary that there be a mechanism to replenish oxaloacetate?
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
How is succinate dehydrogenase unique when compared to the other enzymes in the citric acid cycle
It is the only enzyme embedded in the mitochondrial membrane
It is directly associated with the electron transport chain
