Homework Questions: Exam 2 Flashcards
In the sugar shown, which carbon atom is the anomeric carbon?
A
glucose and galactose are ______ of each other
epimers
Any sugar that has a free aldehyde group is called a(n) _________.
reducing sugar
In the sugar shown, which carbon atom determines the D-L stereochemical designation?
E
to what class of biological molecule does the following belong?
amino acid
In the sugar shown, which C atom determines the D-L stereochemical designation?
D
Unlike proteins and oligonucleotides, polysaccharides _________.
a) are readily metabolized in the absence of specialized enzymes
b) often have branched structures
c) are achiral
d) are always completely water soluble
e) are components of every known living organism
b) often have branched structures
which one of the following steps found in N-linked glycosylation is also part of O-linked glycosylation?
a) a 14-unit oligosaccharide is attached to the protein
b) some of the sugars are removed during processing
c) a 3-residue sequence pattern in the protein determines the sites of glycosylation
d) monosaccharides are added while the protein is in the Golgi apparatus
d) monosaccharides are added while the protein is in the Golgi apparatus
When amylose is suspended in water in the presence of I2, a blue color results due to the ability of I3-, an ion that forms aqueous iodine solutions, to occupy the interior of the helix. A drop of yellow iodine solution on a potato slice turns blue, but when a drop of iodine is placed on an apple slice, the color of the solution remains yellow. Explain why.
potato consists of amylose; apple consists of cellulose
In terms of structure, what is the main difference between a-amylose and cellulose?
cellulose is formed by B-(1->4) glycosidic bonds, but a-amylose is formed by a-(1->4) glycosidic bonds
Which of the following is a major difference between cellulose and chitin?
a) chitin is produced by insects, cellulose is produced by plants
b) chitin contains glucose and glucosamine, cellulose contains only glucose
c) chitin contains B(1->6) glycosidic bonds, cellulose contains B(1->4) glycosidic bonds
d) chitin is a branched polymer, cellulose is linear
e) none of the above
a) chitin is produced by insects, cellulose is produced by plants
In terms of structure, which of the following is the main difference between cellulose and chitin?
cellulose is a linear polymer of D-glucose, but chitin is a linear polymer of N-acetyl-D-glucosamine
In terms of structure, what is the main difference between a-amylose and amylopectin?
both contain a-(1->4) glycosidic linkages of D-glucose, but amylopectin also has a a-(1->6) branches
Which of the following is the major difference between glycogen and amylopectin?
a) glycogen contains a-glycosidic bonds, amylopectin contains B-glycosidic bonds
b) glycogen is branched, amylopectin is linear
c) glycogen contains a reducing end, amylopectin does not
d) glycogen contains about twice the number of branch points as amylopectin
e) glycogen is found in plants, amylopectin is found in animals
d) glycogen contains about twice the number of branch points as amylopectin
Which of the following describes glycosaminoglycans?
a) found in extracellular space
b) associated with the cytoskeleton
c) bound to the other proteins to minimize interactions with water
d) homopolymers composed of only one type of monosaccharide
e) none of the above
a) found in extracellular space
O-linked oligosaccharides are commonly attached to the oxygen of __________.
threonine
digestion of food utilizes enzymes that catalyze _________ reactions.
a) hydrolysis
b) reduction
c) condensation
d) oxidative
e) group transfer
a) hydrolysis
which of the following features are common to all anabolic pathways?
a) they require energy
b) they break down complex molecules
c) their overall free energy change is positive
d) they are oxidative
a) they require energy
which of the following statements about FAD and NAD+ is FALSE?
a) they each contain adenosine
b) they are nucleic acids
c) they are dinucleotides
d) they each contain a base derived from a vitamin
e) they each can reversibly carry two electrons
b) they are nucleic acids
Which of the following molecules is in the most reduced state?
a) methane
b) formaldehyde
c) formic acid
d) methanol
e) carbon dioxide
a) methane
the common products of fuel metabolism in mammals are _______
pyruvate and acetyl-CoA
Which of the following is always involved in biological oxidation-reduction reactions?
a) formation of water
b) transfer of electron(s)
c) oxygen
d) inner mitochondrial membrane
b) transfer of electron(s)
the oxidized form of NADH is _________
NAD+
which of the following vitamins is correctly paired with its biochemical function?
a) folic acid: carboxylation reactions
b) biotin: decarboxylation reactions
c) riboflavin: acyl transfer reactions
d) pyroxdine: amino-group transfer reactions
e) pantothenic acid: redox reactions
d) pyroxdine: amino-group transfer reactions
what is the role of phosphocreatine in muscle?
to make more ATP
change in G’ for the hydrolysis of ATP is -31 kj/mol. how will the standard free energy change be altered if the activity of the enzyme catalyzing ATP hydrolysis is reduced?
it will stay the same
when a reaction is at equilibrium, the change in G is equal to ______
0
why is acetyl-CoA considered a high energy molecule?
it contains a thioester bond
what characterizes the rate-determining step of a metabolic pathway?
it functions far from equilibrium and it has a large negative free energy change
why is an anaerobic fate of pyruvate necessary?
to allow for the re-oxidation of NADH to NAD+, which is in limited supply
which one of the following enzymes catalyzes a substrate-level phosphorylation reaction in the catabolism of glucose?
a) phosphofructokinase-1
b) pyruvate kinase
c) glyceralaldehyde-3-phosphate dehydrogenase
d) hexokinase
b) pyruvate kinase
which of the following is NOT a direct product of pyruvate metabolism?
a) acetyl-CoA
b) lactate
c) oxaloacetate
d) phosphophenolpyruvate
e) both C and D are correct
d) phosphophenolpyruvate
which of the following is a cofactor for the enzyme glyceralaldehyde-3-phosphate dehydrogenase?
NAD+
which of the following contains a high energy bond that is used for a substrate level phosphorylation in glycolysis?
a) fructose 1,6 biphosphate
b) 1,3-biphosphoglycerate
c) acetyl phosphate
d) 2,3-biphosphoglycerate
e) 1-phosphoglycerate
b) 1,3-biphosphoglycerate
which of the following enzymes catalyzes the transfer of a phosphoryl group from ATP to glucose?
a) phosphoglucose isomerase
b) glucose-6-phosphate
c) a transfer such as this does not occur in glycolysis
d) hexokinase
e) phosphoglucose mutase
d) hexokinase
in the glycolytic pathway ATP is synthesized by which one of the following methods?
a) phosphorylysis
b) oxidative phosphorylation
c) substrate-level phosphorylation
d) photophosphorylation
c) substrate-level phosphorylation
what is the most likely fate of pyruvate in mammalian muscle during very vigorous exercise?
conversion to lactate via lactate dehydrogenase
Biochemically, why is ethanol produced by yeast?
cytoplasmic NADH is reoxidizes sustaining glycolysis under anaerobic conditions
pyruvate has several metabolic fates depending on the cell, under aerobic or anaerobic conditions. which one of the following is a metabolic fate for pyruvate?
a) oxidative carboxylation to acetyl-CoA
b) reduction to lactate
c) decarboxylation to oxaloacetate
d) oxidation to ethanol
b) reduction to lactate
which enzyme is responsible for splitting a hexose into two trioses?
aldose
which of the following is a high-energy intermediate produced in glycolysis?
INTERMEDIATE!!!
1,3-BPG
gluconeogenesis is most active in the _____
(organ)
liver
what is the primary purpose of gluconeogenesis is in the liver?
to produce glucose for its release into the circulation to help maintain constant blood glucose levels
the enzyme fructose-1,6-biphosphate is activated by which of the following?
a) ADP
b) fructose-6-phosphate
c) Ca2+
d) none of the above
d) none of the above
which of the following statements regarding gluconeogenesis is TRUE?
a) the conversion of phosphoenolpyruvate to 2-phosphoglycerate occurs in 2 steps
b) fructose-2,6-biphosphate activates gluconeogenesis
c) gluconeogenesis is reciprocally regulated with glycogen synthesis
d) it occurs actively in skeletal muscle during period of exercise
e) it is likely to occur when cellular ATP levels are high
e) it is likely to occur when cellular ATP levels are high
which one of the following processes most completely describes phosphorlysis reactions?
a) removing a phosphate group from a polymer
b) splitting a polymer
c) splitting a polymer and adding a phosphate group
d) hydrolyzing a polymer and adding a phosphate group
c) splitting a polymer and adding a phosphate group
glycogen storage occurs in _____ and _____ tissue
muscle; liver
where are the two major sites doe glycogen storage in humans?
liver and muscle
which of the following statements is TRUE regarding glycogen synthase?
a) it uses glucose-1-phosphate as a substrate
b) it catalyzes formation of glycosidic bonds
c) it is activated by Ca2+ ions
d) it is activated by protein kinases
b) it catalyzes formation of glycosidic bonds
which of the following enzymes catalyzes the conversion of glucose-1-phosphate to glucose-6-phosphate?
a) phosphoglucomutase
b) glucose phosphatase
c) glycogen phosphorylase
d) phosphoglucose isomerase
a) phosphoglucomutase
Which of the following best describes describes the function of the glycogen deb ranching enzyme in glycogenolysis?
it transfers a(1->4) linked trisaccharide to the nonreducing end of an alternate branch, then cleaves the a(1->6) branch point, releasing glucose
which of the following is FALSE regarding glycogen?
a) glucose is stored as a polymer to reduce its chemical reactivity
b) the main chain of the glycogen polymer predominately contains glucose residues linked via 1-6 glycosidic bonds
c) branching enables more rapid breakdown of glycogen
d) the first step in glycogen synthesis is catalyzed by hexokinase
b) the main chain of the glycogen polymer predominately contains glucose residues linked via 1-6 glycosidic bonds
which pathways would “collaborate” to maximize a cell’s production of NADPH from glucose-6-phosphate, assuming that the cell needed NADPH but not ribose?
a) glycolysis and gluconeogenesis
b) the pentose phosphate pathway and gluconeogenesis
c) the pentose phosphate pathway and glycolysis
b) the pentose phosphate pathway and gluconeogenesis
NADPH used in lipid biosynthesis is produced in _________
the pentose phosphate pathway
condensation of ______ with oxaloacetate yields citrate
acetyl-CoA
which of the following are products of the reaction catalyzed by pyruvate dehydrogenase?
i) CO2
ii) NADH
iii) acetyl-CoA
iv) phosphoenolpyruvate
products i), ii), and iii)
what cellular location contains pyruvate dehydrogenase and most of the citric acid cycle enzymes?
mitochondrial matrix
which of the following enzymes catalyzes a substrate-level phosphorylation?
succinylcholine-CoA synthetase
the rate of the citric acid cycle would be increased under which of the following conditions?
a) the ADP/ATP ratio is high
b) the ADP/ATP ratio is low
c) the NAD+/NADH ratio is low
d) the concentration of oxalacetate is low
e) B and C
a) the ADP/ATP ratio is high
what is an intermediate between citrate and isocitrate in the citric acid cycle?
cis-aconitate
in the net reaction of the citric acid cycle, what are the reactants?
3 NAD+ + FAD + GDP + Pi + acetyl-CoA
under which of the following conditions is the entry of acetyl-CoA into the citric acid cycle DECREASED?
a) when ADP levels are elevated
b) when the ADP/ATP ratio is high
c) when NADH is rapidly oxidized via the electron transport chain
d) when the NADH/NAD+ ratio is high
e) when NAD+ levels are elevated
d) when the NADH/NAD+ ratio is high
which of the following is required for the conversion of succinate to fumarate in the citric acid cycle?
a) FAD
b) QH2
c) NAD+
d) GDP
a) FAD
int he net reaction of the citric acid cycle, what are the products?
3 NADH + FADH2 + GTP + 2CO2 + CoA
in the citric acid cycle, what reduced cofactors are derived from the oxidation of one molecule of acetyl CoA to two molecules of CO2?
3 NADH and 1 QH2
where is succinate dehydrogenase located?
mitochondria inner membrane
if all reduced electron carriers are reoxidizes to run oxidative phosphorylation, how many ATP can be regenerated from the oxidation of one acetyl-CoA?
10
which steps of the citric acid cycle can be both inhibited and activated by different molecules?
isocitrate dehydrogenase
which of the following compounds represents energy currency for the cell?
a) ATP
b) GTP
c) NADH
d) ubiquinol
e) all of the above
e) all of the above
anapleurotic reactions are essential to the functioning of the citric acid cycle. which of the following enzymes catalyzes such a reaction?
a) pyruvate carboxylase
b) citrate synthase
c) malate dehydrogenase
a) pyruvate carboxylase
which of the following can cause a large increase in the activity of the citric acid cycle?
a) activation of isocitrate dehydrogenase by ADP
b) activation of a-ketoglutarate dehydrogenase by Ca2+
c) increasing the concentrations of ocaloacetate by pyruvate carboxylase
d) increasing concentrations of a-ketoglutarate by transamination
e) all of the above
e) all of the above
what citric acid cycle intermediate effectively used as a mechanism for the transport of acetyl-coA from the mitochondria to the cytosol?
citrate
which of the following can be converted into glutamic acid in a single enzyme-catalyzed step?
a) isocitrate
b) oxaloacetate
c) malate
d) a-ketoglutarate
e) succinylcholine-coA
d) a-ketoglutarate
the reaction catalyzed by pyruvate is an example of a(n) _______ reaction because it replenishes the citric acid cycle intermediates that have been siphoned off for use in other reactions
anaplerotic
which of the following is considered an omega-3 fatty acid?
a) 9,12-octadecadienoic acid
b) 9,12,15-octadecatrienoic acid
c) 8,11,14-eicosatrienoic acid
d) 5,8,11,14-eicosatetraenoic acid
b) 9,12,15-octadecatrienoic acid
which of the following statements describing the function of cholesterol in biological membranes is FALSE?
a) it prevents close packing of some fatty acyl tails within the bilayer, thereby decreasing van Der wall’s interactions between them
b) it reduces the fluidity of lipid bilayers over a broad temperature range
c) it limits the movements of some fatty acyl tails within the bilayer, thereby increasing van Der wall’s interactions between them
d) it maintains the stability of lipid bilayers over a broad temperature range
b) it reduces the fluidity of lipid bilayers over a broad temperature range
the most notable difference between _______ and other lipids is the presence of four fused rings
cholesterol
what two molecules are used in the synthesis of sphingosine?
palmitic acid and serine
which are the characteristics of most unsaturated fatty acids found within a human cell?
deprotonated carboxylic acid and cis double bonds
in preparation for hibernation, ground squirrels tend to increase the proportion of unsaturated fatty acids incorporated into their membrane lipids. given that the animals must survive a significant drop in body temperature during hibernation, which of the following statements correctly explains why this particular change in fatty acid composition occurs?
the fluidity of the squirrels cell membranes must be increased, and unsaturated fatty acids assist in this because they have fewer van Der Waals interactions between them than saturated fatty acids
which of the following vitamins is derived from cholesterol?
vitamin D
what is the symbol for the fatty acid shown in the figure?
17:1 (triangle)^7
which of the following fatty acids has the highest melting temperature?
a) 18:0
b) 16:1
c) 18:1
d) 16:0
a) 18:0
