560B Biochem of nutrition Flashcards
(94 cards)
1
Q
T or F: For every amino acid, there is a specific, unique transport system for digestion.
A
False
2
Q
T or F: The hemoglobin molecule is more easily saturated with oxygen than is myoglobin, at a given partial pressure of oxygen.
A
False
The affinity of hemoglobin for oxygen is less than its structural analog myoglobin. Myoglobin, on the other hand, has a significantly higher affinity for oxygen and will, therefore, be much less inclined to release it once it is bound.
3
Q
T or F: Ammonia formed from muscle amino acid degradation is transferred in the blood in the form of glutamine
A
True
4
Q
Thermodynamically speaking, which value most specifically and directly defines whether a biochemical reactions spontaneous or not?
A
ΔG (gibbs free energy?)
5
Q
That 3 parts are attached to the central carbon of an amino acid?
A
a hydrogen atom
a carboxyl group
an amine group
6
Q
the urea cycle takes place partly in the ____ and partly in the ____
A
mitochondria, cytosol
7
Q
During transamination, one product is always?
A
glutamate
8
Q
When pyridoxyl phosphate amine is formed, that means that:
A
transamination is occurring
9
Q
What are 3 metabolic sources of ammonia?
A
purines and pyrimidines
the diet
bacterial degradation of urea
10
Q
the _____ forms of amino acids are incorporated into human protein
A
L isomer
11
Q
ionization of the _____ would increase as you went above the pKa, say the body’s pH
A
carboxyl groups
12
Q
What is the significance of the pKa as it applies to the body?
- ultimately it can bear greatly upon the way a protein folds
- it means that some R groups of amino acids will never ionize
- both of the above are true
- none of the above are true
A
not totally sure:
1. ultimately it can bear greatly upon the way a protein folds
From lecture: The electrochemical, oxidative/reductive environment is closely related to local pH, which is a critical factor in the way a protein folds,
(not 3)
13
Q
With regard to ALT and AST:
- they are two muscle proteins that allow muscle contraction
- they have little clinical diagnostic value in the case of liver damage
- they are used in the oxidative deamination process
- they both require pyridoxyl phosphate (vitamin B-6) as a coenzyme
A
they both require pyridoxyl phosphate (vitamin B-6) as a coenzyme
14
Q
Which of the follow is true?
- polypeptides that have similar amino acid sequences and function are analogous
- amino acids within a given protein that do not differ from species to species are defined as invariant, because they are essential to the function of that protein
- insulin is synthesized in zymogen form, but peptide C is not.
- supersecondary motifs and domains are generally not the same thing
A
- amino acids within a given protein that do not differ from species to species are defined as invariant (never changing), because they are essential to the function of that protein
15
Q
With regard to the different forms of water in the cell, which is not true?
- water at the surface of a protein can bare on how much of a particular ion binds to that protein
- sodium and potassium both being positive would be expected to bind to a proteins surface to the same degree
- water is responsible, at least in part, for formation of microenvironments within the cell
- the high specific heat of water helps maintain body temperature in cases where some of the heat energy that is produced from a biochemical reaction (and that is not used for driving other biochemical reactions) is given off as heat
- the ATP-requiring sodium/potassium pump only partly explains the partitioning of sodium and potassium outside and inside the cell membrane, respectively
A
- sodium and potassium both being positive would be expected to bind to a proteins surface to the same degree
16
Q
Which is correct regarding protein structure?
• there are at least two subunits that are needed to form quaternary structure
• most tertiary structures contain a hydrophobic inner center
• multiple subunits make repair of the protein easier, as less energy is wasted repairing places that are not in need of repair
• all of the above are true
A
all of the above are true
17
Q
Which is true regarding protein?
- amino acid pools are small in part because protein is not the main body fuel
- amino acid pools are small in part because there are no proteins and their related enzyme systems designed specifically for amino acid storage
- urea is formed in the liver, because there is a great deal of amino acid degradation there
- all of the above are true
A
- all of the above are true
18
Q
True/false: The Km is a measure of the enzyme’s velocity at the substrates concentration that allows the reaction to reach maximum velocity
A
False
Km= Michaelis constant
defined as the substrate concentration at 1/2 the maximum velocity
19
Q
True/false: the straight line portion of the Michaelis/Mention represents the initial velocity
A
True
20
Q
True false: Regarding enzymes, the sigmoidal shape curve kinetics represents a multi-subunit and/or multi-active site enzyme, which could be subject to both enzyme induction and feedback regulation (inhibition)
A
True
21
Q
True/false: A word with which you could easily associate the taut and relaxed state with would be allosterism.
A
True
allosterism: A change in the activity and conformation of an enzyme resulting from the binding of a compound at a site on the enzyme other than the active binding site
22
Q
Which statement is true regarding collagen?
- it is composed of two helical polypeptides wound around one another
- it is composed of about one third glycine because that amino acid is small and the collagen is compact
- it has a relatively short half-life compared to other proteins, but longer than that of enzymes
- mutations associated with the synthesis of collagen hardly ever occur
A
it is composed of about one third glycine because that amino acid is small and the collagen is compact
23
Q
Regarding sickle cell anemia:
- it arises because of a mutation that inserts a valine to replace glutamine in the beta subunit of the hemoglobin
- electrophoresis of a person’s hemoglobin can identify a patient with sickle cell trait vs. one with full blown sickle cell anemia
- glutamate is replaced with valine, resulting in a hydrophobic protrusion from one of beta subunit finding a hydrophobic pocket of another beta subunit of another hemoglobin, so that the hemoglobins will polymerize with one another
- the polymerization process takes place during the oxygenated state
A
electrophoresis of a person’s hemoglobin can identify a patient with sickle cell trait vs. one with full blown sickle cell anemia
24
Q
Regarding antibody structure:
- the variable region is the only part of the structure that differs among antibodies,thus being theromynamically efficient regarding their synthesis
- the antibody fits with its antigen according to the lock and key theory
- the C regions of an antibody vary considerably from antibody type to antibody type
- all of the above are true
A
the variable region is the only part of the structure that differs among antibodies,thus being theromynamically efficient regarding their synthesis
25
Regarding Insulin:
* it is composed of a single polypeptide chain of 51 amino acids
* it is not synthesized in zymogen form, because it is not a potentially destructive enzyme
* its structure is stabilized by disulfide bonds
* it is synthesized as an inactive precursor known as peptide
its structure is stabilized by disulfide bonds
26
The best theoretical cure for sickle cell anemia would be:
* bone marrow transplants
* gene replacement therapy
* transfusions
* all of the above are equally viable
gene replacement therapy
27
Which of the follow are true regarding enzymes?
* in non-competitive inhibition the Vmax of the enzyme without an inhibitor would be reached
* in competitive inhibition, the Vmax of the enzyme curve can never be reached by adding more and more substrate, because the inhibition is at the active site
* a Lineweaver/Burke plot will show all the information that a Michaelia/Menton plot will show
* none of the above are true
a Lineweaver/Burke plot will show all the information that a Michaelia/Menton plot will show
28
Regarding turnover number of an enzyme:
* carbonic anhydrase is one of the fastest enzymes in the cell
* digestive enzymes would tend to have lower turnover numbers, because the digestive process must not proceed too quickly, or absorption of nutrients would be theoretically be impaired
* as long as the concentration of active sites of an enzyme are known, then the Vmax reveals the turnover number of that enzyme
* all of the above are true
4. all of the above are true
29
Regarding enzymes:
• the activity of the enzyme can be affected by what’s associated with its domains
• lyases catalyze the formation of bonds, such as C-O and C-S, accompanied by the use of ATP
• enzymes alter the equilibrium of a reaction
• allosteric enzymes show a hyperbolic-shape curve
• all of the above are true
the activity of the enzyme can be affected by what’s associated with its domains
30
Regarding enzymes:
* a whole metabolic pathway can be controlled by controlling the activity of a key enzyme that is involved in that pathway
* a transition state is one where the enzyme is complexed to a very high-energy level, relatively unstable intermediate
* for thermal effects upon enzymes, a bell shaped curve would be expected
* all of the above are true
4. all of the above are true
31
Which is true?
* myoglobin can be considered a storage protein in the liver
* myoglobin is identical to either the alpha or the beta subunit of hemoglobin
* myoglobin shows tertiary structure
* all of the above are true
myoglobin shows tertiary structure
32
True/False: protein phosphateases can remove phosphate groups from enzymes
True
33
True/False: Internal respiration centers on the fact that oxygen is the final electron acceptor in the electron transport system.
True
34
True/False: The electron transport system is located within the mitochondrial matrix.
False
| it is found in the inner mitochondrial membrane
35
True/False: The primary reason the Kreb’s cycle turns in one direction is because of the side pathways that generate other products from the cycle.
False: most of the reactions are actually reversible
36
True/False: When the ratio of NAD+/NADH is high, the inter-conversion of lactate and pyruvate favors lactate
False: pyruvate can be converted to lactate.
This occurs when there is insufficient oxygen in the tissue and when there is a high NADH/NAD+ ratio, both occurring in heavily-exercising muscle, for example
37
True/false: A high insulin/glucagon ratio favors glycogenolysis
False: Fructose 2,6-bisphosphate strongly stimulates phosphofructokinase and inhibits fructose 1,6-bisphosphatase. Hence, glycolysis is accelerated and gluconeogenesis is diminished in the fed state.
38
True/false: The covalent regulation of both glycogen synthase and glycogen phosphorylase depends upon their respective states of phosphorylation.
True
39
True/False: The brain has substantial glycogen stores
False
40
True/False: Transamination/deamination can contribute to energy state produced from the Kreb’s cycle
True
41
True/False: Acetyl CoA is the final product of glycolysis which also helps start the Kreb’s cycle.
False: The net end products of glycolysis are two Pyruvate, two NADH, and two ATP
42
Regarding ATP:
* probably about 60% of the energy derived from its hydrolysis dissipates as heat and is not used to drive an endergonic reaction
* the energy derived from the hydrolysis can be used to drive an exergonic reaction
* the energy required to form ATP comes from the reduction of fuels in the body, as, for example, glycoysis or the Kreb’s cycle being coupled to the ETS.
* all of the above are true
probably about 60% of the energy derived from its hydrolysis dissipates as heat and is not used to drive an endergonic reaction
43
Which is true?
* the most realistic structural representation of a simple sugar is the Fisher projection
* glucose and fructose are both isomers of one another and are both aldohexoses
* the low Km value of the Glut 3 transporter represents a critical glucose concentration point for the brain receiving sufficient glucose
* the kidney represents only 0.5% of the body mass, but consumes about 20% of the body’s energy, mostly due to its energy-requiring reabsorption function
the low Km value of the Glut 3 transporter represents a critical glucose concentration point for the brain receiving sufficient glucose
44
Which is true?
* fatty acids are the main fuel for both cardiac and resting skeletal muscle
* cardiac muscle functions almost exclusively aerobically and has large numbers of mitochondria and glycogen reserves
* transamination, deamination, and the urea cycle take place mostly in the liver but also to some degree in muscle
* α-ketoglutarate is the link between glycolysis and transamination.
cardiac muscle functions almost exclusively aerobically and has large numbers of mitochondria and glycogen reserves
45
Which is (are) true?
* the fact that the liver and not skeletal muscle controls plasma glucose levels is due to the fact that the liver glucokinase has a small Km, whereas the muscle hexokinase has a large Km.
* one major purpose of phosphorylating glucose is to keep it within the cell, so as to prevent it from leaving before it’s metabolized
* an aldolase enzyme splits fructose-6-P into two three carbon sugars, thus doubling the glycolytic reactions thereafter
* all of the above are true
one major purpose of phosphorylating glucose is to keep it within the cell, so as to prevent it from leaving before it’s metabolized
46
Which is (are) true?
1. that some compounds have higher phosphoryl potential than ATP is one reason why they can contribute to the formation of ATP from ADP
2. the body can form as much as 40 kg of ATP in a single day
3. electron flow between compounds with a higher phosphoryl potential to one with a lower phosphoryl potential is something that can occur when a body fuel is being oxidized
4. all of the above are true
5. none of the above are true
? not one, the body can form up to 70kg of ATP
3? electron flow between compounds with a higher phosphoryl potential to one with a lower phosphoryl potential is something that can occur when a body fuel is being oxidized
47
Which is (are) true:
* There are four places in the Kreb’s cycle where NAD+ or FAD are used to take part in oxidation/reduction reactions where in each place, two sets of electrons are transferred from the substrate to the NAD+ the or FAD
* we can say that fuels comprise those molecules that lose electrons
* acetyl CoA ties together amino acid, fat, and carbohydrate metabolism, all of which can then enter the Kreb’s cycle
* all of the above are true
* none of the above
* (a,b,c) are true
4. all of the above are true
48
Regarding oxidative phosphorylation:
1. the ATP synthase is driven by a protomotive force where protons accumulate in the mitochondria matrix
2. the glycerophosphate shuttle adds to the total ATP production of burning glucose, even though the reactions initially take place in the cytosol
3. the electron transport system is directly coupled to oxidative phosphorylation and to the each step of the Kreb’s cycle
4. one can uncouple the electron tyransport system from oxidative phosphorylation by drugs like 2,4-dinitorophenol, which make the inner mitochondria membrane impermeable to protons.
?? not 3 or 4
49
Which is true?
1. the ratio of NADP+/NAD+ is very high, accounting for the partitioning of glycolysis from the pentose phosphate pathway
2. gluconeogenesis would be stimulated by a high insulin/glucagon ratio, representing the need for glucose, due to insufficient dietary glucose and/or glucose from glycogen breakdown
3. glucagon stimulates both pyruvate kinase and glucokinase
4. none of the above are true
4. none of the above are true
50
Which is (are) true?
1. the existence of the enzyme phosphoenolpyruvatecarboxy kinase (PEPCK) can be (at least in part) explained by the fact that pyruvate kinase is not reversible
2. there is need for a cytosolic and a mitochondrial PEPCK, because oxaloacetate (OAA) can not cross the mitochondrial membranes
3. malate and aspartate can each and separately take part in gluconeogenesis, because OAA can not cross the mitochondrial membranes
4. all of the above are true
4.all of the above are true
51
T/F: Activation of a fatty acid before its oxidation costs no ATP and involves adding an acyl CoA to the fatty acid.
False: In the first stage-β oxidation-the fatty acids undergo oxidative removal of successive two-carbon units in the form of acetyl-CoA.
52
T/F: Glycoproteins represent some combination of proteins and carbohydrate, collectively known as a conjugated protein
True
53
T/F: β-oxidation requires the fatty acid to be in the acyl CoA form.
True
54
T/F: HMGCoA reductase is inhibited by the cholesterol-lowering statin drugs, thus decreasing cholesterol synthesis.
True
55
T/F: Heavy β-oxidation leads to ketone formation because excess the Kreb’s cycle can not handle the excess pyruvate.
False
56
T/F: Fatty acids can be gluconeogenic precursors.
False: The major noncarbohydrate precursors are lactate, amino acids, and glycerol
57
T/F: Malonyl CoA, essential to fatty acid synthesis, is directly synthesized from acetyl CoA.
True
58
Which is true?
* carnitine is needed for beta oxidation because it is essential for activation of the fatty acid
* medium chain fatty acids do not require carnitine to enter the mitochondria
* lipolysis is inhibited by hormones such as epinephrine and glucagons
* mobilization of fatty acids for fuels involves the formation of glycerol to form triaglycerols
medium chain fatty acids do not require carnitine to enter the mitochondria
59
Regarding glycerol:
* it is produced by triaglycerol hydrolysis via hormone-sensitive lipase
* it can ultimately be converted to glyceraldehyde-3-P
* it represents a connection between carbohydrate and lipid metabolism
* all of the above are true
4. all of the above are true
60
Which is true?
* more than 90% of the lipids stored in humans is in the form of triaglycerols
* most products of lipid digestion have reasonably good water solubility
* most lipids are incorporated into micelles for transport in the blood
* none of the above are true
more than 90% of the lipids stored in humans is in the form of triaglycerols
61
Regarding amount of energy derived from metabolic fuels (i.e. fuel reserve):
* a gram of anhydrous fat stores far more energy than a gram of carbohydrate
* glycogen is a metabolic storage form of glucose and is similar in energy potential to that of the amino acids of muscle protein
* sterols and steroids can act as substantial energy sources
* none of the above are true
1. a gram of anhydrous fat stores far more energy than a gram of carbohydrate
62
Which is (are true)?
* the liver can convert glucose to triaglycerols
* triaglycerols are incorporated into VLDL by the liver
* VLDL-derived fatty acids can contribute to the energy needs of the cells
* amino acids from dietary protein are absorbed into the blood and then oxidized by various tissues for protein-derived structures and non-protein molecules, such as heme and neuropeptides
* all of the above are true
5. all of the above are true
63
During long term fasting:
* free fatty acids rise continuously
* glucose levels continuously decline over a 30 day period
* β-hydroxybutyrate levels rise more than other like molecules or free fatty acids
* because of the lower metabolic rate, ketones are unlikely to be produced from the lack of acetyl CoA being used by the Kreb’s cycle
β-hydroxybutyrate levels rise more than other like molecules or free fatty acids
64
Regarding β-oxidation and fatty acid synthesis:
* more energy is derived from saturated than unsaturated fatty acids of equal carbon length
* NADH is an essential reducing equivalent for fatty acid synthesis
* elongation of fatty acids at the fatty acid synthase complex stops at 18 carbons,and then other enzyme systems carry out elongation, desaturation, and hydroxylation.
* all of the above are true
more energy is derived from saturated than unsaturated fatty acids of equal carbon length
65
Which is (are true)?
* a combination of alcohol use and acetaminophen ingestion can lead to induction of a P-450 enzyme that converts acetaminophen to a toxic product
* The danger of NAPQI to liver cells is that it is toxic, depending upon the availability of glutathione to help detoxify it.
* the detoxification of acetaminophen is an example of Phase II type action of the P-450 system
* all of the above are true
all of the above are true
66
Which is true?
* through free radical reactions, carcinogens in the form of epoxy compounds can be generated from
* otherwise-healthy unsaturated fatty acids
* the oxidized form of glutathione is an important antioxidant
* NADP itself is used to regenerate glutathione
* all of the above are true
through free radical reactions, carcinogens in the form of epoxy compounds can be generated from
otherwise-healthy unsaturated fatty acids
67
Which is NOT true? (be careful of the details of the answers)
* cigarette smoke does not itself contain free radicals
* normal macrophage removal of smoke-derived particulate particles in the lung generates free radicals in the lung
* radiation induced damage to the DNA can occur by direct radiation-energy interaction with the DNA bases, as well from the formation of superoxide radicals generated form the water environment
* all of the above are true
? not 1
can't be 4, see question 72
68
Which of the following is (are) true? (be careful of the details of the answers)
* at the 5’ end of mRNA is a polyadenine tail to which stabilizing and transporting protein binds
* at the 3’ end of the mRNA is a cap end, associated with gene signaling
* anti-codons include stop signals that signal the end of the translation process
* sesquences like TATA boxes signify gene regulatory/promoter region sequences
* all of the above are true
sesquences like TATA boxes signify gene regulatory/promoter region sequences
69
Which is (are) true?
* during DNA synthesis, the complimentary nucleotide bases are added to the growing DNA strand are tri-nucleotides, so two phosphates can be removed to supply the energy needed for the synthesis
* replicases are the enzymes used for unwinding the DNA helix during DNA synthesis
* helicases are essential for DNA synthesis, because they break the sugar phosphate linkage, so that the strands can unwind
* all of the above are true
during DNA synthesis, the complimentary nucleotide bases are added to the growing DNA strand are tri-nucleotides, so two phosphates can be removed to supply the energy needed for the synthesis
70
In the process of excision repair, thymine dimers are actually removed in a step catalyzed by a(n):
* endonuclease
* exonuclease
* DNA repair pol
* polynucleotide ligase
exonuclease
Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3' or the 5' end occurs
71
Which is (are) true?
* the physiological effects exogenous antioxidants is well defined
* antioxidants themselves can become free radicals
* α-tocopherol as an antioxidant is effective in neutralizing free radicals by extracting two hydrogens, as is the case for ascorbate anti-oxidant action
* all of the above are true
antioxidants themselves can become free radicals
72
Xenobiotics that impact upon the P-450 system include:
* pesticides
* food additives
* cigarette smoke and environmental toxins
* all of the above
4. all of the above
73
T/F: Steroid metabolism is included in the P-450 system which is localized to the mitochondria of hormone-producing tissues, such as the ovaries, testes and adrenal cortex
True
74
T/F: In the mitochondrial P-450 system, the electron-transport-like system found in the inner mitochondrial membrane does yield some ATP during the biochemical detoxification processes.
False
75
T/F: Although oxidation of LDL is an important step in the process of cholesterol gaining access to the arterial wall, this oxidation is generally not thought to involve free radicals inducing the chemical change.
False (does involve free radicals?)
76
T/F: In total, the carbons of the pruines and pyrimidines are derived from carbon dioxide, amino acids, and from vitamin derivatives.
True
77
T/F: It is likely that some heavy metals (like cadmium and arsenic) are mutagenic and carcinogenic.
True
78
T/F: Dehydroascobate reductase is important to regenerating the form of ascobate that acts as an antioxidant
True
79
T/F: Microarray analysis is used in nutrigenomics and can be classified under transcriptomics.
True
80
The lower the pKa value, the _____ the _____.
* stronger, base
* stronger, acid
* weaker, base
* weaker, acid
stronger, acid
81
This all translates into the fact that the non-oxidative phase of the PPP pathway is controlled by the availability of _____.
* FAD
* NADPH
* NADP+
* none of the above
NADP+
82
True or False: when you see the word “kinase,” it means an enyzyme that adds a phosphate group
TRUE
83
Km is the substrate concentration that gives ___ maximal velocity
* 1/2
* 1/4
* 2/3
* 100%
1/2
84
True or false: Thus, glycolysis begins with glucose phosphorylation, and it ends with pyruvate formation.
TRUE
85
Biological buffers, mixture of weak acids (the proton ____) and their conjugate bases (the proton ___), help maintain biomolecules in optimal ionic state of pH 7.
* donor, acceptor
* acceptor, donor
donor, acceptor
86
The lack of which muscle enzyme causes glucose when phosphorylated in the muscle to be trapped?
* glucokinase
* glucose-6-phosphatase
* glycerol-3-phosphatase
* hexokinase
glucose-6-phosphatase
87
You eat a cheeseburger and a fresh salad. Which of the following molecules in your food is NOT normally oxidized in aerobic respiration to generate ATP?
lipids
amino acids
nucleic acids
carbohydrates
nucleic acids
88
Which hormone[s] cause[s] the liver to break down glycogen and carry out gluconeogenesis?
insulin
glucagon
epinephrine
glucagon and epinephrine
glucagon and epinephrine (i think)
89
Which hormone[s] trigger[s] adipose tissue to store fatty acids as triacylglycerols?
insulin
glucagon
epinephrine
glucagon and epinephrine
insulin (i think)
90
Catalysts that change the rate of reactions are what category of physiological proteins?
hormones
enzymes, which don’t alter the equilibrium
enzymes, which alter the equilibrium
transport proteins
enzymes, which don’t alter the equilibrium
91
______ (ΔH is positive) requires energy to make that reaction go
Exothermic
Endothermic
Endothermic
92
______ (ΔH is negative) produces heat
Exothermic
Endothermic
Exothermic
o Of that heat produced, some is dissipated and is absorbed by the water contained in the cell, contributing to our constant body temperature (because water has a high specific heat). The rest of that exothermic energy can be utilized to do work. This useful energy (that which is available to do work) is known as the free energy (the G term) of a reaction and is a form of energy upon which countless, life-sustaining biochemical reactions rely, in order to go to completion.
93
NADH just floats over to the inner-membrane and can enter the ETC at complex ___, while FADH2 enters the transport chain at complex ___. NADH and FADH2 are known as electron carriers. This means they are capable of donating electrons to the transport chain.
1 and 2
1 and 3
2 and 3
1 and 2
94
The affinity of _____ for oxygen is less than its structural analog myoglobin. Myoglobin, on the other hand, has a significantly higher affinity for oxygen and will, therefore, be much less inclined to release it once it is bound.
hemoglobin
