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Biochemistry I > Biochemistry I Exam 5 > Flashcards

Biochemistry I Exam 5 Flashcards

1
Q

Autotroph

A

use CO2 from the atmosphere as their sole source of carbon

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2
Q

Heterotroph

A

cannot use atmospheric CO2 and must obtain carbon from their environment

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3
Q

Metabolites

A

series of intermediates through which precursors are converted to product

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4
Q

Intermediary Metabolism

A

the combines activities of all the metabolic pathways that interconvert precursors, metabolites, and products of low molecular weights

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5
Q

Catabolism

A

the degradative phase of metabolism; releases energy

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6
Q

Anabolism (biosynthesis)

A

the building phase of metabolism; requires energy

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7
Q

Energy Transduction

A

changes of one form into another

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8
Q

Free Energy

A

expresses the amount of energy capable of doing work during a reaction at constant temperature and pressure

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9
Q

Enthalpy

A

the heat content of the reacting system

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10
Q

Entropy

A

a quantitative expression for the randomness or disorder in a system

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11
Q

Free Energy Change Equation

A

delta G=delta H-T delta S

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12
Q

Exergonic

A

energy-releasing reaction

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13
Q

Endergonic

A

requires energy input

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14
Q

Exothermic

A

releases heat

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15
Q

Endothermic

A

takes up heat

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16
Q

Understand the relationship between Keq and DG

A

-Keq>1.0=negative delta G (reaction proceeds forward)
-Keq=1.0=zero delta G (reaction is at equilibrium)
-Keq<1.0=positive delta G (reaction proceeds in reverse)

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17
Q

Heterolytic Cleavage

A

cleavage of a covalent bond where each atom leaves the bond as a radical, carrying one unpaired electron

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18
Q

Nucleophile

A

functional groups rich in and capable of donating electrons; combine with and give up electrons to electrophiles

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19
Q

Electrophiles

A

electron-deficient functional groups that seek electrons

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20
Q

Kinase

A

transfer a phosphoryl group from ATP to an acceptor molecule; catalyzes a phosphorylation reaction

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21
Q

Phosphorylases

A

catalyze a displacement reaction where phosphate attacks and becomes covalently attached at the point of bond breakage; catalyze a phosphorolysis reaction

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22
Q

Phosphateses

A

catalyze the removal of a phosphoryl group from a phosphate ester; catalyze dephosphorylation reactions

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23
Q

Synthase

A

catalyze condensation reactions in which no nucleotide triphosphate is required

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24
Q

Synthetases

A

catalyze condensation reactions that require a nucleotide triphosphate

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25
Q

Oxidases

A

catalyze biological reactions where oxygen is the electron acceptor and oxygen does not appear in the oxidized product

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26
Q

Oxygenases

A

catalyze biological oxidation reactions where oxygen is the electron acceptor and oxygen does appear in the oxidized product

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27
Q

Dehydrogenase

A

-catalyze oxidation-reductase reactions in which NAD+ is the electron acceptor and molecular oxygen is not involved
-Electron acceptor is NAD+

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28
Q

What is the relationship between electron donors/acceptors and oxidation/reduction?

A

-NAD going to NADH
-NADH is the reduced form
-NAD is the oxidized form
-If something is getting reduced, something else has to get oxidized

29
Q

What metal ion does ATP associate with and why does hydrolysis of a phosphate lead to energy release?

A

-Magnesium (Mg2+)
-Phosphate groups are negatively charged and thus repel one another when they are arranged in series

30
Q

What is phosphocreatine used for and how does it’s DG compare with ATP?

A

-Phosphocreatine is used to serve in the maintanence and recycling of adenosine triphosphate (ATP) for muscular activity like contractions
- Phosphocreatine Delta G is -12.8 kJ/mol and ATP is -30.5 kJ/mol

31
Q

What compounds are considered high energy and what is the DG cutoff for high energy?

A

-High energy compounds have a DG cutoff of more than -25 kJ/mol
-High Energy Compounds: Adenosine, 1,3-Bisphosphoglycerate, Phosphoenolpyruvate, Phosphocreatine

32
Q

Transphosphorylation

A

the other nucleoside triphosphates (GTP,UTP,and CTP) and all deoxynucleotide triphosphates (dATP, dGTP, dTTP, and dCTP) are energetically equivalent to ATP

33
Q

What do nucleoside diphosphate kinases do?

A

carries phosphoryl groups from ATP to other nucleotides
-high [ATP]/[ADP] ratio normally drives the reaction forward

34
Q

What is the electron motive force?

A

-force proportional to the difference in electron affinity between chemical species
-drives electron flow spontaneously through a circuit
-Biological Circut: electrons from glucose flow through a series of electron-carrier intermediates to another chemical species, such as O2

35
Q

What are the universal electron carriers? How many electrons can they carry?

A

-NAD, NADP, FMN, and FAD
-They can carry 2 e-

36
Q

What vitamin is used to make nicotinamide?

A

Niacin: forms NAD and NADP

37
Q

What vitamin is used to make FMN and FAD?

A

Vitamin B2 (riboflavin)

38
Q

What are the 10 factors affecting enzyme activity and what effects do they have?

A

-1. Extracellular Signals
2. Transcription of Specific Genes
3. mRNA degradation
4. mRNA translation on a ribosome
5. Protein degradation
6. Enzyme sequestered in subcellular organelle
7. Enzyme Binds Substrate
8. Enzyme Binds Ligand
9. Enzyme undergoes phosphorylation/dephosphorylation
10. Enzyme combines with regulatory pathway

39
Q

How does substrate concentration correlate with enzyme kinetics?

A

-Activity drops with lower substrate concentration
-When [S] is greater than Km the reaction rate is linearly dependent on [S]

40
Q

Why would a reaction that is far from equilibrium serve as a regulation point?

A

??

41
Q

Why is AMP a more sensitive indicator than ATP?

A

-The relative change of AMP is 600%
-The relative change of ATP is 10%

42
Q

What are the 10 steps of glycolysis?

A

-Step 1: Phosphorylation of Glucose
-Step 2: Conversion of Glucose 6-Phosphate to Fructose 6-Phosphate
-Step 3: Phosphorylation of Fructose 6-Phosphate to Fructose 1,6-Bisphosphate
-Step 4: Cleavage of Fructose 1,6-Bisphosphate
-Step 5: Interconversion of the Triose Phosphates
-Step 6: Oxidation of Glyceraldehyde 3-Phosphate to 1,3-Bisphosphoglycerate
-Step 7: Phosphoryl Transfer from 1,3-Bispphoglycerate to ADP
-Step 8: Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate
-Step 9: Dehydration of 2-Phosphoglycerate to Phosphoenolpyruvate
-Step 10: Transfer of the Phosphoryl Group from Phosphoenolpyruvate to ADP

43
Q

Which steps of glycolysis are irreversible?

A

-Step 1: Phosphorylation of Glucose
-Step 3: Phosphorylation of Fructose 6-Phosphate to Fructose 1,6-Bisphosphate
-Step 10: Transfer of the Phosphoryl Group from Phosphoenolpyruvate to ADP

44
Q

Which steps of glycolysis use ATP?

A

-Step 1
-Step 3
-Step 10

45
Q

Which steps of glyclolysis use ATP?

A

-Step 1
-Step 3
-Step 10

46
Q

Which steps of glycolysis produce ATP or NADH?

A

-Step 6
-Step 7
-Step 10

47
Q

What are the key products of glycolysis from the prep phase?

A

glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

48
Q

What are the key products of glycolysis from the payoff phase?

A

energy conserved as 2 ATP, 2 pyruvate, and 2 NADH

49
Q

How do glycogen, galactose, and fructose feed the glycolytic pathway?

A
50
Q

What is galactosemia?

A

-Galactosemia: caused by a genetic defect in enzymes controlling dietary galactose; treatment involves carefully controlling dietary galactose

51
Q

What are the “fates” of pyruvate? Which ones apply to humans?

A

-Under aerobic conditions, pyruvate is oxidized to acetyl CoA
-Under anaerobic conditions, pyruvate is reduced to lactate or ethanol
-These apply to humans
-Fermentation: general term for processes that extract energy (as ATP) but do not consume oxygen or change the concentrations of NAD+ or NADH
-Lactic Acid Fermentation: pyruvate accepts electrons from NADH and is reduced to lactate while regenerating the NAD+ necessary for glycolysis
-Ethanol (alcohol) fermentation: pyruvate is further catabolized to ethanol

52
Q

What happens to lactate?

A
53
Q

What is thiamine pyrophosphate and what is it involved in?

A

-Thiamine Pyrophosphate (TPP): coenzyme derived from vitamin B1; thiazolium ring plays an important role in the cleavage of bonds adjacent to a carbonyl group
-Reactions: ethanol fermentation, synthesis of acetyl-CoA in the citric acid cycle, carbon-assimilation reactions of the pentose phosphate pathway

54
Q

What is gluconeogenesis?

A

-Gluconeogenesis: pathway that converts pyruvate and related three-and four-carbon compounds to glucose

55
Q

How does gluconeogenesis overcome the irreversible steps of glycolysis?

A

-They are bypassed with exergonic reactions?

56
Q

What two enzymes and reactions are required to convert pyruvate to PEP?

A

-Reaction 1: pyruvate is converted to oxaloacetate
-Enzyme 1: pyruvate carboxylase (requires coenzyme biotin)
-Reaction 2: oxaloacetate to PEP
-Enzyme 2: phosphoenolpyruvate carboxykinase (requires Mg and GTP)

57
Q

What enzymes are needed to convert fructose-1,6-bisphosphate to fructose-6-phosphate and glucose-6-phosphate to glucose?

A

-fructose 1,6-bisphosphatase (FBPase-1): converts fructose 1,6-bisphosphate to fructose-6-phosphate
-glucose 6-phosphatase: catalyzes the hydrolysis of glucose 6-phosphate to glucose

58
Q

What are glucogenic amino acids?

A

-gluconeogenic amino acids: able to undergo net conversion to glucose
-intermediates of the citric acid cycle can also undergo oxidation to oxaloacetate

59
Q

What factors are regulating glycolysis and gluconeogenesis?

A

-Promoting Glycolysis/Inhibiting Gluconeogenesis: Hexokinase, Phosphofructokinase, Fructose-2,6-bisphosphate, AMP, pyruvate kinase, fructose-1,6-bisphosphate
-Inhibiting Glycolysis/Promoting Gluconeogenesis: Glucose-6–phosphatase, fructose-1,6-bisphosphatase, citrate, phosphoenolpyruvate carboxylkinase, Acetyl-CoA, pyruvate carboxylase

60
Q

How are phosphofructokinase-1 and fructose-1,6-bisphosphatase regulated?

A

-ATP inhibits PFK-1 by binding to an allosteric site
-ADP and AMP allosterically relieve this inhibition by ATP
-FBPase-1 is allosterically inhibited by AMP
-high [AMP], which corresponds to low ATP, inhibits FBPase (slows glucose synthesis
-High [ATP] slows glycolysis and speeds gluconeogenesis

61
Q

What effects do glucagon and insulin have on fructose-2,6-bisphosphate levels?

A

-Glucagon: lowers [fructose 2,6-bisphosphate]; inhibits glycolysis and stimulates gluconeogenesis
-Insulin: increases [fructose 2,6-bisphosphate]; stimulates glycolysis and inhibits gluconenogenesis

62
Q

What does xylulose-5-phosphate do that affects F-2,6-BP levels?

A

-Xylulose 5-phosphate: an intermediate of the pentose phosphate pathway that activates phophoprotein phosphatase 2A; causes an increase in [fructose 2,6-bisphosphate]

63
Q

What effects do glucagon and insulin have on gluconeogenesis and glycolysis?

A

-Glucagon: hormone that signals the liver to produce and release more glucose and to stop consuming it; released when blood glucose level decrease; inhibits glycolysis and stimulates gluconenogenesis
-Insulin: hormone that signals the liver to use glucose as a fuel and as a precursor for the storage of glycogen and triaglycerol; released when blood glucose level increases; stimulates glycolysis and inhibits gluconeogenesis

64
Q

What factors regulate pyruvate kinase activity?

A

-Inhibited by ATP, acetyl-CoA, and long chain fatty acids

65
Q

Name three examples of genes regulated by insulin and what roles do the proteins made by those genes serve?

A

-Hexokinase II, Hexokinase IV, Pyruvate kinase
-Essential for glycolysis, which consumes glucose for energy
-I may have misunderstood this question, IDK

66
Q

What is the purpose of the pentose phosphate pathway?

A

-Purpose is to oxidize glucose 6-phosphate, producing pentose phosphates and NADPH

67
Q

What are some primary products of the pentose phosphate pathway and during which phase are they produced?

A

-Primary Products: NADPH and ribulose 5-phosphate
-Produced in the oxidative phase

68
Q

What is a transketolase reaction?

A

-Transketolase Reaction: catalyzes the transfer of a two-carbon fragment from a ketose donor to an aldose acceptor
-First reaction yields sedoheptulose 7-phosphate
-Second reaction forms fructose 6-phosphate and glyceraldehyde 3-phosphate from erythose 4-phosphate and xylulose 5-phosphate

69
Q

What is a transaldolase reaction?

A

-Transaldolase Reaction: catlayzes the condensation of a three-carbon fragment from sedoheptulose 7-phosphate and glyceraldehyde 3-phosphate, forming fructose 6-phosphate and the tetrose erythrose 4-phosphate

Biochemistry I (6 decks)

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