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Biochemistry > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

biosignaling

A

-reception and conversion of signals from extracellualar environments into cellular responses both timely and appropriate to input signals

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2
Q

cellular responses depend on (receptor or ligand)

A

-specific downstream signaling programs for specific receptors

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3
Q

General features of signal transduction

A
  • signal transduction is universal property of living cells
  • numerous and diverse signals are detected by various cells
  • numerous and diverse responses accomplished by distinct cells
  • sensitive detection and specific responses programmed
  • limited number of conserved mechanisms used to detect signals and to integrate and transduce signals into appropriate cellular responses
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4
Q

other general features of signal transduction

A
  • specificity
  • amplification
  • desensitization
  • modularity
  • integration
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5
Q

In the basic quantitative theory of receptor-ligand binding, what is Kd

A

Kd= 1/Ka

-[ligand] when receptor binding sites are 50% occupied

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6
Q

Scatchard Equation

A

[bound]/[free]= 1/Kd * (Bmax- [RL])

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7
Q

Scatchard Plot

A
  • Bmax is x-intercept

- slope is -Ka (-1/Kd)

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8
Q

cascade of B-adrenergic receptor system

A

epinephrine binds to receptor–> hormone-receptor complex causes GDP bound to Gsa to be displaced by GTP, activating Gsa–> activated Gsa moves to activate adenylyl cyclase–> adenylyl cyclase catalyzes the formation of cAMP –> cAMP activates PKA–> phosphorylation of cellular proteins by PKA causes cellular responses to epinephrine –> cAMP gets degraded reversing the activation of PKA

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9
Q

What is the primary effector in the B-Adrenergic receptor signaling pathway?

A

-adenylyl cyclase

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10
Q

What is the secondary effector in the B-Adrenergic receptor signaling pathway?

A

protein kinase A

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11
Q

describe the insulin receptor

A
  • -receptor tyrosine kinase

- 2 alpha subunits and 2 Beta subunits

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12
Q

list of good nucleophiles

A

negatively charged oxygen

  • negatively charged sulfhydryl
  • carbanion
  • uncharged amine group
  • imidazole
  • Hydroxide ion
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13
Q

List of electrophiles

A
  • carbon atom of carbonyl group
  • protonated imine group (attack will occur at the carbon)
  • phosphorous atom of phosphate group
  • proton
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14
Q

how do cells avoid futile and conflicting cycles of reactions of metabolism?

A

-operating distinct pathways

  • deploying reciprocal regulation: an anabolic pathway activator will be a catabolic pathway inhibitor
  • arranging separate compartmentalization
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15
Q

Name two common ways to study metabolic pathways

A
  • genetic approach: block a point in the pathway with a mutation or by a specific poison and analyze the outcome to order the reactions in the pathway
  • radiochemical approach: trace fate over time of some added radioactive precursor molecule to identify intermediates in the pathway and to temporally order reactions in the pathway
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16
Q

Glycolysis and Gluconeogenesis occur in the

A

-cytoplasm

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17
Q

Please give the net consumption and the net production of glycolysis

A

NET consumption: 1 glucose, 2 ADP and 2 Pi, 2 NAD+

NET production: 2 pyruvate, 2 ATP, 2 NADH

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18
Q

For one molecule INPUT into glycolysis, write the balanced chemical equation for the conversion of input to output by this pathway

A

1 Glucose + 2 ADP + 2 NAD+ + 2 Pi –> 2 Pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

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19
Q

At which reaction step in glycolysis does arsenate prevent ATP from being formed?

A

-Arsenate is not good because it affects reaction 7 (Phosphoglycerate kinase) formation of ATP

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20
Q

What is the only source of usable energy for RBC?

A

-glycolysis

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21
Q

People with partial defects in pyruvate kinase suffer

A

hemolytic anemia

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22
Q

Which reaction steps of glycolysis have the large negative delta g values that keep glycolysis running?

A

reactions 1,3, and 10

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23
Q

feeder pathways

A

-pathways to send alternative fuels into glycolysis

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24
Q

Lactose can be converted into ___ and ____ by the enzyme ___

A
  • glucose and galactose

- enzyme lactase

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25
Q

sucrose can be converted into __ and ___ by the enzyme ____

A
  • glucose and fructose

- sucrase

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26
Q

Inability to hydrolyze lactose leads to

A

-causes lactose intolerance, diarrhea, but is still sustainable to life

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27
Q

inability to hydrolyze sucrose leads to

A
  • causes sucrose intolerance and diarrhea

- mainly just uncomfortable

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28
Q

inability to process galactose to glucose results in

A
  • galactosemia

- can be fatal!

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29
Q

releasing glucose from glycogen may be called

A

-glycogenolysis

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30
Q

making glucose is called

A

-gluconeogenesis

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31
Q

carboxylase

A

adds CO2 and usually requires biotin

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32
Q

glycolysis and PEP carboxykinase enzymes are located

A

-in the cytoplasm

33
Q

pyruvate caroboxylase occurs in the

A

-mitochondria

34
Q

Describe the transport process to get oxaloacetate into the cytoplasm

A
  1. convert oxaloacetate to malate
  2. transport malate out of mitochondrium into cytoplasm
  3. convert malate back to oxaloacetate
    * * this also transports 1 NADH and 3 C out of the mitochondria
35
Q

making one glucose from 2 pyruvates costs:

A

-6 nucleoside triphosphates plus 2 NADH

36
Q

Regulating glycolysis and gluconeogenesis

A

-hexokinase, PFK-1,/FBPase 1, and fructose 2, 6 bisphosphate

37
Q

Hexokinase is regulated by:

A

-allosteric regulation: muscle hexokinase is allosterically inhibited by glucose =-6-phosphate

38
Q

There are __ isozymes of hexokinase, __ have a high affinity for glucose

A

4, 1-3

39
Q

Type 4 of hexokinase

A
  • in the liver
  • has a low affinity for glucose and is effectively regulated by glucose levels available in the blood
  • type 4 is insensitive to glucose-6-P
  • a regulatory protein monitors blood glucose levels and regulates hexokinase 4
40
Q

What is the most crtitical regulatory steps in glycolysis and gluconeogenesis?

A

-allosteric and reciprocal regulation of PFK-1/ FBPase-1

41
Q

insulin stimulates

A

-PFK-2

42
Q

Glucagon stimulates

A

-FBPase-2

43
Q

Phosphofructokinase 1 is activated by

A
  • allosterically activated by fructose- 2,6-bisphosphate

- activated by: high [ADP] and [AMP]

44
Q

Phosphofructokinase-1 is inhibited by:

A

-allosterically inhibited by: ATP and citrate

45
Q

Fructose Bisphosphatase-1 is inhibited by

A
  • fructose 2,6-bisphosphate

- AMP

46
Q

Fructose 2,6-bisphosphate signals

A

high [glucose]

  • signals glycolysis
  • inhibits gluconeogenesis
47
Q

Glycolysis yields

A

2 ATP and 2 NADH

48
Q

What is the potential problem with glycolysis products?

A

-NADH has to be re-oxidized to NAD+ all the time otherwise glycolysis will convert all NAD+ to NADH and then it will stop :(

49
Q

What are two possible ways to re-oxidize NADH?

A
  • If O2 is available: NADH is converted to NAD+ by transferring electrons to O2 (oxidative phosphorylation)
  • if O2 is not available then NAD+ is made from NADH by transferring electrons to some substrate (fermentation)
50
Q

does fermentation yield additional ATP?

A

-no

51
Q

describe the first common fermentation

A

-pyruvate gets reduced by NADH via the enzyme lactate dehydrgenase to L-lactate

52
Q

describe the second common fermentation

A
  • pyruvate gets converted to acetaldehyde by pyruvate decarboxylase with cofactors MG2+ and thiamin pyrophosphate
  • acetaldehyde then gets converted to ethanol via alcohol dehydrogenase. This step oxidizes NADH to NAD+
53
Q

when an animal is poisoned by ethanol uptake, alcohol dehydrogenase makes

A

-acetaldehyde which gets converted to acetic acid to acetyl-CoA

54
Q

what compounds are responsible for the dreaded hangover?

A

-acetaldehyde and acetic acid

55
Q

Cori cycle

A
  • occurs during vigorous exercise
  • pyruvate gets reduced to lactate by fermentation in muscles
  • during recovery the lactate is shipped to the liver to be converted into glucose via gluconeogenesis
  • glucose is then shipped back to the muscle
56
Q

Lactate dehydrogenase 1 is found primarily in

A

-cardiac cells

57
Q

elevated blood levels of lactate dehydrogenase 1 would suggest that

A
  • some cardiac cells have been damaged and are now leaking intracellular enzymes
  • aka heart attack!
58
Q

Pasteur Effect

A

-cells that need to perform energy production in the absence of oxygen show their glycolysis rate is much increased in order to offset the poor yield of ATP per glucose consumed

59
Q

Warburg effect

A

-since tumor cells growth is often faster than angiogenesis they must make most energy from glycolysis and fermentation

60
Q

what is a way that tumor cells can be identified

A 
PET scan (Positron Emission Tomography) 
-radioactive tagged glucose allows PET to visualize where there is increased rates of glycolysis and glucose uptake
61
Q

NADH made by glycolysis must be ___ to ___ or else glycolysis will stop

A

-re-oxidized to NAD+

62
Q

pyruvate decarboxylase uses ____ cofactor to move activated acetaldehyde units

A

-thiamin pyrophosphate

63
Q

general purpose of Pentose Phosphate Pathway

A
  • using glucose as carbon to make NADPH plus ribose

- it is critically important for actively dividing cells with high rates of DNA and RNA and enzyme cofactors

64
Q

NADPH is critically important for

A
  • biosynthetic reactions

- detoxifying xenobiotics and slowing oxidative damage

65
Q

name the redox-active nucleotide cofactor for oxidative pentose phosphate pathway

A

-NADP+ or NADPH

66
Q

how many moles of reduced nucleotide cofactor are produced by the entire oxidative pathway per mole of glucose 6-phosphate

A

2 moles of NADPH

67
Q

name two glucose-derived products of the oxidative pentose phosphate pathway

A

ribulose 5-phosphate and ribose 5 phosphate

68
Q

What are the two branches of the pentose phosphate pathway (PPP)

A

-oxidative and nonoxidative

69
Q

oxidative branch of the PPP

A
  • 1 out of every 6 glucose carbons gets oxidized to CO2

- this yields ribulose-5-phosphate plus 2 NADPH

70
Q

Non-oxidative branch of the PPP

A
  • excess ribulose-5-Phosphate recycled to glucose. This glucose can enter glycolysis or get another round throughPPP to make NADPH
  • —OR—
  • converts glucose to ribulose without making unnecessary NADPH
71
Q

Oxidative PPP: __ reactions with __ irreversible NADPH-yielding steps

A

-4 reactions with two irreversible NADPH-yeilding steps

72
Q

The first irreversible regulatory step in pentose phosphate pathway

A

glucose 6-Phosphate converted to 6-phospho-glucono-delta-lactone via glucose 6 Phosphate dehydrogenase and cofactor NADP+ (gets converted to NADPH)

*** NADPH inhibits glucose-6-phosphate dehydrogenase

73
Q

what compound inhibits glucose 6-phosphate dehydrogenase?

A

-NADPH

74
Q

6-Phosphogluconate dehydrogenase

A

the second irreversible step’s enzyme in the oxidative PPP

-this yields NADPH

75
Q

what is the net gain of the oxidative PPP

A

-Ribulose-5-P + 2 NADPH + Co2

76
Q

non-oxidative PPP

A

-reversibly yields glucose 6-phosphate from ribulose-5-Phosphate
OR
-reversibly yields RIbulose-5-P from glucose-6-phosphate

77
Q

Non-Oxidative PPP is active when

A

-cell needs NADPH, but not Ribose
OR when
-cell needs Ribose, but not NADPH

78
Q

name the two key enzymes of the non-oxidative PPP

A

-transaldolase and transketolase

79
Q

Favism

A
  • sensitivity to broad beans or medication due to defect in G6 PDH
  • x-linked and recessive
  • people with this disease are partially resistent to malaria

Biochemistry (7 decks)

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