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Biochemistry > Chapter 14 > Flashcards

Chapter 14 Flashcards

1
Q

Many organisms use glucose to generate what things?

A
  • amino acids (by breaking glucose down into pyruvate then use pyruvate)
  • membrane lipids
  • nucleotides in DNA and RNA
  • cofactors necessary for metabolism
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2
Q

Gluconeogenesis is the synthesis of glucose from simpler precursors like ______ and ______

A

pyruvate and lactate

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3
Q

What pathway is an alternative pathway for glucose oxidation?

A

the pentose phosphate pathway

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4
Q

Glucose can be efficiently stored in what form?

A

Polymeric (starch, glycogen)

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5
Q

What two things can happen to pyruvate after glycolysis?

A
  1. pyruvate can be further aerobically oxidized
  2. pyruvate can be used as a precursor in biosynthesis
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6
Q

How many ATP molecules are consumed in the preparatory phase of Glycolysis (steps 1-5)

A

2 molecules of ATP

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7
Q

In the payoff phase of glycolysis, how many pyruvate molecules are created for each molecule of glucose

A

2 pyruvate per 1 glucose

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8
Q

What are the reactants for glycolysis?

A

Glucose + 2(NAD+) + 2ADP + 2Pi

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9
Q

What are the products of glycolysis?

A

2 pyruvate + 2NADH + 2H +2ATP + 2H20

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10
Q

The conversion of glucose to pyruvate is (endergonic or exergonic) ?

A

exergonic = favorable
delta G = -146jk/mol

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11
Q

Under standard cellular conditions, glycolysis is (reversible or irreversible) ?

A

irreversible

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12
Q

energy stored in pyruvate can be extracted in which two processes?

A

aerobic and anaerobic processes

Aerobic: oxidative reactions in Krebs, oxidative phosphorylation

Anaerobic: reduction to lactate, reduction to ethanol

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13
Q

What is the purpose of the first step in glycolysis?

A

To trap glucose inside the cell & to lower intracellular glucose levels so that further glucose uptake can occur

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14
Q

Which steps in glycolysis require ATP?

A

steps 1 and 3

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15
Q

Which steps in glycolysis PRODUCT ATP?

A

steps 7 and 10 (substrate level phosphorylations)

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16
Q

Which steps in glycolysis are carried out by isomerases?

A

steps 2 and 5

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17
Q

What are the functions of phosphoryl groups in glycolysis?

A
  • to prevent glycolytic intermediates from leaving the cell
  • to serve as essential components in the enzymatic conservation of metabolic energy
  • to lower the activation energy and to increase the specificity of the enzymatic reactions
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18
Q

In what step of glycolysis does an aldose isomerize into a ketose via an enediol intermediate?

A

Step 2- Isomerization of glucose (an aldose) to fructose (a ketose) via enzyme phosphohexose isomerase

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19
Q

What is the mechanism of the phosphohexose isomerase mechanism in the isomerization of glucose to fructose?

A

General acid-base catalysis

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20
Q

What is the first committed step of glycolysis?

A

Step 3 - The Second Phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate

**fructose 1,6-bisphosphate is committed to becoming pyruvate

**irreversible reaction

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21
Q

What is the least energetically favorable step of the preparatory phase?

A

Step 4 - Aldol cleavage

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22
Q

In step 6, DHAP must be oxidized to _____ via triose phosphate isomerase

A

DHAP OXIDIZED TO GAP

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23
Q

What step completes the preparatory phase of glycolysis?

A

step 5- triose phosphate isomerization

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24
Q

Enzymes that transfer phosphate groups between ATP and various substrates

A

Kinases

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25
Q

Define substrate-level phosphorylation

A

The formation of ATP by phosphoryl group transfer from a substrate

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26
Q

Why does glycolysis need to be regulated?

A

To ensure proper use of nutrients and to ensure ATP is only produced when it is needed

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27
Q

What two molecules is glucose cleaved from?

A

Glycogen and Starch

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28
Q

In step 6 of glycolysis, each molecule of glyceraldehyde-3-phosphate is oxidized and phosphorylated by ________ to form 1,3 Bisphosphoglycerate

A

Inorganic Phosphate (Pi)

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29
Q

What is the purpose of step 2 in glycolysis?

A

makes the next steps in the reaction require less energy - the isomerization of glucose-6-phosphate to fructose-6-phosphate moves the carbonyl to C-2 : a prerequisite for steps 3 and 4

–C1 of fructose is easier tot phosphorylate by PFK , allows for symmetrical cleavage by aldolase

30
Q

What is the purpose of step 3 in glycolysis?

A

the 2nd phosphorylation converts fructose-6-phosphate to fructose-1,6-bisphosphate

– this is the first committed step of glycolysis…b/c fructose 1,6 bisphosphate is committed to becoming pyruvate

31
Q

What is the purpose of step 4 in glycolysis?

A

Step 4 is the aldol cleavage of a 6-carbon sugar into two 3-carbon sugars GAP and DAP

32
Q

What is the purpose of step 5 in glycolysis?

A

This step completes the preparatory phase of glycolysis - allows glycolysis to proceed to the payoff phase by a single chemical pathway

conversion of dihydroxyacetone phosphate to GAP (glyceraldehyde-3-phosphate)

33
Q

What is the purpose of step 6 in glycolysis?

A

The oxidation of GAP produces a high-energy acyl phosphate compound

– incorporates inorganic phosphate
– the first energy-yielding step in glycolysis, produced NADH

34
Q

What is the purpose of step 7 in glycolysis?

A

Substrate level phosphorylation to make ATP

35
Q

Purpose of step 8 in glycolysis?

A

The migration of a phosphate group from C-3 to C-2, sets up for the final steps of the pathway

36
Q

Purpose of step 9 in glycolysis?

A

Dehydration activates the phosphoryl for transfer to ADP in the last step

37
Q

Purpose of step 10 in glycolysis?

A

Production of the 2nd ATP

38
Q

For both phosphorylations in the preparatory phase of glycolysis, what is the phosphoryl group donor?

A

ATP serves as the phosphoryl group donor

39
Q

Which process in glycolysis is endergonic?

A

The formation of ATP from ADP and Pi

40
Q

What is anaerobic glycolysis called

A

Fermentation

41
Q

What is lactic acid fermentation?

A

the reduction of pyruvate to lactate

42
Q

What is ethanol fermentation?

A

the two-step reduction of pyruvate to ethanol

43
Q

What is the CO2 produced in the first step of ethanol fermentation used for?

A

carbonation in beer and dough rising

44
Q

Gluconeogenesis

A

Pathway that converts pyruvate (and its related 3 and 4 carbon compounds) to glucose

45
Q

Is any ATP produced during gluconeogenesis?

A

No

46
Q

What molecules in gluconeogenesis are permeable to the mitochondrial membrane…which are impermeable

A

Permeable molecules = Malate, PEP, pyruvate

IMpermeable = oxaloacetate

47
Q

What is oxaloacetate converted to in order to allow for transport to the cytosol for gluconeogenesis?

A

oxaloacetate can be converted to PEP or malate

48
Q

A reason why gluconeogenesis is physiologically necessary

A

The brain, NS, and red blood cells can only generate ATP from glucose

49
Q

What can animals produce glucose from, what can they not produce glucose from?

A

Animals CAN produce glucose from certain sugars (pyruvate, lactate, oxaloacetate) and from the amino acids capable of being converted to Kreb’s cycle intermediates (al but Leucine and Lycine)

Animals CANNOT produce glucose from fatty acids b/c the product off fatty acid degradation is acetyl-coA

50
Q

What are hexokinase I,II and III all inhibited by?

A

Their product, glucose-6-phosphate

51
Q

What is hexokinase IV inhibited by?

A

Hexokinase IV is inhibited by Fructose-6-phosphate which is an allosteric effector

52
Q

When is pyruvate converted to PEP?

A

when fatty acids are available

53
Q

What are the molecular costs of gluconeogenesis?

A

4 ATP, 2 GTP, 2 NADH

54
Q

During fermentation (anaerobic glycolysis). ATP is generated without consuming ______ or ______

A

generation of ATP without consuming oxygen or NAD+

55
Q

In mammals, where is the main site of gluconeogenesis

A

liver

56
Q

What are the three bypass points (steps) in gluconeogenesis?

A

Pyruvate –> phosphoenolpyruvate (PEP)

Fructose 1,6 bisphosphate —> fructose 6-phosphate

Glucose 6-phosphate –> glucose

57
Q

How is phosphofructokinase-1 (PFK-1) regulated?

A

PFK-1 is regulated by the binding of ATP to an allosteric site - this occurs when there is an excess in ATP

Citrate inhibits PFK-1 by increasing the inhibitory effects of ATP – causes a smaller concentration of ATP to seem like more

58
Q

How is (FBPase) fructose 1,6 bisphosphate ALLOSTERICALY regulated (inhibited)

A

high concentrations of AMP (which corresponds to low concentrations of ATP) inhibit FBPase –> thus slowing glucose synthesis

high ATP concentrations slows glycolysis and speeds up gluconeogenesis

59
Q

What molecule mediates the rapid hormonal regulation of glycolysis and gluconeogenesis?

A

FRUCTOSE 2,6-BISPHOSPHATE

60
Q

How does fructose 2,6-bisphospate regulate PFK-1 (phosphofructokinase-1)

A

Binds to PFK-1 and increases its affinity for fructose-6-phosphate

61
Q

How does fructose 2,6-bisphospate regulate FBPase-1 (fructose 1,6-bisphosphate)

A

binds to FBPase-1 and reduces its affinity for its substrate

62
Q

What molecule catalyzes the formation of FBPase-1 ?

A

PFK-2 (phosphofructokinase-2)

63
Q

What molecules catalyze the BREAKDOWN of FBPase-1?

A

FBPase-2

64
Q

What are the main products of the Pentose Phosphate Pathway?

A

NADPH and ribose-5-phosphate

65
Q

A process by which cells continue using glycolysis to extract energy in anaerobic conditions

A

Fermentation

66
Q

Pentose phosphates can be regenerated into _______ which requires no ATP

A

glucose-6-phosphate

67
Q

A process by which cells can generate pentose phosphates & NADPH

A

pentose phosphate patway

68
Q

Ribose-5-phosphate is a biosynthetic precursor of _______?

A

nucelotides

69
Q

Under aerobic conditions what does pyruvate become?

A

pyruvate gets oxidized to acetyl-coA

70
Q

In the reduction of pyruvate to ethanol, pyruvate decarboxylase requires what two cofactors?

A

Mg2+ and thiamine pyrophosphate (TPP)

71
Q

Tumor cells cause an increased expression of what?

A

LDH (lactate dehydrogenase)

Biochemistry (10 decks)

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