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Biochemistry > Glycolysis > Flashcards

Glycolysis Flashcards

Exam 2

1
Q

What does glycolysis mean?

A

Sweet lysis

Lyse sugars to get energy

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2
Q

Is glucose or fat a better fuel?

A

Fat

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3
Q

What is the starting sugar for glycolysis?

A

Glucose

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4
Q

What happens when glucose is oxidized?

A

It yields energy

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5
Q

What is the storage form of glucose?

A

Glycogen in animals

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6
Q

T/F: Many organisms and tissues can meet their energy needs on glucose only.

A

True

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7
Q

What can glucose be used to generate other than energy?

A

Membrane lipids
Nucleotides in DNA and RNA
Glycoproteins

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8
Q

Is forming glycogen from glucose anabolic or catabolic?

A

anabolic (building up)

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9
Q

Is glucose oxidation via the pentose phosphate pathway anabolic or catabolic?

A

Anabolic

Makes Ribose 5-phosphate

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10
Q

Is glycolysis catabolic or anabolic?

A

Catabolic

Makes pyruvate

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11
Q

What does glycolysis do overall?

A

It is the sequence of 10 steps that are catalyzed by enzymes by which glucose is converted into pyruvate

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12
Q

How does glycolysis keep the reactions pushing forward even when they are endothermic?

A

The products of one reaction is the substrate of another which decreases the product and pushes the reaction to the product side

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13
Q

Where does glycolysis take place in the cell?

A

Cytoplasm

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14
Q

How do we activate glucose in glycolysis?

A

Phosphorylate it so it is anionic and is stuck inside of the cell
This also changes the concentration of glucose inside the cell when it is converted so glucose continues to flow in

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15
Q

Where does the energy from glycolysis come from?

A

High energy metabolites (“BASICALLY ATP” -SARAH)

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16
Q

What is made in one round of glycolysis?

A

2NADH, 2ATP, 2H2O, 2H+ and two pyruvates

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17
Q

How many carbons are in glucose?

A

6

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18
Q

How many carbons are in one pyruvate molecule?

A

3

when we use one glucose we make 2 pyruvate and 3x2=6 which is how many sugars are in glucose

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19
Q

What does the preparatory phase of glycolysis do?

A 
Uses energy (2ATP) to activate sugars 
Makes glucose into 2 trioses
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20
Q

What phase of glycolysis makes ATP?

A

The Payoff phase

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21
Q

Where is hexokinase found?

A

in the muscles

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22
Q

Where is glucokinase found?

A

in the liver

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23
Q

What does hexokinase and glucokinase do?

A

Converts Glucose to Glucose 6-phosphate by using ATP and Mg+ (cofactor)

Phosphorylates the glucose on the C6

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24
Q

What does Mg2+ do for phosphorylation?

A

Stabilizes the close negative charges of phosphate groups

It is a cofactor

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25
Q

Is converting glucose to glucose 6-phosphate exo or endo thermic?

A

Exothermic

-16.7 kJ/mol

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26
Q

What does phosphorylating glucose do?

A

Traps glucose inside of the cell and lowers intracellular glucose concentration to allow further uptake (remember when you phosphorylate a glucose it is no longer glucose)

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27
Q

Where does the energy for phosphorylation come from in glycolysis?

A

Hydrolysis of ATP

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28
Q

How are hexokinases and glucokinases isoenzymes?

A

They both phosphorylate but in different areas of the body
Hexo in the muscles
Gluco in the liver

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29
Q

Is phosphorylation of glucose irreversible?

A

Yes

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30
Q

How is hexokinase inhibited?

A

Allostericly inhibited by glucose 6-phosphate (feedback)

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31
Q

How is glucokinase activated?

A

Allostericly activated by glucose and inhibited by fructose 6-phosphate

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32
Q

What is a molecular sensor of high glucose levels?

A

Glucokinase

It has a low affinity for glucose (higher Km)

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33
Q

Can glucokinase be inhibited by a product?

A

no

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34
Q

What does the liver do when blood glucose levels are high?

A

It pulls in extra glucose and traps it by phosphorylation

Acts as a glucose sensor and stimulates insulin release

35
Q

What can hexokinase phosphoryate?

A

Mannose, fructose, glucose

In most tissues of body

36
Q

T/F Hexokinase has a high affinity for glucose. What is its Km relative to glucokinase?

A

True

Much smaller Km than glucokinase

37
Q

What does phosphohexose isomerase do?

A

Converts glucose 6-phosphate to fructose 6-phosphate
Makes an isomer
Glucose 6-phosphate is an aldose
Fructose 6-phosphate is a ketose

38
Q

What is the cofactor used for phosphohexose isomerase?

A

Mg++

39
Q

TF: Converting glucose 6-phosphate into the isomer fructose 6-phosphate is Irreversible and unfavorable

A

FALSE

It is unfavorable (endothermic) but has a low free energy near equilibrium so it is reversible

40
Q

Since converting glucose 6-phosphate to fructose 6-phosphate is reversible, how does glycolysis keep moving forward and not back?

A

Keeping the product concentration low by pairing it with favorable next step to drive the reaction forward

41
Q

What does phosphofructokinase 1 do?

A

Phosphorylates Carbon 1 on fructose 6-phosphate to make it fructose 1,6-bisphosphate by using ATP and Mg++

42
Q

What is the first committed step of glycolysis?

A

Step 3 using PFK-1

Fructose 1-6 bisphosphate is committed to become pyruvate and yield energy

43
Q

What is the favorability of step 3 with PFK-1?

A

Highly thermodynamically favorable and hence it is IRreversible

44
Q

How is PFK-1 regulated?

A

Allosterically inhibited by ATP and citrate (high energy state)
Allosterically activated by AMP and ADP (low energy state)

45
Q

Why does glycolysis phosphorylate the sugar yet again in step 3?

A

To make it more symmetrical and to further activate glucose

46
Q

What does aldolase do to fructose 1-6 bisphosphate?

A

The six carbon sugar is cleaved into two three carbon sugars to make high energy phosphate trioses (a ketone and an aldehyde)

47
Q

Does glyceraldehyde 3-phosphate or dihydroxyacetone phosphate feed into step 5 of glycolysis?

A 
Dihydroxyaceton phosphate (ketone) to be made into another glyceraldehyde 3-phosphate by triose phosphate isomerase 
(unfavorable)
48
Q

Is step 4 favorable?

A

No it is endergonic and reversible

49
Q

What kind of reaction does glyceraldehyde 3-phosphate dehydrogenase perform in step 6?

A

Redox reaction

50
Q

What must be used in redox reactions?

A

NAD+

coenzyme that will be reduced

51
Q

What does step 6 allow for?

A

Net production of ATP via glycolysis

52
Q

What does step 6 generate?

A

1,3-bisphosphoglycerate which is a high energy phosphate compound

53
Q

Where does the phosphate for step 6 come from?

A

An inorganic phosphate

54
Q

How is NAD+ regenerated after being reduced to NADH?

A

Aerobically by ETC

Anaerobically by lactate dehydrogenase

55
Q

Is step six reversible?

A

Yes it is endergonic

56
Q

What happens in step 7?

A

The 1st production of ATP by phosphoglycerate kinase (phosphorylation of ADP from a substrate 1,3-bisphosphoglycerate)

57
Q

Is step 7 favorable?

A

Yes because you are breaking off a high energy bond from 1,3 bisphosphoglycerate (phosphate) and adding it onto ADP to make ATP and 3-phosphoglycerate

58
Q

Is step 7 irreversible since its favorable?

A

No it is reversible (net ATP is now zero)

59
Q

What does a mutase do?

A

Moves functional groups in same molecule

60
Q

What does phoshoglycerate mutase do?

A

Moves the phosphate from on 3-phosphoglycerate to carbon 2 to make 2-phosphoglycerate

61
Q

What is used for phosphoglycerate mutase?

A

Mg++ cofactor to stabilize the negative charges

62
Q

Is step 8 favorable?

A

No it is endergonic and reversible

63
Q

What does enolase do in step 9?

A

Removes an OH group from C3 and an H group from C2 on 2-phosphoglycerate through dehydration and makes a double bond between C3 and C2 to make phosphoenolpyruvate

Creates an enol through dehydration

64
Q

Why does 2-PG need to be convertedinto phosphoenolpyruvate?

A

Because 2-PG is not a good enough phosphate donor to generate ATP but Enol phosphate is since it is a higher energy compound with a double bond

PEP has a much better phosphoryl transfer potential

65
Q

Is step 9 favorable?

A

No and it is reversible

66
Q

What does step 10 do?

A

Creates pyruvate form PEP and creates an ATP from ADP and the phosphate on C2 of PEP

67
Q

What cofactors does pyruvate kinase need?

A

K+ and Mg++

68
Q

Is step 10 reversible?

A

NO

It is very highly favorable exergonic

69
Q

What is tautomerization?

A

Lowers the concentration of the reaction product and drives the reaction towards ATP formation
Makes pyruvate a keto form from enol form which the keto form predominates and drives ATP production

70
Q

What regulates pyruvate kinase?

A

ATP, divalent metals, and other metabolites

Activated by feed forward regulation by fructose 1,6- bisphosphate

71
Q

What is used in glycolysis/

A

1 glucose, 2 ATP and 2 NAD+

72
Q

What is made in glycolysis?

A

2 pyruvate, 4 ATP, 2 NADH

net 2 ATP

73
Q

WHY is glycolysis regulated?

A

Ensure proper use of nutrients

ensure production of ATP only when needed

74
Q

What cleaves glucose from glycogen?

A

Glycogen phosphorylase

75
Q

What is made when glucose is cleaved from glycogen

A

Glucose 1-phosphate

76
Q

What does lactose hydrolyze into?

A

Glucose and galactose

77
Q

WHat does sucrose hydrolyze into?

A

Glucose and fructose

78
Q

What other sugars can enter glycolysis besides glucose?

A

Fructose
Galactose
Mannose

79
Q

What are the 2 fates of pyruvate?

A

Anaerobic it is converted into lactate

Aerobic it is converted into Acetyl-CoA for the krebs cycle

80
Q

What is fermentation?

A

Generation of ATP without consuming oxygen

Pyruvate to Lactate and this regenerates NAD+ for further glycolysis under anaerobic conditions

81
Q

What converts pyruvate into lactate?

A

Lactate dehydrogenase and NADH and H+

82
Q

Where is lactate converted into glucose?

A

The liver

83
Q

How can tumor cells increase expression of LDH ?

A

By induction

84
Q

What is the warburg effect?

A

When rapidly growing tumors obtain ATP by metabolizing glucose to lactate even in the presence of oxygen

Biochemistry (10 decks)

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