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Biochemistry 2 > Glucose metabolism > Flashcards

Glucose metabolism Flashcards

1
Q

What happens in the mouth when food is ingested?

A 
Mechanical digestion ( chewing and swallowing)
Chemical digestion of carbohydrates and fats
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2
Q

What are the enzymes that are functioning in the mouth

A

Salivary Amylases

Lingual Lipases

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3
Q

What molecules are not digested in the mouth

A

Proteins

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4
Q

What is the benefit of chewing for the food digestion?

A

Breaking in smaller pieces

Bigger surface area for enzyme activity

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5
Q

What happens in the stomach with food ingested?

A

Mechanical digestion ( peristalsis mixing and propulsion)

  • Chemical digestion of proteins, fats
  • Absorption of lipid soluble substances such as alcohol and aspirin
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6
Q

What enzymes function in the stomach

A

Gastrin
Gastric lipase
HCl
Pepsin

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7
Q

Where the enzymes in the stomach secreted

A

Gastric lipase and Pepsin (Chief cells)

HCl( Periatal cells)

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8
Q

Where do lipids digest in the mouth

A

Lingual lipases are secreted in teeth

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9
Q

What does pepsin do

A

Starts the digestion of proteins

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10
Q

where is the most absorption in the small intestine

A

Duodenum

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11
Q

What is done to the food in the small intestine

A

Mechanical digestion includes mixing and propulsion, primarily by segmentation

Chemical digestion of all molecules

Absorption of peptides, AA,glucose,fats,water,minerals, and vitamins

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12
Q

What enzymes are secreted to duodenum and from what place

A 
From the pancreas
Trypsinogen
Chymotrypsinogen
Carboxypeptidase A and B
Active enzymes target specific AA in proteins
Pancreatic amylase/lipase
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13
Q

What is happening in the large intestine?

A

Propulsion and mixing
No chemical digestion( except bacteria)
Absorption of ions, water, minerals, and organic molecules

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14
Q

What is fisculated cow?

A

A cow that has a whole in the stomach, for the research

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15
Q

Why glucose is an excellent fuel?

A
  • Yields good amount of energy
  • can be efficiently stores
  • Many tissues can meet energy needs on glucose only
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16
Q

Glucose is a versatile precursor for

A
  • All AA
  • membrane lipids
  • nucleotides in DNA and RNA
  • Cofactors in metabolism
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17
Q

What is glycolysis

A

Glucose is degraded to puryvate

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18
Q

What is glucoenogenesis

A

Glucose is formed from non-carbohydrate source

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19
Q

What is glucogenesis

A

Glycogen is polymerized from glucose units

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20
Q

What is glycogenolysis

A

Glycogen is degraded to glucose units

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21
Q

What is the first step of glycolysis

A

Glucose->glucose 6-phosphate

Phosphate group is added OH, instead of H on carbon 6

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22
Q

What enzyme does the first step of glycolysis and what does it use

A

Hexokinase

With the use of ATP, the hydrolysis of ATP is helped by Mg

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23
Q

Why conversion of glucose to glucose 6-phosphate is important

A

It traps glucose inside the cell, thus lowering intracellular glucose to allow further uptake

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24
Q

What kind of reaction is the reaction of hexokinase reversible/irreversible?

A

Irreversible

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25
Q

What is the second step in glycolysis

A

Glucose- 6 -phosphate is converted to fructose 6 -phosphate

Isomerization reaction to make the first carbon free

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26
Q

What enzyme is used in the conversion of glucose 6-phosphate to fructose 6-phosphate

A

Phosphohexose isomerase with the help of Mg

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27
Q

What is the role of the reaction with phosphohexose isomerase

A

Makes the next step easier(C1 of fructose os easier to phosphorylate by PFK)
Allow for symmetrical cleavage by aldose

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28
Q

Is reaction with phosphohexose isomerase reversible/irreversible?

A

Reversible

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29
Q

What is the third step of glycolysis

A

Fructose 6-phosphate is converted to fructose 1,6-biphosphate by addition of PO3 to the first carbon

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30
Q

What is the other name for the third step of glycolysis and why

A

2nd priming phosphorylation, because ATP is used to give phosphate group. This hydrolyses is helped by Mg

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31
Q

What is the enzyme of the conversion of Fructose 6-phosphate to fructose 1,6-biphosphate?

A

PFK-1 or phosphofructokinase-1

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32
Q

What is the purpose of conversion of fructose 6-phosphate to phosphate to fructose 1,6-biphosphate

A

Generation of a symmetrical 6-carbon molecule

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33
Q

The reaction with PFK is reversible/irreversible

A

Irreversible

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34
Q

What is the final reaction of investment stage

A

Fructose 1,6 -biphosphate is lysed to dihydroxyacetone phosphate(DHAP) and glyceraldehyde 3-phosphate (G3P). ^ carbon sugar to 2 3 carbon sugars

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35
Q

What enzyme breaks Fructose 1,6 -biphosphate

A

aldolase

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36
Q

What is the role of breaking Fructose 1,6 -biphosphate

A

Generating high energy phosphate sugars

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37
Q

What is triose phosphate interconversion

A

Conversion between DHAP and G3P by triose phosphate isomerase

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38
Q

Is aldose and triose phospahte isomerase reversible/irrevesible

A

Reversible

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39
Q

Why there is triose phosphate interconversion

A

Because only GAP (glyceraldehyde-3-phosphate) is used in pay-off phase

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40
Q

What is the first reaction of pay off phase

A

GAP is converted to 1,3-biphosphoglycerate with the addition of inorganic phosphate group to aldehyde end

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41
Q

What is the enzyme that converts GAP to 1,3-biphosphoglycerate

A

Glyceraldehyde 3-phospahte dehydrogenase (GAPDH)

42
Q

What is used to perform the first reaction of pay-off phase

A

Inorganic phosphate

Nad+->NADH+H+

43
Q

Is the reaction with GAPDH reversible/irreversible

A

reversible

44
Q

Why GAPDH can be used as measurement control when giving a treatment for example

A

Because it is very important and produced a lot by our cells and its concentration do not vary

45
Q

What is the step of the first ATP production

A

1,3-biphosphoglycerate gives off the phosphate group in the aldehyde end to ADP to produce ATP and 3-phosphoglycerate

46
Q

What is the enzyme that helps the transfer of phosphate group to first ADP of glycolysis

A

Phosphoglycerate kinase with the help of Magnesium

47
Q

Atp in glycolysis is produced by

A

Substrate level phosphorylation

48
Q

Is phosphoglycerate kinase reversible/irreversible

A

Reversible

49
Q

What is the migration of the phosphate

A

the step in pay off phase , when 3-phosphoglycerate is converted to 2-phosphoglycerate

50
Q

What enzyme catalyses the conversion of 3-phosphoglycerate to 2-phosphoglycerate

A

Phosphoglycerate mutase with the help of Mg

51
Q

Explain the mechanism of phosphoglycerate mutase

A

the enzyme has histidine in its AA sequence. When histidine is phosphorylated , then the enzyme becomes active. The mutase gives off its phosphate to the second carbon of glycerate and at the same time takes the phosphate group from the third carbon

52
Q

Is the mutase reversible/irrevesible?

A

Reversible

53
Q

What is step after 3-phosphoglycerate is converted to 2-phosphoglycerate

A

2-phosphoglycerate (2-PG) is converted to phosphoenolpyruvate (PEP) by dehydrating 2-PG. OH from the third carbon and H from the second carbon is taken away and the double bond between carbon 2 and 3 is created

54
Q

What is the enzyme of conversion 2-PG to PEP

A

Enolase

55
Q

What is the role of enolase

A

Generation of a high-energy phosphate compound

56
Q

Is the reaction with enolase reversible/ irreversible

A

Reversible

57
Q

What is the second step when ATP is produced

A

PEP is converted to pyruvate, giving off phosphate group from carbon 2 to ADP

58
Q

What is the enzyme for conversion of PEP to pyruvate

A

Pyruvate kinase with the help of Mg and K

59
Q

what does the last step of glycolysis includes

A

Tautomerization -when molecules with the same molecular formula but different connectivity - constitutional isomers, in other words, can easily interchange

60
Q

The reaction of pyruvate production is reversible/irreversible

A

Irreversible

61
Q

Fate of pyruvate

A

1) Hypoxic or anaerobic conditions (2 ethanol+2 CO2)- fermentation to ethanol in yeast
2) In aerobic conditions pyruvate->acetyl-CoA->TCA->CO2 and H2O
3) Hypoxic or anaerobic conditions to 2 lactate

62
Q

What enzyme converts pyruvate to lactate. Reversible/irreversible?

A

Lactate dehydrogenase- reversible

63
Q

What happens when lactate is produced in muscles

A

Lactate goes to the liver, where it is converted back to pyruvate and glucose through gluconeogenetic pathway

64
Q

What is the name of the process when pyruvate is converted to lactate in tissues and then in the liver lactate is converted back to pyruvate

A

Cori cycle

65
Q

Erythtocytes convert ___ to ___

A

Puruvate to lactate

66
Q

Various carbohydrates can be broken down to ___

A

Various carbohydrates intermediates of glycolytic pathway

67
Q

Regulation of anaerobic glycolysis in hypoxic conditions is performed by

A

Hypoxia Inducible Factor (HIF) which is activated in hypoxic conditions

68
Q

Explain the regulation of HIF

A

There is an enzyme prolyl hydroxylase (PHD-2), this is the protein that senses oxygen tension.
In normoxic conditions, it PHD-2 induces HIF ubiquitination and thus degradation

When muscles work vigorously-> hypoxia, PHD-2 does not function, HIF-1 alpha is not degraded, but stabilized. HIF-betacomes and become a functional dimer with alpha.
Once they dimerize, they enter the nucleus and bind to HRE

69
Q

what isomer of HIF is regulated and ubiquinated

A

Alpha

70
Q

What another TF come with HIF alpha and beta

A

p300/CBP (cAMP response element Binding Protein)

71
Q

CBP is regulated by

A

GPCR signaling

72
Q

HIF target genes

A 
GLUT 1/3
Hexokinase
PFK
Aldolase
GAPDH
Phosphoglycerate Kinase
Phosphoglycerate Mutase
Enolase
Lactate dehydrogenase
73
Q

What tissues mainly depend on glucose

A 
Brain
RBC
testes
renal medulla
embryo
74
Q

How we can get glucose from inorganic sources

A

Lactate->pyruvate->PEP->glucose
GLucogenic AA->TCA->PEP->glucose
FA->glycerol->GAP->Glucose
CO2 fixation->3-phosphoglycerate->glucose

75
Q

Recovery after vigorous exercise involves

A

gluconeogensis

76
Q

where does gluconeogenesis occur ( tissues)

A

mainly liver (80%)
Intestinal epithelium
Renal cortex

77
Q

Which three enzymes can drive glycolysis only forward?

A

Hexokinase
Phosphofructokinase-1
Pyruvate kinase

78
Q

What is the last enzyme of glucoenogenesis

A

Glucose 6-phosphatase. It removes phosphate group from glucose

79
Q

What enzyme does the reverse reaction of phosphofructokinase-1

A

Fructose 1,6-biphosphotase-1

80
Q

Which step requires 2 enzymes in glcucoenogenesis

A

from pyruvate to phosphoenolpyruvate

It requires two enzymes: pyruvate carboxylase to transform pyruvate to oxaloacetate and PEP carboxykinase from oxaloacetate to phosphoenolpyruvate

81
Q

What is needed to convert pyruvate to glucose

A

4 enzymes from glucoenogenesis + 7 reversible enzymes of glycolysis + 6 ATP+ 2 NADHs

82
Q

Pyruvate To be converted to oxaloacetate needs to

A

Come inside mitochondria

Pyruvate combines with bicarbonate with the help of pyruvate carboxylase->oxaloacetate

83
Q

Where oxaloacetate can be converted to phosphoenolpyruvate

A

In cytosol or in mitochondria

84
Q

What is used to convert oxaloacetate to phosphoenolpyruvate

A

GTP, but not ATP

PEP carboxykinase

85
Q

What is the alternative fate of G6P

A

Pentose phosphate pathway ( hexose monophosphate pathway)

86
Q

hexose monophosphate pathway is more common in ( what type of cells)

A

Highly proliferative cells ( cancer cells, small intestinal cells)

  • Cells with FA biosynthesis
  • Cells that synthesis sterols ( cholesterol and steroids)
  • Cells with oxidative stress
87
Q

Why leucine and lysine do not contribute to intermediates of glucose synthesis

A

They are converted to acetyl-CoA, which is immediately converted to a ketone.

88
Q

Two phases of pentose phosphate pathway

A

Non-oxidative phase and oxidative phase

89
Q

What enzyme start pentose phosphate pathway and how

A

G6P is converted to 6-phosphogluconate with the help of G6P dehydrogenase that uses NADP+ to NADPH

90
Q

What does phospho-pentose isomerase do

A

Converts Ribulose 5-phosphate to ribose 5-phosphate

91
Q

Why phospho-pentose isomerase is important

A

Because ribose 5-phosphate is the precursor for multiple things (Nucelotides,coenzymes, DNA, RNA)

92
Q

Another reason why phospho pentose isomerase and G6P dehydrogenase are important

A

They produce important reducing power NADPH

93
Q

What enzymes and where are dependent on NADPH

A

FA synthesis in liver, kidney and lactating mammary gland
Cholesterol/steroid synthesis in liver,adrenal and gonads
Glutathionine reductase uses NADPH in tissues exposed to high O2 (cornea and RBC) and thus oxidative damage

94
Q

What is the pathway of oxidative damage

A

O2->( mitochonsrial respirationmsulfa drugs,etc.)->Superoxide radical->hydrogen peroxide->Hydroxyl free radical

Hydroxyl free radical makes damage to lipids, proteins and DNA

95
Q

What is the prevention of oxidative stress

A

Hydrogen peroxide is converted to water with the enzyme glutathione peroxidase. This enzymes requires 2 hydrogens from glutathion (GSH)

96
Q

How GSH is regenerated

A

NADPH from pentose phosphate pathway donates hydrogens to GSSG (oxidized form) with the help of glutathione reductase

97
Q

Describe non-oxidative phase of pentose phosphate pathway

A

Ribose 5-phosphate to Glcuose 6 phosphate in a big picture

ribose 5-phosphate is converted to xylulose 5-phosphate. Transketolase and transaldolases just convert one molecule to another without the addition of carbons or deletion, ultimetely leading to fructose 6-phosphate or Glyceraldehyde 3-phosphate

98
Q

What reactions are reversible in non-oxidative phase

A

Practically all of them, except for fructose 1,6 biphosphatese

99
Q

Where transketolases and transaldolases are over expressed

A

In cancer cells

100
Q

How pentose phosphate pathway is regulated

A

NADPH which is generated can inhibit the reaction that generate NADPH
If the cell needs ATP, G6P will go through glycolysis
If the cell is exposed to oxidative stress or if cell needs a lot of nucleotide synthesize, it will undergo pentose phosphate pathway

Biochemistry 2 (17 decks)

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