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2nd yr- IBMS- Respiration and metabolism > Regulation of Glycolysis and TCA > Flashcards

Regulation of Glycolysis and TCA Flashcards

1
Q

What type of reaction is used to break down glucose?

A

A series of redox reaction

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2
Q

What are redox reactions?

A

Oxidation reduction reactions

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3
Q

What does it mean to be oxidised?

A

It means the molecule has lost electrons

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4
Q

What does it mean to be reduced?

A

It means the molecule has gained electrons

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5
Q

How does a redo reaction help make ATP

A

Redox reactions transfer energy (stored in the glucose bonds) to electron carriers

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6
Q

What is an electron carrier?

A

A molecule that transports electrons during cellular respiration

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7
Q

Give examples of electron carriers?

A

NAD

FAD

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8
Q

How is energy stored using NAD?

A

Energy is stored by adding 2 electrons to NAD+:

NAD+ + 2H-> NADH + H+

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9
Q

How is the stored energy in NAD released?

A

Energy stored is released when FADH2 and NADH are oxidised to NAD+ and FAD
FAD + 2H ->FADH2

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10
Q

What is the net profit of ATP following glycolysis?

A

2 ATP

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11
Q

What is the net profit of NADH following glycolysis?

A

2 NADH

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12
Q

What is the net profit of ATP following TCA?

A

2 ATP

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13
Q

What is the net profit of NADH following TCA?

A

6 NADH

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14
Q

What is the net profit of FADH following TCA?

A

2 FADH

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15
Q

What happens under anaerobic conditions to yeast?

A

Under anaerobic conditions
yeast can not go through
the TCA and ETC
So fermentation occurs

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16
Q

The regeneration of which molecule is important to maintain glycolysis?

A

The regeneration of NAD+

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17
Q

When does fermentation occur in skeletal muscles?

A

When the muscles are deprived of oxygen

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18
Q

Name the three stages of AEROBIC respiration

A
  1. Glycolysis
  2. TCA
  3. Electron transport chain
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19
Q

What happens to the TCA when theres a shortage of oxygen?

A

The TCA does not use oxygen but it does stop in the absence of oxygen because we run out of NAD+ and FAD

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20
Q

Which stage is common in both aerobic and anaerobic respiration?

A

Glycolysis

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21
Q

What is produced as a by product in anaerobic respiration in the skeletal cells ?

A

Lactic acid

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22
Q

Briefly go through glycolysis

A

Glucose is converted into pyruvate which is converted into acetyl coA
The net ATP yield form this reaction is 2

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23
Q

What is the anaerobic pathway?

A

It is the pathway where simple sugars (glucose) are converted into ethanol and carbon dioxide without the presence of oxygen

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24
Q

Where does fermentation occur in yeast cells?

A

Occurs in the cytosol of yeast cells

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25
Q

Following glycolysis what steps occur to convert pyruvate into ethanol?

A
  1. Pyruvate undergoes decarboxylation (CO2 released) aided by pyruvate decarboxylase
  2. This forms acetaldehyde
  3. acetaldehyde reacts wit alcohol dehydrogenase to form ethanol
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26
Q

Name the enzyme that aids pyruvate decarboxylation

A

pyruvate decarboxylase

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27
Q

During glycolysis in yeast which reactions are absent

A

Theres no net oxidation reduction reaction

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28
Q

What is the difference between ATP production in anaerobic and aerobic glycolysis?

A

Glycolysis is maintained in anaerobic glycolysis but only a fraction of energy is produced

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29
Q

What happens to the ethanol and carbon dioxide produced in fermentation in yeast?

A

They are waste product and can be toxic to the yeast cell

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30
Q

What can happen when you distill ethanol from yeast and is this good or bad?

A

You can get methanol which is toxic

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31
Q

How do we cure methanol poisoning

A

Alcohol

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32
Q

What are the three stages of aerobic respiration

A
  1. Glycolysis (yields 2 ATPs)
  2. TCA cycle (Yields 2 ATPs)
  3. Electron transport chain (Yields 28 ATPs)
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33
Q

Why does a shortage of oxygen affect the TCA cycle when oxygen isn’t used up in TCA?

A

The TCA doesn’t use oxygen but it runs out of NAD+ and FAD when oxygen is lacking

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34
Q

Which stages of aerobic reparation are affected when theres a lack of oxygen?

A
  1. TCA as theres no NAD and FAD

2. Electron transport chain as oxygen is the final electron acceptor

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35
Q

What role does oxygen have in the electron transport chain?

A

It is the final electron acceptor

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36
Q

Which process is common in both anaerobic and aerobic respiration?

A

Glycolysis

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37
Q

Where does glycolysis occur in the cell?

A

In the cytoplasm

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38
Q

What are the final products of glycolysis

A

2 ATPs
2 NADHs
2 pyruvate molecules

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39
Q

What happens when the body doesn’t have enough oxygen but needs to keep moving (eg when exercising)

A

The cells begin to do lactic acid fermentation

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40
Q

What is lactic acid fermentation

A

The resection of Pyruvate by NADH to produce lactate (aided by lactate dehydrogenase)

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41
Q

Name the enzyme involved in the reduction of pyruvate into lactate

A

Lactate dehydrogenase

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42
Q

What is produced when pyruvate is reduced into lactate and what does this by product do?

A

NAD+ form which re enters glycolysis

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43
Q

Which 2 monosaccharides is lactose made up of?

A
  1. Glucose

2. Galactose

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44
Q

What happens if you are lactose intolerant?

A

You don’t produce enough lactose enzyme to break down all the lactose so the lactose remain unbroken end persist with in your gut and are fermented by bacteria

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45
Q

Give some symptoms of lactose intolerance

A
  1. Farting
  2. Diarrhoea
  3. Bloating
  4. Stomach cramps and pains
  5. Stomach rumbling
  6. Feeling sick
46
Q

What is Galactosemia?

A

It is an inherited autosomal recessive disorder and can be screened for at birth

47
Q

What can Galactosemia lead to?

A

Can cause:

  1. enlargement of the liver
  2. Central nervous system failure
48
Q

What is Galactosemia caused by?

A

Due to a deficiency of galactose 1-phosphate uridyl transferase

49
Q

What does having a deficiency in galactose 1-phosphate uridyl transferase mean?

A

Means you can’t break down galactose

50
Q

Why is Galactosemia screened for at birth?

A

As babies main source of food is milk so if they have this disease they won’t be able to digest milk

51
Q

Describe the eyes of a patient who is suffering from Galactosemia

A

May develop cataracts in their eyes

52
Q

Why might patients with Galactosemia develop cataracts in their eyes?

A

If lactose cannot be brown down instead Aldose reductase converts the galactose into an alcohol which leads to cataracts

53
Q

Where do bacteria in deep dental plaque get their energy from and why?

A

Get their energy through glycolysis as Dental plaque deep layers are highly anaerobic

54
Q

How does fluoride help fight dental plaque?

A

As floride can inhibit the enzyme enolase (needed in glycolysis) thus stopping glycolysis so bacteria can’t get any energy

55
Q

Briefly summarise glycolysis

A
  1. Bacteria reacts with hexokinase forming glucose 6-phosphate (uses ATP)
  2. G6P reacts reversibly with phosphglucise isomerase to Forman fructose 6-phosphate
  3. fructose 6-phosphate reacts with PFK to form fructose 1-6 biphosphate
  4. fructose 1-6 biphosphate reacts with aldose to form GAP and DHAP
  5. GAP then produces 2 NADHs and 1,3- bisphophate
  6. 1,3- bisphophate reacts with phophuglycerate kinase adncascades down to form 2-phosphoglycerate
  7. Phosphoglycerate reacts with enclave to form 2 ATPs and 2 pyruvate molecules
56
Q

Which molecule do we need to be able to enter the TCA cycle?

A

Acetyle CoA

57
Q

How is pyruvate inverted into Acetyl CoA?

A

Via the enzyme pyruvate dehydrogenase

58
Q

How does acetyl CoA feed into the citric acid cycle?

A

Via a reaction with oxyl acetate

59
Q

What percentage of our genes are used to regulate metabolism

A

12% (2050/20,000)

60
Q

What are the different ways we can regulate metabolism?

A
  1. Genetic regulation

2. Regulating enzyme concentraion

61
Q

How does genetics regulate metabolism?

A

Genetics determines the concentration of enzymes in a cell

62
Q

Name the 4 ways we can regulate enzymes in a cell

A
  1. Association with regulatory proteins
  2. Sequestration (compartmentalisation)
  3. Allosteric regulation
  4. Covalent modification
63
Q

What is allosteric regulation enzymes?

A

It is when an inhibitor binds to our enzymes and actively changes the shape of the enzyme rendering it useless

64
Q

How does covalent regulation help regulate active enzyme concentration in a cell?

A

Covalent modification changes the covalent structure of an enzyme changing its structure

65
Q

How does Association with regulatory proteins help regulate active enzyme concentration in a cell?

A

This limits the amount of enzymes that can associate with in our reactions

66
Q

How does Sequestration (compartmentalisation) help regulate active enzyme concentration in a cell?

A

This alters the accessibility of the enzyme with the substrate

67
Q

How is Sequestration (compartmentalisation) achieved?

A

Achieved through membranes within our cells as they only let what is needed for the ruction into the cell

68
Q

Name the 3 enzymes that can be regulated in glycolysis

A
  1. Hexokinase
  2. Phosphofructokinase
  3. Pyruvate kinase
69
Q

Name the 3 enzymes that can be regulated in the TCA cycle

A
  1. Citrate synthase
  2. Isocitrate dehydrogenase
  3. Alpha ketoglutarate dehydrogenase
70
Q

What does hexokinase do?

A

Aids the reaction of glucose into glucose 6-phosphate

71
Q

What does Phosphofructokinase do?

A

Aids the reaction of fructose 6-phosphate into fructose 1,6-biphosphate

72
Q

What does Pyruvate kinase do?

A

Aids the conversion of phosphoenolpyruvate into pyruvate

73
Q

How is heoxkinase regulated?

A

by allosteric feedback inhibition

74
Q

When do glucose 6-phophate levels increase?

A

When glucose is inhibited at sites further along the pathway as GGP prevents hexokinase form working

75
Q

How do glucose 6-phophate inhibit glycolysis?

A

By preventing hexokinase from working

76
Q

How does glucose 6-phophate inhibit hexokinase from working

A

As it results in allosteric feedback inhibition of hexokinase which ultimately changes the structure of hexokinase

77
Q

The conversion of fructose 6-phosphate into fructose 1,6-biphosphate is metabolically what?

A

Metabolically irreversible

78
Q

What inhibits Phosphofructokinase (PFK1)

A

ATP

79
Q

Why does an increased concentration reduce the effectiveness of Phosphofructokinase ?

A

As High concentrations of ATP lower its affinity for fructose-6-phosphate so conversion into fructose 1,6-biphosphate isn’t as effective

80
Q

What is Phosphofructokinase

A

An enzyme that is made up of of 4 identical proteins

81
Q

Name the substrate for Phosphofructokinase

A

ATP

82
Q

What increases Phosphofructokinase activity>

A

ADP and AMP

83
Q

What is Phosphofructokinase sensitive to other than concentration of ATP, ADP and AMP?

A

pH

84
Q

How does pH effect Phosphofructokinase activity?

A

Acidic conditions reduces the activity of Phosphofructokinase and also prevents excessive formation of lactic acid

85
Q

How is PFK regulated?

A

in 2 ways:

  1. By ATP concentration
  2. Fructose 2,6-bisphosphate Allosterically regulares fructose 6-phosphate
86
Q

How is pyruvate kinase regulated?

A

By allosteric inhibition and covalent modification

87
Q

Give the chemically signs that there’s lots of energy in a cell

A

There will be high levels of ATP and acetyl CoA

88
Q

Name the molecule that activates pyruvate kinase

A

Fructose 1,6 bisphosphate

89
Q

How does ATP affect pyruvate kinase?

A

ATP allosterically inhibits pyruvate kinase

90
Q

How many forms of pyruvate kinase are there and what are they called?

A

2 forms:
1, L form
2. M form

91
Q

What is the L form of pyruvate kinase susceptible to?

A

Susceptible to covalent modification via phosphorylation

92
Q

How does blood glucose affect pyruvate kinase?

A

Low blood glucose means theres more ADP being. made so that ATP can be conserved
In this process phosphate ion is released and forms phosphorylated pyruvate kinase
When the blood glucose level rises the phosphate from phosphorylates pyruvate kinase is removed activating the pyruvate kinase enzyme

93
Q

Name the regulatory point of the TCA cycle

A
  1. The conversion of pyruvate to acetyl CoA
  2. The conversion of isocitrate into alpha ketogulturate
  3. The conversion of alpha ketogulturate into succinylcholine coA
94
Q

Name the enzyme that can be regulated in the TCA cycle?

A
  1. Pyruvate dehydrogenase
95
Q

How is pyruvate dehydrogenase regulated?

A

In 2 ways:

  1. Via allosteric regulation
  2. Via covalent regulation
96
Q

What does Pyruvate dehydrogenase do?

A

Aids in the conversion of pyruvate into acetyl CoA

97
Q

Where do the allosteric regulators of Pyruvate dehydrogenase occur?

A
  1. E2 sites

2. E3 sites

98
Q

What is the E2 site limited by?

A

Acetyle CoA

99
Q

What is the E3 site regulated by

A

NADH

100
Q

How is the pyruvate dehydrogenase covalently regulated?

A

When energy is high ATP is dephosphorylated into ADP
This conversion releases a phosphide ion which reacts with pyruvate dehydrogenase inactivating it
Then when energy Is high again the inactive pyruvate dehydrogenase is dephosphorylated to activate the enzyme again

101
Q

How does acetyl CoA affect pyruvate dehydrogenase?

A

Increase in acetyl coA negatively affects pyruvate dehydrogenase
This prevents the kerbs cycle from occurring if there too much acetyl coA as the body isn’t in need of a lot energy

102
Q

State the reaction that occurs in the TCA cycle

A

Acetyl-CoA + 3NAD+ +FAD+ GDP+ Pi
=>
CO2 +3NADH+ FADH2+ GTP

103
Q

How is the TCA regulated?

A

Allosterically

104
Q

Can the TCA cycle stop?

A

NO it can be regulated and slowed down depending on substrate availability

105
Q

What drives tea TCA cycle when the body is subject to starving conditions

A

Under starving conditions amino acids can be broken down and fed into the TCA cycle as alpha ketogluterate which will speed of the cycle

106
Q

Name the 3 enzymes that catalyse irreversible reactions in the TCA cycle

A
  1. Citrate synthase
  2. Isocitrate degydrigenase
  3. Alpha degydrigenase complex
107
Q

Name the molecule that can allosterically inhibit:

  1. Citrate synthase
  2. Isocitrate degydrigenase
  3. Alpha degydrigenase complex
A

NADH and ATP

108
Q

Which molecules can allosterically inhibit citrate synthase?

A
  1. NADH
  2. ATP
  3. Citrate
  4. Succinyl CoA
109
Q

What molecule can activate isocitrate dehydrogenase?

A

ADP

110
Q

Name the 3 enzymes in glycolysis the can be regulated

A

Hexokinase
Phosphofructokinase
Pyruvate kinase

111
Q

What is Pyruvate dehydrogenase regulated by?

A

Covalent modification

2nd yr- IBMS- Respiration and metabolism (3 decks)

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