Cellular Metabolism Flashcards

1
Q

What are 7 key energy metabolism pathways?

A
Gluconeogenesis 
Krebs cycle 
ETC 
Beta fat oxidation 
Photosynthesis 
Glycolysis 
Fatty acid synthesis 
Photosynthesis ( plants)
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2
Q

What is an exergonic pathway?
What controls them?
Give and example

A

Gluconeogenesis + glycolysis both occur in the cytoplasm

It is an exergonic pathway to avoid a futile cycle ( creating the breaking down via substrate recyling)

Exergonic pathways have a net release of energy/products. Proceed in the forward direction

Specific control points determine which reaction occurs ( glycolysis or gluconeogenesis)

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3
Q

What can affect the rate of a chemical reaction?

A
Conc of reactants + products
Temperature, pH
Catalytic activity 
Conc. of enzyme 
Rate of translation vs rate of degradation
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4
Q

What are 3 ways that can alter enzyme activity?

A
  • Altering number of available molecules in the cell
  • Altering their effective activity
  • Changing activity of the existing molecules
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5
Q

How does substrate conc. alter the ROR?

A

Lower substrate concentrations mean the ROR increases rapidly ( rate is more sensitive at lower conc)

Higher substrate concentrations cause rate to increase more slowly as more enzymes are fully saturated with substrate

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6
Q

What is Km constant?

At what substrate conc. is Km usually achieved?

A

The concentration of substrate/metabolite at which the enzyme is working at 50% of its maximal capacity

Km is normally achieved at the physiological concentration of the substrate

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7
Q

What are regulatory proteins?

A

Bind to enzymes and alter their activity

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8
Q

What happens when there is a fall in ATP concentration?

A

Rapid reduction in the activity of ATP utilising enzymes

Increased AMP formation

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9
Q

What is AMP and why is it more potent?

A

Allosteric regulator that is much more potent

This is because its concentration is very low before ATP degradation and hence reduction occurs

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10
Q

What is AMPK?

What can lead to its activation?

A

AMP activated protein kinase, it is a key regulator fat and carbohydrate metabolism

It phosphorylates target proteins

Activated by: 
Low ATP/High AMP 
Sympathetic nervous system 
Exercise 
Leptin + adiponectin
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11
Q

What is the function of AMPK?

A

It phosphorylates target proteins away from energy consuming processes
It causes extra hepatic tissues to use fatty acids as a fuel source
Triggers gluconeogenesis in the liver to provide glucose to the brain
Stimulates feeding behaviour in the hypothalamus so we eat more

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12
Q

What is the elasticity coefficient?

A

Responsiveness of an enzyme to substrate

Substrate concentrations below the Km an increase in the substrate concentration will increase the rate

At substrate concentrations in XS of the Km there is no increase in enzyme velocity( rate)

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13
Q

Describe the process of glycolysis

A

Glucose broken down
Pyruvate -> acetyl Co enzyme A in mitochondria
Citric acid cycle produces NADH + FADH
Oxidative phosphorylation: ETC produces ATP as an energy source for the cell

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14
Q

What are izozymes?

A

alternative forms of the same enzyme that exist in different proportions in different tissues

Can have different kinetic properties

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15
Q

How many isozymes of hexokinase are there?

Examples

A

4
HK1 is expressed in all tissues at variable levels

HK4 is only expressed in the liver and has a high Km so will respond to high concentrations of glucose substrate. This also means it can clear the blood of glucose at high [glucose]

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16
Q

Give an example of how kinetic properties differ between HK1 + HK4

A

HK1 only responds at a lower glucose concentration

HK4 can respond effectively at higher glucose concentrations as it has a high Km

17
Q

How is hexokinase 4 activity controlled?

A

When fructose-6 phosphate concentration is high

Regulatory proteins bind to HK4 drawing it into the nucleus to prevent it phosphorylating glucose

When glucose concentration is high it can be released from the regulatory protein to phosphorylate glucose

18
Q

What is the function of phosphofructose kinase 1?

A

Catlayses the conversion of fructose 6-phosphate and ATP to fructose 1,6-bisphosphate and ADP

A commitment step in glycolysis

19
Q

How is the activitiy of phosphofructokinase 1 regulated?

A

ATP can kick start glycolysis

Glucose should not be used to produce ATP in glycolysis if large amounts of ATP are already present ( waste of cellular resources)

20
Q

How does ATP affect the activity of phosphofructokinase 1 ?
Effect of low [ATP]
Effect of high [ATP]

A

Low ATP -> Low Km
- The enzyme will have a high rate a low concentration of fructose-6 phosphate

High ATP -> High Km

21
Q

When will glycolysis occur?

A

High AMP

Low ATP

22
Q

When will gluconeogenesis occur?

A

Low AMP

23
Q

What is the role of Fructose-2,6 bisphosphate?

A

Regulator of glycolysis and gluconeogenesis

It activates phosphofructokinase and hence glycolysis ( allows for conversion of fructose 6-phosphate and ATP to fructose 1,6-bisphosphate and ADP)

It inhibits fructose 1,6-biphosphatase and hence gluconeogenesis