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YEAR 2 HUMAN BIOCHEMISTRY > Changes to metabolism > Flashcards

Changes to metabolism Flashcards

1
Q

What is the difference between essential and non essential amino acids?

A

Essential= Cannot be produced by the body, have to be obtained externally. eg. through the diet

Non essential= Can be produced by the body

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2
Q

How many amino acids are there in total?

A

20 amino acids.

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3
Q

Alanine–>pyruvate

How does alanine lose its amino acid group? What does this form and what is it catalysed by?

A
  • Alanine loses its amino group by transamination

-Forms pyruvate, catalysed by alanine aminotransferase

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4
Q

Asparagine —> Oxaloacetate

Asparagine is hydrolysed by what? and what does this liberate?

A
  • Asparagine is hydrolysed by asparaginase
  • Liberating ammonia and aspartate
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5
Q

Asparagine —> Oxaloacetate

Aspartate loses its amino group by transamination via what enzyme? And what does this form?

A

-Aspartate aminotransferase

-Forms oxaloacetate

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6
Q

Glutamine —> alpha-Ketoglutarate

What two things is glutamine converted to? And by what enzyme?

A
  1. Glutamate
  2. Ammonia

-By the enzyme glutaminase

Glutamate is converted to -ketoglutarate by oxidative deamination by glutamate dehydrogenase (1).

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7
Q

Glutamine —> alpha-Ketoglutarate

What is glutamate converted to? and by what?

A
  • Glutamate is converted to alpha-ketoglutarate
  • By oxidative deamination by glutamate dehydrogenase
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8
Q

Tyrosine—>Fumarate is what type of reaction?

A

A multi-step reaction

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9
Q

Tyrosine—>Fumarate:

What are the 4 stages of this reaction?

A
  1. Transamination
  2. Dioxygenation
  3. Isomerisation
  4. Hydrolysis
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10
Q

Tyrosine—>Fumarate:

Transamination:
What 2 reactions occur during this stage?

A
  1. Tyrosine —> Hydroxy-phenylpyruvate
  2. ⍺-ketoglutarate—>Glutamate
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11
Q

Tyrosine—>Fumarate:

Dioxygenation:
What 3 reactions occur during this stage?

A
  1. Hydroxy-phenylpyruvate—> Homogentisate
  2. O2 + Ascorbate (Vitamin C)—> CO2 + H2O
  3. Homogentisate —> 4-Maleylacoacetate
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12
Q

Tyrosine—>Fumarate:

Isomerisation:
What reaction occurs during this step?

A

4-Maleylacoacetate—> 4-Furmarlacoacetate

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13
Q

Tyrosine—>Fumarate:

Hydrolysis:
What reaction occurs during this step?

A

4-Furmarlacoacetate—> Fumarate and Acetoacetate

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13
Q

What are 3 main causes of starvation?

A
  1. Inability to obtain food
  2. Desire to lose weight
  3. Clinical Situations: eg. Trauma (shock), Burns, Injury to face, Tumour
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14
Q

What happens at a metabolic level during starvation:

What are the 2 main things that occur at a metabolic level during starvation?

A
  1. Blood levels of amino acids, glucose, and triacylglycerols fall
  2. Blood insulin levels are very low, glucagon levels are very high
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15
Q

What happens at a metabolic level during starvation:

  1. Blood levels of amino acids, glucose, and triacylglycerols fall
  2. Blood insulin levels are very low, glucagon levels are very high

Both these factors trigger a period of what? and this is characterised by the degradation of what 3 things?

A
  • Trigger a period of catabolism
  • Characterised by the degradation of:
  1. Glycogen —> Glucose
  2. Triacylglycerol —> Fatty Acids and Glycerol
  3. Protein —> Amino Acids
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16
Q

What happens at a metabolic level during starvation:

The degradation of the previous 3 things results in what?

A

Results in an interchange of substrates between:

Liver, Adipose tissue, Skeletal Muscle, Brain

17
Q

What determines the fate of these substrates:

The fate of these substrates is determined by 2 crucial factors:​ What are they?

A
  1. The essential need to conserve glucose for cells &tissues that really need it. eg. red blood cells and brain.​
  2. The need to mobilise fatty acids from adipose tissue andketone bodies from liver. To supply energy to all othertissues, and for these other tissues to adapt to these non-glucose substrates
18
Q

Enzymatic changes in starvation:

In all situations the flow of intermediates through biochemical pathways is controlled by 4 mechanisms:
What are they?

A
  1. Availability of substrates
  2. Allosteric activation/inhibition of enzymes
  3. Covalent modification of enzymes
  4. Reciprocal Induction or repression of enzyme synthesis
19
Q

The Liver in Starvation: Carbohydrate Metabolism

Glycogen is broken down then gluconeogenesis occurs, what objectives does this meet?

A
  • Maintain blood glucose levels
  • Sustain energy provision for the brain and other glucose requiring tissues (e.g. red blood cells).
20
Q

The Liver in Starvation: Carbohydrate Metabolism
Increased glycogen degradation

What is the major source of blood sugar after a meal?

A

Glucose from food

20
Q

The Liver in Starvation: Carbohydrate Metabolism
Increased glycogen degradation

A few hours after a meal, What starts to decline?

A

Blood glucose levels start to decline

21
Q

The Liver in Starvation: Carbohydrate Metabolism
Increased glycogen degradation

Insulin levels drop and glucagon levels increase: what does this stimulate?

Liver glycogen stores will last for 10-18 hours of fasting.

A

Stimulates glycogen breakdown in liver (by cAMP cascade)

22
Q

The Liver in Starvation: Carbohydrate Metabolism
Increased glycogen degradation

How long will liver glycogen stores last whilst fasting?

A

10-18 hours

23
Q

The Liver in Starvation: Carbohydrate Metabolism
Increased gluconeogenesis

What does the liver have the unique ability to do that is vital during starvation?

A
  • Unique ability of liver to synthesise glucose
  • Becomes increasingly active as glycogen stores are depleted
24
Q

The Liver in Starvation: Carbohydrate Metabolism
Increased gluconeogenesis

Where are carbon skeletons derived from?

A
  1. Glycerol
  2. Lactate
  3. Amino acids
25
Q

The Liver in Starvation: Lipid Metabolism

this results in an increased oxidation of what?

A

Increased fatty acid oxidation

26
Q

The Liver in Starvation: Lipid Metabolism

What is a major source of energy for liver during starvation?

A

Oxidation of fatty acids derived from adipose tissue (this spares glucose)

27
Q

The Liver in Starvation: Lipid Metabolism

There is an increased synthesis of what during lipid metabolism?

A

Increased synthesis of ketone bodies

28
Q

The Liver in Starvation: Lipid Metabolism

Ability of the liver to synthesise and release ketone bodies is describes as what?

A

Unique

29
Q

The Liver in Starvation: Lipid Metabolism

When is the synthesis of ketone bodies favoured?

A
  • When the concentration of acetyl CoA that is produced (via fatty acid oxidation), exceeds the maximal rate of the citrate cycle
30
Q

The Liver in Starvation: Lipid Metabolism

Why are ketone bodies vital in starvation?

A
  • Because they can be used by other tissues and cells, provided they have mitochondria
31
Q

The Liver in Starvation: Lipid Metabolism

Once the level of ketone bodies in the blood is high enough, how much of the brain can use them as fuel?

A
  • Up to ⅔ of the brain can use them as fuel
32
Q

The Liver in Starvation: Lipid Metabolism

Utilisation of ketone bodies reduces the need for what?

A
  • Reduces the need for amino acid precursors used in gluconeogenesis
  • This decreases protein breakdown
33
Q

Adipose Tissue in Starvation: Carbohydrate Metabolism

in starvation, insulin levels do what? and how does this effect the use of glucose for fatty acid synthesis?

A
  • In starvation, insulin levels decrease
  • So glucose is not used for fatty acid synthesis (no signal).
34
Q

Adipose Tissue in Starvation: Lipid Metabolism

Increased degradation of triglycerides results in what?

A
  • Decrease in insulin
  • Increase in glucagon (via cAMP cascade)
  • This causes phosphorylation and activation of hormone-sensitive lipase
35
Q

Adipose Tissue in Starvation: Lipid Metabolism

There is an increase in the release of fatty acids during this process, how does this occur?

A
  • Fatty acids obtained from the hydrolysis of stored adipose triglycerides are released into the bloodstream
36
Q

Adipose Tissue in Starvation: Lipid Metabolism

There is an increase in the release of fatty acids:
What do they bind to? and what is there main function after binding?

A
  • Bound to albumin
  • They are transported to lots of tissues for use as a fuel
37
Q

Adipose Tissue in Starvation: Lipid Metabolism

There is an increase in the release of fatty acids: Fill in the blanks:

The glycerol that is produced as the result of ——– ———- ——– is used for ———- by the ——-.

A

The glycerol that is produced as the result of COMPLETE TRIGLYCERIDE HYDROLYSIS is used for GLUCONEOGENISIS by the LIVER.

38
Q
A

YEAR 2 HUMAN BIOCHEMISTRY (12 decks)

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