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MEH > Protein And Amino Acid Metabolism > Flashcards

Protein And Amino Acid Metabolism Flashcards

1
Q

What is Creatinine?

A

A breakdown product/metabolite of Creatine and Creatine phosphate in muscle

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2
Q

What is the function of Creatinine?

A

Has no metabolic function so is excreted by the kidneys in the urine

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3
Q

Clinical relevance of Creatinine levels in the urine

A

Provides an estimate of muscle mass

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4
Q

Clinical relevance of creatinine plasma levels

A

Indicate renal function
High plasma levels and low urine levels = poor blood filtration in kidneys

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5
Q

What is Nitrogen (N) Balance?

A

When rate of nitrogen intake matches the rate of nitrogen lost

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6
Q

What is meant by a positive N Balance?

A

More nitrogen is taken in than is lost
Increase in total body protein

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7
Q

When is it normal to have a positive N Balance?

A

Growth
Pregnancy
Adult recovering from malnutrition

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8
Q

What is meant by a Negative N Balance?

A

The loss of N is greater than the intake of N
Net loss of total body protein

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9
Q

When is a Negative N balance normal?

A

It is NEVER Normal
It indicates trauma, infection or malnutrition

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10
Q

What is protein turnover?

A

The constant breakdown and re-synthesis of proteins in the body

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11
Q

What is a glucogenic amino acid?

A

An amino acid who’s carbon chain can undergo GLUCONEOGENESIS to produce glucose to release energy

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12
Q

What is a ketogenic amino acid?

A

An amino acid who’s carbon Skelton goes into produce Ketone bodies (ketogenesis) and fatty acids to release energy

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13
Q

Give an example of a Glucogenic amino acid

A

Alanine

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14
Q

Give an example of a Ketogenic amino acid

A

Leucine

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15
Q

Give an example of an amino acid which is both glucogenic and ketogenic

A

Phenylalanine

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16
Q

When are protein reserves used for energy?

A

During starvation/extreme stress

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17
Q

What type of molecules regulate mobilisation of protein reserves for energy?

A

Hormones

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18
Q

What hormones stimulate protein synthesis and inhibit proteolysis?

A

Insulin and GH

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19
Q

Which hormone inhibits protein synthesis and simulated proteolysis?

A

Glucocorticoids (Cortisol)

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20
Q

How does excess Cortisol lead to the purple striae in the skin in Cushing’s Syndrome?

A

Cortisol stimulates proteolysis
Proteins in skin broken down
Skin weakens forming striae

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21
Q

How are proteins metabolised?

A

Digested to free amino acids
Either Used to produce cellular proteins or enter the liver
Amino group removed and excreted as urea in urine
Carbon Skeleton used to produce energy, the way this occurs depends on whether the amino acid was glucogenic or ketogenic

22
Q

What are the 9 essential amino acids?

A

Isoleucine
Lysine
Threonine
Histidine
Leucine
Methionine
Phenylalanine
Tryptophan
Valine

23
Q

What are the 3 Conditionally essential amino acids?

A

Arginine
Tyrosine
Cysteine

24
Q

Why can tyrosine be a conditionally essential amino acid?

A

Tyrosine can be made from Phenylalanine
If diet is low in phenylalanine Tyrosine becomes Conditionally essential

25
Q

Why can cysteine be a conditionally essential amino acid?

A

Cysteine can be synthesised from Methionine
If diet is low in Methionine cysteine is conditionally essential

26
Q

Why can arginine be a conditionally essential amino acid ?

A

Small amounts of arginine can be made
Becomes essential in periods of active growth like pregnancy

27
Q

What are the 2 ways by which the amino group of amino acids can be removed to allow the carbon skeleton to be utilised in oxidative metabolism?

A

Transamination
Deamination

28
Q

What happens to the nitrogen removed from an amino acid?

A

Incorporated into other compounds
Excreted as urea

29
Q

What is transamination?

A

Transfer of the amino groups to another molecule

30
Q

What is the name of the enzyme which allows for transamination to occur?

A

Aminotransferase

31
Q

What are the 2 key aminotransferases?

A

Alanine aminotransferase (ALT)
Aspartate aminotransferase (AST)

32
Q

What is the clinical significance of the levels of ALT and AST?

A

Part of the liver function test

Levels high in conditions that cause extensive cell necrosis

33
Q

What is Deamination?

A

When the amino group is removed and forms free ammonia
(Normally happens in liver and kidney)

34
Q

What is the fate of free ammonia?

A

Converted to urea which is non toxic and inert
Ammonia is very toxic

35
Q

What is the purpose of the urea cycle?

A

Safely convert ammonia into urea for excretion in urine

36
Q

Where does the urea cycle take place?

A

Liver

37
Q

How many enzymes are involved in the urea cycle?

A

5

38
Q

How does a high protein diet affect the levels of the 5 enzymes involved in the urea cycle?

A

Increases the enzyme levels since more amino acids are being taken in so more ammonia is going to be produced

39
Q

How does a low protein diet affect the levels of the 5 enzymes involved in the urea cycle?

A

Low protein = less amino acids so less ammonia is going to be produced
Therefore the enzyme levels are reduced

40
Q

How is ammonia toxic?

A

Readily diffusible
Causes alkaline blood
Alters blood brain barrier
Interfere with Krebs cycle

41
Q

What is Phenylketonuria?

A

Autosomal recessive Genetic defect in amino acid metabolism, causes accumulation of phenylalanine in tissues, blood and urine

On chromosome 12

42
Q

What enzyme is deficient in Phenylketonuria (PKU)?

A

Phenylalanine hydroxylase

43
Q

What substances build up as a result of Phenylketonuria?

A

Phenylalanine
Phenylketones

44
Q

What is not produced as a result of a phenylalanine hydroxylase deficiency in Phenylketonuria?

A

Tyrosine

45
Q

What is the significance of being deficient in Tyrosine?

A

Can’t synthesise:
Adrenaline
Noradrenaline
Dopamine
Thyroid hormones

46
Q

What are the symptoms of PKU?

A

Severe intellectual disability
Microcephaly
Seizure

47
Q

How is PKU Treated?

A

Avoid high protein foods
Diet with low phenylalanine and high tyrosine

48
Q

What is Homocystinurias?

A

Autosomal recessive disorder
A problem breaking down methionine causing excess homocysteine to be excreted in urine as homocystine

Homocysteine is what would be present in the plasma (homocystine is the oxidised form of homocysteine formed from methionine being metabolised)

49
Q

Which enzyme is defective in Homocystinurias?

A

Cystathionine B-synthase

50
Q

What problems does Homocystinurias cause?

A

Problems with:
Connective tissues
Muscles
CNS
CVS

51
Q

How does deficiency of cystathionine B-synthase cause disease?

A

Homocysteine and it’s metabolites accumulate causing disease symptoms

MEH (33 decks)

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