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MEH- Aboli > Protein and AA metabolism > Flashcards

Protein and AA metabolism Flashcards

1
Q

Positive nitrogen balance (3 things)

A
  • Intake > output
  • Increase in total body protein
  • Normal in growth, pregnancy or adult recovery from malnutrition
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2
Q

Negative nitrogen balance (3 things)

A
  • Intake < output
  • Net loss of body protein
  • Trauma, infection or malnutrition
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3
Q

Cushing’s syndrome (3 things)

A
  • Excessive breakdown of protein
  • Due to excess cortisol
  • Leads to striae formation (stretch marks)
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4
Q

What controls mobilisation of protein reserves?

A

Hormones

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5
Q

Where do C atoms for non-essential AA synthesis come from (3 things)?

A
  • Intermediates of glycolysis
  • Pentose phosphate pathway
  • Krebs cycle
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6
Q

What is glycine used to synthesise (4 things)?

A
  • Purines
  • Glutathione
  • Haem
  • Creatine
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7
Q

What is tryptophan used to synthesise (3 things)?

A
  • Nicotinamide
  • Serotonin
  • Melatonin
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8
Q

What is cysteine used to synthesise (2 things)?

A
  • H2S
  • Glutathione
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9
Q

What is tyrosine used to synthesise (3 things)?

A
  • Catecholamines
  • Melanin
  • Thyroid hormones
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10
Q

What does histidine synthesise?

A

Histamine

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11
Q

What does arginine synthesise?

A

Nitric oxide

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12
Q

What does glutamate synthesise?

A

GABA

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13
Q

What does serine synthesise?

A

Sphingosine

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14
Q

Transamination key points (4 things)

A
  • Transfers an amine group from an amino acid to a keto group
  • Most aminotransferases use alpha-ketoglutarate to funnel amino group to glutamate
  • Need coenzyme pyridoxal phosphate
  • Derivative of vitamin B6
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15
Q

Key aminotransferases (4 things)

A
  • ALT (alanine to pyruvate)
  • AST (aspartate to oxaloacetate)
  • alpha-ketoglutarate to glutamate too
  • Measured routinely as part of liver function test
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16
Q

What conditions cause extensive cellular necrosis (3 things)?

A
  • Viral hepatitis
  • Autoimmune liver diseases
  • Toxic injury
17
Q

Enzymes used in deamination (3 things)

A
  • Amino acid oxidases
  • Glutaminase
  • Glutamate dehydrogenase
18
Q

Urea cycle key points (4 things)

A
  • Occurs in liver and involves 5 enzymes
  • Amount of enzymes normally related to need to dispose of ammonia
  • Cycle is inducible but not regulated
  • Affected by amount of protein in diet
19
Q

Defects in urea cycle (4 things)

A
  • Autosomal recessive genetic disorders due to enzyme deficiency
  • Mutations cause partial loss of enzyme function
  • Hyperammonaemia
  • Accumulation/excretion of urea cycle intermediates
20
Q

Symptoms of defects in urea cycle (6 things)

A
  • Vomiting
  • Lethargy
  • Irritability
  • Mental retardation
  • Seizures
  • Coma
21
Q

What does the severity of NH3 toxicity depend on (2 things)?

A
  • Nature of defect
  • Amount of protein eaten
22
Q

How to manage urea cycle defects (2 things)

A
  • Low protein diet
  • Replace AA in diet with keto acids
23
Q

What should blood level of NH3 be?

A

25-40 micromol/L

24
Q

Potential toxic effects of NH3 (6 things)

A
  • Interference with AA transport & protein synthesis
  • Disruption of cerebral blood flow
  • pH effects (alkaline)
  • Interferance with metabolism of excitatory AA neurotransmitters
  • Alteration of blood-brain barrier
  • Interference with TCA cycle
25
Q

Transporting AA nitrogen in blood- glutamine (4 things)

A
  • NH3 combined with glutamate to form glutamine
  • Transported in blood
  • Cleaved by glutaminase in liver/kidneys
  • Goes into urea cycle or excreted directly in kidneys
26
Q

Transporting AA nitrogen in blood- alanine (4 things)

A
  • Transamination to glutamate
  • Pyruvate transaminated by glutamate to form alanine
  • Transported in bloodstream
  • Fed into urea cycle whereas pyruvate used to make glucose
27
Q

Clinical problems of AA metabolism (3 things)

A
  • Total or partial loss of enzyme activity
  • That’s why heel prick test done on babies
  • Treated by restricting specific AA in diet
28
Q

Phenylketonuria- PKU (4 things)

A
  • Deficiency in phenylalanine hydroxylase
  • Accumulation of phenylalanine
  • Phenylketones in urine (musty smell)
  • Symptoms can be avoided with early intervention
29
Q

Homocystinuria (4 things)

A
  • Problem breaking down methionine
  • Excess homocysteine
  • Defect in cystathionine beta-synthase
  • Affects CT, muscles, CNS, CVS
30
Q

Treatment for PKU (3 things)

A
  • Low phenylalanine diet enriched with tyrosine
  • Avoid artificial sweeteners
  • Avoid high protein foods (e.g. milk, meat, eggs)
31
Q

Symptoms of PKU (5 things)

A
  • Severe intellectual disability
  • Developmental delay
  • Microcephaly
  • Seizures
  • Hypopigmentation
32
Q

Treatment for homocystinuria (4 things)

A
  • Low methionine diet
  • Avoid milk, meat, fish, cheese, eggs
  • Nuts and peanut butter too
  • Cysteine, B6, betaine, B12 & folate supplements

MEH- Aboli (6 decks)

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