5 protein metabolism and diagnosis Flashcards by Cordelia Kuti

what is transamination?

AA synthesis via exchange of functional groups b/w AA and ketoacid (α-ketoglutarate)

products are glutamate and pyruvate

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what is oxidative deamination?

glutamate converted back to ketoglutarate by glutamate dehydrogenase

products are NADPH (for FA synth) and ammonia (NH3) > quickly reacts w/ H and becomes ammonium (NH4) enters urea cycle

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If Learned This Huge List May Prove Truly Valuable

Isoleucine
leucine
threonine
histidine
lysine
methionine
phenylalanine
tryptophan
valine

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phenylketonuria PKU

inherited

large amount of phenylketones from phenylalanine

phenylalanine oxidised to tyrosine b/c phenylalanine hydroxylase (enzyme) is deficient

metabolised by other pathways to become phenylpyruvate

detected in urine or blood concentration

treat w/ diet low in phenylalanine

could cause lack of brain development

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homocystinuria HCU

rare inherited autosomal recessive

defect in methionine metabolism

deficiency of cystathionine Beta synthase (CBS) enzyme

B/c CBS deficient, homocysteine levels increase converting to methionine

diagnosed w/ high levels of homocysteine/methionine in plasma and urine

treat w/ low diet in methionine

could cause connective tissue, muscle, CNS/CVS disorders

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what amino acids are strictly ketogenic?

lysine and leucine

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most common defect of urea cycle?

Ornithine Transcarboxylase (OCT) deficiency

X linked

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What causes defects in the urea cycle?

Autosomal recessive disorders

cause deficiency of one of enzymes or partial loss of function

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refeeding syndrome?

when pt has been on low protein diet (malnourished)

enzymes of urea cycle are downregulated

refeed 5-10kcal/kg/day raise gradually till full needs met

risk factors - low BMI (<16), unintentional weight loss (15%), or >=10 days w/ no or small nutritional intake

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Why would insulin inhibit gluconeogenesis

Too much glucose outside of cell therefore no more glucose is needed hence inhibition of gluconeogenesis

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Why must ammonia be converted to urea

It is toxic

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Why is removing NH2 from amino acids important

Carbon skeleton of amino acid can be used in oxidative metabolism

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Why is folate and Vitamin B12 used as treatment for homocystinuria

folate and Vitamin B12 promote conversion of homocysteine to methionine (essential amino acid)

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Why does glucagon stimulate gluconeogenesis

Low glucose outside of cell
Stimulate production of glucose from alternative sources

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Why can’t the muscle convert Glucose 6 phosphate into glucose

Muscle lacks glucose 6 phosphatase

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Why are tyrosine supplements given to PKU

Since phenylalanine hydroxylase not present then phenylalanine not converted to tyrosine

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which specific amino acids needed for glutathione

glycine
cysteine

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which specific amino acids needed for catecholamines

Tyrosine

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Where is glycogen stored in the liver

Hepatocytes

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Where is glycogen stored in muscle

Intra and inter myofibrils

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Where is defect in homocystinuria

Cystathionine beta synthase (CBS)

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Where does gluconeogenesis occur

Liver

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Where does deamination occur

Liver and kidney

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Where do carbon atoms for non essential amino acid synthesis come from(3)

Intermediates of glycolysis
Pentose phosphate pathway
Krebs cycle

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When is a branch point created

Every 8-10 glucose residues

What type of genetic disorder is PKU

autosomal recessive

What type of condition is homocystinurias

Autosomal recessive

What tissues need a absolute source of glucose

Erthrocytes Leukocytes Kidney medulla Lens and cornea of eye

What stimulates Hormone sensitive lipase and adipose TAG lipase

Glucagon and adrenaline Phosphorylation

What pathways do low tyrosine affect (5)

Dopamine Adrenaline Noradrenaline Thyroid hormone Protein synthesis

What occurs in deamination

NH2 released as ammonia can converted to ammonium ion and converted to urea

What occurs during intestinal epithelial cell recombination

Fatty acids and glycerol combine to form Triacylglycerol

What molecules are required throughout the whole process of fatty acid synthesis

ATP and NADPH

What molecule combines with fatty acids to travel in the blood

Albumin

What is used a primer for glycogen structure

Glycogenin

What is tyrosine needed for

Thyroid hormone Melanin

What is tryptophan needed for(3)

Nicotinamide Serotonin Melatonin

What is treatment for PKU

Low phenylalanine diet Tyrosine supplements

What is treatment for homocystinuria

Low methionine diet Cysteine Vitamins B6 Folate

What is transamination

Move NH2 from amino acid to ketoacid to create a new amino acid

What is the structure of glycogen

Polymer of glucose residues

What is the process of fatty acid synthesis

Glucose to pyruvate in cytoplasm Pyruvate to Acetyl-CoA and oxaloacetate in mitochondria Oxaloacetate and acetyl-CoA to citrate Citrate cleaved to Acetyl-CoA and oxaloacetate Acetyl-CoA carboxylase produce malonyl-CoA from Acetyl-CoA Fatty acid synthase complex build fatty acids through addition of 2 carbon units provided by malonyl-CoA

What is the process of ammonia transport

Ammonia to glutamate Glutamate to glutamine via glutamine synthetase Glutamine goes from tissue to blood to liver Glutamine to glutamate via glutaminase Glutamate to ammonia to urea via glutamate dehydrogenase

What is the name for fatty acid synthesis

Lipogenesis

What is the enzyme required to convert glucose 6 phosphate to glucose 1 phosphate

Phosphoglucomutase

What is the effect of insulin on gluconeogenesis enzymes

Decreased amount of PEPCK and Fructose 1,6 bisphosphatase

What is the effect of glucagon on gluconeogenesis enzymes

Increased amount of PEPCK and Fructose 1-6-bisphosphatase Stimulate gluconeogenesis

What is some examples of ketogenic amino acids

Lysine Leucine

What is some example of amino acids that are both glucogenic and ketogenic

Tryptophan Isoleucine Threonine

What is pyruvate converted to in fatty acid synthesis

Acetyl-CoA and oxaloacetate in mitochondria

What is glutamate needed for

GABA

What is glucose converted to in fatty acid synthesis

Pyruvate in cytoplasm

What is glucose 6 phosphate converted to in the liver

Glucose

What is an example of disorder caused by excess glycogen storage

Von gierke disorder

What is an example of a condition that is caused by lack of glycogen degradation

McArdle disease

What is acetyl-CoA and oxaloacetate condensed into in fatty acid synthesis

Citrate

What hormones convert Triacylglycerol in adipose tissue to glycerol and fatty acids in blood (2)

Hormone sensitive lipase Adipose TAG Lipase

What happens to glucose 6 phosphate in the muscle

Enters glycolysis to produce lactate

What happens to citrate in fatty acid synthesis

Enters cytoplasm and returns to acetyl-CoA and Oxaloacetate

What goes wrong in phenylketonuria

Accumulation of phenylalanine Phenylketones in urine Phenylketones oxidised to phenylacetate

What goes wrong in homocystinurias

High homocysteine and methionine Homocysteine excreted in urine

What enzymes are used in transamination

Aminotransferase

What enzyme is used to convert glucose-6 phosphate to glucose

Glucose 6 phosphatase

What enzyme is used to convert glucose to glucose 6 phosphate

Hexokinase in most cells Glucokinase in liver

What does homocystinuria affect(4)

Connective tissue Muscle CNS CVS

What does fatty acid synthase complex do

Produce fatty acids through addition of 2 carbon units from malonyl-CoA

What does aspartate aminotransferase (AST) do

Convert aspartate to glutamate

What does Alanine aminotransferase (ALT) do

Convert alanine to glutamate

What does a low creatinine in blood suggest

Muscle wastage

What does a high creatinine in blood suggest

Damage to nephrons

What deficiency is present in PKU

Phenylalanine hydroxylase

What can partial loss of enzyme function in urea cycle lead to

Hyperammonaemia Accumulation of urea cycle intermediates

What can free amino acids be converted to in the liver(2)

Amino group Carbon skeleton

What are the enzymes that can deaminate amino acids (3)

Amino acid oxidase Glutaminase Glutamate dehydrogenase

what are some symptoms of ornithine transcarbamylase deficiency (OCT)

vomiting lethargy seizures coma

What 2 enzymes in gluconeogenesis are controlled by hormones

PEPCK Fructose 1,6 bisphosphatase

What 2 enzymes are rate limiting in glycogen metabolism

Glycogen synthase Glycogen phosphorylase

The enzyme Ornithine transcarbamylase leads that what disorder

Ornithine transcarbamylase deficiency

Plasma levels of ALT and ASL are used to measure function of what organ

Liver