Questão 1
Questão
Body proteins are continuously degraded to amino acids and re-synthesised.
Questão 2
Questão
All proteins have the same half-lives.
Questão 3
Questão
Protein cannot be stored in the body.
Questão 4
Questão
Why is a high protein intake in an already well-fed individual wasteful?
Responda
-
Excess amino acids are catabolised and excreted as urea
-
Excess amino acids cause breakdown of glycogen
-
Excess amino acids cause fat accumulation
-
Excess protein will not be catabolised so will yield no energy
Questão 5
Questão
What is true of healthy adults?
Responda
-
Nitrogen intake = nitrogen excretion
-
Nitrogen intake > nitrogen excretion
-
Nitrogen intake < nitrogen excretion
Questão 6
Questão
When is a positive nitrogen balance (nitrogen intake > nitrogen excretion) required?
Responda
-
Growth in childhood, recovery after illness, after immobilisation, during pregnancy
-
During starvation, during serious illness, in injury and trauma
-
All the time - this is required for healthy adults
Questão 7
Questão
When might a negative nitrogen balance (nitrogen intake < nitrogen excretion) occur?
Responda
-
During starvation, during serious illness, in injury and trauma
-
Growth in childhood, recovery after illness, following immobilisation, during pregnancy
-
In normal circumstances - this is required for healthy adults
Questão 8
Questão
How are most cellular proteins degraded?
Responda
-
Ubiquitin breakdown system
-
Proteolytic enzymes in lysosomes
-
Proteolytic enzymes in the gut
-
Dissolve in the cytosol
Questão 9
Questão
How are exogenous proteins degraded?
Responda
-
Proteolytic enzymes in lysosomes
-
Ubiquitin breakdown system
-
Proteolytic enzymes in gut
-
Dissolve in cytoplasm
Questão 10
Questão
What is oxidative deamination?
Questão 11
Questão
Which enzymes carry out oxidative deamination?
Responda
-
Dehydrogenases
-
Carboxylases
-
Oxidoreductases
-
Lyases
Questão 12
Questão
NADH + H+ are formed from NAD during oxidative deamination.
Questão 13
Questão
Oxidative deamination and transamination are reversible reactions.
Questão 14
Questão
What is a co-product of oxidative deamination?
Responda
-
Ammonia/ammonium ions
-
Pyruvate
-
Amino acids
-
FADH2
Questão 15
Questão
Fill in the blanks below to summarise oxidative deamination.
An amino acid reacts with [blank_start]water[blank_end] to form a [blank_start]keto acid[blank_end] and [blank_start]ammonia[blank_end]. This is catalysed by a [blank_start]dehydrogenase[blank_end] enzyme specific to that amino acid. This is a [blank_start]reversible[blank_end] reaction that forms NADH and H+ from [blank_start]NAD[blank_end].
Responda
-
water
-
keto acid
-
ammonia
-
dehydrogenase
-
reversible
-
NAD
Questão 16
Questão
What is transamination?
Questão 17
Questão
What type of enzymes carry out transamination?
Responda
-
Transaminases
-
Dehydrogenases
-
Decarboxylases
-
Oxidoreductases
Questão 18
Questão
Fill in the blanks below to describe transamination.
An amino acid reacts with a [blank_start]keto acid[blank_end] to form a keto-carboxylate such as [blank_start]pyruvate[blank_end] and the amino acid of the [blank_start]keto acid[blank_end]. This is carried out by [blank_start]transaminase[blank_end] enzymes in a [blank_start]reversible[blank_end] reaction.
Responda
-
keto acid
-
pyruvate
-
keto acid
-
transaminase
-
reversible
Questão 19
Questão
What are glucogenic amino acids?
Responda
-
Amino acids that can be converted back to glucose by the liver during starvation
-
Amino acids that can be degraded to acetyl CoA
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Amino acids that can be incorporated into glycogen
-
Amino acids that stimulate glycogen degradation
Questão 20
Questão
What are ketogenic amino acids?
Responda
-
Amino acids that can be degraded to acetyl CoA
-
Amino acids that can be converted back to glucose by the liver during starvation
-
Amino acids that form ketone bodies in the blood
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Amino acids that cause ketoacidosis
Questão 21
Questão
Which amino acids are ketogenic only?
Responda
-
Leucine
-
Lysine
-
Tyrosine
-
Iseoleucine
-
Phenylalanine
-
Histidine
-
Methionine
-
Alanine
-
Cysteine
Questão 22
Questão
Which amino acids are both glucogenic and ketogenic?
Responda
-
Tyrosine
-
Iseoleucine
-
Phenylalanine
-
Tryptophan
-
Threonine
-
Leucine
-
Lysine
-
Histidine
Questão 23
Questão
Only the liver can convert ammonia to urea for excretion in the urea cycle.
Questão 24
Questão
What does glutaminase do?
Questão 25
Questão
What enzyme forms glutamine from glutamate?
Responda
-
Glutamine synthetase
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Glutamate deaminase
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Glutamate hydrolase
-
Glutamate carboxylase
Questão 26
Questão
When glutamate is formed from glutamine, the enzyme [blank_start]glutaminase[blank_end] catalyses the reaction. This involves [blank_start]water[blank_end] as a reactant and [blank_start]ammonia[blank_end] as a product.
Responda
-
glutaminase
-
water
-
ammonia
Questão 27
Questão
When glutamine is formed from glutamate, ATP and [blank_start]ammonia[blank_end] are required. [blank_start]ATP[blank_end] is hydrolysed to provide energy for the reaction. [blank_start]Glutamine synthetase[blank_end] catalyses this reaction. Glutamine can carry [blank_start]two[blank_end] ammonia equivalents in this way.
Responda
-
ammonia
-
ATP
-
Glutamine synthetase
-
two
Questão 28
Questão
Why do we carry ammonia via glutamine to the liver for urea formation?
Responda
-
Carries 2 ammonia equivalents to prevent its toxic effects
-
The most soluble amino acid
-
Carries 3 ammonia equivalents to prevent its toxic effects
-
The most neutral amino acid
Questão 29
Questão
When ammonium ions combine with CO2/HCO3- in the mitochondria, what is formed?
Responda
-
Carbamoyl phosphate
-
L-Citruline
-
L-Aspartate
-
Urea
Questão 30
Questão
ATP hydrolysis is required for the synthesis of carbamoyl phosphate from CO2/HCO3- and ammonia.
Questão 31
Questão
What does carbamoyl phosphate combine with in the mitochondria to form citrulline?
Responda
-
Ornithine
-
Arginine
-
Fumarate
-
Arginosuccinate
Questão 32
Questão
What is lost when carbamoyl phosphate and ornithine react to form citrulline?
Responda
-
Inorganic phosphate
-
ATP
-
Methyl group
-
Carbonyl group
Questão 33
Questão
Which enzyme catalyses the formation of citrulline from carbamoyl phosphate and ornithine?
Responda
-
Ornithine transcarbamyolase
-
Ornithine pyrophosphatase
-
Citrulline synthetase
-
Carbamoyl pyrophosphatase
Questão 34
Questão
Where does citrulline combine with aspartate to form arginosuccinate?
Responda
-
Cytosol
-
Mitochondria
-
Plasma
-
Endoplasmic reticulum
Questão 35
Questão
Where does argininosuccinate synthase receive its energy to combine citrulline and aspartate to form argininosuccinate?
Questão 36
Questão
What reaction forms arginine and fumarate from argininosuccinate?
Responda
-
Cleavage
-
Condensation
-
Phosphorylation
-
Dephosphorylation
Questão 37
Questão
What does the enzyme argininosuccinase do?
Responda
-
Cleave argininosuccinate into fumarate and arginine
-
Cleave argininosuccinate into malate and arginine
-
Dephosphorylate argininosuccinate
-
Phosphorylate argininosuccinate
Questão 38
Questão
What reaction converts arginine to urea and ornithine?
Responda
-
Hydration
-
Condensation
-
Phosphorylation
-
Dephosphorylation
Questão 39
Questão
What is required to convert arginine to urea and ornithine?
Responda
-
Water
-
Inorganic phosphate
-
Carbon dioxide
-
Bicarbonate
Questão 40
Questão
Fill in the blanks below to describe the ornithine/urea cycle.
1. Ammonium ions react with c[blank_start]arbon dioxide[blank_end] or b[blank_start]icarbonate[blank_end] in the [blank_start]mitochondria[blank_end]. This forms [blank_start]carbamoyl phosphate[blank_end]. This reaction is catalysed by [blank_start]carbamoyl phosphate synthase I[blank_end] and requires [blank_start]ATP[blank_end] hydrolysis.
2. [blank_start]Carbamoyl phosphate[blank_end] combines with [blank_start]ornithine[blank_end] to form [blank_start]citrulline[blank_end] in the mitochondria. [blank_start]Inorganic phosphate[blank_end] is lost in this reaction. This reaction is catalysed by [blank_start]ornithine transcarbamyolase[blank_end].
3. [blank_start]Citrulline[blank_end] is transported into the [blank_start]cytosol[blank_end] where it combines with [blank_start]aspartate[blank_end] to form [blank_start]argininosuccinate[blank_end]. This is catalysed by [blank_start]argininosuccinate synthase[blank_end] and requires [blank_start]ATP[blank_end] hydrolysis.
4. [blank_start]Argininosuccinate[blank_end] is cleaved into [blank_start]fumarate[blank_end] and arginine in a reaction catalysed by [blank_start]argininosuccinase[blank_end].
5. [blank_start]Arginine[blank_end] is hydrated and splits into urea and [blank_start]ornithine[blank_end]. This requires water and is catalysed by [blank_start]arginase[blank_end]. The [blank_start]ornithine[blank_end] combines with more [blank_start]carbamoyl phosphate[blank_end] in the mitochondria to continue the cycle and the [blank_start]urea[blank_end] is excreted.
Responda
-
arbon dioxide
-
icarbonate
-
mitochondria
-
carbamoyl phosphate
-
carbamoyl phosphate synthase I
-
ATP
-
Carbamoyl phosphate
-
ornithine
-
citrulline
-
Inorganic phosphate
-
ornithine transcarbamyolase
-
Citrulline
-
cytosol
-
aspartate
-
argininosuccinate
-
argininosuccinate synthase
-
ATP
-
Argininosuccinate
-
fumarate
-
argininosuccinase
-
ornithine
-
Arginine
-
arginase
-
carbamoyl phosphate
-
urea
-
ornithine
Questão 41
Questão
Fill in the blanks below to describe some of the end products of nitrogen metabolism.
Protein breakdown results in [blank_start]urea[blank_end].
Creatine phosphate breakdown results in [blank_start]creatinine[blank_end].
DNA and RNA breakdown results in [blank_start]uric acid[blank_end].
The control of body pH results in [blank_start]ammonia[blank_end].
Responda
-
urea
-
creatinine
-
uric acid
-
ammonia
Questão 42
Questão
Hyperammonaemia is caused by an impaired conversion of [blank_start]ammonia[blank_end] to [blank_start]urea[blank_end]. This can be caused by liver failure, for example in viral [blank_start]hepatitis[blank_end], c[blank_start]irrhosis[blank_end] or other toxins. This can also be caused by genetic defects, for example causing mutations in the enzymes involved in the [blank_start]urea cycle[blank_end].
The symptoms of this include irratibility, headache and vomiting. In more severe cases hyperammonaemia can result in encephalopathy, seizures and ataxia.
Responda
-
urea
-
ammonia
-
hepatitis
-
irrhosis
-
urea cycle