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Biochem Phys > Exam 3 Lecture 4 > Flashcards

Exam 3 Lecture 4 Flashcards

1
Q

________ is the disposal form of amino groups

A

Urea is the disposal form of urea groups

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2
Q

Urea is synthesized as part of the urea cycle, either from ______ or from ______

A

Urea is synthesized in the urea cycle either from oxidation of amino acids or from ammonia

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3
Q

Approximately ___ of AAs are reutilized

Excess of AA are not stored —-> forms _____

A

Approx 75% of AAs are reutilized

Excess of AAs are not stored… forms urea and gets excreted

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4
Q

In the urea cycle, amino groups donated by ______ are converted to urea, while ____________ act as intermediates

Urea production occurs in the ____ and us regulated by ______ and excreted through kidney

A

In the urea cycle, amino groups donated by ammonia and L aspartate are converted to urea, while L-ornithine, citrulline, L arginosuccinate, and L-arginine act as intermediates

Urea production occurs in the liver, and is regulated by N-acetylglutamate then excreted through kidney

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5
Q

What energy sources go into making urea

A

Synthesis of urea requires 3 mol ATP and an AMP

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6
Q

Urea is found dissolved in the blood…what is the normal range

What is urea excreted as

A

Urea is found dissolved in blood (range of 2.5 to 6.7 mmol/liter)

Urea is excreted as urine

(small amount of urea excreted as sweat)

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7
Q

In mamals, the urea cycle takes place primarily where?

What compound does the urea cycle start and end with?

A

In mammals, urea cycle takes place in the liver, to a lesser extent in the kidney

The urea cycle starts and ends with Ornithine

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8
Q

What are the five enzymes required in the urea cycle?

A

urea cycle enzymes:

Carbamoyl-P synthetase (CPS-1)

Ornithine Transcarbamoylase (OTC)

Argininosuccinate synthetase (ASS)

Argininosuccinate lyase (ASL)

Arginiase (ARG1)

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9
Q

What is the overall reaction for the urea cycle?

A

Overall reaction:

aspartate + NH3+ CO2+ 3ATP + 3 H20 ——->

urea + fumarate + 2ADP + AMP + 4 Pi

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10
Q

What is the major regulated step of the urea cycle?

A

Major regulated step of the urea cycle:

Formation of carbomyl phosphate by the enzyme CPS-1

Absolute requirement for N-acetylglutamate for this reaction

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11
Q

What is an important entry point in the urea cycle?

What is the major regulated step of the urea cycle?

A

Major regulated step is formation of carbmoyl phosphate done by the enzyme carbamoyl phosphate synthetase

ABSOLUTE requirement of N-acetylglutamate for the synthetase

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12
Q

What is the first amino group that enters the urea cycle?

A

Carbamoyl phosphate

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13
Q

Draw the urea cycle

A

Ordinarily careless crappers are also frivilous about urinating:

ornithine, carmaboyl phosphate, critrulline, aspartate, arginosuccinate, fumarate, aspartate, urea

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14
Q

Explain the linkage between the urea cycle and the TCA cycle:

fumarate is converted to ____ in the cytosol where it is then converted to _____ in the TCA cycle

OAA is transaminated and transported into the cytosol to form

A

Fumarate is converted to malate in cytosol, sent to mito to enter TCA cycle to be converted into OAA

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15
Q

Explain the concequences of the various defeciencies:

Carbamyl Phosphate synthetase

Ornithine transcarbamoylase

Arginosuccinate synthetase

Arginase

A

Carbamoyl phosphate synthetase defeciency: hyperammoneia

Ornithine defeciency: mental retardation and death

Arginosuccinate synthetase: excess of cirtulline in the blood and urine

Arginase: rare defeciency, developmental problems

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16
Q

Metabolic disorders or urea synthesis have dire concenquences.

Arise from abnormal function of enzyme and enzyme defeciencies, often cause_____ and ______

Therapy?

A

Often cause coma and death

Therapy:

limit protein intake

remove excess ammonia

replace intermediates

liver transplant

17
Q

_________ is a precursor of citrulline and arginine

______ is synthesized from 3-phosphoglycerate

A

Ornithine is a precursor of citrulline and arginine

Serine is synthesized from 3-phosphoglycerate

(Serine is a precursor of glycine and D-serine)

18
Q

Ornithine ———> _____

Shared intermediate is?

A

Ornithine ——> proline

Shared intermediate: glutamic semialdehyde

19
Q

3- phosphoglycertate———-> ________

A

3-phosphoglycerate goes to serine

20
Q

How can glutamate, alanine, and asartate get broken down?

How does serine get degraded?

How are ornithine and proline degraded?

A

Glutamate, alanine, and aspartate are deaminated by glutamate dehydrogenase

Serine gets degraded to 3 phosphoglycerate via dephosphorylation (note serine can also go to glycine)

Ornithine and proline degrade via glutamic semialdehyde

21
Q

Proline hydroxylation requires _______

What happens when you don’t have it

A

Proline hydroxylation requires ascorbic acid (vitamin C)

The most obvious first effects (gum and hair problems) of absence of vitamin C in humans comes from defect in hydroxylation of proline residues of collagen (causes scurvy)

22
Q

Explain PKU

A

PKU:

Inability to break down phenylalanine into tyrosine

Phe—-> tyrosine by enzyme phenylalanine hydroxylase

causes CNS problems

PKU tested by a blood test in infants

Treatment is diet low in phenylalanine , avoid aspartame

23
Q

Noticable side affect of PKU is what?

A

Musty body odor

24
Q

When would tyrosine become a conditionally essential AA?

A

In an individual with phenyalanine hydroxylase defeciency

25
Q

Explain maple syrup urine disease

A

Maple Syrup Urine Disease:

can’t break down beta branched chain amino acids

26
Q

What AA does epinephrine come from?

What are the steps?

A

Tyrosine goes to epinephrine

Steps: Tyr –> DOPA—> NE—-> Epi

27
Q

What is the cofactor needed to turn epi into NE?

A

S-adenosylhomocystein

28
Q

What AA does melanin come from?

What is phenomelanin?

A

Melanin comes from tyrosine

Phenomelanin contains cystine and is reponsible for red hair

29
Q

What is a quick way for your muscles to generate ATP?

A

The body can resynthesize ATP from ADP with the use of phosphocreatine through a reversible reaction with creatine kinase

30
Q

What is a BUN test?

A

A BUn test is a blood test done to see how well your kidneys are working

Normal creatine ratio is 10: 1 or 15:1

If you have heart failure, or diet high in protein, higher bun ratio

If you have liver damage: lower bun ratio

31
Q

What prevents damage caused by reactive oxygen species such as free radicals and peroxides?

A

Glutathione

32
Q

What is the function of glutamate dehydrogenase

Function of aminotransferase?

Cofactor of aminotransferase?

A

Glutamate dehydrogenase: catalyzes ammonia

Aminotransferase: catalyze transfer of amino groups from aa’s to alpha keto acids

Pyridoxal Phosphate is the cofactor for aminotransferase

33
Q

What are the amino acids that are ketogenic and glucogenic?

A

Both keto and gluco: PITTT

Phenylalanine, Isoleucine, Threonine, Tyrosine, Tryptophan

Biochem Phys (23 decks)

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