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Biochemistry II > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

1
Q

Where can amino acid metabolism occur?

A
  • Peripheral tissues

- Liver

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2
Q

What are the two general steps of amino acid catabolism?

A

Step 1: Removal of amino group (nitrogen)

Step 2: Carbon skeleton

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3
Q

Approximately how many grams of free amino acids are located in the amino acid pool?

A

100-200 grams

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4
Q

Where is most of the free amino acid pool found?

A

In intracellular skeletal muscle

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5
Q

What are the two methods that amino acids are transported throughout the body?

A
  • Free amino acid concentration gradient

- Active transport systems (ATP)

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6
Q

Does taking a lot of one amino acid limit the intake of others sharing the same transporter? True or False?

A

True, it may limit the intake

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7
Q

What is absorbed faster, peptides or free amino acids?

A

Peptides are absorbed faster

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8
Q

Can nitrogen be stored in the body?

A

No

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9
Q

In order to be removed, where is nitrogen first sent?

A

The liver

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10
Q

What are the two processes used to remove amino groups?

A

Transamination and Oxidative Deamination

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11
Q

What form is nitrogen excreted as?

A

Urea

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12
Q

Where does transamination occur?

A

Liver and peripheral tissues

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13
Q

What is the amino group acceptor of transamination?

A

alpha-ketoglutarate

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14
Q

What is the product of transamination after alpha-ketoglutarate accepts an amino group?

A

Glutamate and an alpha-keto acid

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15
Q

What is the required enzyme of transamination?

A

Pyridoxal phosphate (derivative of vitamin B6)

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16
Q

Aminotransferases are the main enzyme used in transamination. What are the three types?

A
  • Muscle alanine aminotransferase (ALT)
  • Liver alanine aminotransferase (ALT)
  • Aspartate aminotransferase (AST)
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17
Q

What is the other name for Muscle/liver alanine aminotransferase and aspartate aminotransferase?

A
  • Glutamate-pyruvate tranaminase (GPT)

- Glutamate oxaloacetate transaminase (GOT)

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18
Q

Where does oxidative deamination occur?

A

Liver and kidney

19
Q

Overall what occurs during oxidative deamination?

A

An ammonia group is released as a free ammonia

20
Q

What is the main enzyme of oxidative deamination?

A

Glutamate dehydrogenase

21
Q

What are the main exports of muscles to the liver?

A
  • Glutamine (glutamate + ammonia)

- Alanine

22
Q

What enzyme is used to create glutamine?

A

Glutamine synthetase

23
Q

Which cycle does the liver utilize to deal with ammonia?

A

Urea cycle

24
Q

This enzyme deaminates glutamate.

A

Glutamate dehydrogenase (GDH)

25
Q

This enzyme transfers amino groups from glutamate to oxaloacetate and eventually forms aspartate.

A

Aspartate aminotransferase (AST) or otherwise known as glutamate oxaloacetate transaminase (GOT)

26
Q

This is the main entry point into the urea cycle.

A

CO2+NH3+2ATP–>carbamyol phosphate

Enzyme: carbomoyl phosphatase

Location: Mitochondrial matrix

27
Q

What are the steps of the urea cycle?

A

Carbamoyl phosphate+ornithine–>citrulline
Citrulline–>argininosuccinate (use aspartate)
Argininosuccinate–>arginine (lose fumarate)
Arginie–> ornithine (lose urea)

Enzyme 1: ornithine transcarbamoylase
Enzyme 2: argininosuccinate synthase
Enzyme 3: argininosuccinate lyase
Enzyme 4: arginase

28
Q

After it is made, where is urea sent to be excreted?

A
  • Transported in the blood to the kidneys

- Some ammonia diffuses back into the blood, sent to GI tract, and excreted in feces

29
Q

How many nitrogen molecules does urea have and what is the precursor to these molecules?

A

Two: one from aspartate and one from free NH3

-Glutamate is the precursor to both

30
Q

When the amino acid group is removed from an amino acid, what is left?

A

Alpha-ketoacid

31
Q

What happens to an alpha ketoacid depends on what four things?

A
  • Energy charge
  • Hormones (glucagon/insulin)
  • Glucose concentration
  • Tissue (liver vs. muscle)
32
Q

What happens to amino acids when there is a low energy charge?

A

The amino acid is oxidized to recreate ATP

33
Q

What happens to amino acids when there is low glucose?

A

The amino aicd is sent to the liver to turn into glucose

34
Q

What happens to amino acids when there is a high energy charge and lots of glucose?

A

The amino acid is sent to the liver and turned into fat

35
Q

What are three key amino acid conversions that can directly enter the aerobic system?

A
  • AlaninePyruvate
  • GlutamineGlutamatealpha-ketoglutarate
  • AsparagineAspartateOxaloacetate
36
Q

What are the two amino acids that cannot turn into glucose?

A

Leucine and lysine (ketogenic)

37
Q

Skeletal muscle is only able to significantly oxidize six amino acids. What are they?

A
  • Leucine
  • Isoleucine
  • Valine
  • Glutamate
  • Aspartate
  • Asparagine
38
Q

Out of the six amino acids that skeletal muscle is able to oxidize, which are branch chain amino acids?

A
  • Leucine
  • Isoleucine
  • Valine
39
Q

What amino acid has the highest intracellular/extracellular ratio?

A

Glutamate

40
Q

What happens to plasma concentrations of glutamate and alanine during exercise?

A
  • Glutamate decreases

- Alanine increases

41
Q

In the absence of nutrient intake, what serves as the principal reservoir to replace blood amino acids taken up by other tissues?

A

Muscle protein

42
Q

What enzyme converts glutamate into glutamine?

A

Glutamine synthetase

43
Q

What enzyme converts glutamine back into glutamate?

A

Glutaminase

44
Q

What are the most abundantly released amino acids in muscle?

A

Glutamine and Alanine

Biochemistry II (16 decks)

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