Amino Acid Metabolism

Question 1

Where can amino acid metabolism occur?

Answer 1

• Peripheral tissues

- Liver

Question 2

What are the two general steps of amino acid catabolism?

Answer 2

Step 1: Removal of amino group (nitrogen)

Step 2: Carbon skeleton

Question 3

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

Answer 3

100-200 grams

Question 4

Where is most of the free amino acid pool found?

Answer 4

In intracellular skeletal muscle

Question 5

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

Answer 5

• Free amino acid concentration gradient

- Active transport systems (ATP)

Question 6

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

Answer 6

True, it may limit the intake

Question 7

What is absorbed faster, peptides or free amino acids?

Answer 7

Peptides are absorbed faster

Question 8

Can nitrogen be stored in the body?

Answer 8

No

Question 9

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

Answer 9

The liver

Question 10

What are the two processes used to remove amino groups?

Answer 10

Transamination and Oxidative Deamination

Question 11

What form is nitrogen excreted as?

Answer 11

Urea

Question 12

Where does transamination occur?

Answer 12

Liver and peripheral tissues

Question 13

What is the amino group acceptor of transamination?

Answer 13

alpha-ketoglutarate

Question 14

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

Answer 14

Glutamate and an alpha-keto acid

Question 15

What is the required enzyme of transamination?

Answer 15

Pyridoxal phosphate (derivative of vitamin B6)

Question 16

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

Answer 16

• Muscle alanine aminotransferase (ALT)
• Liver alanine aminotransferase (ALT)
• Aspartate aminotransferase (AST)

Question 17

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

Answer 17

• Glutamate-pyruvate tranaminase (GPT)

- Glutamate oxaloacetate transaminase (GOT)

Question 18

Where does oxidative deamination occur?

Answer 18

Liver and kidney

Question 19

Overall what occurs during oxidative deamination?

Answer 19

An ammonia group is released as a free ammonia

Question 20

What is the main enzyme of oxidative deamination?

Answer 20

Glutamate dehydrogenase

Question 21

What are the main exports of muscles to the liver?

Answer 21

• Glutamine (glutamate + ammonia)

- Alanine

Question 22

What enzyme is used to create glutamine?

Answer 22

Glutamine synthetase

Question 23

Which cycle does the liver utilize to deal with ammonia?

Answer 23

Urea cycle

Question 24

This enzyme deaminates glutamate.

Answer 24

Glutamate dehydrogenase (GDH)

Question 25

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

Answer 25

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

Question 26

This is the main entry point into the urea cycle.

Answer 26

CO2+NH3+2ATP-->carbamyol phosphate Enzyme: carbomoyl phosphatase Location: Mitochondrial matrix

Question 27

What are the steps of the urea cycle?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

Two: one from aspartate and one from free NH3 | -Glutamate is the precursor to both

Question 30

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

Answer 30

Alpha-ketoacid

Question 31

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

Answer 31

- Energy charge - Hormones (glucagon/insulin) - Glucose concentration - Tissue (liver vs. muscle)

Question 32

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

Answer 32

The amino acid is oxidized to recreate ATP

Question 33

What happens to amino acids when there is low glucose?

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

- AlaninePyruvate - GlutamineGlutamatealpha-ketoglutarate - AsparagineAspartateOxaloacetate

Question 36

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

Answer 36

Leucine and lysine (ketogenic)

Question 37

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

Answer 37

- Leucine - Isoleucine - Valine - Glutamate - Aspartate - Asparagine

Question 38

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

Answer 38

- Leucine - Isoleucine - Valine

Question 39

What amino acid has the highest intracellular/extracellular ratio?

Answer 39

Glutamate

Question 40

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

Answer 40

- Glutamate decreases | - Alanine increases

Question 41

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

Answer 41

Muscle protein

Question 42

What enzyme converts glutamate into glutamine?

Answer 42

Glutamine synthetase

Question 43

What enzyme converts glutamine back into glutamate?

Answer 43

Glutaminase

Question 44

What are the most abundantly released amino acids in muscle?

Answer 44

Glutamine and Alanine