Exam 3 Lecture # 3 (AA metabolism)

Question 1

What are the Essential AA’s?

Answer 1

Essential AA’s:

Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

Question 2

Conditionally Essential AA’s

Answer 2

Conditionally Essential AA’s:

Arginine, Cystine, Tyrosine

Question 3

What are the two ketogenic AA’s?

What does ketogenic mean?

Answer 3

Ketogenic AA’s: Leucine and Lysine

Ketogenic: can be converted to ketones

Question 4

Where can the Ketogenic AA’s enter the metabolism cycle?

Where can the Glucogenic AA’s enter the cycle?

Answer 4

Ketogenic AA’s can enter as Acetyl CoA or as Acetoacetate

Glucogenic can enter as almost anywhere else:

Pyruvate, a-Ketoglutarate, Succinyl CoA, Fumarate, Oxa

Question 5

Most AA’s are obtained from _____

The ____ found in macromolecules of the body comes from the diet, after it has gone from the atmosphere and become fixed as ___ by organisms and plants

Answer 5

Most AA’s are obtained from the diet

The nitrogen found in macros comes from the diet, after the nitrogen in the atmosphere has been fixed as ammonia by microorganisms and plants.

Question 6

Explain what negative vs positive nitrogen balance means

Answer 6

Negative Nitrogen Balance: loss is greater than intake/ more N2 excreted than ingested,

Negative nitrogen balance occurs this occurs with diet defecient in essential AA’s, fever, fasting, and wasting disease

Positive Nitrogen balance: N2 intake more than losses, occurs in growing children, pregnant women, after surgery and trauma, and tissue repair

Question 7

The body degrades/loses the equivalent of ___ of protein every day.

This loss must be replaced by dietary protein.

What is nitrogen excreted as?

Answer 7

The body degrades 55 g of protein everyday.

The 55g must be made up in the diet otherwise we will be in negative nitrogen balance.

Nitrogen is excreted as urea

Question 8

Nonessential AAs are synthesized from _______

The ____ are enzymes that catalyze the transfer of an amino group

Usually, the AA acts as the ___ and the alpha keto acid acts as the _____

Answer 8

Nonessential AAs are synthesized from a-keto acid precursors by transfer of a preexisting amino group from another AA by aminotransferase

The aminotransferases or transaminases are enzymes catalyzing the transfer of an amino group, plus a protin and an electron pair from donor to acceptor

Usually, the AA acts as the donor, and the alpha keto acid acts as the receptor

Question 9

Draw the diagram showing pyruvate to acetyl coA to the krebs cycle and show where each AA enters the pathway

Answer 9

Question 10

What gets deaminated to form pyruvate?

Answer 10

ALANINE can be deaminated to form pyruvate

Question 11

Fumarate is produced from….

Answer 11

Tyrosine phenylalanine and aspartate

Question 12

AA’s are metabolized to intermediates of what three things?

Answer 12

AA’s are metabolized to intermediates of glycolysis and the TCA cycle, and acetyl coA in the liver.

Question 13

Alanine gets ____ to form pyruvate

a-Ketoglutarate gets ____ to form glutamate

What enzyme does this reaction?

Answer 13

Alanine gets DEAMINATED to form pyruvate

a-Ketoglutarate gets transaminated to form glutamate

This over all rxn done by aminotransferase

Question 14

Valine can be formed from what?

Answer 14

Valine can be formed from a-ketoisovalerate only when this compound is administered therapeutically

This is a therapy for hypoammoneumia

Question 15

What two AA’s do not participate in the transamination reaction?

Answer 15

Threonine and Lysine do not participate in the transamination reaction.

Question 16

What two AA’s are involed in most of the transamination reactions as intermediates?

Answer 16

Glutamate and alpha-ketoglutrate are involved in most of the transamination reactions as intermediates.

Question 17

____ is a cofactor for aminotransferases

Answer 17

Pyridoxal Phosphate is a cofactor for aminotransferases

It is a vitamin B derivative

Question 18

Measuring the releease of ______ is used diagnostically to determine tissue damage

Answer 18

Measuring the release of transaminase is used to determine tissue damage

Most common ones they look for are ALT (alanine transaminase) and AST (aspartate transaminase)

Question 19

An increase in what is a sign of liver disease, hepatitis, MI, etc

Answer 19

An increase in glutamate, aspartate, alanine and their aminotransferases is a sign of those problems

Question 20

All of the following are true of the enzyme AST except:

A. sometimes called Aspartate Aminotrasferse

B. can produce glutamate if NADPH and alpha ketoglutarate are substrates

C. can produce a-ketoglutarate and aspartate

D. can produce glutamate and oxaloacetate

Answer 20

B. is not true it cannot produce glutamate if NADPH and alpha keto glutarate are substrates.

the above explanation is talking about glutamate dehydrogenase

Question 21

What is the key amino acid used for AA synthesis to avoid free ammonia

What is the “gateway AA”

Answer 21

Glutamate is the “gateway” between AAs and free ammonia.

Question 22

In the liver ammonia is incorporated into glutamate by which enzyme?

_______ always serves as one of the AA’s in transaminations - gateway between amino groups of most AAs and free ammonia

Answer 22

Glutamate dehydrogenase is the enzyme that incorporates free ammonia into glutamate

Glutamate always serves as one of the AA’s in transmaminations

Question 23

Draw the reaction diagram for glutamate dehydrogenase

Explain allosteric regulation of this pathway

Answer 23

GD is allosterically regulated by purine nucleotides

ADP and GDP increase degradation of glutamate to form alpha ketoglutarate

ATP and GTP increase synthesis of glutamate

Question 24

What is the most abundant circulating AA

Answer 24

Most abundant circulating AA in the blood is GLUTAMINE

Glutamine acts as an ammonia transporter

Question 25

Explain the reaction catalyzed by glutamine synthase

Answer 25

Glutamine synthetase:

Glutamate + NH4 + ATP —–> Glutamine and ADP

Question 26

What happens in the kidney with respect to glutamine

Answer 26

In the kidney, glutamine gets turned into glutamate, freeing up NH3

This reaction is catalyzed by glutaminase

This allows NH3 to be excreted as urea

Question 27

What is the function of aminotransferases

IN ALL CASES what is involved in those rxn’s

Answer 27

Aminotransferases: to produce new AAs or to produce carboskeleton for glucose or ketone bodies in production

IN ALL CASES: alpha-ketoglutarate and glutamate are involved and the cofactor is PP

Question 28

_________ is a mechanism for all cells of the body to avoid free ammonia that is severely toxic

Answer 28

GLUTAMATE is a mechanism for all cells of the body to avoid free ammonia that is severely toxic. Incorporation by dehydrogenase that is regulated allosterically. Occurs when proteins are degraded

Question 29

In the liver NH4 goes to ____

In other tissues____

Answer 29

In the liver NH4 goes to the urea cycle

In other tissues no urea cycle, so glutamate -> glutamine by glutamine synthase and transport to liver or kidney

Question 30

When energy is needed, proteins in skeletal muscle get degraded and the AAs are transformed to _____ and _______

Answer 30

When energy is needed proteins in skeletal muscle get degraded and the AAs are transformed to glutamine and alanine

Question 31

Most glutamine is transported to liver and kidney where it is converted to _____

Answer 31

Most glutamine is transfered is transported to the liver and kidney where it is converted into alanine and ammonia (alanine glucose cycle)

Question 32

Where are urea and ammonia produced?

Where is ammonia from glutamate produced

Answer 32

Urea and ammonia are produced in the liver

Ammonia grom glutamate produced in kidney

Question 33

If the muscle needs to export NH4 it will produce?

If the muscle wants to have glucose returned by the liver, the muscle will produce ____

Answer 33

If muscle needs to export NH4 it will produce glutamine

If the muscle wants to have glucose returned by the liver, the muscle will produce alanine (alanine will be transported to the liver, and then alanine can be turned into pyruvate, which can make glucose)

Question 34

What are the fates of the amino acids?

Answer 34

Question 35

Explain the reaction catalyzed by glutamate dehydrogenase

Answer 35

Glutamate dehydrogenase:

a-keto glutarate + NH4 + NADPH —–> glutamate + NADP