Amino acid catabolism

Question 1

What is the trend with protein intake

Answer 1

Amount of protein we intake is increasing

Question 2

Most AA are metabolized in

Answer 2

The liver

Question 3

Amino acids can be metabolized through

Answer 3

Amino group and urea cycle

And citric acid cycle

Question 4

What happens with ammonia and carbon skeleton in principle

Answer 4

Ammonia- recycled or excreted

Carbon skeleton- TCA cycle or Glucoenogenesis or ketogenesis

Question 5

In what parts of GI protein is digested

Answer 5

Stomach and small intestine

Question 6

What enzymes degrade protein

Answer 6

Peptin
HCl to unwind
Trypsin
Chemotrypsin

Question 7

What is the first reaction of amino acids catabolism

Answer 7

Removal of an amino group

Question 8

Describe how removal of the amino group happens

Answer 8

Through amino transferase alpha-ketoglutarate is transformed to L-glutamate

Question 9

What is the effect on amino acids during transamination reaction

Answer 9

No net loss, it is just transferred from one molecule to another

Question 10

Aminotransferases are ___

Answer 10

AA specific ( e.g. alanine amino transferase)

Question 11

What is the cofactor for amino-transferases

Answer 11

Pyridoxal phosphate (vit.6)

Question 12

Vitamin 6 is also a cofactor for

Answer 12

Glycogen phosphorylase

Question 13

What is the function of L-glutamate

Answer 13

The glutamate then functions as an
amino group donor for biosynthetic pathways or for excretion pathways that lead to the elimination of
nitrogenous waste products.

Question 14

Deanimation of glutamate happens in

Answer 14

Mitochondria

Question 15

What enzyme, product and substrates are needed for deanimation reaction in liver

Answer 15

Glumate-> alpha-ketoglutarate

Enzyme: glutamate dehydrogenase

Using: NAD(P)+, H2O

Question 16

The use of alpha-ketoglutarate

Answer 16

Used for transamination, TCA cycle or glucoeneogenesis

Question 17

Most tissues send their amino group in the form of___

Answer 17

Glutamine

Question 18

Explain transport of ammonia from other tissues

Answer 18

L-glutamate with glutamine synthase is converted to gamma-Glutamyl phosphate ( in all tissues)

with glutamine synthetase gamma-Glutamyl phosphate is converted to L-glutamine

L-glutamine is transported to the liver

Glitaminase in liver mitochodria converts L-glutamine to L-glutamate

Question 19

All deanimmation reaction happen in

Answer 19

The liver

Question 20

What muscles have an addition to glutamate transport system

Answer 20

Muscles send amino groups also through alanine

When alanine gets to the liver it is converted back to pyruvate in the liver, and then pyruvate can go through glucoenogenesis and glutamate-> urea cycle

Question 21

how muscles get alanine

Answer 21

By converting pyruvate to alanine with alanine aminotransferase

Question 22

Excretion of amino group happens through

Answer 22

Urea cycle

Question 23

Where does urea cycle begin and where it continues

Answer 23

Starts in mitochondria and continues in the cytoplasm

Question 24

What are possible sources for urea to urea cycle

Answer 24

Ammonia from intestine (bacterial digestion and amino acid metabolism)

Glutamine

Glutamate ( also from alanine)

Question 25

What happens in before urea cycle in mitochondria

Answer 25

Ammonia group (NH4+) is carboxylated and phosphated with carbamoyl phosphate synthetase I

Question 26

How many energy is required for the synthesis of carbomoyl phosphate

Answer 26

requires 2 ATPs ( one for enzymatic reaction) and one for addition of a phosphate group

Question 27

what happens in parallel to glutamate converting to alpha-ketoglutarate and donating its NH4+ group

Answer 27

Liver cells have TCA cycle itself. So they produce oxaloacetate that is converted to aspartate with aspertate aminotransferase Happens in mitochondria

Question 28

What happens to carbomyl phosphate

Answer 28

It combines with ornithine to yield citrulline with the help of ornitine trans-carbamoylase

Question 29

what happen to citrulline

Answer 29

It goes out of the mitochondria, where arginosuccinate synthetase through an intermediate converts to arginosuccinate

Question 30

What two things are required for the step of conversion citrulline to arginosuccinate

Answer 30

ATP And aspartate

Question 31

What happens to arginosuccinate

Answer 31

It is broken down into fumarate ( can be used in TCA) and arginine with arginosuccinase

Question 32

What happens to arginine

Answer 32

Using arginase, ornithine is synthesized producing urea

Question 33

Urea has how many amino groups and from what sources

Answer 33

2 amino groups 1 from glutamate ->citrulline (from various tissues) 1 from aspartate (TCA cycle in the liver)

Question 34

How urea cycle is regulated

Answer 34

When acetyl-CoA and glutamate are high - synthesize of N-acetylglutamate N-acetylglutamate has positive effect on carbomyl phosphate synthetase I

Question 35

Expression of urea cycle enzymes increases during

Answer 35

High protein diet ( some AA yield acetyl-CoA in the result of metabolism) Starvation,tumor, uncontrolled diabetes (body starts to metabolize muscles and protein in the body)

Question 36

Urea cycle cannot continue without

Answer 36

The TCA cycle running,because of aspartate, coming from oxaloacetate

Question 37

How fumarate is brought to TCA cycle in mitochodria from cytoplasm

Answer 37

Fumurate is converted to malate with fumarase , malate comes in mitochondria and it can be integrated in TCA cycle

Question 38

With what enzyme malate can be converted to oxaloacetate

Answer 38

Malate dehydrogenase

Question 39

Where fumurase and malate dehydrogenase are found

Answer 39

Both in cytoplasm and in mitochondria

Question 40

Amino acids yielding acetyl-CoA are

Answer 40

ketogenic

Question 41

amino acids yielding other end products are

Answer 41

Glucogenic

Question 42

After amino group is removed what happens

Answer 42

Carbon backbone serves as an intermediate for TCA cycle

Question 43

Amino acids that are both glucogenic and ketogenic

Answer 43

``` Isoleucine Pnenylalanine Threonine Tryptophan Tyrosine ```

Question 44

What amino acids are only ketogenic ( do not yield glucose)

Answer 44

Lysine and leucine

Question 45

Pyruvate can be obtained from what AAs

Answer 45

``` From alanine Tryptophan Cysteine Serine Glycine Threonine ```

Question 46

Acetyl-CoA can be obtained from what AAs

Answer 46

``` Tryptophan Lysine Phenylalanine Tyrosine Leucine Isoleucine Threonine ```

Question 47

alpha-ketogluterate can be obtained from what AAs

Answer 47

``` Proline Glutamate Glutamine Arginine Histidine ```

Question 48

Succinyl-CoA can be obtained from what amino acids

Answer 48

Methionine Isoleucine Threonine Valine

Question 49

Oxaloacetate can be obtained from what amino acids

Answer 49

Asparagine | Aspartate

Question 50

Fumurate can be obtained from what amino acids

Answer 50

Phenyalanine | Tyrosine

Question 51

What makes Leucine, Isoleucine and Valine a group

Answer 51

They are used as fuel in muscle/adipose tissue/brain They are called Branched chain amino acids

Question 52

Branched chain aminotransferase is only expressed in

Answer 52

Extra-hepatic cells ( outisde liver)

Question 53

How glutamate dehydrogenase is regulated

Answer 53

Increased by ADP and decreased by GTP

Question 54

How urea cycle is regulated

Answer 54

All four enzymes of urea cycle and carbomoyl phosphate synthase I are regulated by nutritional status (diet and starvation)

Question 55

High energy demand of urea cycle is offset

Answer 55

by NADH (2.5 ATP) when malate is cinverted back to oxaloacetate