M1 Biochemistry: Amino Acid Metabolism

Front 1

Excess ____ produced during the metabolism of amino acids is excreted
as_______ formed in the ______ Cycle.

Back 1

NH3, Urea , Urea Cycle

Front 2

What are the three general reactions involved in amino acid metabolism?

Back 2

- Transfer or removal of the NH3 group
- Removal of carboxyl group
- Transfer of Methyl groups

Front 3

Amino acids are generated from dietary protein and breakdown of intracellular protein over time. If amino acids are not needed for protein synthesis, they are catabolized. People with liver disease (cirrhosis, cancer, hepatitis) have a buildup of ________ in the blood.

Back 3

ammonium ion

Front 4

If the ammonium ion, NH4+ , is not needed for the biosynthesis of amino acids, nucleotides and biologogical amines, what cycle does it go to?

A. aspartate-arginine-succinate shunt of citric acid cycle
B. Urea cycle
C. TCA cycle

Back 4

B. Urea Cycle

note: 3 ATPs are needed to get rid of urea in the urea cycle so it's a pretty energy-costly cycle.

Front 5

What organ is the central organ responsible for most amino acid metabolism?

Back 5

Liver

Front 6

What amino acid plays a central role in amino acid metabolism?

A. Alanine
B. Asparganine
C. Glutamate
D. Glycine

Back 6

C. Glutamate

Front 7

If a person has a diet rich in protein and has excess amino acids, they cannot be stored and will be degraded. For example, people on the _________ diet eat abundant amounts of protein and very little carbohydrates.

Back 7

Atkins

Front 8

Under what circumstances must proteins be used for an energy source?

(ex. after a meal, fasting, etc.)

Back 8

during STARVATION or in patients with DIABETES when carbs are not available for energy

Front 9

Amino acids lose their amino groups forming ________ , which in turn undergo oxidation to ____ and ____.

Back 9

alpha-keto acids, CO2 and H2O

Front 10

When protein is broken down for ENERGY, then most of the energy is derived from [what checmical reaction of what intermediate]?

Back 10

oxidation of alpha-keto acids

Front 11

____________ (inactive Zymogen), secreted by chief cells, is converted to the active enzyme _______ by the low pH environment in the stomach.

Back 11

Pepsinogen --> pepsin

Front 12

Where does pepsin cleave ( amino / carboxyl terminal) ? And which amino acids?

Back 12

Pepsin cleaves on the amino-terminal side of aromatic amino residues Tyrosine, Phenylalanine
and Tryptophan.

Front 13

What type of cells make up the gastric glands in the stomach lining? What does each type of cell secrete?

Back 13

Gastric glands in stomach lining has parietal cells (secrete HCl) and chief cells (secrete pepsinogen).

Front 14

As the contents pass into the small intestine, the pancreas secretes
____________ to neutralize the acid and allow other protein
degrading enzymes to function.

Back 14

bicarbonate

Front 15

__________ is produced in the upper portion of the small intestine (duodenum) and inhibits gastric acid secretion & stomach motility; stimulates the pancreas to release bicarbonate ions and stimulates the gall bladder to secrete bile.

Back 15

Secretin.

Front 16

Tell me about secretin.
A. Where is it produced and released?
B. What does it stimulate?

Back 16

Secretin: produced in the upper portion of the small intestine (duodenum) and inhibits gastric acid secretion & stomach motility; stimulates the pancreas to release bicarbonate ions and stimulates the gall bladder to secrete bile.

Front 17

The zymogen Trypsinogen is converted to the active protease
called Trypsin by an enzyme called ___________________.

Back 17

enteropeptidase (enterokinase)

Front 18

Trypsin cleaves proteins at sites of [ two amino acids ] on the
[ carboxy / n -terminal ] side.

Back 18

Lysine and Arginine, carboxy

Front 19

Chymotrypsinogen is converted to
Chymotrypsin by ....

A. Trypsin
B. Elastase
C. Enteropeptidase (enterokinase)

Back 19

Trypsin

Front 20

Proelastase is converted to the active enzyme Elastase by__________ .

Back 20

Trypsin

Front 21

The zymogen Trypsinogen is converted to the active protease
called Trypsin by an enzyme called enteropeptidase (enterokinase).
Trypsin then cleaves proteins at sites of Lysine and Arginine on the
carboxy-terminal side. Chymotrypsinogen is converted to
Chymotrypsin by Trypsin.Proelastase is converted to the active enzyme Elastase by Trypsin. The Chymotrypsin then cleaves on the carboxy-terminal side of what three amino acids?

Back 21

Tyrosine, Tryptophan and Phenylalanine.

Front 22

Back 22

Front 23

Back 23

Front 24

Back 24

Front 25

During normal synthesis & degradation of cellular proteins…
some amino acids will undergo oxidative degradation if they [ are / are not ] needed for new protein

Back 25

some amino acids will undergo oxidative degradation if they ARE NOT needed for new protein

Front 26

Pepsinogen is changed to pepsin via....

Back 26

low pH (H+)

Front 27

Trypsinogen is changed to Trypsin via...

Back 27

Enteropeptidase

Front 28

Chymotrypsinogen is changed to Chymotrypsin via...

Back 28

Trypsin

Front 29

Proelastase is changed to elastase via...

Back 29

trypsin

Front 30

Procarboxypeptidases change to carboxypeptidases via....

Back 30

trypsin

Front 31

What are the essential amino acids?

Back 31

PVT TIM HALL

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

Front 32

What type of reaction is this and what is the enzyme involved?

Back 32

transamination. note: PLP, PYRIDOXAL PHOSPHATE, is a co-factor (aminated form)

Front 33

For amino acid metabolism reactions involving the amino group, what is a co-factor in the transamination reaction?

Back 33

PYRIDOXAL PHOSPHATE, PLP is a co-factor

(aminated form)

aminotransferase picks up amino group and transfers it to PLP then the amino group can be transferred to alpha-keto Glu or some other alpha keto acid.

Front 34

Regarding amino acid metabolism and reactions involving the amino group, what are the two types of deamination that can occur?

Back 34

Oxidative deamination or non-oxidative deamination.

In deamination, amino group is split off to form ammonia and an alpha ketoglutarate which can be oxidized for energy or used to form a new amino acid. Oxidative because losing ammonia. There is also a non-oxidative type.

Front 35

Regarding amino acid metabolism and reactions involving the amino group, ____________ refers to the direct removal of the NH4 group.

Back 35

deamidation

Front 36

Regarding amino acid metabolism and reactions involving the carboxyl group,
decarboxylation forms.... [ general category ]

Back 36

important biological amines

ex. Tyrosine -> Dopamine -> Norepinephrine ->epinephrine

Glutamate -> gamma-aminobutyrate (GABA)

Histidine -> Histamine

Tryptophan -> Serotonin

Front 37

Regarding amino acid metabolism and reactions involving the carboxyl group, general reaction for decarboxylation includes:
Specific decarboxylases,
also utilizing PLP as a co-factor, remove the carboxyl group from the amino acid thus forming new
________ and liberating ____

Back 37

biological amines and liberating CO2

Front 38

Regarding amino acid metabolism, reactions involving the carboxyl group include:
A. histidine --> __________
B. Tryptophan --> _________
C. Glutamate --> __________

Back 38

A. Histidine --> Histamine
B. Tryptophan --> Serotonin
C. Glutamate --> GABA

note: Tyrosine ---> dopamine

Front 39

Histamine is formed from ____________ by this General Reaction
of ______________ utilizing PLP as a co-factor.

Back 39

Histidine, decarboxylation.

Specific decarboxylases, utilizing PLP as
a co-factor, remove the carboxyl group from Histidine thus
forming a new biological amine and liberating CO2

Front 40

True or False:
Histamine stimulates
acid secretion in the stomach.

Back 40

True.

Cimetidine (Tagamet), an H2 receptor
antagonist and an analog of Histamine is used to treat duodenal ulcers because it blocks gastric acid secretion.

Front 41

___________ is a neurotransmitter in the brain and causes contraction of smooth muscle of arterioles
and bronchioles. ________ is also formed from Tryptophan and is
a "sleep inducing" molecule.

Ingestion of foods rich in Tryptophan (meat & milk) leads to sleepiness because the resulting items are
sleep-inducing. Tryptophan also reduces anxiety & depression and has been called "Nature's Prozac".

A. Melatonin; Serotonin
B. Serotonin; Melatonin

Back 41

B. Serotonin; Melatonin

Front 42

Spermine & Spermidine
are formed by __________ reactions…. They are involved in DNA packaging. Precursors are __________ and __________.

Back 42

decarboxylation; Methionine & Ornithine

Front 43

When the following are decarboxylated, what results?

A. Tyrosine
B. Tryptophan

Back 43

A. Dopamine
B. Serotonin

Front 44

Regarding amino acid metabolism reactions involving the carboxyl group, an example of this type of reaction would be the ultimate transfer of a methyl group
from Methionine to the methyl donor S-Adenosylmethionine (SAM).

Back 44

transmethylation. A variety of enzymes called methyl will then transfer the methyl group to other molecules.

Front 45

Regarding amino acid metabolism reactions involving the carboxyl group, in transmethylation, _____________ is an important methyl donor.

Back 45

SAM, or S-Adenosyl Methionine

Front 46

What three amino acids are NOT degraded in the liver?

Back 46

Leucine, Isoleucine & Valine. They are oxidized as fuels primarily in muscle, adipose, kidney & brain tissue. These tissues contain an enzyme called Branched-Chain Aminotransferase that converts these 3 amino acids to corresponding alpha keto acids.

A defect in the complete catabolism of branched chain amino acids leads
to the metabolic defect called Maple syrup urine disease.

Front 47

A defect in what leads to the metabolic defect called Maple syrup syndrome?

Back 47

A defect in the complete catabolism of branched chain amino acids (defect of branched-chain alpha keto acid dehydrogenase complex) leads to the metabolic defect called Maple syrup urine disease. (Leucine, Isoleucine & Valine, are not degraded in the liver but are oxidized as fuels primarily in muscle, adipose, kidney & brain tissue. These tissues contain an enzyme called Branched-Chain Aminotransferase that converts these 3 amino acids to corresponding alpha keto acids.)

Front 48

Which amino acid has a central role in many amino acid metabolic pathways?

A. Alanine
B. Glutamine
C. Glutamate
D. Methionine

Back 48

C. Glutamate

Front 49

Which amino acid has the most complex degradation pathway?

A. Tryptophan
B. Tyrosine
C. Threonine
D. Cysteine

Back 49

A. Tryptophan

(byproduct of the decarboxylation step is Serotonin)

Front 50

A deficiency of phenylalanine hydroxylase, the enzyme required
to convert Phenylalanine to Tyrosine, can lead to the pathologic condition known
as __________.

Back 50

phenylketonuria PKU

Front 51

Phenylketonuria PKU occurs when you are deficient in the enzyme ___________________ which turns amino acid _____________ into ______________.

Back 51

phenylalanine hydroxylase;
turns Phe intoTyr

Front 52

Name a few dietary sources of phenylalanine from the nine given in class.

Back 52

Cheeses
Nuts and seeds
Meat (excluding fat)
Poultry (excluding skin)
Fish, including shellfish
Milk
Eggs
Aspartame (nutrasweet)

Front 53

Back 53

Front 54

This is an inherited disorder that affects phenylalanine and tyrosine metabolism. This leads to excretion of homogentistic acid in the urine, which makes the urine appear black.

Back 54

Alkaptonuria.
Usually, the condition does not result in any serious ill effects

Front 55

Why is tetrahydrofolate important in amino acid metabolism?

Back 55

It is a key co-factor in many metabolic pathways of amino acids. It exists in several oxidation states and mediates the transfer of methyl groups. Meats and green veggies provide folic acid that is eventually reduced to tetrahydrofolate. N10-Tetrahydrofolate is the precursor of FORMATE that contributes 1 Carbon units to the ring structure of the Purines, too!

Front 56

True or False:

There are several pathologies associated with folate deficiency including affected tyrosine and phenylalanine metabolism which leads to an excess of homogentistic acid.

Back 56

False. Folate deficiency has symptoms of weakness, anemia and anorexia. The symptoms described are for alkaptonuria.

Front 57

Which of the following is FALSE:
A. Alcoholism may compound folate deficiency.
B. Folate deficiency has symptoms of anemia, weakness and anorexia.
C. Folic acid is needed to reduce the level of homocysteine in blood as a high level of these is associated with higher risk of coronary heart disease and stroke.
D. Women at increased risk for a baby with Ehler's-Down Syndrome should take an increased amount of folic acid 1-3 months before becoming pregnant.

Back 57

D. is false. Not Ehler's Down Syndrome but spina bifida.

Front 58

Ammonia itself cannot be transported to the liver for further
metabolic processing. Therefore it is incorporated into Glutamate by the
enzyme__________ to form the non-toxic amino acid _________.
This is a 2 stage reaction and requires ATP.

Back 58

Glutamine Synthetase to form Glutamine.

Bottom line: Glutamine is "blood friendly" whereas ammonia is NOT.

Front 59

What amino acid transports ammonium in the blood stream?

Back 59

Glutamine ;
It is then carried by the blood to the liver where in the mitochondria of the hepatocyte, the amide nitrogen is released as ammonia when the enzyme Glutaminase converts the Glutamine back into Glutamate

Front 60

___________ is a neutral, non-toxic compound and can readily pass through cell membranes whereas Glutamate cannot.

Back 60

Glutamine ;
It is then carried by the blood to the liver where in the mitochondria of the hepatocyte, the amide nitrogen is released as ammonia when the enzyme Glutaminase converts the Glutamine back into Glutamate

Front 61

What two amino acids have their own "cycles" due to their "blood-friendliness"?

Back 61

Glutamine and Alanine.

Front 62

In the _____ cycle, excess ammonia is incorporated into __________ and then transferred to ________ by the action of the enzyme _________________ to form _______. This amino acid, with no net charge at pH near 7, readily passes into the blood where it is transported to the liver. In a reversal of the reaction that took place in the muscle, this is converted back.

Back 62

ALANINE cycle, excess ammonia is incorporated into GLUTAMATE and then transferred to PYRUVATE by the action of enzyme ALANINE AMINOTRANSFERASE to form ALANINE.

Front 63

What cycle does this show?

Back 63

Alanine cycle.

Front 64

True or False:

The urea cycle takes place in the liver mitochondria only.

Back 64

FALSE. It takes place in both the liver mitochondria and the cytosol.

Front 65

How many ATP molecules are required for the production of 1 molecule of urea?

A. 1 ATP
B. 2 ATPs
C. 3 ATPs
D. 5 ATPs

Back 65

C. 3 ATPs

Front 66

Which of the following is false about the urea cycle:
A. Cycle begins in the liver mitochondria
B. Urea is produced in the cytosol
C. Aspartate donates a nitrogen directly to the urea molecule
D. Urea is hydrolyzed from arginine by arginase and excreted, leaving citrulline which goes back into the mitochondrial matrix
E. All of the above are true

Back 66

D. Urea IS hydrolyzed from arginine by arginase and excreted but what is left is ornithine, not citrulline, which goes back into the mitochondrial matrix.

Front 67

When is SAM the cofactor and when is PLP the cofactor?

Back 67

SAM = transmethylation reactions

PLP = decarboxylation, transamination,and deamination reactions