Amino Acid Metabolism (Lec)

Question 1

repetitive process in which proteins are degraded and resynthesized

Answer 1

protein turnover

Question 2

T/F - The rate of protein synthesis is just sufficient to replace the protein being degraded

Answer 2

T (Leads to hydrolysis and resynthesis of 300-400 g of body protein eaach day

Question 3

state that results when the amount of nitrogen taken into the human body as protein equals the amount of nitrogen excreted from the body in waste materials

Answer 3

nitrogen balance

Question 4

amount of nitrogen in urine exceeds consumed amount, also results in tissue wasting

Answer 4

negative nitrogen imbalance

Question 5

rate of protein synthesis (anabolism) is more than protein degradation (catabolism)

Answer 5

positive nitrogen imbalance

Question 5

indicated by the synthesis of large amounts of tissue

Answer 5

positive nitrogen imbalance

Question 6

T/F - Amino acids are not stored by the body, unlike fats and
carbohydrates.

Answer 6

T (must either be obtained from the diet,
synthesized de novo, or produced from normal protein
degradation)

Question 7

T/F - Proteins can be used as an energy source, but is rarely
used as such.

Answer 7

T

Question 8

directed towards conserving tissues to the
greatest extent possible

Answer 8

Metabolism

Question 9

Digestion of protein compromises?

Answer 9

muscle

Question 10

where the mechanical breakdown of the proteins begins

Answer 10

teeth

Question 11

Protein digestion starts in the?

Answer 11

stomach

Question 12

Dietary protein stimulates the release of?

Answer 12

gastrin (a hormone that stimulates the stomach to
release gastric acid (hydrochloric acid) and pepsinogen
(Recall: zymogens))

Question 13

Functions of HCl:

Answer 13

Antiseptic - kill most bacteria
low pH will denature proteins
Acidic environment activates pepsinogen

Question 14

Pepsin affects the hydrolysis of __ of peptide bonds

Answer 14

10%

Question 15

stimulated by the passage of small
amounts of acidic content into the small intestine.

Answer 15

Secretin production
(promotes the secretion of pancreatic digestive
enzymes : trypsin, chymotrypsin, and carboxypeptidase in
their inactive forms)

Question 16

secreted by enterocytes - cells in the intestinal lining - and
further breakdown the remaining polypeptides into amino
acids.

Answer 16

Dipeptidase, tripeptidase, and aminopeptidase

Question 17

The pool of amino acids are then used to:

Answer 17

• synthesize proteins
• synthesize nitrogen-containing compounds (purines,
  pyrimidines)
• turned into glucose, glycogen, fatty acids, ketone bodies,
  water, or carbon dioxide (energy source)

Question 18

the state of which amino acids are especially catabolized
to yield the carbon skeleton and to form intermediates for
carbohydrate and lipid biosynthesis, which are then used as
an energy source.

Answer 18

In the starved state

Question 19

degraded to form ketone bodies ,
which degrade to acetyl-CoA or acetoacetyl-CoA

Answer 19

Ketogenic amino acids

Question 20

degraded to TCA intermediates,
which can then be used for glucose synthesis
(gluconeogenesis)

Answer 20

Gluocgenic amino acids

Question 21

Body protein is catabolized primarily in?

Answer 21

muscle and liver

Question 22

Amino acids released from proteins usually lose their amino
group through?

Answer 22

transamination or oxidative deamination

Question 23

T/F - Each amino acid has a unique degradation pathway

Answer 23

T

Question 24

two main mechanisms involved in the degradation
of amino acids:

Answer 24

transamination and oxidative deamination

Question 25

A reversible process

Answer 25

transamination

Question 25

Aminotransferase used as catalyst =, a-amino acids are converted to alpha Keto acid

Answer 25

Transamination

(Glutamate can be produced through
transamination, with a-ketoglutarate
as amino group acceptor)

Question 26

An alpha-amino acid is converted to
an alpha-keto acid, releasing an
amoonium ion

Answer 26

Oxidative Deamination

Question 27

Occurs in the liver and kidney
mitochondria

Answer 27

Oxidative Deamination

Question 28

Summary of Oxidative Deamination and the Transport of Ammonia to the Liver

Answer 28

the amino acids are broken down, while passing along the amino group with the help of enzymes until it can finally be sent to the urea cycle.

Tissues use glutamine synthase to combine ammonia with glutamate to form glutamine.

Glutamine is then transported in the blood to the liver.

Cleavage is then done by glutaminase to produce glutamate and free ammonia.

Question 29

Cahill Cycle

Answer 29

Alanine is transported by the blood to the liver
where it is converted to pyruvate
Connects with the Cori Cycle. Alanine serves as carrier of ammonia and of the carbons of pyruvate from skeletal muscle to liver (Cori)

Question 30

__ ATP molecules are used to produce ONE urea molecule

Answer 30

4

Question 31

Two molecules of ATP are used in the production of?

Answer 31

carbamoyl phosphate

Question 32

The equivalent of 2 ATP molecules are consumed in the __ step to produce AMP

Answer 32

2nd

Question 33

UREA CYLE

First Step : Carbomoyl
Group Transfer

Answer 33

Carbon dioxide and ammonia are
combined to form carbamoyl phosphate
with the help of carbamoyl phosphate
synthetase (formed in the
mitochondrial matrix)

The carbamoyl group of carbamoyl
phosphate is transferred to ornithine to
form citrulline

Question 34

UREA CYLE

Second Step : Citrulline Aspartate Condensation

Answer 34

Citrulline is then transported into the
cytosol, reacting with aspartate to form
argininosuccinate synthetase, utilizing
ATP.

This step makes use of the enzyme
argininosuccinate synthetase, utilizing
ATP.

Question 35

UREA CYLE

Third Step : Argininosuccinate
Cleavage

Answer 35

Argininosuccinate is cleaved to
arginine and fumarate by the enzyme
argininosuccinate lyase.

Question 36

UREA CYLE

Urea From
Arginine Hydrolysis

Answer 36

Hydrolysis of arginine produces urea
and regenerates ornithine under the
influence of the enzyme arginase.
The oxygen atom present in urea
comes from water. Ornithine is transported back to the
mitochondria, to be reused in the urea
cycle.

Question 37

PRODUCTS OF UREA CYCLE (8)

Answer 37

ORNITHINE
CARBAMOYL P.
CITRULLINE
ASPARTATE
ARGININOSUCCINATE
FUMARATE
ARGININE
UREA

Question 38

The fumarate produced is ultimately
converted to aspartate.

Aspartate reenters the urea cycle at Step 2
Both the urea cycle and the Krebs cycle
were discovered by Hans Adolf Krebs