CH 19: Catabolism of Protein and AA

Question 1

Catabolism of Proteins

What is enzymatically hydrolyzed into AA?

Answer 1

Deitary proteins

Question 2

Catabolism of Proteins

What is the primary proteolytic enzyme of the stomach?

Answer 2

Pepsin

Question 3

Catabolism of Proteins

What does pepsin do and what is its optimal pH?

Answer 3

cuts proteins into peptides, optimal pH is 2

Question 4

Catabolism of Proteins

What enzymes are in the small intestine?

The main place to absorb nutrients

Answer 4

Trypsin and Chymptrypsin

Question 5

Catabolism of Proteins

What do Trypsin and Chymptrypsin do?

Answer 5

Cut proteins and larger peptides into smaller peptides

Question 6

Catabolism of Proteins

What does Aminopeptidase do?

Answer 6

Degrades peptides into amino acids by cutting the amino acid residue from the N-terminal 1-by-1

Question 7

Catabolism of Proteins

What does Carboxypeptidase do?

Answer 7

Degrades peptides into amino acids by cutting the amino acid residue from the C-terminal 1-by-1

Question 8

Catabolism of Proteins

What is Ubiquitin?

Answer 8

a small protein used to to tag cellular proteins so they can be identified as “targeted to destory”. They activate/connect to degrons on proteins

Question 9

Catabolism of Proteins

What is a degron?

Answer 9

Degrons are specifc areas of proteins that indicate if a protein should be degraded

Question 10

Catabolism of Proteins

Where does Ubiquitin bind to?

Answer 10

The C-terminal glycine covalently binds to lysine residues of the protein

Question 11

Catabolism of Proteins

What 3 enzymes are apart of the attachment of Ubiquitin to Proteins?

Answer 11

E1: activating enzyme
E2: conjugating enzyme
E3: protein ligase

Question 12

Catabolism of Proteins

What are Ubiquitin-tagged proteins digested by?

Answer 12

The Proteasome

Question 13

Catabolism of Proteins

In the Proteasome, what does each piece do?

The Catalytic Core and the Stoppers (top and bottom)

Answer 13

Stopper: recognizes the ubiquitin on the target protein and stops protease from digesting healthy AA
Catalytic core: proteases, they remove the ubiquitin, recyle it for further use, then degrade the protein attached

Question 14

Catabolism of AA

What are AA from protein degridation used for?

Answer 14

Primarily: protein synthesis in cells

Question 15

Catabolism of AA

What is done to excess AA?

Answer 15

They are used as metabolic fuel.

Question 16

Catabolism of AA

What is the first step of AA catabolism?

Answer 16

Deamination to remove the a-amino groups

a=alpha

Question 17

Catabolism of AA

In ureotelic organisms, what are excess amino groups converted into and how?

ureotelic = organisms that excrete waste nitrogen through urine

Answer 17

excess amino groups in the form of ammonium ions are converted into urea through the urea cycle

Question 18

Catabolism of AA

What is done with the remaining carbon skeleton after the removal of a-amino groups?

Answer 18

It is converted into major metabolic intermediates which are converted into glucose, fat, or oxidzed in the citric acid cycle.

Question 19

Deamination

What is direct deamination to produce NH4+ called?

Answer 19

oxidative deamination

Question 20

Deamination

Serine can be directly deaminated by …… to produce …..

Answer 20

dehydratases, pyruvate and NH4+

Question 21

Deamination

Threonine can be directly deaminated by …… to produce …..

Answer 21

dehydrates, a-ketobutyrate and NH4+

Question 22

Deamination

Most deaminations go through what process?

Answer 22

Transdeamination

transdeamination is reverable (can also be used in synthesis)

Question 23

Deamination

What is transdeamination?

Answer 23

transamination + oxidative deamination

Question 24

Transdeamination

What is used to transfer an amino group from an AA to a a-keto-acid?

Answer 24

Aminotransferase

Question 25

# Transdeamination What enzyme is used to catalyze an oxidative deamination using NAD+ or NADP+?

Answer 25

Glutamate dehydrogenase

Question 26

# Transdeamination What is the differnce between NAD+ and NADP+?

Answer 26

NADP+: has an extra phosphate, used in photosynthesis (usually anabolic reactions) NAD+: used in cellular respiration (usually catabolic reactions)

Question 27

# Urea Cycle What does it mean when organisms are Ammoniotolic?

Answer 27

They release ammonia into their environment

Question 28

# Urea Cycle How do birds and reptiles release excess nitrogen

Answer 28

In the form of Uric Acid (uricotelic, from purines)

Question 29

# Urea Cycle How do vertebrates and sharks release excess nitrogen?

Answer 29

In the form of urea (ureotolic, from AA, urea cycle)

Question 30

# Urea Cycle Where does the nitrogen for the urea cycle come from?

Answer 30

Carbamoyl phosphate

Question 31

# Urea Cycle Where are the enzymes that catalize this reaction distributed between?

Answer 31

mitrochondrial matrix and sytosol

Question 32

# Urea Cycle How many amino groups are needed to synthesize 1 molecule of Urea?

Answer 32

2: 1 from carbamoyl phosphate and 1 from aspartate

Question 33

# Urea Cycle How much ATP does synthesis of 1 molecule of urea take vs how many bonds need to be broken?

Answer 33

3 ATP and 4 High-energy phosphate bonds

Question 34

# Urea Cycle How can 3 ATP break 4 bonds?

Answer 34

One ATP gets converted to AMP which can break 2 high energy bonds and counts as 2 ATP

Question 35

# Urea Cycle Which AA are not used a building blocks of proteins?

Answer 35

Ornithine and citrulline

Question 36

# Urea Cycle How many steps does the urea cycle have?

Answer 36

Five 1. Formation of Carbamoyl Phosphate 2. Formation of Citrulline 3. Formation of Argununosuccinate 4. Formation of Arginine and Fumarate 5. Formation of Urea

Question 37

# Urea Cycle What enzyme catalyzes carbamoyl phosphate in ? | regulates the whole pathway

Answer 37

Carbomoyl phosphate synthesis I

Question 38

# Urea Cycle How many ATP molecules are hydrolysed for this reaction?

Answer 38

2

Question 39

# Urea Cycle What enzyme catalyzes the formation of citrulline?

Answer 39

Ornithine transcarbamoylase

Question 40

# Urea Cycle Where does the carbamoyl phosphate add onto the ornithine to form citrulline?

Answer 40

On the delta-amino group | other end from COO-

Question 41

# Urea Cycle Where does the citrulline pass into?

Answer 41

The cytosol

Question 42

# Urea Cycle What enzyme catalyzes the formation of argininosuccinate?

Answer 42

Argininosuccinate synthetase | Entry of second amino group, this is where 1 ATP breaks 2 bonds as AMP

Question 43

# Urea Cycle What two molecules make up argininosuccinate?

Answer 43

Citrulline and Aspartate

Question 44

# Urea Cycle What cleaves argininosuccinate and what results from it?

Answer 44

Argininosuccinase, Arginine and Fumarate

Question 45

# Urea Cycle Which of the two molcules is the precursor for Urea, Arginine or Fumarate?

Answer 45

Arginine

Question 46

# Urea Cycle What is fumarate then?

Answer 46

the carbon skeleton from aspartate

Question 47

# Urea Cycle What enzyme catalyzes the formation of urea?

Answer 47

arginase

Question 48

# Urea Cycle What other product is formed when Urea is formed?

Answer 48

Ornithine

Question 49

# Carbon Skeletons are Intermediates of the Central Metabolic Pathway What are Ketogenic AA converted into?

Answer 49

Ketone Bodies

Question 50

# Carbon Skeletons are Intermediates of the Central Metabolic Pathway What are glucogenic AA converted into?

Answer 50

glucose

Question 51

# Carbon Skeletons are Intermediates of the Central Metabolic Pathway Which AA are solely ketogenic?

Answer 51

Leu and Lys

Question 52

# Carbon Skeletons are Intermediates of the Central Metabolic Pathway Which AA are both ketogenic and glucogenic?

Answer 52

Ile, Phe, Trp, Tyr

Question 53

# Carbon Skeletons are Intermediates of the Central Metabolic Pathway Which AA are solely glucogenic?

Answer 53

All the rest