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BioChem Exam 3 > CH 19: Catabolism of Protein and AA > Flashcards

CH 19: Catabolism of Protein and AA Flashcards

1
Q

Catabolism of Proteins

What is enzymatically hydrolyzed into AA?

A

Deitary proteins

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2
Q

Catabolism of Proteins

What is the primary proteolytic enzyme of the stomach?

A

Pepsin

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3
Q

Catabolism of Proteins

What does pepsin do and what is its optimal pH?

A

cuts proteins into peptides, optimal pH is 2

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4
Q

Catabolism of Proteins

What enzymes are in the small intestine?

The main place to absorb nutrients

A

Trypsin and Chymptrypsin

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5
Q

Catabolism of Proteins

What do Trypsin and Chymptrypsin do?

A

Cut proteins and larger peptides into smaller peptides

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6
Q

Catabolism of Proteins

What does Aminopeptidase do?

A

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

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7
Q

Catabolism of Proteins

What does Carboxypeptidase do?

A

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

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8
Q

Catabolism of Proteins

What is Ubiquitin?

A

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

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9
Q

Catabolism of Proteins

What is a degron?

A

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

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10
Q

Catabolism of Proteins

Where does Ubiquitin bind to?

A

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

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11
Q

Catabolism of Proteins

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

A

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

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12
Q

Catabolism of Proteins

What are Ubiquitin-tagged proteins digested by?

A

The Proteasome

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13
Q

Catabolism of Proteins

In the Proteasome, what does each piece do?

The Catalytic Core and the Stoppers (top and bottom)

A

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

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14
Q

Catabolism of AA

What are AA from protein degridation used for?

A

Primarily: protein synthesis in cells

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15
Q

Catabolism of AA

What is done to excess AA?

A

They are used as metabolic fuel.

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16
Q

Catabolism of AA

What is the first step of AA catabolism?

A

Deamination to remove the a-amino groups

a=alpha

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17
Q

Catabolism of AA

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

ureotelic = organisms that excrete waste nitrogen through urine

A

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

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18
Q

Catabolism of AA

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

A

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

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19
Q

Deamination

What is direct deamination to produce NH4+ called?

A

oxidative deamination

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20
Q

Deamination

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

A

dehydratases, pyruvate and NH4+

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21
Q

Deamination

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

A

dehydrates, a-ketobutyrate and NH4+

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22
Q

Deamination

Most deaminations go through what process?

A

Transdeamination

transdeamination is reverable (can also be used in synthesis)

23
Q

Deamination

What is transdeamination?

A

transamination + oxidative deamination

24
Q

Transdeamination

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

A

Aminotransferase

25
Q

Transdeamination

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

A

Glutamate dehydrogenase

26
Q

Transdeamination

What is the differnce between NAD+ and NADP+?

A

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

27
Q

Urea Cycle

What does it mean when organisms are Ammoniotolic?

A

They release ammonia into their environment

28
Q

Urea Cycle

How do birds and reptiles release excess nitrogen

A

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

29
Q

Urea Cycle

How do vertebrates and sharks release excess nitrogen?

A

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

30
Q

Urea Cycle

Where does the nitrogen for the urea cycle come from?

A

Carbamoyl phosphate

31
Q

Urea Cycle

Where are the enzymes that catalize this reaction distributed between?

A

mitrochondrial matrix and sytosol

32
Q

Urea Cycle

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

A

2: 1 from carbamoyl phosphate and 1 from aspartate

33
Q

Urea Cycle

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

A

3 ATP and 4 High-energy phosphate bonds

34
Q

Urea Cycle

How can 3 ATP break 4 bonds?

A

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

35
Q

Urea Cycle

Which AA are not used a building blocks of proteins?

A

Ornithine and citrulline

36
Q

Urea Cycle

How many steps does the urea cycle have?

A

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

37
Q

Urea Cycle

What enzyme catalyzes carbamoyl phosphate in ?

regulates the whole pathway

A

Carbomoyl phosphate synthesis I

38
Q

Urea Cycle

How many ATP molecules are hydrolysed for this reaction?

A

2

39
Q

Urea Cycle

What enzyme catalyzes the formation of citrulline?

A

Ornithine transcarbamoylase

40
Q

Urea Cycle

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

A

On the delta-amino group

other end from COO-

41
Q

Urea Cycle

Where does the citrulline pass into?

A

The cytosol

42
Q

Urea Cycle

What enzyme catalyzes the formation of argininosuccinate?

A

Argininosuccinate synthetase

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

43
Q

Urea Cycle

What two molecules make up argininosuccinate?

A

Citrulline and Aspartate

44
Q

Urea Cycle

What cleaves argininosuccinate and what results from it?

A

Argininosuccinase, Arginine and Fumarate

45
Q

Urea Cycle

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

A

Arginine

46
Q

Urea Cycle

What is fumarate then?

A

the carbon skeleton from aspartate

47
Q

Urea Cycle

What enzyme catalyzes the formation of urea?

A

arginase

48
Q

Urea Cycle

What other product is formed when Urea is formed?

A

Ornithine

49
Q

Carbon Skeletons are Intermediates of the Central Metabolic Pathway

What are Ketogenic AA converted into?

A

Ketone Bodies

50
Q

Carbon Skeletons are Intermediates of the Central Metabolic Pathway

What are glucogenic AA converted into?

A

glucose

51
Q

Carbon Skeletons are Intermediates of the Central Metabolic Pathway

Which AA are solely ketogenic?

A

Leu and Lys

52
Q

Carbon Skeletons are Intermediates of the Central Metabolic Pathway

Which AA are both ketogenic and glucogenic?

A

Ile, Phe, Trp, Tyr

53
Q

Carbon Skeletons are Intermediates of the Central Metabolic Pathway

Which AA are solely glucogenic?

A

All the rest

BioChem Exam 3 (7 decks)

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