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Biochem Exam 3 > 31 - Amino Acid Catabolism > Flashcards

31 - Amino Acid Catabolism Flashcards

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1
Q

In mammals, amino acids derived from the degradation of dietary proteins or the turnover of cellular proteins are deaminated, and the ________ is used for biosynthetic pathways or excreted as urea. The remaining _______ skeletons are metabolized by energy conversion pathways to generate ATP, glucose, fatty acids, or ketone bodies.

A

Nitrogen

Carbon

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2
Q

The _______ has low pH that denatures (unfolds) proteins and activates pepsin (pepsin likes low pH).

A

Stomach

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3
Q

In the small intestines, enteropeptidase (cleaves in middle) in the duodenum cleaves trypsinogen, activating ________ (hydrolyzes peptide bonds).

A

Trypsin

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4
Q

In the small intestines, __________ are exopeptidases, which cleave or “chew” from the N-term (ends).

A

Aminopeptidases

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5
Q

In the small intestines, _________ break apart dipeptides.

A

Dipeptidases

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6
Q

After being broken down, amino acids, dipeptides, and tripeptides are able to be transported into the ______.

A

Cells

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7
Q

Cells have 2 primary structures that degrade proteins, which are…

A

Proteasome

Lysosome

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8
Q

The degrades proteins into bite-size chunks, not individual amino acids.

A

Proteasomes

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9
Q

______ Rule states that the ________ amino acid identity determines the rate of ubiquitination.

A

N-end

N-terminal

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10
Q

Proteins with these type of N-terminal residues last a long time (>20 hours).

A

Small and nonpolar

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11
Q

Proteins with these type of N-terminal residues last from 2-30 minutes (intrinsically destabilizing residues).

A

Large

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12
Q

Proteins with these type of N-terminal residues last from 3-30 minutes (destabilizing residues after chemical modification).

A

Polar/Charged

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13
Q

This is a protein that binds to the proteasome.

A

Ubiquitin

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14
Q

Ubiquitinated proteins are fragmented in the ________. Degradation is a form of regulation.

A

Proteasome

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15
Q

T/F. Ubiquitin is reusable.

A

True

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16
Q

The proteasome costs _______ to remove ubiquitin and degrade proteins.

A

ATP

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17
Q

The proteasome is an _______, and has a ______ piece that is the catalytic/proteolytic domain and ______ piece that is the regulatory domain.

A

ATPase
20S
19S

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18
Q

S stands for Svedberg or ________ units. S units are NOT proportional to size.

A

Sedimentation

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19
Q

20S + 19S = ______ proteasome

20S + 19S + 19S = ______ proteasome

A

26S

30S

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20
Q

Cytosolic ________ further degrade the peptide fragments produced in the proteasome. Eventually, we are left with a pool of individual amino acids.

A

Proteases

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21
Q

What are the 3 things we can do with individual amino acids?

A

Reduce - Dispose of nitrogen through the urea cycle
Reuse - Make new proteins
Recycle - Repurpose the carbon skeletons

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22
Q

What is the first thing we have to do before we can reduce or recycle amino acids?

A

Deaminate the amino acids (leaves behind carbon skeleton)

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23
Q

Most amino acids follow a 2-enzyme mechanism for deamination (normal pathway), which is…

A

Aminotransferase + Glutamate dehydrogenase

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24
Q

Serine and Threonine are deaminated by the action of a single enzyme (special pathway) called…

A

Dehydratase

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25
For deamination (normal pathway), aminotransferases and dehydratases are unique per amino acid but the coenzyme is always...
Pyridoxal phosphate
26
In direct deamination (serine and threonine only), water is removed through ________ then water is added back to remove the NH4+ in ________.
Dehydration | Deamination
27
Serine is deaminated to form...
Pyruvate
28
Threonine is deaminated to form...
Alpha-keotbutyrate (intermediate)
29
In the normal pathway of deamination, step 1 involves aminotransferases making _______.
Glutamate
30
T/F. The normal pathway of deamination is not reversible.
False. The pathway is very reversible.
31
There are two special aminotransferases, this is the name for the Aspartate Aminotransferase (AST).
Serum Glutamate-Oxaloacetate Transaminase (SGOT)
32
SGOT catalyzes the interconversion of _______ and _______.
Aspartate | Oxaloacetate
33
Alpha-amino acid + ___________ = ___________ + Glutamate (*Enzyme is aminotransferase)
Alpha-ketoglutarate | Alpha-keto acid
34
There are two special aminotransferases, this is the name for the Alanine Aminotransferase (ALT).
Serum Glutamate-Pyruvate Transaminase (SGPT) ***Not reversible
35
SGPT catalyzes the interconversions of ________ and ________.
Alanine | Pyruvate
36
In the normal pathway of deamination step 2, ________ _______ releases an ammonium (NH4+) ion.
Glutamate dehydrogenase
37
What is put into the reaction for step 2, and what is released?
NAD+; H2O | NADH; NH4+
38
What is formed at the end of the normal deamination pathway?
Alpha-ketoglutarate
39
What is the intermediate in step 2 of the normal deamination pathway?
Schiff-base intermediate (after NAD+, before H2O)
40
This is a toxic byproduct of amino acid catabolism.
NH4+
41
NH4+ can be converted to ______ in the liver, which is then transported to the kidneys to be excreted from the body.
Urea
42
Urea is composed of 4 pieces, which are...
2 amines 1 oxygen 1 carbon
43
Carbamoyl Phosphate Synthetase I (CPSI) combines CO2 and NH3 to make ________ ________, using 2 ATP. Creation of this is the committed step of the urea cycle.
Carbamoyl Phosphate
44
______ is an allosteric CPSI.
NAG
45
Ornithine and Citrulline are __________ amino acids.
Nonproteinogenic
46
________ must move into the mitochondria to combine with Carbamoyl Phosphate to form ________, which is then exported to the cytoplasm.
Ornithine | Citrulline
47
In the urea cycle, Aspartate donates an NH3 at the cost of 2 ATP-equivalents. The rest of Aspartate is ________, and the amino acid _______ is created (from aspartate and citrulline).
Fumarate | Arginine
48
In the urea cycle, Fumarate is converted to _________ which is used in the TCA cycle or it is converted back to Aspartate by the SGOT aminotransferase.
Oxaloacetate (OAA)
49
________ is created when urea is removed from Arginine. The addition of _______ when cleaving Arginine adds the final O of urea.
Ornithine | Water
50
At the end of the urea cycle, ornithine enters into the _________ and continues the cycle again.
Mitochondria
51
Adult humans produce about ______ grams of urea each day, accounting for about ______ percent of ATP consumption in the liver.
30 | 50
52
Aquatic animals can excrete _______ directly, so amphibians only express urea cycle enzymes at metamorphosis.
Ammonia
53
Amino acids can be degraded to 7 different molecules, which are...
``` Pyruvate OAA Alpha-ketoglutarate Succinyl-CoA Fumarate Acetyl-CoA Acetoacetate ```
54
Amino acids are ________ if they are degraded into intermediate molecules that can feed through gluconeogenesis to reform Glucose.
Glucogenic
55
Amino acids are ________ if they are degraded into intermediate molecules that can be used to create ketone bodies.
Ketogenic
56
Many amino acids can be degraded to more than one possible molecule. Sometimes, amino acids can be both ________ and ________.
Glucogenic | Ketogenic
57
In Fate 1, amino acid carbon skeletons are converted to _______.
Pyruvate
58
What are the amino acids in Fate 1 that are converted to pyruvate?
``` Serine Threonine Glycine Alanine Cysteine ``` ***CATSG
59
Serine is ________ directly to pyruvate.
Deaminated
60
Threonine is converted to ________ after deamination, which then converted to Serine and deaminated directly to pyruvate.
Glycine
61
Glycine is converted to ________ in a THF-dependent reaction. This is then deaminated directly to pyruvate.
Serine
62
Alanine is exchanged with pyruvate by the action of ______.
SGPT
63
Cysteine must be ________ and ________ to form pyruvate.
Deaminated | Desulfonated
64
In Fate 2, amino acid carbon skeletons are converted to ________.
Oxaloacetate (OAA)
65
What are the amino acids in Fate 2 that are converted to OAA?
Asparagine Aspartate ***ND
66
Asparagine is ________ first from the side chain to form _____ and Aspartate. Aspartate is then exchanged with OAA by the action of ______.
Deaminated NH4+ SGOT
67
In Fate 3, amino acid carbon skeletons are converted to...
Alpha-ketoglutarate
68
What are the amino acids in Fate 3 that are converted to Alpha-ketoglutarate?
``` Glutamine Proline Arginine Histidine Glutamate ``` ***PHREQ
69
Glutamine is deaminated first from the side chain to form ______ and ________. This is then converted to alpha-ketoglutarate by Glutamate Dehydrogenase.
NH4+ | Glutamate
70
Proline, Arginine, and Histidine can all be converted to ________, which is then converted to alpha-ketoglutarate by Glutamate Dehydrogenase.
Glutamate
71
Glutamate is converted to Alpha-ketoglutarate by...
Glutamate Dehydrogenase
72
In Fate 4, amino acid carbon skeletons are converted to _________.
Succinyl-CoA
73
Which amino acids are converted to Succinyl-CoA in Fate 4?
Methionine Valine Isoleucine ***MIV
74
Methionine, Valine, and Isoleucine can be converted into ________ in a B12-dependent pathway. Part of Methionine's conversion is through S-Adenosylmethionine (SAM). Propionyl-CoA is then converted to Succinyl-CoA.
Propionyl-CoA
75
Even though the conversion of Propionyl-CoA to Succinyl-CoA is used in the Beta-oxidation of fatty acids with an odd number of carbons, we care more that Succinyl-CoA can be used in the...
TCA Cycle
76
In Fate 5, amino acid carbon skeletons are converted to _______.
Fumarate
77
In Fate 6, amino acid carbon skeletons are converted to ________.
Acetyl-CoA
78
In Fate 7, amino acid carbon skeletons are converted to ________.
Acetoacetate
79
The remaining amino acids that follow Fates 5, 6, or 7 are more complex. Oftentimes they are split to multiple fates, such as these two amino acids...
Phenylalanine | Tyrosine
80
What are the ketogenic amino acids?
Leucine | Lysine
81
What are the BOTH glucogenic and ketogenic amino acids?
``` Isoleucine Phenylalanine Threonine Tryptophan Tyrosine ```

Biochem Exam 3 (10 decks)

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