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Medical Biochemistry > Topic 10: Amino Acid Catabolism > Flashcards

Topic 10: Amino Acid Catabolism Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the branched chain amino acids (BCAAs)?

A

Leucine (L), Isoleucine (I), Valine (V)

They are also hydrophobic with alliphatic side chains

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2
Q

What are the hydrophobic alliphatic side chain AAs?

A

Ala, Pro, Leu, Ile, Val, Met, Cys

APVLIMC

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3
Q

What are the hydrophobic aromatic side chain AAs?

A

Phe, Tyr, Trp

FYW

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4
Q

What are the hydrophilic uncharged side chain AAs?

They have OXYGEN (O or OH) in their side chains.

A

Ser, Thr, Asn, Gln

STNQ

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5
Q

What are the hydrophilic charged, BASIC side chain AAs?

Basic have long side chains with NITROGEN, normally have an accepted extra H+

A

His, Arg, Lys

HRK

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6
Q

What are the hydrophilic charged, ACIDIC side chain AAs?

Acidic have short side chains with a CARBOXY (COO-), normally missing an H+

A

Glu, Asp

DE

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7
Q

What is the simplest, uncharged, neither hydrophobic nor hydrophilic AA?

A

Gly

G

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8
Q

What other molecule is alanine very similar to?

A

PYRUVATE - pyruvate is alanine with an amino group

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9
Q

What are the two SULFUR containing AAs?

A

Cysteine and Methionine

So if you SEE SULFUR it is Cys or Met!!!

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10
Q

How could you recognize the aromatic AAs?

A

Phe is alanine with a phenyl group (aromatic ring)

Tyr is Phe with an added OH

Trp is the other one… has DOUBLE RING STRUCTURE

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11
Q

What AAs are in over-represented in muscle?

A

BCAAs – when muscle begins to break down in the body you will see elevated levels of these AAs

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12
Q

Where does primary AA digestion take place?

A

Small intestine: duodenum and jejunum

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13
Q

What type of enzymes are trypsin and chymotrypsin? (endo or exo)

A

ENDONUCLEASES

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14
Q

How are AAs absorbed into the enterocytes?

A

Na+ symport. They rely heavily on the sodium gradient. Even in times of low [AA] the high Na+ gradient will drive absorption from the lumen.

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15
Q

How does the Na+/K+ pump work?

A

3 Na+ OUT

2 K+ IN

uses ATP

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16
Q

How are AAs stored?

A

THEY ARE NOT STORED. If AAs are not needed they are broken down. Protein and Peptides are not storage molecules for AAs.

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17
Q

How is glutamate converted into its ketoacid? This reaction is reversible, what happens in reverse?

A

Glu via Glutamate-DH has amino group removed and water added to become alpha-KG

NADH is generated, H2O used, amino group generated

Reverse:
NADPH is used and NADP+ is generated, H2O generated, amino group put back on

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18
Q

What’s another name for Alanine Transferase (ALT)?

A

Serum Glutamate Pyruvate Transferase (SGPT)

19
Q

How does Alanine become Pyruvate?

A

Ala amino group removed by ALT, replaced with O and amino is given to a-KG. Ala becomes pyruvate and a-KG becomes Glu.

20
Q

What is another name for Aspartate Aminotransferase (AST)?

A

Serum Glutamate Oxaloacetate Transaminase (SGOT)

21
Q

How does Asp become OAA?

A

Asp amino group removed by AST, replaced with O and amino is given to a-KG. Asp becomes OAA and a-KG becomes Glu.

22
Q

How does Asp become Asn?

A

ATP generates Pyrophosphate (PPi) to drive reaction. Amino group is taken from Gln and added to Asp, H2O is removed, yields Asparagine. Glu is generated.

23
Q

What vitamin do AA transferases require?

A

Vitamin B6/Pyridoxine – Pyridoxyl Phosphate

24
Q

How do AA Oxidases directly remove amino groups?

A

FMN reduces AA to make FMNH2. (Requires B2/Riboflavin)
This generates H2O2.
AA Oxidase rips off the remaining NH2 to generate free ammonia.

25
Q

How can you get ammonia to the liver from muscle?

A

One way is put it on Glutamate (Glu) to make Glutamine –> go to liver –> recover Glu and give NH3 to UREA CYCLE

26
Q

What are the KETOGENIC ONLY AAs?

A

Leucine (Leu/L) and Lysine (Lys/K)

27
Q

What are the ketogenic AND gluconeogenic AAs?

A

Isoleucine, Phenylalanine, Tryptophan, Tyrosine

Ile, Phe, Trp, Tyr

I,F,W,Y

28
Q

What vitamin(s) is(are) needed to turn proprionate into succinyl-CoA?

A

Biotin/B7 and B12/Cobalamin

29
Q

What AA can make Acetyl CoA?

A

Leucine, Isoleucine and Tryptophan

30
Q

What AA can make Acetoacetyl CoA?

A

Leucine, Lysine, Phenylalanine, Tryptophan, Tyrosine

31
Q

What causes the Maple Syrup Urine Disease?

A

a defect in catabolism of the BCAAs, the second enzyme: alpha-KetoAcidDeHydrogenases

problem comes from the buildup of all 3 BCAAs a-KA’s but smell comes from ISOLEUCINE’s a-KA

32
Q

What causes the smell from MSUD?

A

ISOLEUCINE’s alpha-ketoacid, alpha-keto-beta-mehtylglutarate

33
Q

What are signs/symptoms of ketoacidosis?

A

Neuro Signs:

poor appetite, lethargy, irritability, mental retardation, physical disabilities, seizures, vomiting, coma, death

34
Q

How does MSUD/ketoacidosis affect neonate cattle?

A

Show signs within 24 Hours!! Death within 5 days

35
Q

What AA breakdown product causes the SWEATY FOOT smell?

A

Leucine’s breakdown product: isovaleryl CoA

36
Q

What AA breakdown product causes the CAT URINE smell? (this can make any animals urine smell like tomcat stank!)

A

Leucine’s breakdown product: beta-methylcrotonyl CoA

37
Q

What enzyme causes the blackening of bananas and potatoes?

A

TYROSINASE

Tyrosine is converted to melanin by tyrosinase.

38
Q

What cofactor does TYROSINASE require to function properly? Why do we care?

A

COPPER

We care because some soils are deficient in copper and animals can become deficient in this essential cofactor.

39
Q

What would you expect to see in a copper deficient animal?

A

some Loss of Hair Pigment, especially around the eyes. (spectacles!!)

Also: iron deficiency anemia, CT problems, Immune system problems, muscle loss, weakness, low protein, mood disorders, liver damage, hypothyroid, low body temp, and low NTs Epi, NorE, and Dopamine

40
Q

Why is Tyrosine conditionally essential?

A

Tyrosine is derived from Phenylalanine! If you can’t get Phe then you can’t make Tyr!!

Some animals have a deficiency in the enzyme Phenylalanine Hydroxylase (PAH) (puts the OH on Phe to make Tyr) and require Tyr as essential in their diet.

41
Q

What happens to animals deficient in PAH?

A

PKU!

Phe is converted to Phenylpyruvic acid (a phenylKETOACID) ==> PHENYLKETONURIA

Phenylpyruvate is then converted to Phenylacetate which can give urine and sweat a MOUSY smell

42
Q

Why do PKU patients lack pigment?

A

PKU can’t make Tyrosine which is the foundation for Melanin.

43
Q

How does Gln become Glu? This is a reversible reaction, how does it occur in reverse?

A

Glutaminase removes an amino group from Gln and adds H2O to make Glu.

Glutamine synthetase adds an amino group to Glu to make Gln. Uses ATP and generates water

Medical Biochemistry (26 decks)

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