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Biochemistry > Module 8 > Flashcards

Module 8 Flashcards

1
Q

• A state where the amount of nitrogen ingested each day is balanced by the amount excreted, resulting in no net change in the amount of body nitrogen

A

Nitrogen Balance

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2
Q

Nitrogen intake should equal nitrogen excretion

A

Nitrogen Metabolism

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3
Q
  • Intake > Excretion

* Net accumulation of proteins as in growth and pregnancy

A

Positive Nitrogen Balance

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4
Q

• Intake

A

Negative Nitrogen Balance

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5
Q

– refers to Protein synthesis and degradation
–300-400 g per day
– Amount of protein degraded and resynthesized from Amino Acid

A

Protein Turnover

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6
Q

–Sum of all free amino acids in cells and ECF
–Three possible sources:
•Degradation and turnover of body protein
•Dietary intake
•Synthesis of nonessential amino acids

A

Amino Acid Pool

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7
Q

Remember that proteins have __, so this is the logic behind high protein diets&raquo_space; protein comprise the calories in the diet, but are degraded eventually

A

no storage form

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8
Q

MARKING: __ binds to endogenous protein (proteins that are created intracellularly) that needs to be degraded by proteosome pathway ( GRABAGE disposal) energy dependent manner) – alpha carboxyl of glycine of ubiquitin to lysine amino group of protein substrate

A

Ubiquitin-proteosome mechanism (energy dependent)

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9
Q

> > degraded in the lysosomes (non-energy dependent manner)

A

Exogenous (extracellular)

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10
Q

Digestion of protein begins in the stomach with __

A

HCl and Pepsin

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11
Q

Digestion by pancreatic enzymes that are initially secreted as zymogens. __ is the common activator.

A

Trypsin

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12
Q

__ in the brush border liberate amino acids and dipeptides

A

Aminopeptidase

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13
Q

Free amino acids are absorbed by __

A

secondary active transport

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14
Q

Can you name other substances absorbed by secondary active transport in the small intestine?

A

glucose and galactose

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15
Q

After absorbing the products of protein digestion, which of the following products can you see inside enterocytes?

A

Dipeptides and tripeptides are also absorbed into the GIT, not just amino acids.

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16
Q
  • The presence of an alpha-amino group keeps amino acids safely locked away from oxidative breakdown
  • Removing the alpha amino group&raquo_space; OBLIGATORY step in the catabolism of all Amino Acid
A

Amino Acid Catabolism

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17
Q

Remember that the presence of an alpha amino group keeps the AA safe from breakdown&raquo_space; therefore its removal is an OBLIGATORY step in the catabolism of AA

A
  • 1st phase: throw away amino group sa urea cycle

* 2nd phase: recycle whats left of aa

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18
Q

First Phase of Amino Acid Catabolism

A

Removal of the α-amino group (a process called deamination) forming ammonia and a corresponding α-ketoacid

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19
Q

(First Phase of Amino Acid Catabolism)

What happens to ammonia?

A
  • Maybe excreted as free ammonia in urine and stool

- Majority is converted to urea before being excreted in urine (urea is the major disposal form of nitrogen)

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20
Q

Second Phase of Amino Acid Catabolism

A

Carbon skeletons of α-ketoacids are converted to common intermediates of energy-producing metabolic pathways

  • Glycolysis
  • Krebs Cycle
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21
Q

(Excretion of Excess Nitrogen)

–seen in telostean fish, which excrete highly toxic ammonia

A

Ammonotelic

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22
Q

(Excretion of Excess Nitrogen)

–seen in land animals, including humans, who excrete non-toxic, water-soluble urea

A

Ureotelic

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23
Q

(Excretion of Excess Nitrogen)

–seen in birds, which excrete uric acid as semisolid guano

A

Uricotelic

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24
Q

__ is relatively move toxic than uric acid, that’s why is has to be diluted in urine in the body. Uric acid is not very toxic, and may be concentrated to a semi-solid paste without causing toxic effects.

A

Urea

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25
Q

Phase 1: Removal of Nitrogen

•2 main steps in removing nitrogen from Amino Acids

A

–Transamination

–Oxidative Deamination

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26
Q

–Occurs in all cells of body

–All amino acids must transfer their amino groups to α-ketoglutarate to form glutamate

A

Transamination

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27
Q

These amino acids perform direct deamination

A

Lysine and Threonine

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28
Q 
(Transamination)
Enzymes: \_\_
• Found in the cytosol of cells throughout the body (liver, kidney, intestine)
•Alanine aminotransferase (ALT)
•Aspartate aminotransferase (AST)
A

Aminotransferases (formerly transaminases)

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29
Q

Co-enzyme of all transamination

A

Pyridoxal phosphate (Vitamin B6)

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30
Q

Remember the pairings:

A 
glutamate = α-ketoglutarate
alanine = pyruvate
aspartate = oxaloacetate
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31
Q
  • is also known as SGPT (serum glutamate:pyruvate transferase)
    Pyruvate and alanine interconvert with transamination
A

ALT

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32
Q
  • is also known as SGOT (serum glutamate:Oxaloacetate transferase)
  • Aspartate and oxaloacetate interconvert with transamination
A

AST

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33
Q

How are they useful as markers of liver disease?

A

Plasma AST and ALT are elevated in nearly all liver diseases&raquo_space; located intracellularly (never seen in plasma)

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34
Q

–Occurs in the liver and kidney only
–Only for glutamate
–Glutamate is oxidized and deaminated to yield free ammonia (NH3) which is used to make urea

A

Oxidative Deamination

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35
Q

Enzyme for Oxidative Deamination

A

glutamate dehydrogenase

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36
Q

Removal of Nitrogen from Amino Acids

A
  • Liberates the amino group as free ammonia and also alpha-keto acids&raquo_space; pathway for metabolism
  • Vitamin B6 cofactor
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37
Q

Transamination and Oxidative Deamination

A

Transamination only exchanges amino groups. NO FREE AMMONIA.&raquo_space; Oxidative deamination actually LIBERATES AMMONIA.&raquo_space; Ammonia enters the UREA CYCLE to become urea.

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38
Q

(Removal of Nitrogen)

• Excess nitrogen from the peripheral tissues can also reach the liver through __

A

glutamine

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39
Q

Glutamate + Ammonia&raquo_space; Glutamine (Enzyme: __)

A

Glutamine Synthetase

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40
Q

What about the muscle?

A
  • Excess nitrogen from the peripheral tissues can also reach the liver through alanine, especially in muscle

*Pyruvate + Glutamate&raquo_space; Alanine + α-ketoglutarate
Enzyme: alanine aminotransferase (ALT or SGPT)

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41
Q
  • Deaminates glutamine to produce ammonium ion (NH4+), which is excreted from the body
  • Present in two tissues: kidneys and small intestines
A

Glutaminase

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42
Q

What do you call the metabolic pathway whereby lactate produced during anaerobic respiration in muscles is reconverted to glucose in the liver?

A

Cori Cycle

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43
Q

Where can you find Glutaminase?

A
  1. Kidneys - eliminates ammonium in urine
  2. Small Intestine - ammonium ion sent to the liver via the portal circulation for the urea cycle
  3. Liver
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44
Q

Where can you find Glutamate?

A
  1. Liver
  2. Muscle
  3. CNS
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45
Q

Glutamine Synthetase vs Glutaminase

A

Glutamine Synthetase - for transporting ammonia

Glutaminase - for getting rid of ammonium ions

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46
Q
  • Urea is the major disposal form of amino groups (accounts for 90% of N-containing compounds in the urine)
  • Pathway for removal of nitrogenous waste products in the body
  • Present only in the liver
  • Urea is formed in the liver&raquo_space; enters the blood&raquo_space; excreted in urine
A

Urea Cycle

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47
Q

__ is the immediate precursor of ammonia and aspartate nitrogen

A

Glutamate

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48
Q

Urea Cycle

A
  1. NH3 from free ammonia
  2. NH3 from aspartate
  3. Carbon from CO2
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49
Q

(Urea Cycle)

1st 2 reactions (leading to synthesis of urea) occur in the mitochondria and the rest are in the __

A

cytosol

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50
Q

(Urea Cycle)

1. CO2 + NH2&raquo_space;> __ (enzyme: Carbamoyl Phosphate Synthethase I)

A

Carbamoyl phosphate

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51
Q

(Urea Cycle)

2. Ornithine + Carbamoyl Phosphate = __ (enxyme: Ornithine Transcarbamoylase)

A

Citrulline

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52
Q

(Urea Cycle)

Citrulline + Aspartate = __ (enzyme: Arganinosuccinate Synthetase_

A

Argininosuccinate

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53
Q

(Urea Cycle)

Argininosuccinate = __ (enzyme: Argininosuccinase)

A

Fumarate + Arginine

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54
Q

(Urea Cycle)

Arginine = __ (enzyme: Arginase)

A

Urea + Ornithine

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55
Q

Urea Cycle: Substrates/Raw Materials

A

–NH3, aspartate, and CO2

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56
Q

Urea Cycle: Rate Limiting Step

A

–Reaction: CO2 + NH3&raquo_space; carbamoyl phosphate

–Enzyme: Carbamoyl Phosphate Synthetase I (CPS-I)

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57
Q

Urea Cycle: Energy Requirement

A

4 moles of ATP

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58
Q

Urea Cycle: Co-Factors

A
  1. N-acetylglutamate – the allosteric activator of CPS-I

2. Biotin – for carboxylation reaction

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59
Q

What will happen if there is an increase amounts of N-acetylglutamate?

A

More urea because it activates the rate-limiting step

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60
Q

Fate of Urea

A
  • Diffuses from the liver and is transported in the blood to the kidneys, where it is filtered and excreted in the urine
  • A portion of urea diffuses from the blood into the intestine, and is cleaved to CO2 and NH3 by bacterial urease
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61
Q

Hereditary Hyperammonemia: Enzyme defect in the urea cycle

A
  • Type 1: carbamoyl phosphate synthetase I

* Type 2: ornithine transcarbamoylase

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62
Q

– Causes hyperammonemia, elevated blood glutamine, decreased BUN
– Presents with lethargy, vomiting, hyperventilation, convulsions, cerebral edema, coma, death
– Treat with low protein diet, administration of sodium benzoate or phenylpyruvate to capture and excrete excess nitrogen

A

Hereditary Hyperammonemia

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63
Q

– Compromised liver function

– Presents with tremors, slurring of speech, somnolence, vomiting, cerebral edema and blurring of vision

A

Acquired Hyperammonemia

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64
Q

Ketogenic

A
  • Leucine

- Lysine

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65
Q

Ketogenic and Glucogenic

A 
FYI, Double You = FYIW
F - Phenylalanine
Y - Tyrosine
I - Isoleucine
W - Tryptophan
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66
Q

Amino Acids whose catabolism yields pyruvate or intermediates of the Krebs Cycle:

  1. glucose (via gluconeogenesis)
  2. glycogen in muscle or liver
A

Glucogenic

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67
Q

α-ketoglutarate

A

Glutamine, GLUTAMATE, Proline, Arginine, Histidine

68
Q

Pyruvate

A

ALANINE, Serine, Glycine, Cysteine, Threonine, Tryptophan

69
Q

Fumarate

A

Phenylalanine, Tyrosine

70
Q

Succinyl CoA

A

Methionine, Valine, Isoleucine, Threonine

71
Q

synthesized from transamination of α-ketoacids

A

Alanine, Aspartate, Glutamate

72
Q

synthesized from amidation of glutamate and aspartate

A

Glutamine, Asparagine

73
Q

synthesized from glutamate

A

Proline

74
Q

made from methionine and serine

A

Cysteine

75
Q

made from 3-phosphoglycerate

A

Serine

76
Q

made from serine

A

Glycine

77
Q

made from phenylalanine

A

Tyrosine

78
Q

(Raw Material in Biosynthesis)

heme, purines, creatine, also conjugated to bile acids

A

Glycine

79
Q

(Raw Material in Biosynthesis)

phospholipid and sphingolipid, purines, thymine

A

Serine

80
Q

(Raw Material in Biosynthesis)

GABA

A

Glutamate

81
Q

(Raw Material in Biosynthesis)

thioethanolamine of CoA, taurine

A

Cysteine

82
Q

(Raw Material in Biosynthesis)

histamine

A

Histidine

83
Q

(Raw Material in Biosynthesis)

creatinine, polyamines, nitric oxide

A

Arginine

84
Q

(Raw Material in Biosynthesis)

serotonin, niacin, melatonin

A

Tryptophan

85
Q

(Raw Material in Biosynthesis)

catecholamines, thyroid hormones (T3 and T4), melanin

A

Tyrosine

86
Q

• Caused by a deficiency of phenylalanine hydroxylase
• Phenylalanine&raquo_space; tyrosine
• there is ↓phenylalanine hydroxylase or ↓tetrahydrobiopterin cofactor
•Tyrosine becomes essential and phenylalanine builds up, leading to excess phenylketones in urine:
–Phenylacetate
–Phenyllactate
–Phenylpyruvate

A

Phenylketonuria

87
Q

Phenylketonuria

A
  • Findings: mental retardation, growth retardation, fair skin, eczema, musty body odor
  • Treatment: ↓phenylalanine and ↑tyrosine in diet
  • Decreased thyroid hormones = mental and growth retardation
  • Decreased melanin = albinism
88
Q

Tyrosine derivatives

A
  • True - Tyrosine
  • Love – L-Dopa
  • Does - Dopamine
  • Not - Norepinephrine
  • Exist - Epinephrine
  • To – Thyroid hormones
  • Me – Melanin (not melatonin)
  • Melatonin is derived from serotonin
89
Q
  • Congenital deficiency of homogentisic acid oxidase in the degradative pathway of tyrosine
  • Resulting alkapton bodies cause urine to turn black on standing
  • Also, the connective tissue is dark (ochronosis)
  • Benign disease but may have debilitating arthralgias
  • Tx: diet low in protein (phenylalanine and tyrosine)
A

Alkaptonuria

90
Q
  • Blocked degradation of branched amino acids (isoleucine, valine, leucine) due to a deficiency in branched chain α-ketoacid dehydrogenase
  • Causes an ↑α-ketoacid in the blood, especially leucine
  • Causes severe CNS defects, mental retardation and death
A

Maple Syrup Urine Disease

91
Q

Amino Acid Catabolism: 2 stages

A
  1. Removal of α-amino group

2. Degradation of remaining carbon skeleton

92
Q

Why Glutamate is the final acceptor in Transamination?

A

Glutamate is the only amino acid capable for oxydative deamination

93
Q

Removal of α-amino nitrogen by transamination is the first catabolic reaction, EXCEPT for the following amino acids:

A
  1. Proline
  2. Hydroxyproline
  3. Threonine
  4. Lysine
94
Q

__ are converted to Citric Acid Cycle intermediates or their precursors so that they can be metabolized to CO2 and H2O or used in gluconeogenesis. Accounts for 10 – 15% of metabolic energy generated by animals

A

Carbon Skeletons of Amino Acids

95
Q

CLASSIFICATION OF AMINO ACIDS (based on degradation)

A
  1. GLUCOGENIC AMINO ACIDS

2. KETOGENIC AMINO ACIDS

96
Q

– Carbon skeletons are degraded to pyruvate,

α-ketoglutarate, succinyl CoA, fumarate or oxaloacetate and are therefore glucose precursors

A

GLUCOGENIC AMINO ACIDS

97
Q

– Carbon skeletons are broken down to acetyl CoA or acetoacetate and can thus be converted to fatty acids or ketone bodies

A

KETOGENIC AMINO ACIDS

98
Q

Which one is a purely ketogenic amino acid?

A

Leucine

99
Q

AMINO ACIDS CONVERTED TO PYRUVATE

A
  1. ALANINE
  2. Cysteine
  3. Glycine
  4. Serine
  5. Threonine
  6. Tryptophan
100
Q

AMINO ACIDS CONVERTED TO OXALOACETATE

A
  1. ASPARTATE

2. ASPARAGINE

101
Q

AMINO ACIDS CONVERTED TO α-KETOGLUTARATE

A
  1. Arginine
  2. GLUTAMATE
  3. GLUTAMINE
  4. Histidine
  5. PROLINE
102
Q

AMINO ACIDS CONVERTED TO FUMARATE

A
  • ASPARTATE
  • TYROSINE
  • PHENYLALANINE
103
Q

AMINO ACIDS CONVERTED TO SUCCINYL-CoA

A
  1. Isoleucine
  2. Methionine
  3. Valine
104
Q

AMINO ACIDS DEGRADED TO ACETYL CoA

AND/OR ACETOACETATE

A
  1. Isoleucine
  2. Leucine
  3. Threonine
  4. Lysine
  5. Phenylalanine
  6. Tryptophan
  7. Tyrosine
105
Q

• Transamination forms pyruvate which can then be decarboxylated to acetyl CoA

A

ALANINE

106
Q

• Splits to CO2 and NH4+ and N5, N10 Methylene
Tetrahydrofolaten
• Transamination of glycine to glyoxylate with Glu or Ala

A

GLYCINE

107
Q
  • Degraded to glycine (tetrahydrofolate) and N5, N10 methylene tetrahydrofolate
  • Can be converted directly to pyruvate
A

SERINE

108
Q

• carrier of 1 carbon unit(which is usually from Serine)

A

Folic Acid (Tetrahydrofolate)

109
Q

CYSTINE AND CYSTEINE

A

• Cystine – converted to cysteine
• Cysteine – catabolized via 2 pathways
1. Direct oxidative pathway
2. Transamination pathway

110
Q

• 2 cysteine residue that is linked by a disulfide bond will result to __

A

CYSTINE

111
Q

Cysteine: Catabolized via 2 pathways

A
  1. Direct oxidative pathway - 1st step is OXIDATION

2. Transamination pathway - 1st step is TRANSAMINATION

112
Q

• Cleaved to acetaldehyde and glycine; acetaldehyde is then oxidized to acetate which is then converted to acetyl CoA

A

THREONINE

113
Q

• Transamination forms oxaloacetate

A

ASPARTATE

114
Q

• Undergoes hydrolysis to aspartate

A

ASPARAGINE

115
Q

• Transamination forms α-ketoglutarate

A

GLUTAMATE

116
Q

• Undergoes hydrolysis to glutamate

A

GLUTAMINE

117
Q

• Amino acid that can be synthesize through nitrogen fixation (an inorganic nitrogen that is attached to organic molecule)

A

Glutamine and Glutamate

118
Q

• Oxidized to dehydroproline which adds water forming
glutamate γ-semialdehyde;
• This is then oxidized to glutamate and transaminated to
α-ketoglutarate

A

PROLINE

119
Q

• Converted to ornithine which then undergo
transamination to glutamate γ-semialdehyde
• Intermediate of the Urea cycle

A

ARGININE

120
Q

• Non-oxidativelydeaminated then hydrated and its imidazole ring cleaved to form Nformiminoglutamate
(FIGLU); formimino group is then transferred to TH4 to form N-formiminoTH4 and
glutamate

A

HISTIDINE

121
Q

Excretion of FIGLU following a dose of histidine can be used to detect __

A

folic acid deficiency

122
Q

• First reaction in its degradation is its hydroxylation to tyrosine

A

PHENYLALANINE

123
Q

• Transaminated to p-hydroxyphenyl-pyruvate followed by concerted ring hydroxylation and side chain migration to form homogentisate with ascorbate as reductant; aromatic ring opens and is hydrolyzed to fumarate and acetoacetate

A

TYROSINE

124
Q

• from argininosuccinate to fumarate (from the urea cycle)

A

ASPARTATE

125
Q

• Condenses with ATP to form S-adenosylmethionine

SAM, an important methyl donor

A

METHIONINE

126
Q

• Removal of methyl group forms
S-adenosylhomocysteinewhich is hydrolyzed to adenosine and homocysteine
• Homocysteine combines to serine to yield cystathione which subsequently forms cysteine and α-ketobutyrate
• α-Ketobutyrate is degraded to propionyl CoA and then to succinyl CoA

A

METHIONINE

127
Q

• is converted to propionyl CoA

A

ISOLEUCINE

128
Q

• is converted to methylmalonyl CoA

A

VALINE

129
Q
  • Has several pathways for degradation but the pathway that proceeds VIA FORMATION OF SACCHAROPINE predominates in mammalian liver
  • Pathway involves transamination, oxidative decarboxylation and reactions similar to fatty acyl CoA oxidation
A

LYSINE

130
Q

• Carbon atoms of side chain and aromatic ring completely degraded via KYNURENINE-ANTHRANILATE PATHWAY
• Initial reaction involves cleavage of indole ring
with incorporation of 2 atoms of molecular
oxygen by tryptophan oxygenase

A

TRYPTOPHAN

131
Q
  • An iron porphyrin metalloprotein
  • Inducible in the liver by adrenal corticosteroid and by tryptophan
  • Feedback inhibited by nicotinic acid derivatives including NADPH
A

TRYPTOPHAN OXYGENASE

132
Q
  • Purely ketogenic amino acid
  • Degraded to HMG CoA which is converted to acetoacetate and acetyl CoA
  • To be discuss together with the other branched chain amino acids
A

LEUCINE

133
Q

BRANCHED CHAIN AMINO ACIDS

A
  1. Valine
  2. Isoleucine
  3. Leucine
134
Q
  • Shares the same first 3 reactions that employs common enzymes
  • Resulting products are then catabolized by distinct pathways
A

BRANCHED CHAIN AMINO ACIDS

135
Q

SAME FIRST 3 REACTIONS SHARED BY BRANCHED CHAIN AMINO ACIDS

A
  1. Transamination to corresponding α-ketoacids
  2. Oxidative decarboxylation to corresponding acyl CoA
  3. Dehydrogenation by FAD to form a double bond
136
Q
  • Almost always associated with amino acid catabolism rather than amino acid biosynthesis
  • Sufficient amounts of all amino acids – whether essential or non-essential – are present in a well-balanced diet
  • Failure to catabolize amino acids will result in accumulation of the amino acid and its metabolites to the point that they become toxic
A

AMINO ACIDOPATHIES

137
Q

–Defect in the catabolism of tyrosine
–Deficiency of enzyme, homogentisate oxidase
–Most striking manifestation is the darkening of urine that stands in air due to the presence of homogentisate
–Later develops arthritis and connective tissue pigmentation

A

Alkaptonuria

138
Q

–Results from the inability to convert phenylalanine to tyrosine
–Defect may be in the enzymes phenylalanine hydroxylase (classic PKU), tetrahydrobiopterine synthase or dihydrobiopterine reductase
–Major consequence is mental retardation
–Treatment is a diet low in phenylalanine

A

Phenylketonuria

139
Q

–Defect in the intestinal and renal transport of neutral amino acids including tryptophan
–Manifest with pellagra-like signs and symptoms because of limited conversion of tryptophan to niacin

A

Hartnup Disease

140
Q

– Defect is absence of branched chain α-Ketoacid Dehydrogenase Complex (resembles pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complexes)
– Odor of urine resembles maple syrup or burnt sugar
– Brain damage develops unless promptly treated with a diet low in BCAA

A

Maple Syrup Urine Disease

141
Q

• Used primarily as building blocks for protein synthesis
•Also serves precursors of many biologically important compounds such as heme, purines, pyrimidines, neurotransmitters (serotonin, epinephrine, norepinephrine,
dopamine, GABA) and hormones (thyroid hormones)

A

AMINO ACIDS

142
Q
  • Constitutes a major fraction of free amino acids in plasma together with glycine
  • Serves as carrier of ammonia and the carbons of pyruvate from the skeletal muscles to the liver
A

ALANINE

143
Q
  • Carrier of nitrogen atoms in urea biosynthesis
  • Guanidino group incorporated into creatine
  • Following conversion to ornithine, its carbon skeleton becomes polyamines – putrescine and spermine
A

ARGININE

144
Q

Converted to nitric oxide (NO) by NO synthase

• Nitric oxide – serves as neurotransmitter, smooth muscle relaxant and vasodilator

A

ARGININE

145
Q
  • Participates in the biosynthesis of COENZYME A by reacting with pantothenate
  • Converted to TAURINE which reacts with cholyl CoA to form the bile acid taurocholic acid
  • Component of glutathione
A

CYSTEINE

146
Q
  • Involved in the degradation of hydrogen peroxide
  • Acts as conjugating agent of many electrophilic xenobiotics which are potential carcinogens to facilitate their excretion
  • Important intracellular anti-oxidant and reductant helping to maintain essential -SH groups of enzymes in their reduced state
A

GLUTATHIONE

147
Q

• Forms water-soluble conjugates that facilitates the excretion of many metabolites and drugs
*Glycocholic acid, a bile acid
*Hippuric acid formed from the food additive
benzoate

A

GLYCINE

148
Q
  • Incorporated into creatine
  • Incorporated into the pyrrole rings and methylene bridge carbons of heme
  • Forms C4, C5 and N7 of the purine ring
A

GLYCINE

149
Q

• Decarboxyled to histamine

*Histamine mediates allergic reactions and gastric secretion

A

HISTIDINE

150
Q

Forms carnosine and homocarnosine
• Carnosine and homocarnosine are major constituents of
excitable tissues, brain and skeletal muscles

A

HISTIDINE

151
Q
  • has been shown to play significant role in muscle pH regulation
  • Intramuscular acidosis has been attributed to be one of the main causes of fatigue during intense exercise
  • Increase muscle carnosine content and therefore total muscle buffer capacity has been hypothesized to improve physical performance during high-intensity exercise
A

CARNOSINE

152
Q
  • Converted to S-adenosylmethionine (SAM), the principal source of methyl groups in the body
  • Following decarboxylation of Sadenosyl-methionine, three carbons and the alpha-amino group contribute to the biosynthesis of the polyamines – spermine and spermidine
A

METHIONINE

153
Q
  • Because of their multiple positive charges, polyamines readily associate with DNA and RNA
  • Function in cell proliferation and growth; growth factor for cultured mammalian cells; stabilize intact cells, subcellular organelles and membranes
  • Have hypothermic and hypotensive actions
A

SPERMINE AND SPERMIDINE

154
Q
  • Participates in the biosynthesis of sphingosine
  • As source of the carbon units carried by tetrahydrofolate, provides C2 and C8 of purines and methyl group of thymine
  • is the most important source of substituted folate for biosynthetic reactions
A

SERINE

155
Q

• Following hydroxylation and subsequent decarboxylation forms serotonin, a potent vasoconstrictor and stimulator of smooth muscle contraction

A

TRYPTOPHAN

156
Q

• N-acetylation of serotonin followed by O-methylation in the pineal gland forms melatonin
*Melatonin – involve in the regulation of sleep wake pattern

A

TRYPTOPHAN

157
Q
  • Converted by neural tissues to dopamine, epinephrine and norepinephrine
  • Forms melanin
  • Precursor of triiodothyronine and thyroxine
A

TYROSINE

158
Q

• Decarboxylated to form gaminobutyrate (GABA), an inhibitory neurotransmitter

A

GLUTAMATE

159
Q

• Undergoes phosphorylation ( to phosphoserine, phosphothreonine and phosphotyrosine) and dephosphorylation in enzymes as a means of regulation of its activity and in proteins that participate in signal transduction cascades

A

SERINE, THREONINE AND TYROSINE

160
Q

• is synthesized from, glycine, arginine and methionine

A

Creatine

161
Q

• is formed by the irreversible non-enzymatic dehydration of creatine phosphate in muscles

A

Creatinine

162
Q
  • Biosynthesis and catabolism occurs in the mitochondria
  • Formed from dimethylglycine
  • Catabolized back to glycine; reaction serves as source of one-carbon units
A

SARCOSINE

163
Q
  • Are non-α-amino acids present in tissues in free forms

* Are formed during catabolism of the pyrimidines uracil and thymine

A

β-ALANINE AND β-AMINOISOBUTYRATE

164
Q
  • Consist of carnosine and anserine
  • Activate myosine ATPase, chelate copper and enhance copper uptake
  • Buffers the pH of anaerobically contracting skeletal muscles
A

β-ALANYL DIPEPTIDES

165
Q

• is synthesized from arginine, glycine and methionine

A

Creatinine

166
Q

• is made up of the amino acids – glutamate, cysteine and glycine

A

Glutathione

167
Q

is a precursor for the synthesis of sphingosine and the source of the onecarbon units carries by tetrahydrofolate

A

Serine

Biochemistry (9 decks)

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