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Biochemistry- Unit Two
Protein (T Pierce)
49
Medical
Post-Graduate
02/27/2009

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Cards

Term
Define nitrogen balance
Definition
  • relationship between dietary uptake of nitrogenous compounds and loss of nitrogenous compounds
  • normal: intake = loss
Term
Compounds through which nitrogen is lost
Definition
  • creatinine
  • bilirubin
  • uric acid
  • ammonia
  • urea
Term
Describe negative nitrogen balance
Definition
  • intake is less than loss
  • results in catabolism of body proteins
  • if not corrected, leads to death
Term
Describe when positive nitrogen balance it is needed
Definition
  • growth
  • pregnancy and lactation
  • recovery from surgery
  • recovery from illness
Term
Define what is ment by quatity of usable protein. Average need value?
Definition
both total amount and DIGESTIBILITY of protein (usually need 800 mg of protein/day/kg body weight)
Term
Example of protein that is not digestable and usable
Definition
keratin
Term
Define quality of protein
Definition
AA content
Term
Define essential AA
Definition
AA that cannot be synthesized
Term
What are the essential AA's?
Definition
  • Leu
  • Ile
  • Val
  • Met
  • Thr
  • Lys
  • Phe
  • Trp

Cant make aromatic ring, cant do the branching

Term
Describe the starndards used for the quaility of protein
Definition
  • compare to casein (in milk) and ovalbumin (in egg white)
  • high quality- mix of all the AA we need and in the right proportions
  • low quality- low conc. of one or more of the essential AA's
    • ex: collagen- has nothing but Gly and hydroxy-Pro
    • ex- plant proteins
Term

Name the non-essential AA's

Definition
  • Ser
  • Ala
  • Glu
  • Asp
  • Gly
  • Gln
  • Asn
  • Pro
Term
What AA is corn deficient in?
Definition

Trp

Term
Effect of not having enough calories, esp. carbs, in the diet
Definition
  • increase demand to catabolize proteins
  • this leads to breakdown of negative nitrogen balance
Term

Effect of overbundance of protein and total callories

Definition
excess AA's stored as fat
Term
Examples of deficiency states
Definition

Kwashiorkor

Nutritional Marasmus

Term
Define Kwashiorkor syndrome
Definition
protein deficiency with sufficient calloric intake (protruding abdomen)
Term
Define nutritional marasmus/protein calorie malnutrition
Definition
there is a general malnutrition where there is a protein deficiency and caloric deficiency
Term
What nitrogenous compounds are lost via the urin
Definition

ammonia

urea

creatinine

uric acid

Term
Nitrogenous compound lost via the stole
Definition
bile
Term
Major components to AA metabolism in body
Definition
  • synthesis/breakdown of tissue protein
  • synthesis of important nitrogenous compounds and their degredation
  • metabolism of individual AA's

TISSUE PROTEIN does not contribut much to this AA pool

Term

AA precursor for heme and its breakdown product?

Definition
  • N source for heme is Gly
  • the breakdown product is bilirubin
Term

AA that is the precursor to creatine. Breakdown product?

Definition
  • use Gly (one N) and Arg (2 N's)
  • breakdown product is creatinine
Term
AA precursor for pyrimidines? breakdown product
Definition
  • N sources is Gln, Asp
  • no breakdown product (reusable)
Term
AA precursor to purines. Breakdown product?
Definition
  • N source is Gly, Gln, Asp
  • breakdown products
    • uric acid (excrete in urine)
    • ammonia (also made from other sources like deamination of AA's)
    • urea (synthesized in liver as end product of ammonia detox)
Term
Define gout
Definition
accumulation of uric acid (shown by increase in uric acid in urine)
Term
AA precursor to thyroxine/T4
Definition
Tyr
Term
AA precursor to serotonin
Definition
Trp
Term
AA precursor to histamine
Definition
His
Term
AA precursor to GABA
Definition
Glu
Term

Process of AA breakdown

Definition
  • deaminate to produce alpha keto acid
  • breakdown alpha keto acid into glucose and acetyl-CoA
Term
Define ketogenic AA
Definition
AA's which convert directly into acetyl-CoA (aka fat)
Term

Examples of ketogenic AA's

Definition
  • Lys
  • Leu
Term
Define glucogenic AA's
Definition
AA's who carbon backbones are converted to glucose (most AA's are glucogenic)
Term
What AA's are both ketogenic and glucogenic
Definition
  • Ile
  • Phe
  • Tyr
  • Trp

Some C's go to glucose while others go to acetyl CoA.

Term
Ways to remove amino group of AA
Definition

transamination

deamination

Term
General rxn mechanism for transamination
Definition
  • takes a donor alpha amino acid and an acceptor alpha keto glutaric AA
  • donor AA binds to pyridoxal phosphate in aminotransferase
  • acceptor alpha keto glutaric acid comes in and picks up the amino group to form Glu

FREELY REVERSIBLE (if I need to make/remove it, YES I CAN!!!!)

Term
The major aminotransferases
Definition

Ala aminotransferase (ALT)

Asp aminotransferase (AST)

Term

Enzyme responsible for deamination of Glu

Definition
glutamic dehydrogenase (only AA dehydrogenase found in humans) (also freely reversible)
Term
Deamination: mechanism of deamination of flavoproteins
Definition

acts as a oxidase to D and L AA's

Term
Mechanism of deamination of Ser/Thr
Definition
  • via serine/threonine dehydrogenase
  • use water (take away for intermediates than add it back to teh fainal product)
  • NON reversible
Term
Mechanism of deamination of Cys
Definition
  • via serine dehydrognase
  • involves using H2S
  • NON reversible
Term
AA deaminated through non oxidative mechansims
Definition

Cys

Ser

Thr

Glu

Term
Precursor pyridoxin vitamin
Definition
  • vitamins- start with pyridoxOL and make pyridoxAL (the aldehyde form)
  • coezyme- when phosphate adds to pyridoxal
Term
Where does the AA bind to with pyridoxal phosphate?
Definition
AA binds to the aldehyde group by forming a Schiff base with pyridoxal phosphate (remember we split out water with the serine dehydrogenase)
Term
Effect of deficiency of pyridoxal phosphate
Definition
defects in AA metabolism
Term
Only dehydrogenase for the AA's
Definition
glutamate dehydrogenase
Term
Location of alanine aminotransferase and aspartic aminotransferase
Definition
  • ALT- cytosol
  • AST- mitochondria
Term
Location of glutamate dehydrogenase
Definition
mitochondria
Term
Relation btw glutamate dehydrogenase and aminotransferase ineraction
Definition

These enzymes work together to form keto acid and glutamate, respectively.

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