Exam 1 (AA's, Proteins, Non-Protein Nitrogens) Flashcards
20 amino acids are divided into two groups:
Essential
Non-essential
How are essential amino acid supplied:
through diet when we eat proteins
How are non-essential amino acids supplied:
They are made from the essential amino acids, converted by liver enzymes
This is the transfer of one amine group from 1 amino acid to another, done by liver enzymes to make new amino acids from recycled ones:
transamination
The removal of an amino group from an amino acid; produces ammonia which is converted to urea and excreted in urine:
Deamination
Amino acids consist of these parts:
Amino group
Carboxyl group
Hydrogen
R-group
Formation of a peptide involves the ___terminal end of one amino acid reacting with the ___terminal end of another through this type of reaction:
C-terminal, N-terminal hydrolysis reaction (H2O is released)
Define polypeptide:
chain of amino acids linked via peptide bonds
Why are amino acids zwitterions:
Amino has + charge
Carboxyl group has - charge
*net charge = 0
*makes them good buffers
Describe secondary peptide structure:
coiling into helix by h bonds of neighboring peptides
Describe tertiary peptide stucture:
Folding of peptide chain by many forces
The interaction of the polypeptides results in a :
protein
Proteins have ___ main stages of assembly:
Primary, Secondary, Tertiary, Quaternary
T/F All proteins contain all 20 amino acids:
False
When errors in metabolism occur, these can build up in blood and urine and be detected by the lab:
amino acids
T/F When certain amino acids accumulate in blood, they can be toxic and result in death:
True
What are the two categories of aminoacidopathies:
Primary
Secondary
Describe primary vs secondary aminoacidopathy:
- Primary: inherited defect in enzymatic pathway
* Secondary: disease of a specific organ where amino acid is synthesized (liver, kidney)
List the 6 Primary (inherited) amioacidopathies:
Alkaptonuria Cystinuria ??? Homocystinuria Maple Syrup Urine Phenylketonuria Tyrosinemia
In alkaptonuria, what enzyme is inhbitied, and what builds up:
- enzyme: homogentisic acid oxidase
* builds up: homogentisic acid
Which aminoacidopathy creates a buildup of homogentisic acid, causing generalized pigmentation and arthritic-like degeneration:
Alkaptonuria
In alkaptonuria, this will happen to urine up standing, and is caused by a buildup of what:
- urine will darken
* buildup of homogentisic acid
Cystinuria is not an enzymatic defect, but a defect in _____ _____:
renal absorption
Buildup of cysteine causes:
renal calculi (cysteine stones)
This aminoacidopathy is caused by a defect in Branched Chain Ketoacid Dehydrogenase:
Maple Syrup Urine Disease
MSUD
What builds up in MSUD:
Ketoacids (leucine, isoleucine, valine)
What signs/symptoms result from MSUD:
- maple syrup smell in urine, skin, breath
- mental retardation
- convulsions
- acidosis
- death
What is the defect in MSUD:
the defect is in the Branched Chain Ketoacid Dehydrogenase
ketoacids then buildup
What is the defect in Type 1 Tyrosinemia:
FAA hydrolase (most severe)
Which type of Tyrosinema is most severe?
Type 1
What is the defect in Type 2 Tyrosinemia:
Tyrosine aminotransferase
What builds up in both types of Tyrosinemia?
Tyrosine
it needs to be broken down for complete amino acid metabolism
What does Type 1 tyrosinemia cause:
severe liver disease
death in infants
What does Type 2 Tyrosinemia cause:
eye involvement and skin lesions
What amino acid is not metabolized in Homocysteinuria:
Methionine
The enzyme Cystathionine B-synthase is blocked in _______, causing a buildup of this amino acid:
- Homocysteinuria
* Methionine
This aminoacidopathy is similar to Marfan’s Syndrome:
Homocysteinuria
List some signs and symptoms of Homocysteinuria:
- mild to severe cases
- mental retardation
- lens dislocation in eye= nearsightedness
- chest deformities
- long, spindly limbs
- scoliosis
- thrombosis (Increased homocysteine levels can lead to CVA)
Increased levels of this amino acid can lead to CVA:
Homocysteine
This causes a buildup of phenylalanine and causes severe mental retardation if not treated:
PKU
For mandated amino acid testing, is it required that an effective treatment must be available:
yes
List the requirements for state mandated amino acid testing:
1) high incidence disorder
2) must have effective treatment available
3) inexpensive screening for high volume
4) test has high sensitivity/specificity
T/F Blood sample for amino acid testing must be drawn after 6-8 hour fast and avoiding absorbed dietary proteins:
True
Why must you be careful to avoid WBC and PLT when aliquotting specimen for amino acid testing:
they contain amino acids
What do you do with an aliquotted blood specimen for amino acid testing:
de-proteinize (aliquot) and freeze immediately
T/F Random urine can be used for amino acid test screening:
True
When using urine to test for amino acids, this is required for confirmation:
24 hour urine
What is the card test used to screen newborns for aminoacidopathies/PKU:
Guthrie test
Describe the Guthrie test:
1) start with culture of Bacillus subtilis (requires phenylalanine to grow)
2) add inhibitor to media to prevent bacteria from growing
3) add blood sample
* positive = bacteria will grow (still need confirmation)
* negative = no bacterial growth
Why will the Bacillus subtilis grow in the Guthrie test if the patient has PKU:
If defect exists, blood will contain much phenylalanine, feeding B. subtilis
Amino acid testing requires ___-____ filtrate:
protein free
What other methods can be used to test for amino acids:
- TLC
- Ninhydrin (stains aa’s blue)
- HPLC
- Capillary electrophoresis
- MS/MS
PKU is caused by a defect in the gene that helps create the enzyme _____:
phenylalanine hydroxylase
What type of test of albumin is run for short term blood sugars:
glycosylated albumins
Albumin is this type of reactant:
Negative phase reactant
Which blood sample has highest protein concentration:
plasma (contains the protein fibrinogen)
Which is preferred for protein testing, serum or plasma:
serum (does not contain the protein fibrinogen)
T/F Urine and CSF have protein in them:
True, but smaller quantities so need to concentrate samples if quantitating
Are proteins too large to pass through vessels?
Yes
The presence of protein draws water; distributing extracellular fluid between vascular bed and interstitial space, keeps water out of tissues, maintaining this:
oncotic pressure
The presence of ___ differentiates proteins from carbohydrates and lipids:
Nitrogen
Proteins denature when ____ and ____ structure bonds break:
Tertiary and Quaternary
List methods of denaturing proteins:
- heat
- pH
- Enzymatic action
- heave metals
- urea exposure
- UV light
The function of albumin:
maintain osmotic pressure
keep fluid in vessels and out of tissues
T/F Proteins can act as pH buffers:
True. They are amphiprotic zwitterions.
These can act as hormones/hormone receptors:
Proteins