PROTEIN Flashcards
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sequence of the AA in the polypeptide chain (linear)
Primary Structure
determines the overall shape of the protein
Primary Structure
Analytical processes of primary structure
- chromatography
- electrophoresis
- dye binding
- light absorbance
Analytical processes: chromatography, electrophoresis, dye binding and light absorbance depends on this sequence
Primary sequence
conformation of the segments of the polypeptide chain
Secondary structure
secondary structure maintained by:
Hydrogen Bond
Important for the strength and flexibility of proteins
secondary structure
arises from the interaction among the different segments of a polypeptide chain
secondary structure
3 structures of secondary structure
- Alpha-Helix
- Beta-Pleated sheets
- Random coils
Chain forms a regular helix; coil
resembling a spring
Alpha-Helix
In fully extended structures; flat, corrugated structure
Beta-Pleated sheets
secondary structure that has no apparent pattern
Random coils
Actual 3-dimensional structure of folding pattern of the protein
Tertiary Structure
tertiary structure is maintained by
covalent disulfide bond
responsible for many of the physical and chemical properties of proteins
tertiary structure
association of several polypeptide chains into larger “oligomeric” aggregate unit
quaternary structure
Quaternary structure is an association of several polypeptide chains into larger_
“oligomeric” aggregate unit
quaternary structure is maintained by_
non-covalent bond (hydrogen bond)
stable complexes of quaternary structure
- dimers
- trimers
- tetramers
examples of quaternary structure
- hemoglobin
- lactate dehydrogenase
- creatine phosphokinase
factors that cause loss of functions of proteins:
- heat
- hydrolysis by strong acid or alkali
- enzymatic reaction
- exposure to UV light
contain peptide chains that hydrolysis yield only AA
simple proteins
relatively symmetrical with compactly folded and coiled polypeptide chains
globular
examples of globular simple proteins
- hemoglobin
- plasma proteins
- enzymes
- peptide hormones
more elongated and asymmetrical and have a higher viscosity
fibrous
examples of fibrous simple protein
- fibrinogen
- troponin
- collagen
Protein (apoprotein) + nonprotein (prosthetic group)
conjugated proteins
prosthetic group
- lipid (lipoprotein)
- carbohydrate (glycoprotein)
- metals (metalloprotein)
types of simple proteins
a. globular
b. fibrous
major plasma proteins
- Pre-albumin
- Albumin
- Globulins
Migrates ahead of albumin in the classic electrophoresis of serum or plasma proteins
Pre-Albumin
Transport of thyroid hormones (thyroxine and triiodothyronine)
pre - albumin
binds with retinol-binding protein to form complex that transports retinol (Vitamin A)
pre-albumin
rich in tryptophan and contains 0.5% carbohydrate
pre-albumin
increased in pre-albumin
- alcoholism
- chronic renal failure
- steroid treatment
largest plasma protein fraction
albumin
what is the fraction of Albumin
52-62%
Synthesized in the liver at a rate that is dependent on protein intake
albumin
serves as circulating reservoir of AA
Albumin
regulator of osmotic pressure (fluid balance)
Albumin
Transport protein because of ease of binding with blood components
Albumin
indicator of nutritional status
albumin
reference values of Albumin
3.5 – 5.0 g/dL (35 – 50 g/L)
- No clinical significance
- Hemoconcentration, dehydration
- Excessive albumin infusion
Increased Albumin (Hyperalbuminemia)
- Impaired synthesis (primary= liver disease; secondary = diminished
protein intake) - Decreased synthesis (liver impairment)
- Malabsorption or malnutrition
- Nephrotic syndrome (renal loss)
- Severe burns
Decreased Albumin (Hypoalbuminemia)
Heterogenous complex mixture of protein molecules
(α1, α2, β and γ fractions)
Globulins
Elevated concentration of globulin in early cirrhosis will balance loss of albumin resulting to normal levels
of total protein
Globulins
Normal A/G ratio
1.3-3:1
Low Albumin/Globulin ratio causes
- liver diseases
- infectious diseases
- multiple myeloma
- nephritis