C - Chapter VII: Proteins Flashcards
PROTEINS
-covalently linked polymers of (?)
amino acids
PROTEINS
- amino acids are linked via (?) (formed upon removal of a water molecule)
peptide bond
PROTEINS
- synthesized in the liver & secreted by the hepatocyte into the circulation EXCEPT (?)
immunoglobulins (plasma cells)
PROTEIN
- provide (?) of the total daily body energy requirement
12 – 20%
PROTEINS
- composes (?) of the cell’s dry weight
50 – 70%
- amphoteric
PROTEINS
sequence of the amino acids in the polypeptide chain
Primary structure
analytical processes:
chromatography, electrophoresis, dye binding and light absorbance depend on this sequence
arises from the interaction among the different segments of a polypeptide chain
Secondary structure
– chain forms a regular helix ; coil resembling a spring
a. alpha-helix
– in fully extended structures; flat, corrugated structure
b. beta-pleated sheets
– no apparent pattern
c. random coils
– actual 3-dimensional structure or folding pattern of the protein
- Tertiary structure
– association of several polypeptide chains into larger “oligomeric” aggregate unit
- Quaternary structure
stable complexes:
dimers, trimers, tetramers
Classification
- Simple
- Conjugated
contain peptide chains that on hydrolysis yield only AA
- Simple
protein (apoprotein) + nonprotein (prosthetic group)
- Conjugated
prosthetic group :
lipid (lipoprotein) , carbohydrate (glycoprotein) , metals (metalloprotein) , etc.
: relatively symmetrical with compactly folded and coiled polypeptide chains
a. globular
: more elongated and asymmetrical and have a higher viscosity
b. fibrous
Functions
- Repair (?)
- Important in (?)
- For transport of (?)
- Maintenance of (?)
- Maintenance of (?) (buffers)
- Bio-(?)
body tissues
blood coagulation and immunologic function
metabolic substances
osmotic pressure
blood pH
-catalysts
Metabolism
- Dietary Intake
- Absorption
- Production
- Storage
- Destruction
MAJOR PLASMA PROTEINS
- PRE-ALBUMIN (Transthyretin)
- ALBUMIN
- GLOBULINS
− Migrates ahead of albumin
− Rich in tryptophan and contain 0.5% carbohydrate
PRE-ALBUMIN (Transthyretin)
− Serves as transport protein for T3, T4 and retinol (Vit. A)
PRE-ALBUMIN (Transthyretin)
− Increased: alcoholism, chronic renal failure, steroid treatment
PRE-ALBUMIN (Transthyretin)
− Decreased: poor nutrition, liver disorder, malignancy
PRE-ALBUMIN (Transthyretin)
− largest plasma protein fraction (52-62%)
ALBUMIN
− synthesized in the liver at a rate that is dependent on protein intake
ALBUMIN
− serves as circulating reservoir of amino acids
ALBUMIN
− regulator of osmotic pressure
ALBUMIN
− transport protein because of ease of binding with blood components
ALBUMIN
− a “negative acute phase reactant”
ALBUMIN
− sensitive & highly prognostic marker in cases of cystic fibrosis
ALBUMIN
ALBUMIN
Reference values:
3.5 – 5.0 g/dL (35 – 50 g/L)
Increased − hemoconcentration, dehydration
ALBUMIN
Increased
− excessive infusion
albumin (Hyperalbuminemia)
− decreased synthesis (liver impairment)
Decreased albumin (Hypoalbuminemia)
− malabsorption or malnutrition
Decreased albumin (Hypoalbuminemia)
Decreased − nephrotic syndrome (renal loss)
albumin (Hypoalbuminemia)
Decreased − severe burns
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
GLOBULINS
normal A/G ratio :
1.3 – 3 : 1
GLOBULINS
low A/G ratio
– liver diseases, infectious diseases, multiple myeloma, nephritis
Alpha1-globulins
a. α-1-antitrypsin
b. α-1-fetoprotein
c. α-1-Acid Glycoprotein (orosomucoid)
d. α-1-Antichromotrypsin
Alpha2-globulins
A. Haptoglobin
B. Ceruloplasmin
Beta-globulins
a. Transferrin (Siderophilin)
b. β2-Microglobulin
GLOBULINS
(1) Alpha1-globulins
(2) Alpha2-globulins
(3) Beta-globulins
(4) GAMMA-GLOBULINS
(5) FIBRINOGEN
(6) LIPOPROTEIN
(7) COMPLEMENT
(8) C-REACTIVE PROTEIN
– 90% of the α1-globulin band
α-1-antitrypsin
- an acute phase reactant
α-1-antitrypsin
- neutralize trypsin-like enzymes
α-1-antitrypsin
- major inhibitor of protease activity
α-1-antitrypsin
inhibit lysosomal elastase released from PMNs during their
α-1-antitrypsin
- Increased: inflammation, pregnancy and contraceptive use
α-1-antitrypsin
- Decrease: associated with emphysematous pulmonary disease & juvenile hepatic cirrhosis
a. α-1-antitrypsin
b. α-1-fetoprotein
c. α-1-Acid Glycoprotein
α-1-antitrypsin
synthesized initially by the fetal yolk sac & then the parenchymal cells of the liver
- used as a tumor marker (hepatic & gonadal CA)
a-1-fetoprotein
- screening test for any fetal conditions, increase passage of fetal proteins into the amniotic fluid; detects neural tube defects
a-1-fetoprotein