📖 Biochemistry
PHOSPHORUS
BiochemistryPHOSPHORUS
Serum level of phosphate is 3-4 mg/dl for adults and 5-6 mg/dl in children. Consumption of calcitriol increases phosphate absorption.
Functions of phosphorus
(a) Plays key role in formation of tooth and bone
(b) Production of high energy phosphate compounds such as ATP, CTP, GTP etc.,
(c) Synthesis of nucleotide co-enzymes such as NAD and NADP
(d) Formation of phosphodiester backbone structure for DNA and RNA synthesis
Hypophosphatemia is the condition which leads to decrease in absorption of phosphorus. it leads to hypercalcamia
Hyperphosphatemia, increase in absorption of phosphate was noticed. Hyperphosphatemia leads to cell lysis, hypocalcemia and thyrotoxicosis.
FACTORS AFFECTING ENZYME ACTIVITY
BiochemistryFACTORS AFFECTING ENZYME ACTIVITY
Velocity or rate of enzymatic reaction is assessed by the rate of change in concentration of substrate or product at a given time duration. Various factors which affect the activity of enzymes include:
1. Substrate concentration
2. Enzyme concentration
3. Product concentration
4. Temperature 5. Hydrogen ion concentration (pH)
6. Presence of activators
7. Presence of inhibitor
Effect of substrate Concentration : Reaction velocity of an enzymatic process increases with constant enzyme concentration and increase in substrate concentration.
Effect of enzyme Concentration: As there is optimal substrate concentration, rate of an enzymatic reaction or velocity (V) is directly proportional to the enzyme concentration.
Effect of product concentration In case of a reversible reaction catalyzed by a enzyme, as per the law of mass action the rate of reaction is slowed down with equilibrium. So, rate of reaction is slowed, stopped or even reversed with increase in product concentration
Effect of temperature: Velocity of enzymatic reaction increases with temperature of the medium which they are most efficient and the same is termed as optimum temperature.
Effect of pH: Many enzymes are most efficient in the region of pH 6-7, which is the pH of the cell. Outside this range, enzyme activity drops off very rapidly. Reduction in efficiency caused by changes in the pH is due to changes in the degree of ionization of the substrate and enzyme.
Highly acidic or alkaline conditions bring about a denaturation and subsequent loss of enzymatic activity
Exceptions such as pepsin (with optimum pH 1-2), alkaline phosphatase (with optimum pH 9-10) and acid phosphatase (with optimum pH 4-5)
Presence of activators Presence of certain inorganic ions increases the activity of enzymes. The best examples are chloride ions activated salivary amylase and calcium activated lipases.
Effect of Inhibitors The catalytic enzymatic reaction may be inhibited by substances which prevent the formation of a normal enzyme-substrate complex. The level of inhibition then depends entirely upon the relative concentrations of the true substrate and the inhibitor
The Hemoglobin Buffer Systems
BiochemistryThe Hemoglobin Buffer Systems
These buffer systems are involved in buffering CO2 inside erythrocytes. The buffering capacity of hemoglobin depends on its oxygenation and deoxygenation. Inside the erythrocytes, CO2 combines with H2O to form carbonic acid (H2CO3) under the action of carbonic anhydrase.
At the blood pH 7.4, H2CO3 dissociates into H+ and HCO3 − and needs immediate buffering.
3-D Structure of proteins
Biochemistry3-D Structure of proteins
Proteins are the main players in the life of a cell. Each protein is a unique sequence of amino acid residues, each of which folds into a unique, stable, three dimentional structure that is biologically functional.
Conformation = spatial arrangement of atoms that depends on rotation of bonds. Can change without breaking covalent bonds.
- Since each residue has a number of possible conformations, and there are many residues in a protein, the number of possible conformations for a protein is enormous.
Native conformation = single, stable shape a protein assumes under physiological conditions.
- In native conformation, rotation around covalent bonds in polypeptide is constrained by a number of factors ( H-bonding, weak interactions, steric interference)
- Biological function of proteins depends completely on its conformation. In biology, shape is everything.
- Proteins can be classified as globular or fibrous.
There are 4 levels of protein structure
- Primary structure
- linear sequence of amino acids
- held by covalent forces
- primary structure determines all oversall shape of folded polypeptides (i.e primary structure determines secondary , tertiary, and quaternary structures)
- Secondary structure
- regions of regularly repeating conformations of the peptide chain (α helices, β sheets)
- maintained by H-bonds between amide hydrogens and carbonyl oxygens of peptide backbone.
- Tertiary structure
- completely folded and compacted polypeptide chain.
- stabilized by interactions of sidechains of non-neighboring amino acid residues (fibrous proteins lack tertiary structure)
- Quaternary structure
- association of two or more polypeptide chains into a multisubunit protein.