Isoelectric pH.

• It is the pH at which biomolecules exist as dipolar ion possessing same amount of positive and negative charge on their surface with net zero.
• Biomolecules contain different ionizable groups on their surface.
• Depending on the pH of solution these ionizable groups act either as proton donor or as proton acceptor and thereby express charge on their surface.
• At one definite pH called isoelectric pH, every biomolecule expresses both the charges on its surface in equal amount and exists as zwitter ion, when the net charge on the surface of biomolecule is zero because positive and negative charge equalize each other. So zwitter ions are electrically neutral without any electrohoretic mobility during electrophoresis.
• At pH below the isoelectric pH biomolecules accept protons from the medium and exist as cations with positive charge on their surface and at pH above the isoelectric pH biomolecules release proton to the medium and exist as anions with negative charge on their surface. 

pH of a solution.

P^H is the negative logarithm of hydrogen ion concentration of a solution, when H⁺ concentration is expressed in terms of molarity

 

[H+] in mol/L	Calculation of pH	pH
10-7	-log 10-7	7
10-8	-log 10-8	8
10-3	-log 10-3	3

What is free acidity and what is titratable acidity.

Free acidity:

• Free acidity of a solution is its instant H ion concentration measured without any manipulation.
• Free equimolar concentration of strong acid and weak acid, the free acidity will be very high in strong acid solution compared to that in weak acid solution because strong acids are completely dissociated and weak acids are partially dissociated into hydrogen ions.

Titratable acidity:

• Titratable acidity of a solution is its total H ion concentration that would be if the acid was allowed to ionize totally to hydrogen ion following its titration with alkali.
• For equimolar concentration of strong acid and weak acid the total hydrogen ion concentration of both the solution will be same at the end of complete ionization following titration with alkali.
• Very small amount of weak acid usually ionize to hydrogen ion and majority fail to ionize. During titration when alkali is added to the medium, the hydrogen ion concentration of the medium decreases which facilitate the unionized weak acid to ionize completely to hydrogen ion.
• Equimolar concentration of strong acid and weak acid differ with respect to free acidity, but they are same the respect to the titratable or total acidity.        

What is Amphoteric substance?

These are the substances which can act both as acid as well as base in different situation.

Properties of alkaali.

• Alkali are metallic hydroxides of alkaline metals, which in solution ionize to hydroxyl ions that can bind H to form H2O and thereby can remove hydrogen ion from solution.
• Strong alkalis are those which rapidly and almost completely ionize to hydroxyl ions that quickly remove hydrogen ion from solution.
• Weak alkalis are those which slowly and partially ionize to hydroxyl ions that slowly remove hydrogen ion from solution.
• In fact all alkalis are also regarded as base, but all bases are not alkalis. 

Properties of Base.

• Bases are proton acceptor in aqueous solution.
• Bases may be charged particle or may be without charge.
• Strong bases are those which have greater tendency to accept proton. They bind rapidly and strongly with strongly with proton, so quickly remove from solution.
• Weak bases are those which have very low tendency to accept proton. They bind slowly and weakly with proton, so slowly remove proton from solution.
• Conjugate acid of a base is the acid formed by that base after accepting proton. So conjugate acid of a strong base is weak and that of a weak base is strong.

Properties of Acid.

• Acids are proton donor in aqueous solution.
• Acids are molecules having hydrogen atom and capable to release hydrogen ion in aqueous solution.
• Acids may be the molecular species with positive charge or negative charge or may be without charge.
• Conjugate base of an acid is the remaining anionic part of an acid after removal of proton from that acid.
• Strong acid is the acid which rapidly and completely ionizes into H+ and its conjugate base in solution.
• Weak acid the acid which slowly and partially ionizes into hydrogen ion and its conjugate base in solution.
• For strong acid degree of dissociation and dissociation constant is high with low pK value. Conversely for weak acid degree of dissociation and dissociation constant is low with high pK value.
• In case of strong acid the conjugate base shows less affinity to proton because of which they can rapidly and completely ionize to proton. So conjugate bases of strong acids are weak in nature. On the other hand, in case of weak acid the conjugate base shows strong affinity to proton because of which they partially ionize to proton. So conjugate bases of weak acids are strong in nature. 

Radiation hazard

Radiation hazards are as follows:

1. Immediate hazards
• Bone marrow depression
• Immune suppression
• Damage to intestinal mucosa causing diarrhea and malabsorption.
• Baldness
• Rough and scaly skin
• In pregnancy: Fetal growth retardation, congenital malformations of fetus, fetal death.
2. Delayed hazards
• Carcinogenesis
• Sterility
• Cataract
3. Genetic defects
• DNA damage
• Mutation

Name the radio-sensitive tissue.

The following tissues are sensitive to radiation. These are mostly rapidly dividing tissues.

1. Bone marrow
2. Gonads
3. Lymph node
4. Skin
5. Intestine.