Chemical Basis of Life

1. Chemical Basis of Life protons (+ charged) nucleus energy levels neutrons (no charge) electrons(-) charged [The structure of an atom] Atom: Atoms are the basic building blocks of matter. They cannot be subdivided any further by any ordinary chemical means.

2. Element:Elements are made up of only one kind of atom. e.g. Iron (Fe), Oxygen (O), diamond, Neon (Ne) Compound:Two or more kinds of atoms are combined in definite proportions. e.g. H2O, CO2, glass 2H O C 2O

3. Inorganic Molecules Water Acids, Bases and Salts Minerals Organic Molecules Carbohydrates Lipids Proteins Vitamins Nucleic Acids ATP Basic Components of Living Things

4. WATER • Water is a polar molecule. H partially negative - O + partially positive H

5. WATER Hydrogen Bonds in Water

6. WATER Properties of water Adhesion It is the force of attraction between the molecules of two different substances. Ex: Water molecules can dissolve most polar substances. Cohesion It is the force of attraction between the molecules of the same substance. Ex: Water molecules are attached to each other with cohesion forces.

7. WATER Properties of water Adhesion Cohesion

8. WATER

9. WATER • Water is good solvent. • Water is essential for biochemical reactions. • Water is the medium of transport for foods, minerals and other substances in living systems. • The harmful substances formed by metabolic activities are removed from body by water. • Many organisms can only use oxygen dissoved in water; therefore they live in water. • Water is transparent that makes penetration of light possible into deep water.

10. WATER • The density of water is maximum at 4°C. So water at 4°C moves downward and exchanges heat with surrounding water. This helps deep sea water have fairly narrow temperature change. • Below 0°C, hydrogen bonds can’t break, and they lock water molecules in the bonding pattern of ice. During winter freezes, ice sheets form on ponds, lakes and streams. They hold in water’s heat and help protect aquatic organisms from freezing.

11. WATER • Water is a great molecule by means of temperature stabilization. When water is liquid, its hydrogen bonds are constantly breaking and forming again. With enough heat energy, hydrogen bonds stay broken and molecules at the water’s surface escape into the air. This is called evaporation. Because water has a very high specific heat molecules take away energy when they leave the surface and lower the temperature. This is the reason why we cool off when we sweat.

12. Acids and Bases: • Acids: An acid is any compound that produces hydrogen ions in solution. When acids are dissolved in water, the hydrogen breaks lose a hydrogen ion (H+). • Acids are sour in taste. • Examples: lemon, apple, vinegar, tomato, grapefruit. • HCl H+ + Cl • H2SO4 2H++SO4-2

13. Bases: A base is a compound that produces hydroxide (hydroxyl) ions when dissolved in water. • Bases are bitter in taste. • Examples: sea water, ammonia water, soap • NaOH Na + OH- • NH3 + H2O NH4 + OH-

14. Neutral substances:Any chemical that contains equal amounts of H+ and OH- ions are said to be neutral. Ex:H2O H+ + OH-

15. ACIDS Have sour taste Turn blue litmus paper’s color into red HCl and H2SO4 are strong acids Acetic acid and citric acid are weak BASES Have bitter taste Turn red litmus paper’s color into blue Organic bases generally have C and N NaOH, KOH are example of bases

16. The pH Scale: • The H+ concentration is indicated by a unit of measure called pH. The pH scale has been set up in such a way that; • high concentrations of H+ have a low pH, • low concentrations of H+ have high pH values. Acidic Basic Neutral 0 7 14 [H+] > [OH-] [H+] = [OH-] [H+] < [OH-]

18. Acid and Base Indicators Any chemical that has different colors in acids and in bases is called indicator. Blue; turns red in acidic solution Litmus paper Red;turns blue in basic solution pH paper gives exact pH value Methyl orange changes from yellow to red in acidic solutions Phenolphtalein changes from colorless to red (pink) in basic solutions

19. Buffers: Chemical reactions are very sensitive to even slight shifts in pH. Maintaining the pH balance of blood and tissue fluid is very important. The addition and removal of H+ ions has to be controlled continuously in order to protect the stable internal environment of the body. A buffer is any molecule that can combine with H+ ions, release them or both, and so help stabilize pH. HCO3- + H+ H2CO3

20. Neutralization: When solutions of an acid and a base are mixed, a reaction takes place. The hydrogen ions from the acid combine with the hydroxide ions from the base to form water. HCl + NaOH NaCl + HOH (acid) (base) (salt) (water) The ionic compound produced by the neutralization reaction between an acid and a base is called a salt.

21. Chemical Compounds in Living Things What are the most abundant elements in living things? • Hydrogen • Nitrogen • Oxygen • Carbon Less frequently the elements Phosphorus (P), Sulfur (S), Iron (Fe), Calcium (Ca), Sodium (Na), Chlorine (Cl), Magnesium (Mg), and Potassium (K) are found in organic compounds.

22. Chemical Compounds Organic Compounds Inorganic Compounds • contain C (carbon) atoms • also contain H (hydrogen) and O (oxygen) atoms Ex: carbohydrates, lipids, proteins, vitamins, ATP, nucleic acids • do not contain C (carbon) atoms • exceptions: CO2, CaCO3 (although they contain C atoms these are inorganic compounds because they do not contain H) Ex: H2O, minerals

23. Why carbon is so special? It is the unique element which have the ability to form covalent bonds that are strong and stable. C has 6 electrons: -2 of them are in the first energy level, -the other 4 electrons are in the second energy level. For this reason carbon can take 4 electrons that means carbon can form 4 single covalent bonds. H first energy level H C H second energy level H Carbon Atom Methane Molecule (CH4)