TAILIEUCHUNG - Lecture Human anatomy and physiology - Chapter 2: Chemistry comes alive (part b)
Biochemistry is the study of the chemical composition and reactions of living matter. All chemicals in the body fall into one of two major classes: organic or inorganic compounds. Organic compounds contain carbon. All organic compounds are covalently bonded molecules, and many are large. All other chemicals in the body are considered inorganic compounds. These include water, salts, and many acids and bases. Organic and inorganic compounds are equally essential for life. | Part B: Chemistry Comes Alive: Inorganic compounds Water, salts, and many acids and bases Do not contain carbon Organic compounds Carbohydrates, fats, proteins, and nucleic acids Contain carbon, usually large, and are covalently bonded 60%–80% of the volume of living cells Most important inorganic compound in living organisms because of its properties High heat capacity Absorbs and releases heat with little temperature change Prevents sudden changes in temperature High heat of vaporization Evaporation requires large amounts of heat Useful cooling mechanism Polar solvent properties Dissolves and dissociates ionic substances Forms hydration layers around large charged molecules, ., proteins (colloid formation) Body’s major transport medium Figure Water molecule Ions in solution Salt crystal – + + Reactivity A necessary part of hydrolysis and dehydration synthesis reactions Cushioning Protects certain organs from physical trauma, ., cerebrospinal fluid Ionic compounds that dissociate in water Contain cations other than H+ and anions other than OH– Ions (electrolytes) conduct electrical currents in solution Ions play specialized roles in body functions (., sodium, potassium, calcium, and iron) Both are electrolytes Acids are proton (hydrogen ion) donors (release H+ in solution) HCl H+ + Cl– Bases are proton acceptors (take up H+ from solution) NaOH Na+ + OH– OH– accepts an available proton (H+) OH– + H+ H2O Bicarbonate ion (HCO3–) and ammonia (NH3) are important bases in the body Acid solutions contain [H+] As [H+] increases, acidity increases Alkaline solutions contain bases (., OH–) As [H+] decreases (or as [OH–] increases), alkalinity increases pH = the negative logarithm of [H+] in moles per liter Neutral solutions: Pure water is pH neutral (contains equal numbers of H+ and OH–) pH of pure water = pH 7: [H+] = 10 –7 M All neutral solutions have a pH 7 Acidic solutions [H+], pH Acidic pH: 0– pH scale is logarithmic: a pH 5 solution
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