Section 2c Biochemistry The study of the chemical composition and reactions of living matter. Biochemistry • Organic compounds – Contain carbon, are covalently bonded, and are often large • Inorganic compounds – All other chemicals in the body – Do not contain carbon – Water, salts, and many acids and bases Today • We will go over – Water – Salts – Acids – Bases – pH – Buffers Water Most abundant and important inorganic compound in living material. Makes up 60% - 80% of the volume of most living cells. Properties of Water • High heat capacity – absorbs and releases large amounts of heat before changing temperature – This prevents sudden changes in body temperature cased by external factors like sun or wind or internal factors like heat released during vigorous muscle activity – As a part of blood, water redistributes heat among body tissues, ensuring temperature homeostasis Properties of Water • High heat of vaporization – changing from a liquid to a gas requires large amounts of heat – As we sweat, perspiration (mostly water) evaporates from our skin removing large amounts of heat – This is a very efficient cooling mechanism for our bodies! Properties of Water • Polar solvent properties – Water is often called the universal solvent – dissolves ionic substances – forms hydration layers around large charged molecules – serves as the body’s major transport medium Properties of Water • Reactivity – an important part of hydrolysis and dehydration synthesis reactions – Food is digested to their building blocks by adding a water molecule to each bond - Hydrolysis reactions – Carbohydrates and proteins are synthesized from smaller molecules by removing a water molecule for each bond formed – dehydration synthesis Properties of Water • Cushioning – resilient cushion around certain body organs – Helps protect organs from physical trauma – Cerebrospinal fluid surrounding the brain is an example Salts Salts • Inorganic compounds • Contain cations other than H+ and anions other than OH– • Are electrolytes; they conduct electrical currents Salts • Maintaining proper ionic balance in our body fluids is one the most crucial homeostatic roles of the kidneys. • When this balance is severely disturbed, virtually nothing in the body works. Acids and Bases Acids and Bases are also electrolytes, Conduct electrical current Acids • Tastes sour • Dissolves many metals • Acids release H+ and are therefore proton donors HCl H+ + Cl – Acids are proton donors! Bases • Tastes bitter • Feel slippery • Bases release OH– and are proton acceptors NaOH Na+ + OH– Bases are proton acceptors! Acid-Base Concentration (pH) • Acidic solutions have higher H+ concentration and therefore a lower pH • Alkaline (basic) solutions have lower H+ concentration and therefore a higher pH • Neutral solutions have equal H+ and OH– concentrations Acid-Base Concentration (pH) • Acidic: pH 0–6.99 • Basic: pH 7.01–14 • Neutral: pH 7.00 Figure 2.12 Neutralization • When acids and bases are mixed, they react with each other in a displacement reaction to form water and a salt. HCl + NaOH -> NaCl + H2O Buffers • Systems that resist abrupt and large swings in the pH of body fluids are buffering systems • If blood pH varies from the narrow range of 7.35 – 7.45 by more than a few tenths, it can be fatal! • Homeostasis of acid-base balance is regulated by the kidneys and lungs and by chemical systems called Buffers. Buffer systems • Carbonic acid-bicarbonate system is a very important chemical blood buffer – Carbonic acid dissociates reversibly, releasing bicarbonate ions and protons – The chemical equilibrium between carbonic acid and bicarbonate resists pH changes in the blood Quiz Next time!