Section 2c

The study of the chemical composition and reactions of living matter.

• 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

• We will go over
– Water
– Salts
– Acids
– Bases
– pH
– Buffers

Most abundant and important inorganic compound in living material.
Makes up 60% - 80% of the volume of most living cells.

• 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

• 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!

• 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

• 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

• Cushioning
– resilient cushion around certain body organs
– Helps protect organs from physical trauma
– Cerebrospinal fluid surrounding the brain is an example

• Inorganic compounds
• Contain cations other than H + and anions other than OH –
• Are electrolytes; they conduct electrical currents

• 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 are also electrolytes,
Conduct electrical current

• Tastes sour
• Dissolves many metals
• Acids release H + and are therefore proton donors
HCl  H + + Cl –
Acids are proton donors!

• Tastes bitter
• Feel slippery
• Bases release OH – and are proton acceptors
NaOH  Na + + OH –
Bases are proton acceptors!

(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

• Acidic: pH 0–6.99
• Basic: pH 7.01–14
• Neutral: pH 7.00
Figure 2.12

• When acids and bases are mixed, they react with each other in a displacement reaction to form water and a salt.
HCl + NaOH -> NaCl + H
2
O

• 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.

• 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!