Section 2c

BiochemistryBiochemistry

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

WaterWater

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 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 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 propertiesPolar 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• ReactivityReactivity

–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

• CushioningCushioning

– resilient cushion around certain body organs

–Helps protect organs from physical trauma

–Cerebrospinal fluid surrounding the brain is an example

SaltsSalts

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 donorsHCl 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)

•AcidicAcidic solutions have higher H+ concentration and therefore a lower pH

•Alkaline (basic)Alkaline (basic) solutions have lower H+ concentration and therefore a higher pH

•Neutral 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

QuizQuiz

Next time!