Chemistry of Life

Chemistry is the study of how matter interacts, thus we need to understand some of the basic rules and ideas about matter to understand how living things work.

Element - substance that cannot be separated into simpler substances by chemical means.

92 occur naturally 13 made by humans

Compound - combination of two or more elements

Vocabulary

Life Elements

Typical living thing composed (99.9% wt) of six elements:

C, H, N, O, P, and S.

Seventeen other elements occur in minute quantities or as traces.

Atoms - smallest particle into which an element can be divided and still have the properties of that element.

Molecule - two or more atoms joined together by molecular bonds.

Vocabulary

Atom OrganizationSub-atomic

particle

charge Wt. (amu) location

proton + 1 Nucleus

neutron none 1 Nucleus

electron - 0 Orbit nucleus

Atomic Number = # protonsNote: "normal" atom the number of electrons =

number of protons (atom has no net charge)

Atomic Wt (Mass) = # protons + # neutrons

Formulas

Atomic Variants

1. Isotopes - differ in the number of neutrons in the nucleus, thus changing wt. of element.

2. Ions - number of electrons differs from the number of protons, thus giving element net negative or a net positive.

Electrons In Orbit

Number electrons in outer-most energy level gives each atom its unique chemical behavior. (E.g) H is an odorless gas; C is a black

powdery substance.

Electrons In Orbit

* Maximum number electrons / orbital determined by the formula

X = 2N2

(where X = maximum number of electronsin energy level number N).

ATOMIC STRUCTURE

MOLECULAR BONDS:

two or more atoms bonded together by energy links

Types of Molecular BondsCovalent Bonds-

• Most common type• occurs when two or more atoms share pair elec.• may form single, double, or triple bonds

1. POLAR COVALENT = un-equal sharing of elec

2. NON-POLAR COVALENT = elec pair equally shared

2. Hydrogen Bond

bond between the negative pole of a polar molecule and the slight positive charge on a hydrogen atom that is participating in another polar molecule.

weakest

3. Ionic Bonds

a complete transfer of electrons from one molecule to another. It is most common when one molecule needs just one or two to complete its outermost shell and the other has only one or two in its outermost shell.

Properties of Water

1. High Specific Heat - takes 1 calorie (a unit of heat energy) to raise the temperature of one gram of water 1o Centigrade.

* keeps environment of cells constant

2. High Heat of Vaporization - takes 540 calories of heat to change 1 gram of liquid water at 100o C to 1 gram of water vapor at 100o C

* sweating can help to cool organisms

Properties of Water

3. High degree Cohesion + Adhesion = capillary action* plants use this to draw water against gravity

4. High Surface Tension - tendency of molecules at the surface of a liquid to cohere to each other and not to the air above.

* some insects use this to walk on water!

5. Ice floats - Ice is less dense than liquid water and hence floats (WHY??)

* allows fish and other organisms to survive winter

Properties of Water

6. Universal Solvent - dissolves ionic & most polar substances * excellent medium for cytoplasm!

Solvent = that which dissolves anotherSolute = that which is dissolved

Solution = solvent + solute

Hydrophilic ("water-loving") substances readily dissolve in water while hydrophobic ("water-fearing") substances do not dissolve in water.

Properties of Water

7. Water Dissociation- slight tendency to fall apart (dissociate) into hydrogen ions (H+) and hydroxide ions (OH-).

An Acid is a substance that gives off hydrogen ions when dissolved in water.

A Base is a substance that accepts hydrogen ions (thereby increasing the hydroxide ions).

PH Scale : 0_______________7___________________14 Acids Neutral Bases

Highest H+ conc. Lowest H+ conc.

4 Classes of Organic Molecules

1. Proteins2. Carbohydrates3. Lipids4. Nucleic Acids

Functions of Proteins1. Structural proteins - form cell parts

2. Regulatory proteins - control cell processes

3. Enzymes - facilitate (help) many chemical reactions; they do this by lowering the amount of energy needed to start the reaction; the enzyme is not permanently altered in the process.

4. Hormones - chemical messengers

5. Transport proteins - carry other substances around cells or from cell to cell.

Carbohydrates

• Most abundant types organic molecules

• Function: energy sources & structural components • monomers of carbohydrates = isomers of C6H12O6

3 Major Categories Carbohydrates

1. Monosaccharides

2. Disaccharides

3. Polysaccharides

Lipids

Fats, oils, waxes, steroids, & phospholipids. Function: energy storage, waterproof coatings, chemical messengers.Three categories of lipids:

Triglycerides (saturated & unsaturated fats)WaxesPhospholipidsSteroids

Nucleic Acids

Nucleic Acids - Large moleculescarry coded genetic information Polymers of nucleotides (monomer) Two main types:

Deoxyribonucleic acid (DNA) Double helix of anti-parallel nucleotide chains

Ribonucleic acid (RNA)Single nucleotide chain