The Chemical Basis of Life

All the chemistry you need to know

Matter is anything that occupies space and has mass.

Energy is the capacity to do work, or put mass into motion.

Potential (stored) energy

Kinetic energy (energy of motion)

Some forms of energy:• Radiant energy - energy that travels in

waves

• Electrical energy – flow of charged particles

• Heat – kinetic energy of molecules

• Chemical energy - potential energy, the way living things store energy

Elements are substances which cannot be splitinto simpler substances by ordinary chemical reactions.

Each element has a one or two letter chemicalsymbol.

C

O

H

N

Ca

Cl

Na

K

Carbon

Oxygen

Hydrogen

Nitrogen

Calcium

Chlorine

Sodium

Potassium

O, C, H, N = 96 % of body weight

Add

Ca and P = 98.5 % of body weight

Add

K, S, Cl, Na and Mg = 99.9.% of body weight

“Bulk Elements”

Atoms are the smallest unit of an element that still has the chemical properties of that element.Atoms:Have a central nucleus

Protons (+)Neutrons (0)

Orbitals on the outside that hold

Electrons (-)

The number of electrons in the outermost shell determines how each atom interacts with other atoms.

Atomic number = the number of protons in the atom.

Atomic weight (or Mass number) = the total number of protons and neutrons.

Isotopes are atoms of an element that all have the same number of protons, but have different numbers of neutrons.

The time it takes for half of a radioactive substance to decay is called its half-life.

When two or more atoms combine in a chemical reaction, a molecule is formed. This molecule may have very different properties than the elements that formed it.

When a molecule contains two or more atoms of different elements, it is called a compound.

CO2 H2O NaCl C12H22O11

• Atoms are most stable when their outermost shell contains eight electrons. They may accept, give up or share electrons with another atom to do this.

• The outer most shell is the valence shell and the number of electrons that must be gained or lost to fill or empty that shell is called the valence number.

Atoms are held together by forces of attraction called chemical bonds, which are forms of potential energy.

Ionic bonds

Covalent bonds

Hydrogen bonds

In an ionic bond electrons are transferred from one atom to another. Opposing charges hold the atoms together.

An ion is a charged particle (atom or molecule).

Na+ Ca++ positive charge - cations Cl- HCO3

- negative charge – anions

Substances that breaks into positively and negatively charged ions in solution are called electrolytes.

Covalent bonds are formed when atoms share electrons. These are the strongest bonds. C - C

Double covalent bonds C=C

Triple covalent bonds N≡N

(atmospheric nitrogen)

• Electronegativity – electron “hog”

When one end of molecule has a positive charge and the other has a negative charge, the molecule is polar.

When molecules have a more uniform distribution of charges they are called nonpolar molecules.

Polar molecules are hydrophilic .“water loving”

Nonpolar molecules are hydrophobic.“water fearing”

Hydrogen bonds are weak but important bonds. They do not bind atoms into molecules, but are important in giving large molecules their shape.

Chemical reactions involve making and breaking bonds.

Making bonds requires the input of energy.

Energy is stored in molecules in the chemical bonds.

Breaking bonds usually releases energy.

Water• Water is denser as a liquid than a solid

– Ice floats

• Water has a high heat capacity– Allows for heat loss by sweating or panting

• Water is cohesive– Water strider = good– Lungs = bad – Surfactant reduces the surface tension of

water

Water cont.

• Water clings to surfaces – adhesion– This is how plants bring water up to their

leaves

• Water is a good solvent– Substances dissolved in water are solutes– Many important biological molecules are

amphipathic – (both – feeling) hydrophilic and hydrophobic ends

Water participates in chemical reactions:

dehydration synthesis - combines atoms with the removal of water

hydrolysis – breaks apart molecules with the addition of water.

Water breaks up into hydrogen ions (H+)

and hydroxide ions (OH-)

Chemical equilibrium = balance

pH

• The negative log of the hydrogen ion concentration. The more hydrogen ion a solution has, the lower its pH is.

• “power of hydrogen”

In water:

Acids - one or more hydrogen ions (H+) and one or more anions.

Bases - hydroxide ion (OH-) and one or more cations.

A salt ionizes into anions and cations, neither H+ nor OH-

pH regulation (homeostatsis)

• 7.35 – 7.45

• CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+

• Buffer systems

• Respiratory system

• Excretion by kidney