Chapter 2The Chemistry of Life

I. atomatom-smallest part of an element.

A. Made up of:

1. Nucleus

Protons (+)

Neutrons (neutral)

a. Protons’ mass = neutron mass

2. Electrons (e-) (-)

a. Move around nucleus b. Move in cloudy pathway called orbitalsorbitals.

c. Much smaller than a proton or neutrond. Same # as protons

e. (+) charge of nucleus holds the (-) e- in their orbitals.

B. ElementElement- pure substance that consists entirely of one type of atom.

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CCarbon12.011

1. The difference between atoms of different

elements is the # of protons and electrons it has.

2. IsotopesIsotopes- atoms of the same element that have a different number of neutrons.

a. Radioactive isotopeRadioactive isotope- isotopes that have an unstable nucleus.

6 electrons6 protons8 neutrons

6 electrons6 protons7 neutrons

6 electrons6 protons6 neutrons

Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14

i. Used to determine the age of rocks and fossils, treat cancer, kill bacteria, and trace different molecules through organisms.

II. Chemical bondsChemical bonds-linkbetween atoms

A. Make:

1. CompoundsCompounds-bonding of at least two different elements.

B. Why do atoms bond to each other?

1. To fill their electron orbitals.

2. MoleculeMolecule-two or more atoms joined together by a covalent bond.

C. Types of bonds 1. Covalent bondsCovalent bonds-e- are

shared between 2 atoms.

a.Can be:

i. Single bond

ii. Double bond

iii. Triple bond

2. Ionic bondsIonic bonds- when e- are lost or gained, then the resulting ions attract.

a. ionion- an atom that has gained or lost e-, therefore acquiring a charge.

Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)

Transferof electron

Protons +11Electrons -11Charge 0

Protons +17Electrons -17Charge 0

Protons +11Electrons -10Charge +1

Protons +17Electrons -18Charge -1

Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)

Transferof electron

Protons +11Electrons -11Charge 0

Protons +17Electrons -17Charge 0

Protons +11Electrons -10Charge +1

Protons +17Electrons -18Charge -1

3. Van der Waals forcesVan der Waals forces- an attraction between oppositely charged parts of nearby molecules.

D. Chemical formulas

1. Examples:

a. H2O

b. C6H12O6

c. CH4

III. WaterA. Properties of water1. PolarPolar- has a slight positive

charge on one end of the molecule, and a slight

negative charge on the other end b/c one atom pulls e- closer than the other.

a. O pulls harder than H

2. Forms hydrogen bonds.

a. Because of this water has:

i. CohesionCohesion- attraction between molecules of the same substance.

- causes water’s surface tension.

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b. AdhesionAdhesion- attraction between molecules of different

substances.

- causes capillary action (how water gets from the roots to stem and leaves)

3. Water is the universal solvent.

a. b/c it’s polar, it pulls apart other molecules (things

dissolve in it easily).

b. SolventSolvent- substance in which the solute dissolves.

c. SoluteSolute- substance that is dissolved.

d. SolutionSolution- mixture of two or more substances where

each substance is evenly distributed.

e. Aqueous solutionAqueous solution- when something is dissolved in water.

IV. pH scale (ranges from 0-14)

A. H20 H+ + OH-

C. basebase- produces OH- ions (>7-14).

B. acidacid- produces H+ ions (0<7).

D. BufferBuffer- weak acids or bases that react with strong

acids or bases to prevent a sudden change in pH.

V. Compounds of Life

A. Carbon=most important element in life

1. Why?

a. Can form 4 strong covalent bonds.

b. Can form long chains or rings.

c. Can form single, double, or triple bonds.

Methane Acetylene Butadiene Benzene Isooctane

2. Organic compoundOrganic compound-any compound that contains carbon.

3. Inorganic compoundsInorganic compounds- any compound that

does not contain carbon.

VI. Macromolecules

1. MonomerMonomer- small molecule that makes up polymers.

2. PolymerPolymer- large molecules made of smaller molecules (monomers).

3. MacromoleculeMacromolecule- large polymers.

A. Four major classes of macromolecules (Carbohydrates, Lipids, Proteins, Nucleic Acids)

a. Living things use them as their main

source of energy.

1. CarbohydratesCarbohydrates- made of carbon, hydrogen,and oxygen.

b. Include sugars (monomers) and starches (polymers)

c. Simple sugars (glucose & fructose) = C6H12O6

i. Simple sugars are also called monosaccharidesmonosaccharides.

d. Organisms store simple sugars by linking them into polymers.

i. These polymers are called polysaccharidespolysaccharides.

ii. In plants = starch iii. In animals = glycogen

2. LipidsLipids- are made mostly of carbon and hydrogen and includes waxes, fats, & oils.

a. Lipids are used to store energy.

b. Lipids are an important part of biological membranes.

c. Lipids are made of glycerol and fatty acids (monomers).

b. Two kinds of fats:

i. Saturated fatSaturated fat- fatty acids have the max # of H’s

ii. Unsaturated fatsUnsaturated fats- fatty acids don’t have maximum # of H’s.

3. Nucleic acidsNucleic acids- polymers assembled from individual monomers called nucleotides.

a. Nucleic acids store and transmit heredity or genetic information.

b. Two kinds of nucleic acids:

i. DNA (Deoxyribonucleic acid)

ii. RNA (Ribonucleic acid)

b. Each nucleotide (monomer of nucleic acids) is made up of:

i. 5-carbon sugar (Ribose in RNA and Deoxyribose in DNA)

ii. Phosphate group

iii. Nitrogenous base

3. ProteinsProteins- polymers of molecules of amino acids.

a. There are 20 different amino acids.

b. Each amino acid has an amino group (NH2) and a carboxyl group (COOH) at the end.

General structure Alanine Serine

Amino group

Carboxyl group

c. Each also has an “R” group that is different for every amino acid.

d. When two amino acids bond, the COOH bonds to

the NH2 to form a peptide bond and water (H2O).

e. polypeptidepolypeptide- (another name for protein) several amino acids bound togetherf. The instructions for

arranging a protein are in the DNA.

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g. Proteins have many functions including:

i. Providing structure (making muscle, bone, etc.)

ii. Transport substances in and out of the cell.

iii. Fight off diseases.

iv. Control the rate of chemical reactions and regulate cell processes.

V. Chemical ReactionChemical Reaction- process that changes one set of chemicals into another set.

A. Your body uses chemical reactions everyday.

C. ex: CO2 + H20 H2CO3

ReactantsReactants ProductsProducts

B. Chemical reactions always involve breaking bonds

and making new bonds.

D. Energy is released when chemical bonds are broken; energy is stored when chemical bonds are made.

E. Activation energyActivation energy- energy that’s needed to get a

reaction started.

1. CatalystCatalyst- molecule that speeds up a chemical reaction.

Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Products

Activation energy

Activation energy

Reactants

Reactants

2. EnzymeEnzyme- protein catalyst in living things.

a. An enzyme lowers the amount of activation energy it takes to start a reaction.

Glucose

Substrates

ATP

Substratesbind toenzyme

Substratesare convertedinto products

Enzyme-substratecomplex

Enzyme(hexokinase)

ADPProducts

Glucose-6-phosphate

Productsare released Active site

b. Factors that can affect how an enzyme works:

i. Temperature

ii. pH