Chemistry of LifeChapter 2

2.1 Nature of MatterOrganisms are chemical machines All organisms consist of atoms

– Subatomic particles Electron (e-) – located in electron cloud Proton (p+) – located in the nucleus Neutron (no) – located in the nucleus

Oxygen atom (O)

Nucleus:8 protons (+)8 neutrons

outermost energy level: 6 electrons (-)

inner energy level: 2 electrons (-)

Elements– Differ in the number of protons in

the nucleus.– Number of protons = Number of

electrons Elements are neutral on the periodic table

– Atomic Number = Number of protons– Atomic Mass = Number of protons +

Number of neutrons

http://www.privatehand.com/flash/elements.html

Using the Periodic Table, Complete the following:

Name Symbol # p+ # e- #no

Tin

25

N

15

12

Isotopes Differ in the number of neutrons they

contain in the nucleus– Example:

Carbon 12 – 6p+, 6e-, 6no

Carbon 13 – 6p+, 6e-, 7no

Carbon 14 – 6p+, 6e-, 8no

Chemical Bonding – Compounds are made of joined atoms of two or more different elements.

Valence shell – outermost electron shell– Atoms with a full valence shell are inert

(unreactive)– Atoms without a full valence shell can form

bonds (reactive).

Complete the following table and answer the question in your notebook:

Name Symbol # p+ # e- #no

Oxygen

6

K

53

- Why do all isotopes of an element have the same chemical properties? (Use your book to help you answer this)

Bohr Atom Models The first electron shell of every atom

can hold a maximum of 2 electrons. Each additional shell can hold a

maximum of 8 electrons.

Draw the electron configurations of an atom of the following elements:

1. Fluorine

2. Boron

3. Sodium

Covalent bonds – atoms share electrons

– Ex: H2, O2, CO2

covalent bonds

Oxygen atom (O) Carbon atom (C) Oxygen atom (O)

Carbon dioxide (CO2 )

Ionic Bonds Ionic Bonds – atoms gain or loose

electrons– Atoms form ions + charge – cation - charge – anion

Ex: NaCl

2.2 Hydrogen Bonds Hydrogen Bonds – weak chemical

attraction between polar molecules– Water is a polar molecule because the

electrons of O and H are shared unequally.

Special Properties of water Cohesion

• Surface tension Adhesion

• Capillary action Heat Capacity

• A large amount of heat is required to increase the temperature of water

Solutions Water’s polarity gives it the ability to

dissolve other polar molecules as well as ionic compounds

pH H2O H+ + OH-

The pH scale indicates the concentration of H+ ions in a solution.• Acids – contain more H+ ions therefore have

a pH below 7 The lower the pH the greater the acidity

• Bases – contain more OH- ions therefore have a pH above 7 The higher the pH the more basic

• Neutral – contain equal OH- and H+ ions

2.3 Carbon Compounds• 70% of your body is made of water.• The remaining 30% is made up

mostly of organic compounds (Carbon-based molecules).– Carbon is a unique element because it

forms four covalent bonds and can form a lot of different structures.

Many carbon-based molecules are made of many small subunits bonded together.– Monomers are the individual subunits.– Polymers are made of many monomers.

Carbohydrates Key source of energy found in

most foods Fruits, vegetables, and grains

Made up of single sugars called monosaccharides.

Glucose, fructose

Disaccharides - two monosaccharides are joined

Sucrose (table sugar)

Polysaccharides – chains of three or more monosaccharides

Starch, cellulose, glycogen

Polymer (starch)

Starch is a polymer of glucose monomers that often has a branched structure.

Polymer (cellulose)Cellulose is a polymer of glucose monomers that has a straight, rigid structure

monomer

Lipids Nonpolar molecules not soluble in

water Fats, phospholipids (make up the cell

membrane), steroids (cholesterol), waxes Saturated fatty acids

Solid at room temperature Butter, lard, grease

Unsaturated fatty acids Liquid at room temperature Olive oil, fish oil

Proteins Formed by chains of linked amino

acids Many functions including:

Enzymes Structural (imbedded in the cell membrane) Antibodies

Nucleic Acids Formed by chains of nucleotides

Two types : DNA (deoxyribonucleic acid)

Double strand of nucleotides Stores hereditary information

RNA (ribonucleic acid) Single strand of nucleotides Plays a key role in making proteins

Nucleotide

Another important biological moleculeATP (adenosine triphosphate)

– Consists of a single nucleotide with 2 extra phosphate groups.

– ATP stores energy temporarily.– All cells require ATP to function.

2.4 Chemical Reactions Chemistry allows life to function!

Everything living things do is possible due to chemical reactions

The chemistry of breathing

Chemical reactions release or absorb energy.

Activation energy is the amount of energy that needs to be put in to start a chemical reaction.

Exothermic reactions release more energy than they absorb.– Excess energy is released by the reaction

as heat.

Endothermic reactions absorb more energy than they release.– Energy is absorbed by the reaction.

Enzymes– Proteins that increases the speed of a

chemical reactions in cells– Act as a catalyst (reduces the activation

energy needed in a reaction)

Any factor that changes the shape of an enzyme can affect the enzyme’s activity.– An enzyme’s function depends on its

structure.– Denaturing (changing the structure) the

protein by changes in temperature or pH– Example: pepsin