Chapter 2

The Chemistry of Life

2.1 The nature of matter• Atom: the smallest particle of an

element that has the properties of that element

• Atom is made of three subatomic particles:

1) Proton * Positive, nucleus

2) Electron * Negative, outside nucleus in energy levels First energy level -- 2e Second energy level -- 8e Third energy level -- 18e

3) Neutron * No charge, nucleus

                                                                                                                                                                                                                                                                                                                                 

• Number of protons usually is equal to the number of electrons so that the overall charge of an atom is neutral!! 

• If atoms of the same element have different number of neutrons, they are called isotopes! EX. C - 12 , C - 13, C - 14

• When two or more atoms of different elements are chemically combined you create what is called a compound. EX. Water

Compounds can be made with three different

kinds of bonds: 1) Covalent

Share electrons to be stable

Strongest and most common bond

Molecule: group of atoms held together with covalent bonds with no overall charge

Van der Waals forces (what holds molecules together)

2) Ionic Gain / lose electrons

to be stable Ion: a charged

particle Less abundant in

living things than covalent bonds

3) Hydrogen

Mixtures & Solutions • Mixture: a combination of substances

in which the individual components retain their own properties

•  Solution: a mixture in which one or more substances are distributed evenly in another substance

– Two parts to every solution: 1. Solute --- What is being dissolved 2. Solvent -- What is doing the dissolving

* Most common... WATER

pH

• pH: a measure of how acidic or basic a solution is – Acid: substance that forms H+ ions in water

• 0 - 7

– Base: substance that forms OH- ions in water

• 7 – 14

Acids & Bases

Acids

• Higher concentration of H+ ions

• pH value less than 7

• Sour taste

• React with metals

• Blue litmus paper will turn red if an object is an acid

Bases

• Lower concentration of H+ ions

• pH value more than 7

• Bitter taste

• Slippery

• Turn red litmus paper blue if an object is a base

2.2 Water and Diffusion

• Perhaps the most important compound in living organisms is water!

• Properties of water:1) Polarity

• Has a positive and negative end

• Gives water its dissolving property

2) Resists Temperature Changes

3) Water expands when it freezes

4) Adhesion Graduated cylinder• Adhesion is greater between glass & water than

water & water!

2.3 Carbon Compounds

• The one element that defines living organisms is Carbon!

• Carbon has four electrons in its outermost shell; therefore, it can combine with almost every other element

• Any compound that contains carbon is considered to be an organic compound!

• If it does not contain carbon it is inorganic.

Four types of Organic compounds:

1) Carbohydrates: Made of C, H, O (C to H ration is 2 to 1) Monomer: monosaccharide Function: Provide quick energy EX. Glucose: how animals store food

Starch: how plants store food

Cellulose: composes cell walls of plants

2) Lipids

• Made of C, H, O --- (C to H ratio higher than 2 to 1)

• Monomer: Glycerol & 3 fatty acids

• Function: 1) Store energy 2) Insulation 3) Protection

• EX. Fats and Oils

3) Proteins

• Made of C, H, O, N, Sulfur

• Monomer: Amino Acid– 20 AA

• Function: 1) Build Muscle 2)Transportation (blood -- hemoglobin)

3) Speed up chemical reactions (enzymes)

4) Nucleic Acids

• Made of C, H, O, N, Phosphorus

• Monomer: Nucleotide

• Function: Store genetic information

• EX. DNA (Deoxyribose Nucleic Acid) – Master

RNA (Ribose Nucleic Acid) -- Copy of DNA

2.4 Chemical Reactions and Enzymes

• Chemical reaction = changes one set of chemicals into another set of chemicals

• Chemical reactions have two parts:1. Reactants

2. Products

• CO2 + H2O H2CO3

Reactants Product

Enzymes

• Enzymes are proteins that act as a biological catalyst.

• Catalyst: a substance that speeds up the rate of chemical reaction

• Enzymes speed up chemical reactions that take place in the cell.

Enzyme Action

• The enzyme-substrate complex– Enzymes are substrate specific.– They act like a lock and key.– Enzymes will only catalyze their substrates.

• Regulation of Enzyme Activity– Enzymes can be affected by:

• Heat • pH• Concentration of Substrate• Proteins that turn enzymes “on” and “off”

Example of what an enzyme does!How enzymes work

Potato + Peroxide water + oxygen (catalase)

Where are enzymes?

• Enzymes regulate many chemical reactions such as:– Photosynthesis– Cellular respiration– Digestion

• Enzymes are reusable– Once they work with one substrate they

release and go to another substrate.