Chapter 2

The Chemistry of Life

Section 1 – The Nature of Matter

• Atoms are the basic unit of matter.• Subatomic particles that make up atoms are

protons, neutrons, and electrons.• Protons – positively charged particles• Neutrons – carry no charge, neutral• Protons and neutrons are found in the nucleus

of the atom

Electrons

• Electron – negatively charged particle• In constant motion in the space surrounding

the nucleus.

Elements

• Element – pure substance that consists entirely of one type of atom.– Represented by a one- or two- letter symbol.– Elements are arranged into the periodic table.

Chemical Compounds

• A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions.

Chemical Bonds• Ionic bonds – formed when one or more electrons

are transferred from one atom to another.• Covalent bonds – formed when electrons are

shared between atoms.• Van der Waals forces – when molecules are close

together, a slight attraction can develop between oppositely charged regions of nearby molecules. These attractions are not as strong as ionic or covalent bonds.

Section 2 - Properties of Water

• Polarity – a molecule in which the charges are unevenly distributed is a polar molecule.– A water molecule is polar because there is an

uneven distribution of electrons between the oxygen and hydrogen atoms.

Hydrogen Bonds

• A single water molecule may be involved in as many as four hydrogen bonds at the same time.– Cohesion: an attraction between molecules of the

same substance.– Adhesion: an attraction between molecules of

different substances.

Mixture

• Mixture – a material composed of two or more elements or compounds that are physically mixed together but not chemically combined.

Solutions

• Solution – all components are evenly distributed throughout.– Solute – the substance that is dissolved– Solvent – the substance in which the solute

dissolves

Suspensions

• Suspension – mixture of water and non-dissolved materials.– Materials will separate into pieces but do not

settle out

Acids, Bases and pH

• The pH scale – a measurement system that indicates the concentration of H+ ions in a solution.– Ranges from 1 – 14– 7 is neutral– Under 7 is acidic– Above 7 is basic

Acids

• Any compound that forms H+ ions in solutions.– pH value below 7

Bases

• Any compound that produces hydroxide (OH-) ions.– pH value above 7

Buffers

• Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.– Help control pH and retain homeostasis in the

body.

Section 3 – Carbon Compounds

• Macromolecule: LARGE carbon molecule • Polymer: Large molecule formed when many

smaller molecules bond together

Carbohydrates

• 2 H atoms for every O & C– 1. Simplest carbs: Called Monosaccharides

(one sugar)-Ex: glucose; fructose

- 2. Disaccharides – two sugars -Sucrose (glucose + fructose) - 3. Polysaccharides – many sugars

-Starch, glycogen, and cellulose

Lipids

• Lipids: Fats; Organic compounds that have a large proportion of C-H bonds and less O than carbs.

• Insoluble in water because lipids are nonpolar• Saturated Fat: Animal fats• Unsaturated Fat: Oils

Proteins

• A large, complex polymer composed of carbon, hydrogen, oxygen, nitrogen, and usually sulfur; have an “R” group that makes each different

• Made from amino acids • 20 common amino acids • Proteins are the building blocks of many

structural components

Proteins

• Amino Acids are linked together when an H-group and –OH group are removed to form water

• The covalent bond formed between A.A. is a PEPTIDE BOND

Nucleic Acids

• A complex macromolecule that stores cellular info. in the form of a code

• Nucleic acids are made up of smaller subunits called Nucleotides

• Nucleotides consist of three basic parts:– 1. Nitrogen-containing base– 2. Pentose sugar– 3. Phosphate group

Types of Nucleic Acids

• 1. DNA: Deoxyribonucleic acid– Master copy of organism’s genetic info.– Contains instructions used to form organism’s

enzymes and proteins

2. RNA: Ribonucleic acid– Forms a copy of DNA for use in making copies and

proteins

Section 4 - Chemical Reactions

• Chemical formulas describe the substances in the reaction and arrows indicate the process of change

• Reactants – starting substances on the left side of the arrow

• Products – substances formed during the reaction on the right side of arrow

• Arrow can be read as “yields” or “react to form”

Energy in Reactions

• Key to starting a chemical reaction is energy• Energy in the form of heat is need• Most compounds in living things cannot

undergo chemical reactions without energy

Activation Energy

• Minimum amount of energy needed for reactants to form products in a chemical reaction

Energy Change in Chemical Reactions

• In every chemical reaction, there is a change in energy due to the making and breaking of chemical bonds

• Exothermic reactions – energy of the product is lower than the energy of the reactants– Energy is released in the form of heat

• Endothermic reactions – energy of the products is higher than the energy of the reactant– Heat energy is absorbed

Endothermic Reaction

Exothermic Reaction

Enzymes

• Catalyst – substance that lowers the activation energy needed to start a chemical reaction

• Enzymes – special proteins that are the biological catalysts that speed up the rate of chemical reactions in biological processes– Essential to life– Not used up by the chemical reaction– Can be used again– Most enzymes are specific to one reaction

Enzymes

• Substrates – reactants that bind to the enzyme

• Active Site – specific location where a substrate binds on an enzyme– The active site and substrates have

complementary shapes– Only the substrate with the same shape as the

active site will bind to the enzyme– Example : Lock & Key

Enzymes

• Once the substrates bind to the active site, the site changes shape and forms the enzyme-substrate complex

• The new complex helps chemical bonds in the reactants to be broken and new bonds are formed

• The substrates react to form products• The enzyme then releases the products• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

Enzymes

• Factors such as pH, temperature, and other substances affect enzyme activity

• Enzymes affect many biological processes– Examples: • Photosynthesis• Respiration• Snake bite• Fruit ripening