The Chemistry of Life Unit One Biology Notes

The Atom Atom – smallest particle of an element Composed of 3 subatomic particles: 1. Proton – positively charged particle found within the nucleus 2. Neutron – particle with no charge found within the nucleus 3. Electron – negatively charged particle found outside the nucleus

Elements Element – pure substance made of one type of atom Periodic Table – Organizes elements Atomic Number - # of protons Atomic Mass - # of protons + neutrons

Compounds Compound – a substance that is made of atoms of different elements chemically combined. Water is a compound H2O Properties are different from those of the individual elements. Table salt (NaCl) – which is made of Na and Cl

Compounds

Chemical Bonds An atom is most stable when outer most shell is full Atoms will gain, lose, or share electrons with other atoms to become stable Valence electrons – electrons in the outermost energy level which are involved in bonding.

Bond Types Ionic Bond – electrons are gained or lost Ion – an atom that has gained or lost electrons Covalent Bond – sharing electrons Molecule – a group of atoms held by covalent bonds and have no charge A molecule of water is represented by H2O

Ionic Bond

Covalent Bond

The Water Molecule Water is one of the most important compounds in living organisms. Water serves as a means of transport. Water makes up 70 – 95% of organisms Water is an example of a polar molecule Polar molecule – molecule with an unequal distribution of charge. Has positive and negative ends = dissolve things Hydrogen Bond – weak bond between hydrogen and oxygen

Hydrogen Bond

Solutions and Mixtures Mixture – a combination of substances in which individual substances retain own properties Ex. Mix sand and sugar – they neither change nor combine Solution – a mixture in which one or more substances are distributed evenly in another substance – Ex. Kool-aid mix and water Solute – substance being dissolved – sugar Solvent – being dissolved in – Water is the universal solvent

Solute vs. Solvent

Solution Na+ Cl - Water

Carbon Compounds Carbon – a very unique and important element It can share bonds with other carbon atoms or other elements Can form single, double, or triple bonds Can form chains, rings, and large complex molecules

Macromolecules Large molecules (polymers) formed by linking many smaller molecules (monomers) Main categories of macromolecules: 1. Carbohydrates 2. Lipids 3. Nucleic Acids 4. Proteins

Carbohydrates Carbohydrates – organic compounds composed of carbon, hydrogen, and oxygen. Main source of energy for almost all living things A. Monosaccharides – simplest type of carbohydrate – glucose and fructose B. Disaccharide – two monosaccharides linked together – sucrose or table sugar C. Polysaccharide – many monosaccharides (starch, cellulose, and glycogen)

Lipids Lipids – fats used to store energy. Insoluble in water (important to membranes)

Nucleic Acids Contain C, H, O, N, and P Store information Made up of monomers called nucleotides - RNA – ribonucleic acids - DNA – deoxyribonucleic acids

Nucleotides

Proteins Proteins – contain C, H, O, N. Made of monomers called amino acids.

Chemical Reactions Reactants – substances undergoing the reaction. On left side of arrow Products – substances being produced. On right side of arrow Equations – must always be written balanced H2 + O2 H2O

Enzymes Catalyst – any substance that speeds up a chemical reaction without being used up in the process. Lowers the activation energy Enzyme – a protein that acts as a catalyst in a living organism. Changes in temperature or pH can adversely affect enzymes Substrate – substance that is acted on by the enzyme. It binds to enzyme where a new product is formed and released