UNIT 1: Foundations of Biology Chapter 2: Chemistry of Life

Essential Questions How do the unique properties of water allow life to exist in all of Earth’s biomes? List and describe the molecules necessary for life to exist. How do enzymes affect biological systems?

Composition of Matter Matter is anything that occupies space and has mass. Mass is the quantity of matter an object has. Mass and weight are different; weight is the force produced by gravity acting on mass. Elements are substances that cannot be broken down chemically into simpler kinds of matter . Elements are listed on the periodic table. An atom is the simplest particle of an element that retains all of the properties of that element. In an atom, the number of positively charge protons is balanced by an equal number of negatively charged electrons.

Composition of Matter The central region of an atom is called the nucleus; it makes up the bulk of the mass of an atom. Consists of two subatomic particles: Positively charged proton Neutral (no charge) neutron. The number of protons in an atom is known as the atomic number. The atomic number is found above the chemical symbol on the periodic table. The mass number of an atom is equal to the total number of protons and neutrons in the atom. The mass number is located beneath the chemical symbol and is equal to the total number of protons and neutrons.

Composition of Matter There are just as many negatively charged electrons in an atom as there are protons. Electrons are high-energy particles with very little mass. They buzz around the nucleus at high speeds in orbitals. An orbital is the three dimensional space around a nucleus that indicates the likely location of an electron. Not all atoms of an element have the same number of neutrons; those with a different number of neutrons are known as isotopes. The difference in the number of neutrons changes the mass of the element. C12 and C14

Composition of Matter

Energy 6O2 + C6H12O6  6CO2 + 6H2O Reactants Products Bonds break and form during chemical reactions. Chemical reactions change reactants into products by breaking or forming bonds between atoms. 6O2 + C6H12O6  6CO2 + 6H2O Reactants Products

Energy Chemical reactions release or absorb energy. Energy is required to break bonds in reactants, and energy is released when bonds form in products. Bond energy is the amount of energy required to break a bond between two atoms . Activation energy is the amount of energy that must be absorbed for a reaction to start.

Energy Oxidation Reduction Reactions. R3actions that transfer electrons are called oxidation reduction reactions. In an oxidation reaction the reactant loses one or more electrons and becomes more positively charged. In a reduction reaction, a reactant gains one or more electrons and becomes more negatively charged.

Energy

Energy Enzymes are catalysts that lower activation energy. Enzymes are often proteins.

Energy Reactions may be exothermic or endothermic. An exothermic reaction releases more energy than it absorbs; it is often given off as light or heat. An endothermic reaction absorbs more energy than it releases due to the higher bond energy required to form its products.

Water and Solutions Life depends on hydrogen bonds in water. Water is a polar compound; its atoms have unequal pulls on the electrons they share. Atoms in a polar compound may have a slight negative or positive charge due to the unequal pulls. A water compound is made of one (-) oxygen molecule and two(+) hydrogen molecules; forming hydrogen bonds. Properties of hydrogen bonds: high specific heat, cohesion, & adhesion.

Water and Solutions

Water and Solutions Many compounds dissolve in water. Compounds and ions cannot take part in chemical processes inside cells unless they dissolve in water. When one substance dissolves in another, a homogenous solution is formed. Solutions are formed by two parts: A solvent is the substance that is present in greater amount and dissolves another substance. A solute is a substance that dissolves in a solvent.

Water and Solutions Water molecules stick to each other as a result of hydrogen bonds. Cohesion is the attractive force that holds molecules of a single substance together. Cohesion contributes to the upward movement of water in plants.

Water and Solutions Surface tension is related to cohesion and allows water to act as if it as a thin skin on its surface. This is how water bugs can walk on water. Adhesion is the attractive force of two particles of different substances (e.g. water and glass molecules). Capillarity is the property caused by the attraction between molecules that results in the rise in the surface of a liquid when contacting a solid.

Water and Solutions Acidity or alkalinity is a measure of the relative amounts of hydronium ions and hydroxide ions dissolved in a solution. One molecule of water pulls apart another, or dissociates, into two ions of opposite charge. The OH- ion is known as the hydroxide ion. H2O  H+ + OH- The H3O+ ion is known as the hydronium ion. H+ + H2O  H3O+

Water and Solutions Some compounds form acids or bases. Acids form if the number of hydronium ions in a solution is greater than the hydroxide ions dissolved in the solution. Bases form when the solution contains more hydroxide ions than hydronium ions.

Essential Questions How do the unique properties of water allow life to exist in all of Earth’s biomes? List and describe the molecules necessary for life to exist. How do enzymes affect biological systems? Describe and list the chemicals necessary for life to exist.