Chapter 2 : The Chemistry of Life

Chemistry All living things depend on chemistry - The structure and function of all living things are governed by the laws of chemistry. Why is it important to understand chemistry in biology?

Section 1 COMPOSITION OF MATTER

Matter Everything in the universe is made of matter. Matter is anything that occupies space and has mass. Mass is the quantity of matter an object has

Elements and Atoms Elements are substances that cannot be broken down chemically into simpler kinds of matter. Information about elements is summarized on a chart called the periodic table. The simplest particle of an element that retains all of the properties of that element is an atom.

Elements and Atoms

The Nucleus Nucleus – the central region that makes up the bulk of the mass of the atom. Consists of: Protons - positively charged particles Neutrons – particles with no charge

Electrons Net electrical charge of an atom is ZERO.

Electrons – small, negatively charged particles. Move around the nucleus at very high speeds Located in orbitals – regions around a nucleus that show the probable location of an electron. Orbitals correspond to specific energy levels.

Elements Atomic Number = number of protons in an element. Mass Number = total number of protons and neutrons in the atom.

Isotopes Atoms of the same element that have a different number of neutrons. Average atomic mass of an element takes into account the relative amounts of each isotope in the element.

PRACTICE In groups, we are going to practice drawing elements on white boards. Group 1 – Draw and identify the element that has 6 protons, 6 neutrons, and 6 electrons. Group 2 – Draw and identify the element that has 7 protons, neutrons, and electrons.

Group 3 – 8 protons, neutrons, and electrons

Compounds Compounds are made up of atoms of two or more elements in fixed proportions. Chemical formula shows the kinds and proportions of atoms of each element that forms a particular compound (Ex: H20) Compounds are usually very different from the elements that form them.

Compounds Most atoms are not stable in their natural state, so they tend to react with other atoms in different ways to become more stable. Chemical bonds are the attractive forces that hold atoms together.

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 Single, double, and triple bonds Ion – atom or molecule with an electrical charge (Na+, Cl- ) Molecule - simplest part of a substance that retains all of the properties of that substance and can exist in a free state

Section 2 ENERGY

Energy All living things use energy. Amount of energy in the universe stays the same. Can change from one form to another. Transfer of energy is very important in biology.

Energy – the ability to do work Energy and Matter Energy – the ability to do work Occurs in various forms and one form of energy can be changed to another form. Important forms of energy in biological systems. Chemical, thermal, electrical, and mechanical.

States of Matter The atoms and molecules in any substance are in constant motion. The motion and spacing between atoms or molecules determine the substances state: solid, liquid, or gas.

http://www.harcourtschool.com/activity/states_of_matter/ States of Matter

Energy and Chemical Reactions Chemical Reaction –one or more substances change to produce one or more different substances. Energy is absorbed or released when chemical bonds are broken and new ones are formed. Living things undergo many thousands of chemical reactions every day.

Energy and Chemical Reactions Reactants – substances or molecules that participate in a chemical reaction. Products - substances that form in a chemical reaction.

Energy and Chemical Reactions Metabolism – the sum of all the chemical reactions that occur in an organism. Energy your body needs is provided by sugars, proteins, and fats found in foods. Body continuously undergoes chemical reactions to break down stored energy from foods into substances your body can use for energy.

Activation Energy Activation Energy - the amount of energy needed to start a chemical reaction. Catalysts – Chemical substances that reduce the amount of activation energy that is needed for a reaction to take place. Enzymes – biological molecules that speed up metabolic reactions without being permanently changed or destroyed!

Water & Solutions (Section 3) Chemical reactions of all living things take place in the watery environment of the cell Water has several unique properties that make it one of the most important compounds found in living things.

Polarity Polar – compounds with an uneven distribution of positive and negative charges.

Solubility of Water The polar nature of water allows it to dissolve polar substances, such as sugars, ionic compounds, and some proteins. Water does not dissolve nonpolar substances such as fats like oil.

Hydrogen Bonding The polar nature of water causes water molecules to be attracted to one another. Hydrogen bond – the force of attraction between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial or full negative charge.

Cohesion and Adhesion Cohesion Adhesion - An attractive force that holds molecules of a single substance together. - An attractive force between two particles of different substances

Capillary Action – Attraction between molecules that results in the rise of the surface of a liquid when in contact with a solid.

Questions How are cohesion and adhesion similar? How are they different? How do they contribute to capillarity?

Solid water is less dense than liquid water Density of Ice Solid water is less dense than liquid water This is the opposite of all other substances! Hydrogen bonding causes ice crystals to have large amounts of open space.

Why is it important that ice is less dense than water?

Solutions Solution – a mixture in which one or more substances are uniformly distributed in another substance. Solute - substance dissolved in the solvent (may be ions, atoms, or molecules) Solvent – substance in which the solute is dissolved. Sugar dissolved in water – which one is the solvent and which is the solute?

Solutions Solutions – a mixture in which one or more substances are uniformly distributed in another substance. Solute – substance dissolved in the solvent (may be ions, atoms, or molecules) Solvent – substance in which the solute in dissolved. Sugar dissolved in water – which one is the solvent and which is the solute?

Solutions Solutions can be composed of various proportions of a given solute in a given solvent Concentration of a solution is the amount of solute dissolved in a fixed amount of the solution. A saturated solution is one in which no more solute can be dissolved.

Aqueous solutions - solutions in which water is the solvent. Important to living things Marine microorganisms spent their lives in the sea. Most nutrients plants need are in aqueous solutions in moist soil. Body cells exist in an aqueous solution and are filled with aqueous solution.

Important Properties of Water Property What It Does/Means Importance Cohesion Water molecules stick together Movement of water in plants, surface tension Adhesion Water sticks to another substance Capillarity High heat capacity Absorb and release large amounts of heat energy without a big change in temp Stabilizes global temps, keep cells at even temps. Solvent Water can dissolve many different substances Marine organisms, plant nutrients, body cells.

Acids and Bases What do the words acids and base mean?

Ionization of Water As water molecules move, they bump into each other. Some of these collisions are strong enough to result in a chemical change. One water molecule loses a proton while another gains a proton.

Ionization of Water

Ionization of Water H3O+: Hydronium Ion OH- : Hydroxide Ion Acidity or alkalinity is a measure of the relative amounts hydronium ions and hydroxide ions dissolved in a solution.

Acids Bases Number of hydronium ions (H3O+) GREATER than the number of hydroxide ions (OH-) Tend to have a sour taste. Number of hydronium ions (H3O+) LESS than the number of hydroxide ions (OH-) Alkaline Bitter taste

pH pH scale – scale for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution. Ranges from 0-14. Change in 1 pH unit is a 10-fold change in acidity or alkalinity.

Buffers Buffers are chemical substances that neutralize small amounts of either an acid or base added to a solution. Control of pH is important for living systems. Enzymes can functions only within a very narrow pH range.