Chemistry of Life Chapter 2

Questions 1. What is the difference between an element and an atom? 2. What is makes up the mass of matter?

Standard: Students must be able to explain how atoms interact with each other and cause living tissues to function. To accomplish this students must: – Know the parts of the atom – Know how to identify them on the periodic table – Know how to identify and explain bonding of elements to each other

Matter Matter is anything that takes up space and has mass. All living and non-living things are made up of matter Chemistry is important to understanding of how biological processes occur in living things. You must know basic chemical principles to understand biology

Composition of Matter ELEMENTS Elements are found on the periodic table. Element – cannot be broken down any further without losing the properties of the material Elements are made up of atoms – Atoms are made up of Subatomic particles Neutron – no charge, found in the nucleus Proton – positive charge, found in the nucleus Electron – negative charge, orbits around the nucleus

Atomic structure Nucleus contains protons and neutrons Electrons fly around it.

Composition of Matter Atomic number –is the number of protons, and determines what element it is on the per. table Atomic mass – Is the Sum of the number of protons plus neutrons – Electrons are so tiny they do not contribute to mass so the mass is not included Isotopes – Are Elements with same number of protons, but a different number of neutrons (mass is different!)

Compounds Are Made up of atoms of two or more elements in a fixed proportion Remember: Most elements do not exist alone in nature, so they form compounds Forming compounds changes the chemical properties of each element, so they act differently – Example: Sodium reacts with water in the air and explodes. Chlorine is a poisonous gas. But when in compound (NaCl) is makes food tasty, and is harmless!

Compounds Elements alone are usually not stable They want to be stable, so they will combine with other elements to form compounds Elements want their pockets full (their outer electron shell) usually 8 electrons! In order to accomplish this, they must bind with other elements (or sometimes an element of the same type)

So what is a molecule? A group of atoms bound together. They are the smallest number of atoms that can be put together and then make a new substance of that kind. We usually use the term molecule and compound interchangeably because you must have a compound to make an atom. Examples:

Chemical Bonding Ionic bonds – Donate/receive electrons from another element – Metal join to non-metals Covalent bonds – Sharing of electrons, does not have to be equal – Non-metals join to non-metals – Covalent bonds cause Polarity Polar covalent bonds have unequal sharing of electrons This results in a stronger charge one end of the atom than the other

Ionic or covalent? 1. I 2 2. LiF 3. O 2 4. CaCl 5. NO 3

Topic: Energy Bellwork: 1.What two things do catalysts do to reactions? 2. What important property of catalysts makes them unique in chemical reactions? 3. On the activation energy graph, what happens to the energy “line” when a catalyst is present?

Energy All living things require energy to carry out daily processes.  In biology, the important forms of energy are: Chemical (breaking down food) Thermal (heat) Electrical (nerve impulses) Mechanical (movement)

Energy  Metabolism – all of the chemical reactions involving energy in the body Atoms combine and make compounds and Compounds break apart releasing energy  Energy is absorbed or released when chemical bonds are broken and formed Exergonic reactions – release energy (exo=out) Endergonic reactions – absorb energy(endo=in)

Activation Energy Most chemical reactions in the body require energy input in order to start the reaction Catalysts are substances that help reduce the amount of energy required to start the reaction  Enzymes are the main biological catalysts in the body – Enzymes are known as proteins and some RNA

Energy Without biological catalysts, most of the reactions that occur in the body cannot occur or occur too slowly to sustain life Enzymes are not part of the reaction, and they are used over and over again.

REVIEW What is the name of the energy that starts biological chemical reactions? What is the name of the catalysts found in the human body? What two important things do catalysts do in chemical reactions?

Water & Solutions

Importance of Water Your body is 60-70% water Water’s unique properties are due to the structure of the molecule – Water is a polar which means it has two ends like the Earth, neg. on one end, pos. on the other. – Polarity of water allows water to dissolve other polar molecules, attracting them like magnets. – Dissolved particles are critical to daily functioning of our body cells.

Water Vocabulary The polarity of water also causes it to be “sticky” – COHESION: Water is attracted to other water molecules : water sticks to water to make large drops – ADHESION: Attraction of water to other surfaces like the sides of a glass cylinder – CAPILLARY ACTION: movement of water (and aqueous solutions) upward against gravity, like up a tree from roots to the top.

Specific Heat of Water Water also has a high specific heat. – This means that water can absorb large amounts of energy and only change its temperature a small amount. – This is important in controlling body temperature – Also important in regulating temperature of the Earth (our external environment)

Solutions Mixture of one or more substances Can be solid, liquid or gas Solute – substance being dissolved Solvent – substance doing the dissolving Saturated solution – Solution in which the max amount of solute is dissolved

Solutions - vocabulary Aqueous solution – a solution in which water is the solvent Our body cells are in aqueous solution (remember that the majority of our body and cells are water) Water helps us maintain homeostasis (a balanced internal environment)

Acids/Bases As water moves around, it is likely that the polarity will cause some hydrogen molecules to come apart from the water molecule (forming hydrogen ions & hydroxide ions) – Basically, H 2 0  H + + OH - The free hydrogen ions can associate with other water molecules to form hydronium ions (H 3 O + ). These are what are measured as “acids”. This hydronium ion “burns “ our skin.

Acids/Bases BASES, when on our skin, leave slimy films as they eat our skin. ALKALINE – refers to “bases”. A solution is alkaline if it has more OH molecules in it than H3O. OH- is known as a HYDROXIDE ion.

BUFFERS A buffer is what neutralizes an acid or a base. If you have an acidic upset stomach, you add a base buffer. The H3O ion will be neutralized by the OH buffer (water will be produced). If you have chlorox (a base) on your hand, you can wash it off with vinegar (an acid).

Acids/Bases Acidity and alkalinity are related to the measure of the hydroxide and hydronium ions in the solution – Equal OH - & H 3 O + = neutral solution – More OH - than H 3 O + = basic solution – More H 3 O + than OH - = acidic solution

Acids/Bases pH – – 0-14 scale – 0 being most acidic, 7 neutral, 14 being most basic Our body is constantly carrying out reactions that form acids, water is constantly moving around, chemicals are constantly buffering these acids. Our body is extremely sensitive to pH changes. – Your blood ph is – Most of our enzymes require a pH in that range to function. – DEATH is the result of these getting out of range.