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 MatterELEMENTS

• 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. I2• 2. LiF• 3. O2• 4. CaCl• 5. NO3

Topic: EnergyBellwork:

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 energyEnergy is absorbed or released when chemical

bonds are broken and formedExergonic 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 endslike 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, H20 H+ + OH-

• The free hydrogen ions can associate with other water molecules to form hydronium ions (H3O+).

• 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- & H3O+ = neutral solution

– More OH- than H3O+ = basic solution

– More H3O+ 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 7.35 -7.45.– Most of our enzymes require a pH in that range to function.– DEATH is the result of these getting out of range.