The Chemistry of Life

Chapter 2Page 35

Homework – due tomorrow

Point form, please

• Page 39 1 and 2• Page 57 11 to 16

Life depends on chemistry.

Everything an organism takes into its body, in fact, the body itself, relies on chemical

reactions and their products.

• Even though all cells come from pre-existing cells and the cell is the basic unit of life, cells themselves are made up of non-living substances called chemicals. (proteins, COH, lipids, nucleic acids)

• These organic compounds are the chemicals of life.

C:\Users\joanne.currie\Desktop\BBC.The.Cell.1of3.The.Hidden.Kingdom.XviD.AC3.MVGroup.org.avi

• Elemental composition of a human• Element Percent by mass Atomic percent (calc.) • Oxygen 65% • 25.6% • Carbon 18% • 9.5% • Hydrogen 10% • 63% • Nitrogen 3% • 1.3% • Calcium 1.5% • 0.24% • Phosphorus 1.2% • 0.24% • Potassium 0.2% • 0.03% • Sulfur 0.2% • 0.04% • Chlorine 0.2% • 0.04% • Sodium 0.1% • 0.03% • Magnesium 0.05% • 0.01% • Iron 3 g in men, 2.3 g in women• Cobalt, Copper, Zinc, Iodine < 0.05% each• Selenium, Fluorine < 0.01% each• (from Chang, Raymond (2007). Chemistry, Ninth Edition. McGraw-Hill. pp. p. 52. ISBN 0-07-110595-6. )[1]

• Chemical reactions are constantly occurring in an organism. Bonds are broken; bonds are formed in the continuous cycle of matter called metabolism.

– Anabolic reactions – Process by which smaller molecules are combined to create macromolecules. Uses energy. Building

– Catabolic reactions – Process by which macromolecules are broken down into their subunits. Produces energy. Breaking

Chemical Bonds (continually broken and reformed)

• http://www.youtube.com/watch?v=-mjRmqWgWsY

Atoms, elements and compounds review

Atoms

• Atoms are the basic building blocks of all matter – solids, liquids, gases.

• Atoms are so small that there are millions and billions and trillions in the tiniest speck you can see.

Subatomic particles that make up atoms are:

• Protons

• Neutrons

• Electrons

• Elements are the kinds of atoms there are. An element is a pure substance that consists entirely of one type of atom.

• All the elements we know of are represented by a one or two letter symbol and are listed in the periodic table.

Elements

The number of protons in an atom of an element is its atomic number.

The number of electrons in an atom is equal to the number of protons.

Isotopes

• But, atoms of an element can have different numbers of neutrons.

– Carbon C• Some carbon atoms have 6 neutrons, some have 7 and

some have 8.

Isotopes

• Atoms of the same element that differ in the number of neutrons are called isotopes.

• The sum of the protons and neutrons in the nucleus of an atom is called its mass number. Isotopes are identified by their mass number.

• The weighted average of the masses of an element’s isotopes is called its atomic mass.

• Because they have the same number of electrons, all isotopes of an element have the same chemical properties.

Radioactive isotopes

• Some isotopes are radioactive which means that their nuclei are unstable and break down at a constant rate over time.

• The radiation is dangerous but often can be used for specific purposes.

Compounds

• Chemical compounds are made by joining 2 or more elements in definite proportions. These elements are held together by their outer electrons which form a chemical bond.

The main types of bonds are:

• Ionic bonds – One or more electrons are transferred from one

atom to another.– An atom that gains an electron has a negative

charge.– An atom that loses an electron has a positive

charge.– An atom with a charge is called an ion.– Ions of different charges are attracted to each other.

This attraction is called an ionic bond.

• Covalent bonds– Between certain atoms, electrons are shared,

travelling in the orbitals of both atoms.– When the atoms share 2 electrons, it is a single

covalent bond; 4 electrons, double covalent bond; 6 electrons, triple covalent bond.

Molecules

When atoms are joined together by covalent bonds, they make molecules. For example, two atoms of hydrogen bond together to form a molecule of hydrogen, H2 for short. The molecule is the smallest unit of most compounds.

Van der Waals Forces

are intermolecular forces of attraction (What!?!)

• Within a molecule, atoms have a stronger attraction for electrons than others (see notes on water). This gives the molecules areas with slightly positive and slightly negative charges.

• http://www.youtube.com/watch?v=h3ETLdQS_iU

• A molecule in which the charges are unevenly distributed is called a polar molecule.

• When polar molecules are close together, a slight attraction can occur between the oppositely charged regions of nearby molecules.

• These intermolecular forces of attraction are called Van der Waals forces.

• Van der Waals forces are not as strong as ionic or covalent bonds, but they can hold molecules together.

Water

• http://www.youtube.com/watch?v=DVCYlST6mYQ

Water (information to take away)

• A water molecule is polar because there is an uneven distribution of electrons between the hydrogen and oxygen atoms.

• The charges on a polar molecule are written in parenthesis to indicate that they are weaker than the charges of ions. (+) or (-) rather than Na+

• Cohesion is an attraction between molecules of the same substance.

• Adhesion is an attraction between molecules of different substances.

• Capillary action is the tendency of water to rise in a thin tube. (Cohesion holds molecules of water together as it rises.)

• A hydrogen bond is the attraction between a hydrogen atom of one molecule to another atom, usually of a different molecule.

• Hydrogen bonds are not as strong as covalent or ionic bonds.

A mixture is a material composed of two or more elements or compounds that are physically mixed together but are not chemically combined.

Living things are, in part, made of mixtures involving water.

There are two types of mixtures involving water:

• Solutions---Solute and solvent = solution– all components of a solution are equally

distributed throughout the solution.

• Suspensions---mixtures of water and non-dissolved particles that float in the water. (not on the water or “at the bottom”, in the water. Think jello with fruit in it!

The Chemistry of Carbon

• http://www.youtube.com/watch?v=QnQe0xW_JY4

Be able to answer the following:• Page 39 1 and 2• Page 57 11 to 16