The Chemistry of Biology What does chemistry have to do with biology?

Laws of chemistry -govern the structure & function of all living things. All organisms are made of matter – In living things matter is constantly being rearranged through changes called chemical reactions EXAMPLE of a chemical in the body: This crystal is uric acid, normally found in urine. It displays double refraction under a microscope with polarized light.

Everything in the universe is made of matter! Matter- anything that occupies space and has mass. Mass- the quantity of matter in an object -the total number of sub-atomic particles (electrons, protons and neutrons) in the object. **The chemical properties of matter depend on its organization at the following levels: Subatomic Atomic Molecular

A. The Subatomic level (inside the atom) Inside the Nucleus: Proton- positively charged particle 2. Neutron- neutral, no electrical charge Outside the nucleus 3. Electron –small, negatively charged particles The Total electrical charge of atom is zero

* Atoms are composed mostly of empty space - between nucleus and the orbiting electrons high energy particles with very little mass. move around outside the nucleus at very high speeds in areas called orbitals. An orbital- is a region around the nucleus that indicates the probable location of an electron.

Isotopes All atoms of an element have the same # of protons. All atoms of an element do not necessarily have the same # of neutrons. Isotopes are atoms of the same element with a different # of neutrons. The additional neutrons change the mass of the atom. Most elements are a mixture of isotopes.

Atomic level- atoms of each element Element -A substance that cannot be broken down by chemical means. Elements are defined by their number of protons (Atomic Number) Example- an atom of Hydrogen, (H -1)Oxygen (O -8), Carbon (C-6) *The number of electrons in the outer most energy level determine bonding properties

Elements in Living things- Approx. 25 elements occur in living things. 6 elements of critical importance: Carbon – Hydrogen – Nitrogen – Oxygen – Phosphorous - Sulfur “CHNOPS” These are found in the 4 major groups of ORGANIC molecules: Carbohydrates - Lipids Proteins -Nucleic Acids

In the Human Body Note the amounts of “CHNOPS” plus Ca

The Periodic table

Groups or “Families” vertical columns in the periodic table these elements share characteristics & traits groups have similar configurations of the outermost electron shells of their atoms. Example: Group 14 is the carbon group- Each of the elements in this group has 4 electrons in its outer energy level. That leaves 4 empty spots for additional electrons- so they form 4 chemical bonds

C. Molecular level Compound- a pure substance made up of atoms of two or more elements **Most elements undergo chemical reactions- combine in ways that arrange their atoms so the outer electron shell is full & stable **Compounds have specific formulas Molecule- the simplest part of a substance that retains all of the properties of the substance and can exist in a free state

2. Chemical bonds –atoms want to form stable molecules - Covalent Bonds – some elements are more stable when sharing electrons - Ionic Bonds- some elements really want to lose or gain an electron- forming cation (+) or anions (-)

Covalent Bonds Formed when 2 or more atoms share one or more pairs of electrons

Forming ions

Ionic Bonds Form when a positively and a negatively charged particle called IONS attract each other These positive and negative IONS form when an atom loses or gains an electron to become “stable” and have a complete # of electrons in the outer shell Example- LiF

Energy transfer in Living Things Definition of Energy- the ability to do work or cause change Free Energy –the energy in a system that is available for work For example, in the cell, it is the amount of energy available to fuel cell processes. Energy can be converted- breakfast food (chemical E) -to thermal E & mechanical E

C. Chemical Reactions -many complex chemical reactions occur in living things every second Reactant: substances that enter a chemical reaction Product: substances produced by chemical reactions

Example: Chemical reaction in body Reactants & Products CO2 + H20 == H2CO3 Reactants Products Reaction is reversible- shows the reaction of water and carbon dioxide to carbonic acid in blood

Photosynthesis: Cellular metabolism: Which are the reactants & which are products in each reaction. Is this reaction reversible? Explain. Photosynthesis: 6CO2 + 6H2O + Energy (sun) C6H12O6 + 6O2 Cellular metabolism: C6H12O6 + 6O2  6CO2 + 6H2O + Energy (ATP)

D. Energy for reactions 1. Activation Energy- The amount of energy needed to start a chemical reaction Catalysts & Enzymes – chemical substances which are able to lower the amount of activation energy needed for a reaction. Enzymes- are biological catalysts- they lower the activation Energy needed for chemical reactions in living things. Why are enzymes so important?

Features of a catalyzed reaction Lower activation E needed for reaction w/ catalyst

Enzymes and chemical reactions in the body Lactase is one of many hard working enzymes. It breaks up the chemical bond holding the sugar lactose together. What happens if you don’t have enough of this enzyme in your body?