Unit One “Science Introduction and Cellular Function”

1. Unit One“Science Introduction and Cellular Function” “The Chemistry of Life”

2. Basic Chemistry Anything that has mass and takes up space is Matter All matter (solid, liquid, gas, and plasma) is made of atoms, that may or may not be combined into molecules and compounds An Atom is defined as the smallest unit of matter that still retains the properties of the element to which the atom belongs

3. Basic Chemistry An atom with one proton is an atom of the element Hydrogen, and is given the shorthand designation of “H” An atom with two protons is an atom of the element Helium, and is given the shorthand designation of “He” All atoms of all elements have a certain number of 3 types of subatomic particles: Protons, Neutrons, and Electrons Protons and Neutrons are found in the central region of the atom, the Nucleus Electrons are found orbiting around the nucleus in somewhat specific “pathways”

4. Basic Chemistry Protons have a positive charge Neutrons have no charge Electrons have a negative charge In an atom, the number of electrons equals number of protons The number of protons in the nucleus is the Atomic Number The number of protons and neutrons in the nucleus of an atom is the Mass Number

5. Basic Chemistry How an atom interacts with other atoms is determined by the electrons; therefore, the chemical behavior of the atom is due to the actions of the electrons All atoms seek to be chemically stable by attempting to obtain 8 electrons in their outer shell called the Valence Shell Those “pathways” mentioned earlier are areas in which the electrons travel while orbiting the nucleus. The pathways are often referred to as Orbitals In order for an atom to achieve the desired chemical stability it will attempt to either gain or lose electrons from the orbitals of the valence shell

6. Helium

7. Carbon

8. Basic Chemistry The orbitals in which electrons are commonly found are the “S”, “P”, “D”, and “F” The S orbital can have up to 2 electrons The P orbital can have up to 6 electrons The D orbital can have up to 10 electrons The F orbital can have up to 14 electrons

9. Ions Atoms in which the number of electrons does not equal the number of protons are Ions If an atom has fewer electrons than protons it is positively charged (the + protons outnumber the – electrons); these are called Cations If an atom has more electrons than protons it is negatively charged (the –electrons outnumber the + protons); these are called Anions He+ (cation), Cl- (anion)

10. Isotopes Atoms of an element that have different numbers of neutrons are called Isotopes Isotopes of an atom of a specific element have the same atomic number (# of protons) but different mass number (protons + neutrons) Radioactive Isotopes are used in medicine to detect and treat cancer, and they are used to determine the approximate age of fossils

11. Molecules • A Molecule is a group of atoms held together by the energy of interacting electrons • There are 2 categories of bonds that electrons form when interacting with each other: • Ionic Bonds – unequal sharing of e- • Covalent Bonds – equal sharing of e- • Because covalent bonds involve the sharing of electrons, single, double, and triple bonds exist in order to optimize the presence of the electrons in an attempt to fill the valence shell of each atom

12. Molecules The atoms of most inorganic (nonliving) substances form ionic bonds, whereas, the atoms of most organic (living) substances form covalent bonds Examples of elements which are commonly found in organic substances are: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus Examples of elements which are commonly found in inorganic substances are: Aluminum, Chlorine, Lead, Silver, and Gold

13. Molecules Hydrogen bonds are weak chemical bonds that play a special role in biology Two key properties of hydrogen bonds cause them to play an important role in biological molecules: they are weak, and as a result of their weakness, they are highly directional The bottom line is that hydrogen bonds stabilize the shapes of many important biological molecules

14. Water and Hydrogen Bonds • Due to the hydrogen bonds that hold a water molecule together, water has some very unique physical properties: • Heat Storage of Water – heats up slowly and holds its temperature for longer • Ice Formation – solid water (ice) is less dense than liquid water • Cohesion – allows water molecules to stick together and form droplets “Surface Tension” • Adhesion – allows a water molecule to stick to another polar molecule that is not water

15. Water and Hydrogen Bonds Polar molecules other than water are called Hydrophilic because they are attracted to the hydrogen bonds of water Nonpolar molecules are called Hydrophobic because they are repelled by the hydrogen bonds of water If polar molecules dissolve in water they are Soluble

16. Ionization of Water • The Chemical Formula for water is H2O • The Structural Formula for water is:

17. Ionization of Water • Water can be broken apart into two ions: • H+ and OH- • H+ is a Hydrogen Cation • OH- is a Hydroxide Anion • H+ equals acidic • OH- equals basic • The way to measure the acidity or basidity of a substance is by using the pH scale

18. pH Scale – “Percentage of Hydrogen” The scale ranges from 0 to 14 O to 6.9 is acidic, with 1 and 2 being very acidic 7 is neutral (neither acidic or basic) 7.1 to 14 is basic, with 13 and 14 being very basic Again, if there are many hydroxide anions (OH-) in solution, then the solution is basic If there are many hydrogen cations (H+) in solution, then the solution is acidic

19. pH Scale

20. pH Scale and Buffers In order to change the pH of a solution, a buffer can be added A buffer is a solution of known pH that can lower or raise the pH of the solution in question Buffers do the above by either absorbing or releasing H+ cations into solution Buffers are important in that they keep solutions from becoming too acidic or too basic; buffers keep solutions’ pH in an acceptable range