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BIOL125_Ch2 Lecture Notes

BIOL125_Ch2 Lecture Notes - BIOL 125(Microbiology Lecture...

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BIOL 125 (Microbiology) Lecture Notes Chapter 2: The Chemistry of Biology 1. MATTER AND ATOMS a. Matter – any substance that occupies space and has mass. i. It can be solid, liquid, or gas, and is composed of atoms. b. Atom – simplest form of matter. i. Atoms are not divisible into simpler substances, and are composed of three subatomic particles: protons, neutrons, and electrons. 1) Protons – located in the nucleus; have a positive charge; and weigh 1 dalton. 2) Neutrons – located in the nucleus; have a neutral charge; and weigh 1 dalton. 3) Electrons – located in the orbital or electronic cloud; have a negative charge; and weigh 1/2000 dalton (negligible). 2. CHARACTERISTICS OF ELEMENTS a. Elements – pure substances that are made of a single type of atom. They have a characteristic number of protons, neutrons, and electrons. i. There are more than 100 types of elements and each has a predictable chemical behavior. ii. The periodic table is arranged in columns and rows, based on the element’s chemical properties. b. Isotopes – variant forms of an element. They have the same number of protons and electrons, but differ in the number of neutrons. i. Because they have the same number of electrons in the shell(s), they will have the same chemical properties. 3. FACTORS THAT DETERMINE THE CHEMICAL PROPERTIES OF AN ELEMENT a. Atomic Number – number of protons in the nucleus of an atom. b. Mass Number – sum of the number of protons and the number of neutrons in an atom. c. Electron Orbitals – volumes of space surrounding the atomic nucleus where electrons are likely to be found. i. Shell – location of individual pair of electrons with varying energy. Several shells with varying energy levels are found in an orbital. Those closer to the nucleus have more energy than those farther away. d. Valence Electrons – electrons that are found in the last shell of the orbital and are important to forming chemical bonds. 4. IMPORTANT ELEMENTS FOUND IN CELLS a. Hydrogen (H), Sodium (Na), Magnesium (Mg), Carbon (C), Nitrogen (N), Oxygen (O), Chlorine (Cl), File: 85ca90873df9ee6b33822d43e45a7bdcd594854b.doc Updated 8/14/09
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Lecture Notes Chapter 2 Page 2 Phosphorus (P), Sulfur (S), Calcium (Ca), and Potassium (K). i. Those that form organic compounds include: Carbon (C), Hydrogen (H), Oxygen (O), Sulfur (S), Phosphorus (P), and Nitrogen (N). ii. Other elements essential to cell survival include: Magnesium (Mg), Chlorine (Cl), Sodium (Na), and Potassium (K). 5. MOLECULES AND COMPOUNDS a. Molecule – distinct chemical substance that results from the combination of two or more atoms of the same element (ex. O 2 , N 2 ). i. All living and non-living things are made of molecules. b. Molecular Weight ( Formula Mass ) – sum of atomic masses of the atoms found in a compound or a molecule (ex. H 2 O = 18, CO 2 = 44). c. Compound – molecules that are combinations of two or more different elements (ex. H 2 O), CO 2 ).
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