Biol 105 Easy to follow Lecture 1 Notes

Bio 105 lecture 1: DW01_chemistry

 Biology is the scientific study of living things (organisms).
 Characteristics of organisms:
 -Made of a common set of chemical components: carbohydrates, fatty acids, nucleic acids, amino acids
 -Most are made of cells enclosed by plasma membranes
 -Convert molecules from their environment into new biological molecules
 -Extract energy from the environment and use it to do biological work
 -Contain genetic information that uses a universal code to specify proteins
 -Share similarities among a fundamental set of genes, and replicate this genetic information when reproducing
 -Self-regulate their internal environment, maintaining conditions that allow them to survive
 -Exist in populations that evolve through changes in frequencies of genetic variants over time
 Biology Is Studied at Many Levels of Organization (1)
 Eventually, some cells did not separate after division and started living as colonies. This allowed some cells to specialize for
certain functions, which led to multicellular organisms (plants, animals, and fungi).
 Cells became specialized, and a hierarchy emerged: differentiated cells are organized into tissues (e.g., muscle). Different tissue
types form organs (e.g., a heart); organs are grouped into organ systems (e.g., the circulatory system).
 A group of individuals of the same species is a population.
 Populations of all the species that live and interact in a defined area are called a community.
 Communities together with their abiotic (nonliving) environment constitute an ecosystem.
 The Fundamental Properties of Matter
 All matter is composed of atoms.
 Atoms are composed of a dense positively charged nucleus, and one or more
negatively charged electrons.
 Electrons move around the nucleus.
 The nucleus always contains a positively charged proton and, sometimes,
neutral neutrons.
 The number of protons determines the identity of an atom.
 Variations in the number of neutrons give rise to isotopes.
 Unstable isotopes are radioisotopes
 Electrons and the Properties of Elements
 Electrons orbit around the nucleus in defined shells.
 The 1st shell has the capacity to accommodate 2 electrons.
 The 2nd and 3rd shell can accommodate 8 electrons each.
 The number of electrons in the outermost shell determines the reactivity of an atom.
Atoms with unfilled orbitals are unstable and will undergo reactions to fill the orbitals.
 Elements with the same number of electrons in the outermost shell (the valence shell) share similar reactive properties.
 Chemical Bonds and Interactions
 Atoms react with each other (via electrons) to form chemical bonds.
 Energy is stored in chemical bonds.
 Energy is liberated in the breaking of chemical bonds.
 Covalent Bonds are Formed by Sharing
 Each hydrogen atom lacks one electron in its outer shell. It can
participate in the formation of one covalent bond.
 In sharing the 2 electrons, the 2 nuclei in the hydrogen molecule —
H2 — both have 2 electrons in their outer (“valence”) shells.
 The 2 electrons orbit both nuclei, holding them together by a
covalent bond.
 Each carbon atom lacks 4 electrons in its outer shell. It can
participate in the formation of 4 covalent bonds.
 In the formation of the 4 covalent bonds, the carbon atom forms
the center of a tetrahedron
 Outer Shell Electrons and Valency
 In general, the electron deficit in the outer shell of an atom is
correlated with the valency — the number of covalent bonds that
can be formed
 Hydrogen Bonds
 Sharing of electrons may be unequal among atoms within a
molecule.
 Since electrons are charged, distribution of charges becomes polarized within the molecule.