BIOL205 topic 1 review notes

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BIOL 205
Kathreen Ruckstuhl

Reading Guide for Topic 1: Membranes In this course, the goal of the assigned readings is to help you learn the definitions, vocabulary and basic background for a topic so that you will get more out of class. The reading guides are intended to help you focus on the information in the textbook that is relevant to our course, as the textbook covers more topics and goes into more detail than we will. The on-line quizzes will deal with the material addressed in the questions below. Your performance on the quizzes indicates which material you should review again, and also helps me to know what material in the text is particularly problematic for students. If you can answer all of the questions below, you should be well prepared for the quiz and for class. Assigned readings: Ch. 2 Sections 2.4, 2.6, 2.7, 2.8, 2.9, 2.10, 2.14; Ch. 3 Sections 3.1, 3.2, 3.8, 3.9, 3.11; Ch. 4 Section 4.5; Ch. 5 Section 5.1. The questions below indicate which parts of each section you need to read and which parts you can omit (i.e., if there are no questions about material in one part of a section, then you do not need to read it). Ch. 2 Section 2.4 1. What is an atom? What are the 3 kinds of particles that make up an atom that are relevant to the chemistry of life, what type of charge does each have, and where in an atom is each located? a. AnAtom is the smallest unit of matter that still retains the properties of an element. b. The 3 kinds of particles are protons, electrons, and neutrons c. Protons has a positive charge, electrons have a negative charge, and neutrons have no charge. d. Protons and neutrons are located in the nucleus of an atom, while electrons orbit the nucleus 2. What keeps electrons near the nucleus? What is the “electron cloud”? a. The attraction between the negatively charged electrons and the positively charged protons keep the electrons near the nucleus. b. The “electron cloud” is a spherical cloud of negative charge created by the rapidly orbiting electrons around the nucleus. Section 2.6 1. Of the 3 particles that make up an atom, which particle(s) are directly involved in chemical activity and reactions? a. Only electrons are directly involved in chemical activity. 2. What determines how much energy an electron will have? What is an electron shell? a. The farther an electron is from the nucleus, the greater its energy. b. An electron shell is an energy level representing the distance of an electron from the nucleus of an atom. 3. What happens to an atom that has an unfilled outer electron shell? a. Atoms that have unfilled outer electron shells tend to interact with other atoms/ participate in chemical reactions. Skip paragraph 4 and go to the last paragraph in Section 2.6. 4. What happens when two atoms with unfilled outer shells interact? What are chemical bonds? a. When two atoms with unfilled outer shells interact, each atom either shares, donates, or receives outer electrons, so that both partners end up with complete outer shells. b. Chemical Bonds are attractions between two atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells. Section 2.7 1. What is an ion? What is an ionic bond? (Don’t worry about the information dealing specifically with sodium chloride). a. An Ion is an atom that has gained or lost one or more electrons, this acquiring a charge. b. An Ionic bond is a chemical bond resulting from the attraction between oppositely charged ions. Section 2.8 1. What is a covalent bond? a. Aconvalent bond is an attraction between atoms that share one or more pairs of outer- shell electrons; symbolized by a single line between the atoms. For Table 2.8: you don’t need to know the terms for the 4 ways that molecules can be represented. You do need to understand how to read a structural formula (e.g. need to know that a pair of lines like this = indicates a double bond). Section 2.9 1. What is electronegativity? Under what conditions will a covalent bond be termed a nonpolar covalent bond? When is a covalent bond a polar covalent bond? What is the term for a molecule that has an unequal distribution of charges? a. Electronegativity is an atom’s attraction for shared electrons. b. When molecules of one element, such as H2 or O2 exert an equal pull on the electrons/ electrons are shared equally between atoms, it is a nonpolar covalent bond. c. Apolar covalent bond is a covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atoms, making it slightly more negative and the other atom slightly positive. d. An unequal distribution of charges in a molecule is a polar molecule. Section 2.10 1. What kind of bonds hold large molecules in a particular 3-dimensional shape? a. Weak bonds 2. What is a hydrogen bond? How does it form? How is it different from a covalent bond? a. Ahydrogen bond is a type of weak chmical bond formed when the parually positive hydrogen atom paeticipating in a polar covalent bond in one molecule I attracted to the partially negative atom participating in a polar covalent bond in another molecule. Section 2.14 1. What do the terms “solution”, “solute” and “solvent” mean? What is an aqueous solution? a. Asolution is a liquid consisting of a uniform mixture of two or more substances. b. Asolute isa substance that is dissolved, a solvent is the dissolving agent (ex:water) c. An aqueous solution is one in which water is the solvent 2. How does water’s polarity make it a good solvent for many solutes, including large molecules? 2 a. Water is a good solvent because it dissolves an enormous variety of solutes. Ions are attracted to water due to their opposite charges, polar moelcules form hydrogen bonds, and large molecules dissolve if they have polar and ionic regions on their surface. Ch. 3 Section 3.1 1. The molecules that make up cells are based on carbon (C). What is the term for C-based molecules? How many covalent bonds can each C atom form? a. Carbon based molecules are called o
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