Campbell and Reece 8th edition Chapter 2 ppt

BROOKLYN COLLEGE Of The City University of New York Spring 2011 Bio 1002 – General Biology 2 – Mon/Wed 3:40-4:55 pm, Room 113 NE Sections: MW3A, MW3B, MW3AF, MW3C, MW3BF Lecturer: Prof. Dan Eshel Email: deshel@brooklyn.cuny.edu, Telephone: 718-951-5000, ext. 2015 Office Hours: Wednesday: 2-3 pm, Room 300 NE or by appointment.   Blackboard This syllabus, all announcements, PowerPoint presentations and exam grades will be posted on the course page on CUNY’s Blackboard. Course Requirements and Policies Textbook: Biology by Campbell and Reece. Seventh Edition or newer. Laboratory: All information regarding the laboratory part of this course will be given by your lab instructor. Grading: Lecture and lab are 50% each of your final grade. Point distribution for lecture is as follows: 3 midterm exams, 12.5% each Final exam (not cumulative) 12.5%   Lecture Exam Dates Feb 23 Mar 23 Apr 27 Final: May 25   Lecture evaluation Three midterm exams and a final exam will be given on the dates listed above. The exams will assess your ability to retain and recall the material covered in lecture as well as your ability to integrate and extrapolate the material covered by solving problems. All exams will consist of multiple choice questions.   There are no make-up exams. If you miss one exam it will be entered as a 0. Failure to take 2 exams constitutes an F for the course. Attendance and Policies -It is expected that students will attend every lecture. -Tardiness is not a socially acceptable practice. You should be in your seat and set up before the instructor begins. - If you miss a lecture you are responsible for the material covered. -You are responsible for all announcements made in lecture. If you miss a class or come late, be sure you obtain missed information from a classmate. -All initial inquiries regarding your grade for the course should be directed to the laboratory instructor. -You are expected to turn off your cell phone before class starts.   PLEASE NOTE: There are no negotiations for grades. Your grade is the sum of the components listed above. There will be no curving or scaling of grades. There are no extra credit, make-up or “pity” points. It is expected that you give 100% effort in all your endeavors including this course. Therefore there are no extra points for “working hard”.   How to succeed in Biology: -Attend all lectures and labs. -Read the text BEFORE class. -Review your class notes as soon as possible after lecture and immediately before lecture. -Know the vocabulary! The study of biology is like learning a new language. You need to know the vocabulary in order to understand the concepts. Chapter 2 The Chemical Context of Life Biology is a multidisciplinary science Living organisms are subject to basic laws of physics and chemistry Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter Matter is anything that takes up space and has mass Elements and Compounds Matter is made up of elements An element is a substance that cannot be broken down to other substances by chemical reactions A compound is a substance consisting of two or more elements in a fixed ratio A compound has characteristics different from those of its elements Fig. 2-3 Sodium Chlorine Sodium chloride Essential Elements of Life About 25 of the 92 elements are essential to life Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur Trace elements are those required by an organism in minute quantities Table 2-1 Fig. 2-4a (a) Nitrogen deficiency Fig. 2-4b (b) Iodine deficiency Goiter (thyroid enlargement) An element’s properties depend on the structure of its atoms Each element consists of unique atoms An atom is the smallest unit of matter that still retains the properties of an element Subatomic Particles Atoms are composed of subatomic particles Relevant subatomic particles include: Neutrons (no electrical charge) Protons (positive charge) Electrons (negative charge) Neutrons and protons form the atomic nucleus Electrons form a cloud around the nucleus Neutron mass and proton mass are almost identical and are measured in daltons Cloud of negative charge (2 electrons) Fig. 2-5 Nucleus Electrons (b) (a) Atomic Number and Atomic Mass Atoms of the various elements differ in number of subatomic particles An element’s atomic number is the number of protons in its nucleus An element’s mass number is the sum of protons plus neutrons in the nucleus Atomic mass, the atom’s total mass, can be approximated by the mass number Fig. 2-9 Hydrogen 1H Lithium 3Li Beryllium 4Be Boron 5B Carbon 6C Nitrogen 7N Oxygen 8O Fluorine 9F Neon 10Ne Helium 2He Atomic number Element symbol Electron- distribution diagram Atomic mass 2 He 4.00 First shell Second shell Third shell Sodium 11Na Magnesium 12Mg Aluminum 13Al Silicon 14Si Phosphorus 15P Sulfur 16S Chlorine 17Cl Argon 18Ar Isotopes All atoms of an element have the same number of protons but may differ in number of neutrons Isotopes are two atoms of an element that differ in number of neutrons (same atomic number but different atomic mass) Radioactive isotopes decay spontaneously, giving off particles and energy Electron Distribution and Chemical Properties The chemical behavior of an atom is determined by the distribution of electrons in electron shells Atoms are electrically neutral: The number of protons equal the number of electrons The periodic table of the elements shows the electron distribution for each element Fig. 2-9 Hydrogen 1H Lithium 3Li Beryllium 4Be Boron 5B Carbon 6C Nitrogen 7N Oxygen 8O Fluorine 9F Neon 10Ne Helium 2He Atomic number Element symbol Electron- distribution diagram Atomic mass 2 He 4.00 First shell Second shell Third shell Sodium 11Na Magnesium 12Mg Aluminum 13Al Silicon 14Si Phosphorus 15P Sulfur 16S Chlorine 17Cl Argon 18Ar Valence electrons are those in the outermost shell, or valence shell The chemical behavior of an atom is mostly determined by the valence electrons Elements with a full valence shell are chemically inert The formation and function of molecules depend on chemical bonding between atoms Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms These interactions usually result in atoms staying close together, held by attractions called chemical bonds Covalent Bonds A covalent bond is the sharing of a pair of valence electrons by two atoms In a covalent bond, the shared electrons count as part of each atom’s valence shell Fig. 2-11 Hydrogen atoms (2 H) Hydrogen molecule (H2) A molecule consists of two or more atoms held together by covalent bonds A single covalent bond, or single bond, is the sharing of one pair of valence electrons A double covalent bond, or double bond, is the sharing of two pairs of valence electrons The notation used to represent atoms and bonding is called a structural formula For example, H–H This can be abbreviated further with a molecular formula For example, H2 Fig. 2-12a (a) Hydrogen (H2) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model Fig. 2-12b (b) Oxygen (O2) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model Fig. 2-12c (c) Water (H2O) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model Fig. 2-12d (d) Methane (CH4) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model Covalent bonds can form between atoms of the same element or atoms of different elements A compound is a combination of two or more different elements Bonding capacity is called the atom’s valence Electronegativity is an atom’s attraction for the electrons in a covalent bond The more electronegative an atom, the more strongly it pulls shared electrons toward itself In a nonpolar covalent bond, the atoms share the electron equally In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equally Unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule Fig. 2-13 ? – ?+ ?+ H H O H2O Ionic Bonds Atoms sometimes strip electrons from their bonding partners An example is the transfer of an electron from sodium to chlorine After the transfer of an electron, both atoms have charges A charged atom (or molecule) is called an ion Fig. 2-14-1 Na Cl Na Sodium atom Chlorine atom Cl Fig. 2-14-2 Na Cl Na Cl Na Sodium atom Chlorine atom Cl Na+ Sodium ion (a cation) Cl– Chloride ion (an anion) Sodium chloride (NaCl) A cation is a positively charged ion An anion is a negatively charged ion An ionic bond is an attraction between an anion and a cation Compounds formed by ionic bonds are called ionic compounds, or salts Salts, such as sodium chloride (table salt), are often found in nature as crystals Fig. 2-15 Na+ Cl– Weak Chemical Bonds Most of the strongest bonds in organisms are covalent bonds that form a cell’s molecules Weak chemical bonds, such as ionic bonds and hydrogen bonds, are also important Weak chemical bonds reinforce shapes of large molecules and help molecules adhere to each other Hydrogen Bonds A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom In living cells, the electronegative partners are usually oxygen or nitrogen atoms Fig. 2-16 ? ? ?+ ?+ ? ? ?+ ?+ ?+ Water (H2O) Ammonia (NH3) Hydrogen bond Van der Waals Interactions If electrons are distributed asymmetrically in molecules or atoms, they can result in “hot spots” of positive or negative charge Van der Waals interactions are attractions between molecules that are close together as a result of these charges Molecular Shape and Function A molecule’s shape is usually very important to its function Biological molecules recognize and interact with each other with a specificity based on molecular shape Molecules with similar shapes can have similar biological effects Fig. 2-18a Natural endorphin Morphine (opiate) Key Carbon Hydrogen Nitrogen Sulfur Oxygen Structures of endorphin and morphine (a) Fig. 2-18b Natural endorphin Endorphin receptors Brain cell Binding to endorphin receptors Morphine (b) Chemical reactions make and break chemical bonds Chemical reactions are the making and breaking of chemical bonds The starting molecules of a chemical reaction are called reactants The final molecules of a chemical reaction are called products Fig. 2-UN2 Reactants Reaction Products 2 H2 O2 2 H2O Some chemical reactions go to completion: all reactants are converted to products All chemical reactions are reversible: products of the forward reaction become reactants for the reverse reaction Chemical equilibrium is reached when the forward and reverse reaction rates are equal