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Biology 213 chapter 2 lecture

by: Neha simon

Biology 213 chapter 2 lecture 70855

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These notes cover the atomic structure and the importance of water.
cell structure and function
Class Notes
Biology, Water, properties
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This 10 page Class Notes was uploaded by Neha simon on Thursday September 15, 2016. The Class Notes belongs to 70855 at George Mason University taught by in Fall 2016. Since its upload, it has received 64 views. For similar materials see cell structure and function in Science at George Mason University.


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Date Created: 09/15/16
Biology chapter 2 lecture 2.1: How does atomic structure explain the properties of matter? A. All matter is composed of atoms  1. What do atoms  1. Electrons: negligible mass; neg charge.  contain? 2. Protons: Have mass; positive charge. 3. Neutrons: Have mass; no charge. B. Elements: pure substance containing only one kind of atom.  1. Each element has a unique chemical symbol.  C. 98% of every living organisms is composed of 6 elements:  1. Carbon (C). Hydrogen (H), Oxygen (O), Nitrogen (N), Sulfur (S), and  phosphorus.  2. What is an element?  a. The number of protons identifies an element.  D. # Of protons= atomic number  3. Living organisms are  a. Written as subscript to the left of chemical symbol composed of what?  E. Mass number: number of protons + number of neutrons. (written as  superscript).  4. What is the atomic  number? 5. What is the mass  number? Biology chapter 2 lecture 6. How do you find the #  F. Number of neutrons  of neutrons? a. Mass #­ atomic # = # of neutrons.  G. Isotopes: forms of element that has different number of neutrons, and so  7. What is different about  has different mass #.  isotopic elements?  Ex: carbon 12 has 6 neutron       Carbon 13 has 7 neutron        Carbon 14 has 8 neutron  a. Atomic weight: average of mass numbers of isotopes of naturally  occurring proportions.  8. What is the atomic  b. Some Isotopes are unstable: weight?  i. Radioisotopes: give off energy in the form of alpha, beta and  gamma radiation from the nucleus.  ii. Radioactive decay transforms the atom, sometimes resulting in a  change of protons.  iii. Released radiation can be used to detect the presence of  radioisotopes.  iv. Radioisotopes are incorporated into molecules to be used as a  tag to track certain molecules.  9. How can we detect  H. Chemical reactions involve changes in the distribution of electrons  radioisotopes?  between atoms.  a. Locations of electrons are described by orbitals.  I. Orbitals: region where an electron is found.  II. Orbitals have characteristic shapes and orientations and can be occupied by two electrons.  III. Orbitals occur in a series called electron shells, also called  energy levels.  10. What’s found in the  orbitals?  11.How do orbitals occur?  What is this called?  Biology chapter 2 lecture b. Electron shells: composed of orbitals.  I. 1  shell: one s orbital (holds 2 electrons).  12.How many electrons  II. 2  shell: one s orbital and 3 p orbitals.  does the s orbital hold? III. The further a shell is from the nucleus the higher the energy  shell.  IV. The outer most shell (valence shell) determines how atom  13.Which shell determines  behaves.  how atoms behave? ­ If the outer most shell is full than the atom is stable.  o Ex: the noble gases.  ­ Reactive atoms have unpaired electrons in the outer  14.What does it mean if the  outer shell is full?  most shell.  ­ The octet rule: tendency of atoms to form stable 8  electron molecules.  15.What is the octet rule?   Biology chapter 2 lecture 2.2 How do atoms bond to form molecules?  16.What is a covalent  A. Chemical bond: the attractive force that links atoms together.     1. Covalent bonds: Atoms share electrons so the outer shells are filled.  bond?      2. Compound: a molecule made up of two or more elements bonded  together in a fixed ration.           Ex: H2O (2 hydrogen: 1 Oxygen) B. Organic Chemistry:        1. Study of carbon compounds. 17.What is organic         2. Carbon has 4 valence electrons.  chemistry?             ­ Form 4 covalent bonds.  C. Covalent bonds are very strong and require a lot of energy to break them.       1. Covalent bonds can be.           ­  Single:  1 pair of electrons.           ­  Double: 2 pairs of electrons  18.Why are covalent bonds          ­  Triple:   3 pairs of electrons. special? D. The length, angle and direction of bonds between any two elements are  always the same.            ­ The shape of molecules can change as atoms rotate around a covalent  bond.  E. Attractive force that an atomic nucleus exerts on electrons.       ­ The further the electrons are away form the nucleus the smaller the  electronegativity. Biology chapter 2 lecture 19.What type of bond is  F. Hydrogen bonds: weak type of bond.  hydrogen bond? a. Attraction between partially negative end of one molecule and the  partially positive hydrogen end of another molecule.  b. Very important in DNA structure.  c. Polar molecules that form hydrogen bonds w/ water are hydrophilic.  d. NON­POLAR molecules, such as hydrocarbons that interact with each  other but not with water are hydrophobic.  G. Van der Waals forces: attractions between nonpolar molecules that are close together.  20.What’s Van der Waals  ­ Individual interactions are brief and weak.  force?  ­ Can be a large force when summed over in a large molecule.  2.3 How do atoms change partners in chemical reactions?  A. Chemical reactions: occurs when atoms collide with enough energy to  combine or change their bonding partners.      ­ Energy is neither created nor destroyed.  B. Energy: capacity to change or do work.  ­ Energy usually changes form during chemical reactions.  Biology chapter 2 lecture 2.4 What makes water so important for life? 21.Why is water  A. Water is very important. important? ­ Polar molecule  ­ Forms hydrogen bonds  ­ Tetrahedral shape.  B. Ice floats: Solid water is less dense than liquid water.      ­ Hydrogen bonding occurs in both liquid and solid form.     ­ Ice is more structured, but less dense than liquid water.  C. Water has a high heat of vaporization: amount of energy required to  change water from liquid to a gas state.         ­  Heat energy must be absorbed from the environment in contact with  water and results in cooling.  D. Cohesion: Water molecules resist coming apart from one another.       ­ Helps water move through plants.       ­ Results in surface tension: water molecules above the surface are  hydrogen­ bonded to other water molecule below them.  E. Types of analysis: ­ Qualitative analysis: identification of substances involved in chemical  reactions.  ­ Quantitative analysis: measuring concentrations of the substances.  ­ Mole: the amount of substance that is numerically equal to its molecular  weight.   1 mole of Na = 23 g 22.Difference between   1 mole of H = 2 g  2  qualitative and   The # of molecules in 1 mole is constant for all substances quantitative analysis?  6.02 x 10 = Avogadro’s number.    23.What is a mole? 24.What is the number of  molecules in a mole  equal to? Biology chapter 2 lecture F. Acids and bases? ­    Acids release H    ions   25.Difference between  o HCL is a strong acid; it fully dissolves in water (ionizes).  +  acids and bases?  ­    Bases accept H    ions o NaOH is a strong base.  ­ Organic acids have a carboxyl group ­­  +  26.What do organic acids  o –COOH ­COO  + H have?  ­ Ionization of strong acids and bases is irreversible  ­ Ionization of weak acids and bases are reversible  ­ Water acts as both a weak acid and weak base.  o Ionization of water is important to all organisms because we are  made up of water and H is very reactive.  G. pH= neg log of the molar concentration of H ions.  +  +  ­ pH= ­log(H ).  ­ Lower pH numbers mean higher H concentration. Or greater acidity.  ­ Buffer help maintain constant pH.  o A buffer is a weak acid and its corresponding base. Biology chapter 2 lecture Biology chapter 2 lecture ­ pH= neg log of the molar concentration of H ions.  +  +         ­ pH= ­log(H ).  +         ­ Lower pH numbers mean higher H concentration. Or grater acidity.        ­ Buffer help maintain constan pH.             ­ A buffer is a weak acid and its corresponding base.        Biology chapter 2 lecture


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