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BLY121 Chapter 2 and 3 Notes

by: Ashley Truax

BLY121 Chapter 2 and 3 Notes BIO121

Marketplace > University of South Alabama > Life Sciences > BIO121 > BLY121 Chapter 2 and 3 Notes
Ashley Truax
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About this Document

These notes cover what will be on the exam.
General Biology
Class Notes
Biology, DNA, RNA, half, life
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This 4 page Class Notes was uploaded by Ashley Truax on Friday August 19, 2016. The Class Notes belongs to BIO121 at University of South Alabama taught by in Fall 2016. Since its upload, it has received 5 views. For similar materials see General Biology in Life Sciences at University of South Alabama.


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Date Created: 08/19/16
BLY 121 Chapter 2 Notes August 23, 2016 Atomic Theory Socrates-Born in Ancient Greece ~500 BC All matter is made up of tiny invisible particles named “atoms” Matter has mass and occupies space (Composed of chemical elements) “type” of matter depends on atomic structure Atom: smallest unit of matter which retains the physical and chemical properties of an element. Consists of protons, neutrons, and electrons. Atomic Structure (Niels Bohr-Quantum Physics): Nucleus composed of protons and neutrons and surrounded by orbiting electrons.  Protons and neutrons have roughly the same mass (1 Dalton)  Electron’s weight is negligible.  Atomic number= # of protons  Atomic mass/weight= mass of protons and neutrons combined (i.e. Carbon’s atomic number is 6 and atomic mass is 12.01, so the number of electrons is 6.) Isotopes: atoms of an element that contain a different number of neutrons (i.e Carbon-12, Carbon-13, and Carbon-14) *Note: Isotopes (e.g. Carbon-14) are unstable and decay at a constant rate. (disappear) Example: After death, Carbon-14 atoms decay at a constant rate (half- life=amount of time for 50% of atoms to decay) Carbon Dating: Measures ratio of Carbon-14 (decreasing) to Carbon-12 (stays the same) in a fossil and compares to ratio in living organisms (which is constant). (Tells how long the organism has been around, living, or dead) Radiometric Dating:  Other isotopes have much longer half lives  After mineralization, radioactive atoms begin to decay  Provides evidence for a very old earth. Approximately 4.6 billion years old! Electrons: orbit around nucleus (drawn by positive charge of protons) Chemical Bonds: attractive forces between atoms that result from accepting, donating, or sharing electrons.  Atoms will accept, donate, or share electrons with other atoms to fill the valence (outermost) shell and become stable. 1  Bonding Capacity: # of bonds atom will form  Octet Rule: atoms will accept, donate, or share electrons to fill outermost “shell” with 8 electrons (most stable).  Molecule: two or more atoms held together by chemical bonds- elements can be the same (ex. H2, NaCl)  Compound: substance composed of two or more different atoms (ex. NaCl) Ions: atoms in which the number of electrons does not equal the number of protons.  Cation: atoms which loses electrons is now positively charged.  Anion: atom which gains electron is now negatively charged. **Types of Chemical Bonds: Ionic Bonds:  Complete transfer of electrons  Atoms held together by electrostatic attraction between oppositely charged cation and anion. Ionic Bonding: 1. Na becomes (+) 2. Cl becomes (-) 3. Resulting compound neutral 4. Bonds weak Covalent Bonds: formed between two atoms by the sharing of electrons.  Strength of bond increases with the number of shared electrons.  Strong  H2, O2  H2O  Molecule is neutral Can be polar… Polar Covalent Bonds:  One atom of a molecule attracts electrons more strongly than other atoms (unequal sharing).  Molecule still electrically neutral but has charged parts. Polar Molecule:  Oxygen slightly (-)  Hydrogen slightly (+)  Polar covalent bond  H2O = popular molecule 2 Hydrogen Bonds: Occur when the (+) hydrogen atom of one polar molecule is attracted to the (-) atom of another polar molecule. ***Clicker question: 1. Variation of an atom in which the number of neutrons is altered…Isotope 2. Type of chemical bonding in which electrons are unequally shared between atoms…Polar covalent 3. With the exception of Hydrogen and Helium atoms, reactivity of an atom is lowest when it has…8 electrons in its outermost shell. Water:  Polar molecule  Molecules bound to each other by hydrogen bonds  Why is water unique? 1. Heat storage/Resistant to vaporization (specific heat-gives us the ability to thermo-regulate) 2. Ice formation  H+ bonds in water form a crystal lattice structure which traps air  Causes solid water to be less dense than liquid (air trapped) 3. Cohesion: attraction of water molecules to each other. (Surface tension is caused by cohesion.) ~getting water up a tree 4. Adhesion: the attraction of water molecules to other polar molecules 5. High polarity: polar hydrophilic molecules are highly soluble in water. ~Non-polar hydrophobic molecules are insoluble in water. pH:  pH is the potential hydrogen of a substance  pH of pure water is 1 Dalton or 1 H+ per liter of water This is neutral: H+ = OH-, or pH7 Acids:  pH is 0-6.9 is Acidic  Readily dissociate in water and donate H+ ions.  Adding H+ ions decreases pH. Hydrochloric Acid:  Dissociates into H+ and Cl-  Increases concentration of H+ in the solution  Makes more acidic Bases:  pH 7.1-14 are said to be Alkali (basic).  Readily dissociate in water and decrease H+ ions.  Decreasing H+ ions increases pH. 3 Sodium Hydroxide (NaOH):  Dissociates into Na+ and OH-  OH- combines with H+ H2O  Removes H+ from the solution and thus makes the solution more basic. Buffers: accept or donate H+ ions  Carbonic acid buffers the pH of the blood


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