BSCI105 Week 1 Notes (1/29 and 2/1)
BSCI105 Week 1 Notes (1/29 and 2/1) Bsci105
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This 3 page Class Notes was uploaded by clcindy.lin on Monday February 1, 2016. The Class Notes belongs to Bsci105 at University of Maryland taught by Dr. Alewall in Summer 2015. Since its upload, it has received 26 views. For similar materials see Intro to biological sciences in Biological Sciences at University of Maryland.
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Date Created: 02/01/16
BSCI105 Lecture Notes: Week One (1/29/162/1/16) Chemical Principles: ∙ 4 kinds of atoms make up about 96% of the human body (carbon, hydrogen, oxygen and nitrogen) ∙ 7 other atoms make up almost the rest of the human body (about 4%) ∙ There are 15 trace elements (element that you only need a little to stay healthy; example: iodine). ∙ lements and compoundsare pure chemical substances, which are defined by the atom they contain. oElements: one kind of atom (can't be broken down into other chemical substances.) o Compounds: more than 1 atom (can be broken down.) Structure of ato: ∙ Nucleus: contains protons and neutrons ∙ Electrons surround the nucleus (electron cloud) ∙ Atomic Number: number of protons (which also equals to the number of neutrons) o Chemical properties of an atom depends on the atomic number ∙ Atomic mass: the sum of protons and neutrons ∙ Number of electrons limited inshel, where the electrons are located around the nucleus: o 1 shell: 2 electrons nd o 2 shell: 8 electrons o 3 shell: 8 electrons ∙ Outmost shellalence shell o An atom is stable when its valence shell has its full complement of electrons. ∙ he valence shells may be filled by: o Electrons of the same atom o Electrons shared with another atom (covalent bonds) o Electrons abstracted from another atom (creates ions) ∙ Elements in the same column have similar chemical properties. Covalent Bonds: ∙ Atoms with unfilled valence shells can form covalent bonds by sharing valence electrons. ∙ Molecules consists of atoms linked by covalent bonds o Ex: H, O, HO, CH 2 2 2 4 ∙ The shape of the molecules depends on the orbitals that the valence electrons are in. Electrons in shells are located in o (each orbital holds 2 electrons) ∙ 1 shell:orbital ∙ 2 shellorbital and orbitals Hybrid orbita: ∙ When an electron shell is full and has no doub p orbitals hybridize to sp3m 4 (or p2orbitals BSCI105 Lecture Notes: Week One (1/29/162/1/16) ∙ The 3sporbitals are all equivalent and they have a tetrahedral orientation (the angle 2 between them is 109.5 degrees) Polar, nonpolar and ionic bonds: ∙ Atoms differ in their affinity for electrons (electronegativity) ∙ The greater an atom’s electronegativity, the greater its attraction for electrons ∙ When the affinities of two bonded atoms are roughly equal, their bonding electrons will be shared equally (nonpolar bond) (eg H2 and O2). The electric charge on each atom will be equal. These are strong bonds. ∙ When two atoms with different affinities form a covalent bond, the electrons in the bond will unequally by the two atoms (polar bond). The more electronegative atom will have a partial negative charge and the less electronegative atom will have a partial positive charge. These are weaker bonds. ∙ Atoms with very different electronegatives form ionic bonds. In water, these are very weak bonds. ∙ Electronegativities of atoms increase ACROSS periodic table from left to right (as number of protons/charge in nucleus increases) and UP the periodic table (as valence shell gets closer to nucleus) Hydrophobicity and Hydrophilicity: ∙ Solubility in water is an extremely important molecular property ∙ Solubility requires electronegative atoms (O, N) ∙ Molecules that are soluble in water are saidydrophilic love water) ∙ olecules that are not soluble in water are saidydrophobic (fear water) Acids and Bases ∙ cids: release protons ∙ ases: absorb protons ∙ pH scale indicates the acidity of a solution o H=–log10 [H+] (or –log10 [H3O+]) o In pure water [H+]=107M o pH=7pH of acidic solutions is less than 7 o H of basic solutions is greater than 7 o pH + pOH always equals 14. Buffers ∙ Buffers minimize the change in pH produced by adding acids and bases. ∙ They do this by adding H+ to basic solutions and removing H+ from acidic solutions. ∙ Cells are very sensitive to changes in pH, so they must be buffered. ∙ Examples of buffers: bicarbonate and phosphate ions BSCI105 Lecture Notes: Week One (1/29/162/1/16)
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