Bio Exam 1 Lecture 1-9- Elements: cannot be broken down into simpler substance- Atoms : smallest unit of an element retaining its properties- Compounds : combinations of elements in different proportions- Molecules : smallest part of a compound retaining its properties- Atoms of each element have a characteristic number of protons - The number of protons equals the number of electrons in an uncharged atom- Atomic mass : sum of protons and neutrons- Atomic number : protons and electrons-Isotope: 2 atoms of an element that differ in number of neutrons. Same chemical properties but different physical properties.- Electrons occupy shells, electrons in lower shells have less energy. Each shell had orbitals and each orbital can hold 2 electrons. The first shell has one orbital and can hold only 2 electrons, the next 2 shells have 4 orbitals and can hold a maximum of 8 electrons- Valence : the number of electrons to gain or lose. Atoms attempt to gain or lose electrons until outer shell has 8 paired electrons. - Atoms stabilize by sharing electrons-- Covalent bond- Non-polar covalent bond : equal sharing of electrons between 2 identical atoms (H-H, C-H, C-C, O-O)- Polar-covalent bond : one atom has the electrons more often, electronegativity difference (O-H, N-H)- Ionic bonds : when an electron is “stolen” (NaCl)- Hydrogen bond s: covalent bond between H and N, O, or F- Bond Strength : covalent (70-100), ionic (10-20), Hydrogen (4-5), van der walls (1-2)- O-H and N-H covalent bonds are polar with oxygen and nitrogen holding a partial negative charge and the hydrogen having a partial positive charge. C-C and C-H covalent bonds are nonpolar- Molecular Weight: sum of atomic weights of atoms in a molecule- Mole : amount of compound equal to molecular weight in grams- Molarity : moles of solute dissolved in a liter of solution (M=m/L)- Solvent : the dissolving substance- Solute : the substance being dissolved- Killo = 1000, milli = 10^-3, micro = 10^-6- Equilibrium : when there is no net change in the concentrations of reactants and products- A + B ----- C + D- Keq = CD/AB- Water hydrogen bonds to other water molecules, polar covalently.- Ice expands upon freezing, hydrogen bonds are stable, ice formation warms the water, and is less dense- Water is both cohesive (sticks to itself) and adhesive (sticks to something else)- Heat: measures the total kinetic energy- Temperature : measure of heat intensity (C)- Specific heat : amount of heat needed to lose or gain for the temperature to change 1 degree C- Water has specific heat because of hydrogen bond ability- High specific heat of water minimizes temperature fluctuation- Evaporative cooling : when water evaporates, the liquid is cooled-- temperature control- Hydrophilic : water loving, dissolves in water (polar covalent or ionic)- Hydrophobic : water hating, does not dissolve (non polar covalent)- Ionic substances dissociate when they dissolve in water and hydrophobic subsances in general become coated with water molecules (interactions of partial charges) when dissolved or in contact with water.- Acid : dissolve in water yeilding H+ and an anion (donates protons)- HCL---> H+ + Cl-- Base : dissolves and produces hydroxyl ion (accepts protons)- NaOH---> Na+ + OH-- pH scale : measure of dissolved H+ concentration- pH = -log(H+) neutral when H+ = OH-- Strong Acid : pH < 7 (HCl)- Strong Base : pH > 7 (NaOH)- Weak acids and bases do not dissociate completely, they are buffers- Buffers : minimize pH change, gain or lose electrons depending on pH- Carbon has a valence of 4 and participates in covalent bonds with H, N, and O. These covalent bonds are largely nonpolar. H has one electron to share, N has 3, and O has 2.- Organic molecules have a carbon skeleton (C can bond to itself by either a single or double bond) and have H, O, N and a few other atoms attached to C.- Isomers: same chemical formula, but different structures and properties- Structural isomers : differ in the covalent arrangement of the same atoms- Geometric isomers : the same atoms and bonds but different arrangement around the double bond (cis- on the same side of the bond, trans- on the opposite side)- Enantiomers : differ in arrangement of 4 groups around a C- Hydroxyl (-OH) polar, hydrogen bond with water- Carbonyl (>C=) sugars- Carboxyl (OH>C=O) acidic- Amino (-NH2) base- Sulfhydryl (-SH) react forming covalent bonds, stabilizes, lose H- Phosphate ( O ) negative charge, double bond on one O, high energy O-P-O O- Methyl (-CH3) non reactive, non polar- Biological macromolecules are built by condensation (dehydration) reactions and broken down by hydrolysis- Carbs (sugars) contain a carbonyl group (aldehyde or ketone)- monosaccharide : single, (CH2O), linear or cyclic- disaccharide : double, formed from 2 monosaccharides by dehydration- polysaccharide: polymers, mono joined by glycosidic bonds- Carbs contain 1 or more asymmetric carbons and so can exist as enantiomers- Glucose is a 6 C monosaccharide, sucrose is a disaccharide composed of glucose and fructose- Glucose forms 2 important polysaccharides: Starch (glycogen) and Cellulose. - Starch is used for energy storage and celluose is used in plants to build cell walls. - Starch is composed of 1-4 linked a-glucoses with occasional 1-6 linked side chains.- Cellulose is composed of multiple chains of 1-4 linked B-glucoses (different glucose enantiomer than found in starch) and the individual chains are hydrogen bonded together, which makes cellulose highly resistant to dehydration (hydrolysis).- Fats: glycerol and fatty acids, glycerol is a 3 C alcohol with hydroxyl group on each C. Fatty acid is carboxyl attached to C skeleton. 1 fatty acid attached to each OH in glycerol with an ester bond.- Phospholipids: 2 fatty acids and phosphate group attached to glycerol- Steroids : lipids with 4 C-C rings- Saturated fats : 3 fatty acids, stack together, solid (butter)- Unsaturated fats : 1 or more unsaturated fatty acids, plants and fish, liquid (oil), double bonds- All lipids are hydrophobic but phospholipids have a double character by having a charged polar head group and a long hydrophobic tail- Cell membranes are composed of phospholipid bilayers in which the hydrophobic tails of the phospholipids cluster together on the inside of the bilayer and the hydrophilic heads (with the charged
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