9/16/15. Properties of Water. Benefits of Water. More properties of water

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1 Properties of Water Solid/Liquid Density Water is densest at 4⁰C Ice floats Allows life under the ice Hydrogen bond Ice Hydrogen bonds are stable Liquid water Hydrogen bonds break and re-form Benefits of Water Temperature Moderator Evaporative cooling High specific heat capacity Water has a great capacity to absorb and retain heat Because of this, the oceans act as heat buffers for the Earth, thus stabilizing Earth s temperature More properties of water Cohesion Water molecules attracted to each other Adhesion Water molecules attracted to other substances ( ) ( ) O H H (+) (+) ( ) ( ) O H H (+) (+) Adhesion Water- conduc3ng cells Direc3on of water movement 150 µm Cohesion 1

2 More properties of water Water repels non-polar substances Hydrophobic water fearing Any nonpolar substance Hydrophilic water loving Any polar or ionic substance ph Acids release hydrogen ions (H + ) in water ( ph) E.g. of a strong acid: HCl H + + Cl - E.g. of a weak acid: H 2 CO 3 H + + HCO - 3 Bases remove H + in water ( ph) ODen by releasing hydroxide ions (OH - ) NaOH Na + + OH - Buffers Buffer = resists ph changes Consists of weak acid and a weak base Removes or replaces hydrogen ions (H + ) in water Buffer systems = maintain ph homeostasis in body fluids E.g. carbonic acid-bicarbonate buffer system CO 2 + H 2 O H 2 CO 3 HCO H + Carbonic acid functions as a weak acid» Gives up H + Bicarbonate functions as a weak base» Takes up H + 2

3 Acids and Bases pure water (a) Starting with pure water Pure water is a neutral substance in terms of its ph levels. (H2O) (b) Making water more acidic HCl (c) Making water more basic NaOH Hydrochloric acid (HCl), poured into the water, dissociates into H+ and Cl- ions. With a higher concentration of H+ ions in it, the water moves towards the acidic end of the ph scale. An equal concentration of sodium hydroxide, poured into water, dissociates into Na+ and OH ions, moving the water toward the basic end of the scale. (d) Combining acidic and basic solutions When the acid and base solutions are poured together, the OH ions from (c) accept the H+ ions from (b), forming water and keeping the solution at a neutral ph. acid base neutralized solution ph H+ concentration (moles/liter) ph acidic ph scale measure of H+ concentration battery acid smaller number, higher lemon juice, gastric (stomach) juice hydrochloric acid cola, beer, wine, vinegar concentration of H+ tomatoes ph scale is logarithmic black coffee 3 to 2 is a 10x increase in H+ 3 to 1 is a 100x increase in H+ urine neutral water human blood seawater This scale runs from 0 to 14, with baking soda human blood is slightly basic Great Salt Lake 0 most acidic,14 the most basic, and 7 neutral household ammonia household bleach oven cleaner basic lye Organic compounds Primarily composed of C and H, and usually O too Four classes 1. Carbohydrates (sugars, starch, glycogen, cellulose, chitin) 2. Lipids (fats, oils, etc.) 3. Proteins 4. Nucleic acids (DNA and RNA) Also high-energy compounds (e.g. ATP) 3

4 Carbohydrates General formula = (CH 2 O) n I.e. carbon and water (carbo- + hydro-) Water-soluble General functions (in humans): Energy source and energy reserve E.g. glucose, starch and glycogen Structural molecules E.g. deoxyribose in DNA backbone Classifications of carbohydrates: Monosaccharides (e.g. glucose, fructose) Disaccharides (e.g. sucrose, maltose) Polysaccharides (e.g. starch, glycogen) Examples of mono- and disaccharides Glucose (represented 3 different ways) dehydration synthesis Example of a polysaccharide Glycogen (a short segment of it) 4

5 Lipids C, H, and O (but way less O compared to carbohydrates) Not water-soluble General functions: Concentrated energy storage (over 2X as energy-dense as carbos) Cell membrane components Hormones (most) 3 main types: 1. Triglycerides (fats and oils) 2. Phospholipids 3. Steroids Triglycerides = glycerol + 3 fatty acids Functions: Stored energy Insulation Protection (physical cushioning) Types: Saturated fats (solids at room temp.) Unsaturated fats (liquids at room temp.) X 3 Monoglyceride Triglyceride Phospholipids Two fatty acid tails (nonpolar/ hydrophobic) + phosphate-containing head (polar/ hydrophilic) Function: important component of cell membranes 5

6 Steroids = cholesterol and its derivatives General functions: Hormones A component of cell membranes Proteins = large, complex 3-D molecules made up of long chains of amino acids joined by peptide (covalent) bonds Some general functions: Structural support (e.g. bone, hair) Contraction/movement (e.g. muscle) Enzymes = biological catalysts that speed up chemical reactions Oxygen carriers (e.g. hemoglobin) Hormones (e.g. insulin, growth hormone) General structure of amino acids and short pepndes The R group (side chain) variable and gives each amino acid its specific properties Nonpolar Glycine Alanine Valine Leucine Isoleucine (Gly or G) (Ala or A) (Val or V) (Leu or L) (Ile or I) Methionine Phenylalanine Trypotphan Proline (Met or M) (Phe or F) (Trp or W) (Pro or P) Polar Serine Threonine Cysteine Tyrosine Asparagine Glutamine (Ser or S) (Thr or T) (Cys or C) (Tyr or Y) (Asn or N) (Gln or Q) Electrically charged Acidic Basic Aspartic acid Glutamic acid (Asp or D) (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) 6

7 4 levels of protein structure 1. Primary structure: linear sequence of amino acids in polypeptide 2. Secondary structure: folding of parts of polypeptide into a helix or pleated sheet 3. Tertiary structure: overall 3-D shape of polypeptide 4. Quaternary structure: interactions between two or more polypeptides to form a larger protein complex Enzymes Bring specific substrates together and speed up chemical reactions without being consumed in the process Active site Active site Nucleic acids General function: encode genetic information (instructions for synthesizing specific proteins) = long chains of nucleotide subunits 2 main types: DNA RNA 7

8 RNA = ribonucleic acid Single-stranded Sugar: ribose Function: aid in protein synthesis Nitrogenous bases: Cytosine (C), which can pair with Guanine (G) Adenine (A), which can pair with Uracil (U) DNA = deoxyribonucleic acid Double-stranded and twisted into a helix shape Sugar: deoxyribose Function: genetic code for protein synthesis; inherited genetic material Makes up genes, which are located on chromosomes Nitrogenous bases: Cytosine (C), which again can pair with Guanine (G) Adenine (A), which can pair with Thymine (T) I.e., T is to DNA what U is to RNA ATP = adenosine triphosphate ATP is a nucleonde with 2 addinonal phosphates that are connected by high- energy bonds FuncNon: energy currency ; temporary storage and quick release of chemical energy to meet immediate energy demands of cells Energy acquired from breakdown of molecules like glucose must first be converted to ATP before being used 8