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Basic Chemistry for Biology Element substance that can’t be broken down into a simpler substance made of only one kind of atom Atom smallest particle of an element made of three subatomic particles protons ( positive charge ) in the nucleus neutrons ( no charge ) in the nucleus electrons ( negative charge ) orbit the nucleus in energy levels Electron energy levels 1st level filled with 2 electrons 2nd level filled with 8 electrons ( an octet ) 3rd level filled with 18 electrons Stability atoms are stable with filled electron levels Isotopes atoms of the same element with a different number of neutrons in the nucleus C12 ( 6 p+ , 6 n0 ) C13 ( 6 p+ , 7 n0 ) C14 ( 6 p+ , 8 n0 ) Radioactive isotopes used to diagnose and/or treat disease kill bacteria on surfaces and in food destroy rapidly growing cancer cells imaging of body functions Compound substance made of two or more kinds of atoms chemically bonded together results in stability for all atoms involved due to the transfer or sharing of electrons has properties different from the constituent atoms Bonding in compounds Ionic bonds electrons are transferred from one atom to another results in charged atoms called ions oppositely charged ions ( positive and negative ) attracted to each other holding compound together ionic compounds dissolve ( dissociate ) in water ionic solutions conduct electricity important to nerve impulses example : NaCl made of Na+ and Cl- Covalent bonds electrons shared between atoms results in molecules very strong bonds examples : H2O ( water ) CH4 ( methane ) C6H12O6 ( glucose ) Acids and Bases Acid : Any substance that releases H+ ions when dissolved in water examples: HCl, HNO3, H2SO4, H3PO4, H2CO3 Base : Any substance that releases OH- ions when dissolved in water examples: NaOH , KOH , Mg(OH)2 , Ca(OH)2 Dissociation : The ions of ionic substances come apart in water examples: HCl KOH H+ Cl- + K+ + OH- Neutralization reaction : When mixing acids and bases, the H+ and OH- react to form water and the solution is neither acidic nor basic example : HCl + NaOH H2O + NaCl Indicators : Chemicals that have different colors depending on the acidity of the solution they are in examples: litmus is red in acid and blue in base phenolphthalein is pink in base pH scale : 0-2 3-4 strong acid 5 – 6.9 7 7.1 - 9 10 - 11 12 - 14 neutral strong base stomach acid, battery acid soft drinks, tomato juice coffee, urine, milk water blood, sea water detergent, rolaids ammonia, oven cleaner Scale only used for weak or diluted acids and bases Many chemical reactions in living systems are sensitive to a particular pH level Buffer: A weak acid or base that reacts with a strong base or acid to prevent sudden changes in pH. Water Makes up 70 – 95% of most living things Many things dissolve in water so important to life processes Molecular formula : H2O Shows polarity : atoms in the molecule do not share the electrons equally so the oxygen side is slightly negative and the hydrogens are slightly positive hydrogen bonding : weak bonds between water molecules due to their polarity Unique properties of water due to polarity and the extra attraction caused by hydrogen bonding : dissolves a variety of substances surface tension cohesion and adhesion capillarity high heat of fusion and vaporization high specific heat expands on freezing Macromolecules Carbohydrates Subunit : simple sugar Function : structure, energy storage Examples : sugar, starch Lipids Subunit : fatty acids linked by glycerol Function : energy storage, membranes, hormones, pigments Examples : fats, oils Proteins Subunit : amino acid Function : structure, enzymes, hormones Examples : muscle, hemoglobin Nucleic acid Subunit : Function : Examples : nucleotide 5 carbon sugar phosphate nitrogenous base genetic information, protein production DNA, RNA Metabolism Dehydration synthesis Combining subunits by removing water molecules Hydrolysis Breaking apart subunits by adding water molecules Enzymes Have an active site Bind to the substrate Lower the activation energy Reusable