Chemistry Comes Alive Chapter 2

Energy Potential energy: stored energy or energy of position. Kinetic energy: energy of motion

Forms of Energy Chemical Thermal/Radiant Electrical Mechanical

The Composition of Matter

Atoms and Chemical Elements Matter - anything that occupies space and has mass Atoms - smallest units of matter - have their own distinct properties Chemical element – a basic chemical substance composed of one type of atom Unique

Atomic Structure Nucleus Electron Shell Protons (+) Neutrons (0)

Structure of the Atom

Elements of the Human Body

Elements Oxygen - O Magnesium - Mg Carbon - C Chlorine - Cl Hydrogen - H Nitrogen - N Calcium - Ca Phosphorus - P Sulfur - S Sodium – Na Potassium - K Magnesium - Mg Chlorine - Cl Iron - Fe Iodine - I Manganese - Mn Copper - Cu Zinc - Zn Cobalt - Co Fluorine - F

Elements (cont’d) More than 90% of the mass of living things composed of just 4 elements: Carbon ( C ) Hydrogen (H) Oxygen (O) Nitrogen (N)

Chemical Bonds

Chemical Bonds Energy relationship between electrons of reacting atoms. Valence shell – atom’s outermost energy level or that portion that is reactive. Octet Rule or Rule of 8 – key to chemical reactivity Reactive and inert elements

Ionic Bonds Positive ions and negative ions held together Electrostatic - forces of attraction A gain or loss of electrons Cations - positively charged ions Anions - negatively charged ions Unstable in water Ex. NaCl

Ionic Bond

Covalent Bond Sharing electrons with other atom Most bonds in body Strong bonds – not easily broken Stable in water H-H O=O

Single Covalent Bond

Covalent Bonds

Hydrogen Bonds Weak bonds between hydrogen and a weak negative charge In large numbers they provide strength within molecules Important in DNA Common in water

Hydrogen Bonding in Water

Hydrogen Bonds in DNA

Chemical Reactions

Synthesis Reactions AB  A + B Requires formation of new bonds between combining units (reactants) Important - repairing worn or damaged parts. Anabolism - synthesis reactions within the cell

Decomposition Reactions A + B  AB Breaking down of molecules into simpler molecules Digestion Catabolism - decomposition reactions within the cell

Exchange or Displacement Reactions AB + C  AC + B AB + CD AD + CB Involve both synthesis and decomposition Ex. ATP transfers phosphate group to glucose

Oxidation-Reduction Decomposition, plus exchange of electrons. Reactant losing electrons or H atom – oxidized Reactant gaining electrons or H atom– reduced “OIL RIG” Not always a complete transfer of electrons Ex. Cellular respiration

Reversibility All chemical reactions theoretically reversible. Many biological reactions go in one direction Energy is lost Removal of reaction products

Factors Influencing Rate of Chemical Reactions Temperature – higher  quicker Particle size – smaller  faster Concentration – higher  faster Catalysts – increase rate of reaction w/o themselves becoming chemical changed Enzymes

Chemical compounds of the cell

Inorganic Compounds Generally lack carbon (exception CO2) Tend to be simpler and smaller molecules than organic

Inorganic Compounds (cont’d) Water

Inorganic Compounds (cont’d) Water Makes up about 60-70% of total body mass The universal solvent (a medium that dissolves a solute) Important transport medium Has a high heat capacity - absorbs and releases heat slowly

Inorganic Compounds (cont’d) Water (cont’d) High heat of vaporization – helps to cool body Important reactant Effective lubricant Cushions organs

Inorganic Compounds (cont’d) Salt Dissolves or ionizes when placed in water - dissociates All are electrolytes - can conduct an electric current

Inorganic Compounds (cont’d) Acids and Bases Acids – when dissolved in water, release one or more hydrogen ions pH < 7 Bases - reduce the concentration of hydrogen ions in a solution (bind w/ H+ ions) pH >7

pH scale

Inorganic Compounds (cont’d) Acids and Bases (cont’d) When acids and bases are mixed – neutralization Form water and salt Buffer – regulate acid-base balance in body

Organic Molecules Carbon containing compounds All fairly large, covalently bonded molecules All synthesized by dehydration synthesis and decomposed by hydrolysis.

Organic Molecules (cont’d) Carbohydrates Sugars & starches Energy source – readily easy source of fuel Monosaccharide - simple sugar (glucose) Disaccharide – double sugar (table sugar - sucrose) Polysaccharide - lack sweetness Longer term energy storage Glycogen - synthesized by animals. Stored in liver and muscles.

Organic Molecules (cont’d) Lipids Do not dissolve in water Fats Must be broken down by body before used Solid or liquid Saturated or unsaturated Provide insulation and reserve body fuel

Organic Molecules (cont’d) Lipids (cont’d) Phospholipid – plasma membrane Steroids Cholesterol (produced by liver) Cell membranes Vitamin D synthesis Production of steroid hormones

Organic Molecules (cont’d) Proteins Made up of amino acids Covalent bond between 2 amino acids form peptide bonds Chain of 10 or more amino acids = polypeptide One or more polypeptide = protein

Organic Molecules (cont’d) Proteins (cont’d) Function Basic structural material of body Enzyme – biological catalyst – increase rate of chemical reaction – decrease activation energy

Organic Molecules (cont’d) Nucleic Acids DNA Contain nucleotides: deoxyribose sugar, nitrogen bases (T, A, C, G), phosphate group Double helix Directs protein synthesis

Organic Molecules (cont’d) Nucleic Acids (cont’d) RNA Nucleotides: Ribose sugar, nitrogen bases (U, A, C, G), phosphate group Carries out protein synthesis

Organic Molecules (cont’d) ATP Universal energy compound used by all cells of the body Energy released by oxidation of glucose (in cellular respiration) and captured in bonds of ATP for later use