Elements of Life 25 elements Hint: Remember CHNOPS 96% : C, O, H, N ~ 4% : P, S, Ca, K & trace elements (ex: Fe, I) Hint: Remember CHNOPS

Bonds Covalent Ionic Hydrogen All important to life Form cell’s molecules Quick reactions/ responses H bonds to other electronegative atoms Strong bond Weaker bond (esp. in H2O) Even weaker Made and broken by chemical reactions

1. Polarity of H2O O- will bond with H+ on a different molecule of H2O = hydrogen bond H2O can form up to 4 bonds

Examples of Benefits to Life H2O Property Chemical Explanation Examples of Benefits to Life Cohesion polar H-bond like-like ↑gravity plants, trees transpiration Adhesion unlike-unlike plants xylem bloodveins Surface Tension diff. in stretch break surface bugswater Specific Heat Absorbs & retains E oceanmoderates temps protect marine life (under ice) Evaporation liquidgas KE Cooling Homeostasis Universal Substance Polarityionic Good dissolver solvent

ie. amino acid  peptide  polypeptide  protein Monomers Polymers Macromolecules Small organic Used for building blocks of polymers Connects with condensation reaction (dehydration synthesis) Long molecules of monomers With many identical or similar blocks linked by covalent bonds Giant molecules 2 or more polymers bonded together ie. amino acid  peptide  polypeptide  protein larger smaller

Dehydration Synthesis (Condensation Reaction) Hydrolysis Make polymers Breakdown polymers Monomers  Polymers Polymers  Monomers A + B  AB AB  A + B + H2O + + H2O +

Differ in position & orientation of glycosidic linkage I. Carbohydrates Fuel and building Sugars are the smallest carbs Provide fuel and carbon monosaccharide  disaccharide  polysaccharide Monosaccharides: simple sugars (ie. glucose) Polysaccharides: Storage (plants-starch, animals-glycogen) Structure (plant-cellulose, arthropod-chitin) Differ in position & orientation of glycosidic linkage

II. Lipids Fats: store large amounts of energy saturated, unsaturated, polyunsaturated Steroids: cholesterol and hormones Phospholipids: cell membrane hydrophilic head, hydrophobic tail creates bilayer between cell and external environment Hydrophilic head Hydrophobic tail

Four Levels of Protein Structure: Primary Amino acid sequence 20 different amino acids peptide bonds Secondary Gains 3-D shape (folds, coils) by H-bonding α helix, β pleated sheet Tertiary Bonding between side chains (R groups) of amino acids H & ionic bonds, disulfide bridges Quaternary 2+ polypeptides bond together

amino acids  polypeptides  protein

Protein structure and function are sensitive to chemical and physical conditions Unfolds or denatures if pH and temperature are not optimal