Midterm 1

• Oxygen, carbon, hydrogen, and nitrogen make up 96% of our bodies
• elements: most fundamental unit of chemistry that cannot be broken down, life requires about 25
• atom: smallest unit that retains properties of element
• Elements in the same family exhibit similar bonding patterns
• Isotopes: atoms with same number of protons as electrons but different number of neutrons, less stable so break down emitting E
• Chemical bonds in order of strength: covalent, ionic, hydrogen, hydrophobic, van der waals
• in biological systems, weak bonds are needed for flexibility and strong ones are needed for structure
• covalent: sharing of electron pairs
• ionic: attraction of opposite charges
• hydrogen bonds: allow partial positive hydrogen to be shared with nearby negative atom , important for macromolecules and properties of water
• properties of water: cohesion, high specific heat capacity, solid less dense than liquid, universal solvent
• hydrophobic interactions: interactions of nonpolar substances in presence of polar substances, clump together. Allow insects to stand on water because they have waxy legs
• Hydrophobic interaction in water: nonpolar groups move away from water or change shape to shield, force of self assembly
• amphiphilic/amphipathic: molecules have both hydrophobic and hydrophilic regions
• van der waals: weak intermolecular forces between molecules of nonpolar substances and all substances. Example: geckos
• Bond energies: The energy required to break a covalent bond between two atoms. Covalent bonds have highest.
• Macromolecules: polymers made from monomers covalently bonded. Sugars, Lipids, Proteins, Nucleic Acids
• functional groups: groups of atoms that determine the chemical and physical properties of molecules
• negatively charged functional groups: carboxyl and phosphate
• positively charged functional groups: amino
• Neutral but polar functional gorups: hydroxyl, sulfhydryl, carbonyl, aldehyde, ketone
• Nucleotides --> nucleic acids
• amino acids --> proteins
• glycerol, fatty acids, steroids --> lipids
• glucose and other monosaccharides--> polysaccharides
• Dehydration synthesis: removing water from molecules for polymerization
• Hydrolysis: adds a water molecule, breaking bonds for depolymerization
• Sugars: aldehyde or ketone group, plus two or more hydroxyl groups. monosaccharides are monomers, disaccharides are dimers, and polysaccharides are polymers.
• Polysaccharide examples: cellulose, starch, glycogen
• Proteins: made from combination of 20 different amino acids, which are linked together by peptide bonds
• Lipids: hydrophobic or amphipathic molecules made from glycerol and fatty acids
• Saturated fatty acids: all single bonds, completely reduced, packs together well, relatively straight, solid at RT
• Unsaturated Fatty Acids: at least one double bond, kinked or bent shape, does not pack together well
• Trans unsaturated fatty acids: created synthetically by hydrogenation, lead to high cholesterol levels and atherosclerosis
• fatty acids with longer tails are less soluble
• Functions of proteins: Enzymes, defense, storage, transport, hormones, receptors, contractile/motor, structural
• Enzymatic proteins: selective acceleration of chemical reactions ex) digestive enzymes catalyze hydrolysis
• Defensive proteins: protection against disease Ex) antibodies
• Storage proteins storage of amino acids. ex) casein for baby mammals
• Transport proteins: transport of sunstances. ex) hemoglobin for oxygen