Transcript Chapter 1-3
What is Biology? Study of life & characteristics of life Expectations/learning outcomes: – Understand, explain, describe, & integrate the natural world of living things – Focusing on: • How life works… rather than the “meaning of life” Characteristics of Life? In other words… what are the essential properties/functions of “living” systems? • DNA • Cells • Acquire & use energy • Highly complex & organized • Growth & development • Metabolize chemicals • Reproduce • Evolve by natural selection Levels of organization • • • • • • • • • • • • • Biosphere Ecosystem Community Population Organism Organ system Organ Tissue Cell -------functional units of life Organelle Molecule Atom Subatomic particle How can we study: all these characteristics, diversity, complexity… and, try to make sense of it? • Scientific Method – What? – Why? – How? Scientific Method Inductive approach: from specific observations to the general Deductive approach: use general principles in predicting specific outcomes Complexity builds from the atomic level up (Ch. 2) • Atoms – Chemical unit – Made up of subatomic particles • Nucleus of an atom – Protons – Neutrons positive charge neutral charge • Electrons – negative charge – Orbit around nucleus in energy shells (2,8,8…) – Determine chemical nature, reactivity, and interactions with other elements …incomplete shells create potential for interactions. Lets make an atom of Carbon… • Symbol for Carbon element • Atomic number 6 protons • Nucleus w/ 6 protons & 6 neutrons • 1st shell with 2 electrons • Second shell with only 4 electrons 6 C 12.011 …has space for 4 more e- • Atomic mass? 6 protons 6 neutrons 6 electrons = 12.011 (electrons negligible mass) 1 H 1 Relationships between atoms & molecules or, Bonds • Interactions of outer shells or valence electrons • Form molecules of multiple atoms • Form compounds of multiple molecules • Covalent bonds – Atoms share electrons (e-) between pairs to satisfy each of their valence shells Example 1 – Unequally charged ions… e- transferred from one ion to another (gain/loss of e-) 11 1 H • Ionic bonds 1 + H 1 Na 22 17 + Cl 35.4 Although the strongest bonds are Covalent, it is the weak Hydrogen bonds that are perhaps the most significant to cell functions. • Polar molecules – Covalent bonds of unequal sharing (H20) – O is more electronegative than H • Hydrogen bonds include H • Opposites (+ & -) attract creating H-bonds between water molecules What else do we know about water? • Naturally occurs in 3 forms with varying levels of energy and density. – Solid, liquid, gas • Which is the most dense? • Molecules in constant motion – Breaking & making H-bonds • Varies with temperature, density, and dissolved particulates Water is a common solvent that dissolves substances (solutes) to form an aqueous solution • Additional water molecules dissociate leaving some hydrogen ions (H+) and some hydroxide ions (OH-) • These ions are very reactive • [H+] in solution = acidic Therefore a lower pH • [OH-] in solution = basic Therefore a higher pH The importance of Organic chemicals… (Ch. 3) • contain at least one C atom – 4 electrons in outer shell – in need of 4 more – covalent bonds with H, O, N, or other C • Molecules of only C and H are called hydrocarbons • Bonding determines shape • Functional groups – determine properties & functions of organic compounds – Are usually polar, thus soluble in water, thus more reactive than carbon backbone by itself Common Functional Groups Most of a cells molecules are variations and extensions of a small set of small molecules. Making Macromolecules • Many repeating smaller molecules • Polymers of monomers • Built by dehydration synthesis reaction (rxn) Hydrolysis – breaking polymers Classes of Macromolecules • Carbohydrates – Simple & complex sugars – Monosaccharides & Polysaccharides • Lipids – Fats, oils, waxes, etc. • Proteins – Made of 20 Amino acids • Nucleic Acids – DNA made of only 4 monomers (nucleotides) Carbohydrates • E.g. glucose, fructose, lactose, sucrose, starch, glycogen, cellulose… • Fuel to do work • Raw material for bigger molecules • 2 sugars linked = disaccharide via dehydration synthesis • More sugars = polysaccharides Note: Animals can’t hydrolyze cellulose very well, therefore use bacteria to do it for us -- Byproduct is methane gas Lipids • Fats, oils, waxes, steroids • Polymers of fatty acids and glycerol • Energy storage molecules • • Hydrophilic heads (w / polar functional group(s); interacts easier with water) & hydrophobic tails (nonpolar; insoluble) • Saturated fats – – – • Very few double bonds Lots of H’s Solid at room temperature (butter, lard, and most animal fats) Unsaturated fats – – – – Kinked due to double bonds, less H’s, take up more space Liquid at room temperature E.g. oils, margarine, and most plants fats Hydrogenating unsaturated fats make them solid (margarine); trans fats Steroids • Lipids with backbones bent into rings • Cholesterol – functions in digestion of fats – Important component in cell membranes (see ch 5) – Starting material of other steroids like sex hormones Note: Anabolic steroids (synthetics) mimic testosterone (see ch 12) Proteins – have many roles Made from 20 different amino acids monomers • Structural – hair, cell, cytoskeleton • Contractile – muscles, motile cells • Storage – sources of amino acids (egg whites) • Defense – antibodies, membrane proteins • Transport – hemoglobin, membrane proteins • Signaling – hormones, membrane proteins • Catalyst – free enzymes, membrane proteins Protein properties… • Amino group • Carboxyl group • Variable R group – Could be a single H – Or, C’s with functional groups – Determines specific properties and protein diversity • Nonpolar & hydrophobic • Polar & hydrophilic are easier to dissolve in a cells aqueous solution • Linked to form polymer proteins by peptide bonds – Specific covalent bond between amino acids – Two aminos bonded = dipeptide – More aminos = polypeptides Protein’s shape determines function • 1o structure: unique sequence of amino acids • 2o structure: coils or folds via H-bonding • 3o structure: 3-D globular or fibrous subunit via bonds of R-groups • 4o structure: multiple subunits Nucleic Acids • Polymers of 4 specific monomers = nucleotides – Via dehydration synthesis between sugars • Builds chain w/sugarphosphate backbone • Single stranded RNA • Double stranded DNA