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2. The Chemistry of Life

by: Gemma Williamson

2. The Chemistry of Life BISC 102

Marketplace > University of Mississippi > Biology > BISC 102 > 2 The Chemistry of Life
Gemma Williamson
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Week 2 notes
Inquiry Into Life Human Biology
Dr Carr
Class Notes




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This 5 page Class Notes was uploaded by Gemma Williamson on Thursday September 8, 2016. The Class Notes belongs to BISC 102 at University of Mississippi taught by Dr Carr in Fall 2016. Since its upload, it has received 3 views. For similar materials see Inquiry Into Life Human Biology in Biology at University of Mississippi.


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Date Created: 09/08/16
2. The Chemistry of Life 2.1. Atoms Make up All Matter - Matter = material that takes up space and has mass • occurs in 3 forms - solid Smallest mass to largest - liquid 1. Electron - gas 2. Proton - Energy = ability to do work (moving matter) 3. Atom • energy used by most ecosystems from the sun • heat, light and chemical bonds A. Elements are Fundamental Types of Matter - Matter consists of elements - Element = pure substance, cannot be broken down • oxygen, carbon, nitrogen, sodium, hydrogen - Scientists noticed patterns in chemical behavior in mid 1800s - Dmitry Mendeleyv invented the periodic chart - 92 naturally occurring elements - 25 elements essential to life - bulk elements required in large amounts (96% of human body) • carbon • hydrogen • oxygen • nitrogen - 3.5% of body consists of other bulk phosphorus • sulfur • • sodium • magnesium • potassium • calcium - Trace elements required in small amounts—> 0.5% of body • iron • zinc B. Atoms are particles of elements - Atom = smallest piece of an element that retains charc. of element • contains three particles - proton: + charge - neutrons: uncharged - both form nucleus • - charged electrons surround nucleus - atoms take up a lot of space, but when they are moving, like a fan, they take up mass - Atomic Number: number of protons in nucleus • periodic table has elements arranged sequentially by atomic number • protons = electrons, the atom is electrically neutral • ion: atom that has gained or lost electrons therefore has a net - or + charge C. Isotopes have different numbers of neutrons - Atoms mass number = protons + neutrons (in nucleus) - atomic number - mass = number of neutrons - Isotope: atoms of the same element that differ in number of neutrons—> same protons, diff. mass numbers • radioactive isotopes: excess neutrons = unstable - emit energy as rays when they break down into more stable forms - half-life = time for half to decay to stable form - used in x-rays - excessive exposure can lead to sickness and mutations - Atomic weight: average mass of all isotopes 2.2. Chemical Bonds Link Atoms Atoms in organisms arranged into molecules - Molecules: two or more chemically joined atoms - Compound: molecule composed of 2 or more diff. elements - Molecular formula: representation of atoms in a compound; CH4 (methane) A. Electrons determine bonding - Orbitals: describe location for an election relative to its nucleus • Energy shell: group of orbitals; first holds 2 electrons, after that it can hold up to 8; outer shells have higher energy • valence: outermost energy shell; no. of electrons determine chemical reactivity of atom - if full (with 8) = stable; octet rule • number of orbitals in each shell determines the amount of electrons it can hold - Electronegativity: measures atoms ability to attract electrons (high = strip from others) - Chemical bond: transfer of electrons from one atom to another, holds atoms together B. In an ionic bond, one atom transfers electrons to another atom - Ion: an atom that has lost or gained electrons - Ionic: a highly electronegative atom fills its valence by taking electrons from another atom • donator has + charge after atom that accepts has - charge • • held together through opposite charges C. In a covalent bond, atoms share electrons - Covalent: two atoms share electrons to complete outer shell - Double: share two pairs of electrons (O2) - Polar: one nucleus exerts stronger pull on shared electrons; diff. electronegativity values - Non polar: 2 atoms exert approx. equal pull Ionic, polar and non polar represent points along a continuum. • so electronegative, rips electrons, = ionic bond form • atom tugs at shared electrons more than the other = covalent bond is polar • 2 atoms with similar electronegativity share equally = non polar D. Partial changes on polar molecules create hydrogen bonds - Hydrogen: partially + H atom in 1 water molecule attracted to partially - O atom in another molecule; opposite partial charges on adjacent molecules attract each other - WATER IS POLAR - allows it to form hydrogen bonds 2.3 Water is Essential to Life The polarity of a water molecule and the hydrogen bond b/w water molecules account for its unique properties A. Water is Cohesive and Adhesive - Cohesion: ability of molecules to cling to each other due to hydrogen bonding • stops water evaporating instantly surface tension: hold together at its surface - • Adhesion: ability of polar water molecules to cling to polar surfaces (e.g. glass), due to + and - poles B. Many substances dissolve in water - Solvent: chemical in which other substances (solvents) dissolve - Solution: one or more solutes (aqueous solution) - Hydrophilic substances: polar or charged, readily dissolve in water (e.g. salt) - Hydrophobic: non polar; do not dissolve or form hydrogen bonds with water (fats) C. Water regulates temperature - Resists temp. changes - Heat is needed to raise water’s temp than other liquids, as hydrogen bonds counteract ability to absorb energy and move faster - Evaporation: conversion of liquid into a vapor D. Water expands as it freezes - Ice formation • liquid water = unstable H bonds = molecules close together • freezes = H bonds expand and become more stable • ICE LESS DENSE, so floats in liquid water • if it were denser, sink and ponds would freeze solid bottom up - can be deadly: expansion of ice kills outer membrane in cell - mammals have thick layers of fur to stay warm - pond surface freezes, when temp drops, it retains heat in water below E. Water participates in life’s chemical reactions - In a chemical reaction 2 or more molecules ‘swap’ atoms to yield diff. molecules - Reactants: molecules that enter reaction - Molecules formed from reaction = products 2.4 Cells Have an Optimum pH - H+ ions = important substance dissolved in water - Determine whether a solution is acidic or basic by examining proportion of hydrogen and hydroxide ions in the solution • Acid: increase the H+ concentration of a solution —> pH < 7 - dissociate in water and release H+ (lemon juice, vinegar) • Bases (BLUE): decrease H+ or increase OH- —> pH > 7 - either take up H+ or release OH- (milk of magnesia) • Neutral: (water) equal number of H+ and OH- - Measure through pH scale - Buffer: chemical or a combo, that keeps pH within normal limits (e.g. blood) 2.5 Cells Contain Four Major Types of Organic Molecules - Organic: chemical compounds contain both carbon and hydrogen—> contain core of carbon atoms, other attach - Molecular connectors: (diagram) each reactive group of atoms occur in 1 or more organic molecules - Living organisms composed of biological molecules: • carbs • lipids • proteins • nucleic acids A. Large organic molecules are composed of small subunits - Polymer: (protein, nucleic acid, carbs) chains of small molecular subunits called monomers (individual subunits) - Common examples that act as molecular to hook one subunit of organic to another • hydroxyl • carboxyl • amino • phosphate - Dehydration synthesis: chemical reaction used by cells to link monomers into polymers - Enzyme reaction: water molecule, -OH and an -H is removed - Functional groups: determine an organic molecules chemical properties - Hydrolysis: breaks the covalent bonds that link monomers 4. Carbohydrates include simple sugars and polysaccharides - monosaccharides - Organic molecules that consist of carbon, hydrogen, oxygen—> 1:2:1 - Energy source for cells - Sugars (simple carbs): • monosaccharides (monomer): contain 5 or 6 carbon atoms, simple sugars (glucose) • disaccharide: 2 mono. joined by dehydration synthesis (maltose, sucrose, lactose) • polysaccharides (polymer): may sugars joined (starch- store energy) (cellulose- structural building materials) - Complex Carbs chains of mono. • poly. are huge molecules consisting of many mono. monomers • - long chains of glucose - e.g. cellulose: plant cell walls C. Proteins are complex and highly versatile - amino acids - Variable structures and functions - Structure shows functions • collagen = protein fibre; structural support • Actin = muscle proteins; contractile (contraction in muscles) • Membrane channel proteins = transport • enzyme = digestive protein - monomers (building blocks) of proteins are amino acids (20) • form a repeating part of amino acids R group of amino acids is variable • - join 2 amino (buliding blocks) together - remove h2o through dehydration to synthesis (build) new molecule, to form a peptide bond or depitide - A polypeptide must properly fold into a protein or it cant do its job (denature) - Protein structure has 4 levels (each fold): • primary • secondary • tertiary • quaternary - If you change pH or apply heat, it will undo and change its structure and hence change its function—> called denaturation loss of function D. Nucleic Aids Store and Transmit Genetic Information - nucleotides - Nucleic acid is a polymer consisting of monomers called nucleotides - Cells contain 2 types of NA: • deoxyribonucleic acid (DNA) • ribonucleic acid (RNA) - Monomer consists of: • centre is a 5 carbon sugar (ribose in RNA, deoxyribose in DNA) • at least one phosphate attached to each carbon • opposite side has nitrogenous base - Uses dehydration and hydrolysis E. Lipids are hydrophobic and energy rich - glycerol, fatty acids - includes triglycerides (fatty acids) and steroids - hydrophobic, hard to dissolve in water - Not built from chains of monomers - dehydration links three fatty acids to a glycerol molecule, forming triglyceride - hydrolysis separates fatty acids from glycerol - saturated = all possible numbers of hydrogens around the carbons it can have, forming straight carbon chains • all carbons of a saturated fatty acids are bonded to 4 other atoms • solid at room temp. and of animal origin - unsaturated fatty acid contains at least 1 double bond, so at least 2 carbons are only bonded to 3 other atoms • poly: more then one double bond • mono: one double bond • double bonds create kinks in fatty acids that prevent them from packing close together • unsat. like oils are therefore liquids - steroids are lipid molecules - cholesterol is in animal cell membranes, and several hormones are derived from it - trans fats • unsaturated fats, originally from plant origin • industry has modified the fats by putting the hydrogen on the opposite side to each other to make trans fat; hydrogenated oils - behave like saturated fat, being solid at room temp. - increases shelf life of product - not good for digestive system and overall health - steroids • 4 interconnected carbon rings (vitamin D) • cholesterol is a key part of animal cell membranes


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