Lecture - Ch.2(1)
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Transcript of Lecture - Ch.2(1)
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Title
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 2Lecture
Slides
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Chapter 2
The Chemical Basis of LifeThe Chemical Basis of Life
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Atomic Structure
Atoms: composed ofsubatomic particles
Neutrons: no electrical
charge
Protons: one positive charge
Electrons: one negative
charge
Nucleus: formed by protons
and neutrons
Most of the volume of an
atom occupied by electrons
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Isotopes and Atomic Mass Isotopes: two or more forms of same element with same
number of protons and electrons but different neutronnumber For example; there are three types of hydrogen
Denoted by using symbol of element preceded by mass number as1H, 2H, 3H
Atomic Mass: average mass of naturally occurringisotopes
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Electrons and Chemical Bonding Intramolecular bonding occurs
when outermost electrons are eithershared with or transferred toanother atom
Ionic Bonding: atomsexchange electrons
Covalent Bonding: two ormore atoms share electron pairs
Ion: an atom loses or gainselectrons and becomes charged
Cation: positively charged ion Anion: negatively charged ion
In an ionic bond, cations andanions are attracted to each otherand remain close to each other
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Intermolecular Forces:
Solubility and Dissociation
Solubility: ability of onesubstance to dissolve in another
For example, sugar or saltdissolves in water
DissociationorSeparation: inionic compounds, cations areattracted to negative end andanions attracted to positive endof water molecules; the ions
separate and each becomessurrounded by water molecules
Electrolyte: dissociation of anionic compound in water
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Electrolytes and Nonelectrolytes
Electrolytes: solutions made by the
dissociation of cations (+) and anions (-) in
water
Have the capacity to conduct an electric current
Currents can be detected by electrodes
Nonelectrolytes: solutions made by
molecules that dissolve in water, but do notdissociate; do not conduct electricity
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2.2 Chemical Reactions and Energy
Atoms, ions, molecules or compounds interact
to form or break chemical bondsReactants: substances that enter into a chemical
reaction.
Products: substances that result from the reaction
Chemical bonds are made (synthesis;anabolism) and broken (decomposition;catabolism) during chemical reactions
Metabolism: collective term used for the sumof all of the anabolic and catabolic reactions inthe body
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Synthesis Reactions Two or more reactants chemically combine to form a new and larger
product. Anabolism.
Chemical bonds made; energy stored in the bonds.
Responsible for growth, maintenance and repair
Dehydration: synthetic reaction where water is a product
Produce chemicals characteristic of life: carbohydrates, proteins, lipids, and
nucleic acids
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Decomposition Reactions A large reactant is broken down to form smaller products.
Catabolism. Chemical bonds broken; energy released.
Hydrolysis: water is split into two parts that contribute to theformation of the products
Example: the breakdown of ATP to form ADP and inorganicphosphate with a concomitant release of free energy
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Oxidation-Reduction Reactions
Oxidation: lossof an electron by a substance
Reduction: gainof an electron by a substance
Oxidation-Reduction Reactions: the complete or
partial loss of an electron by one substance isaccompanied by the gain of that electron by another
substance
Synthetic/decomposition reactions can be oxidation -
reduction reactions
Reactions can be described in more than one way
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ATP and Potential Energy
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Heat Energy
When a chemical bond is broken and
energy is released, only some of that energy
is used to manufacture ATP. Energy that is released but not captured is
released as heat.
Heat is used by mammals to maintain bodytemperature.
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Activation Energy and Enzymes
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2.3 Inorganic Chemistry
Inorganic Chemistry: generally,substances that do not contain carbon
Water, oxygen, calcium phosphate, metal ions
Exceptions: CO, CO2
, and HCO3
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Organic Chemistry: study of carbon-
containing substances. Those that are
biologically active are called biochemicals.
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Acids and Bases; Salts and Buffers
Acid: a proton donor or any substance thatreleases hydrogen ions
Base: a proton acceptor or any substance
that binds to or accepts hydrogen ions Salt: a compound consisting of a cation
other than a hydrogen ion and an anion
other than a hydroxide ion. Example: NaCl Buffer: a solution of a conjugate acid-base
pair in which acid and base components
occur in similar concentrations
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Oxygen and Carbon Dioxide
Oxygen (O2): required in the final step in
the series of reactions used to extract energy
from food.
Carbon dioxide (CO2): produced during the
catabolism of organic compounds.
Metabolic waste product.
Combines with water in plasma and forms H+
thus affecting acid/base balance
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2.4 Organic Chemistry Carbohydrates: composed of carbon, hydrogen, oxygen.
Divided into monosaccharides, disaccharides, polysaccharides
Energy sources and structure
Lipids: composed mostly of carbon, hydrogen, oxygen. Relatively insoluble in water.
Functions: protection, insulation, physiological regulation,
component of cell membranes, energy source Proteins: composed of carbon, hydrogen, oxygen,
nitrogen, sometimes iodine. Functions: regulate processes, aid transport, protection, muscle
contraction, structure, energy
Nucleic Acids: composed of carbon, hydrogen, oxygen,nitrogen, phosphorus. Examples: ATP, DNA, RNA
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Carbohydrates: Monosaccharides Simple sugars.
Six-carbon sugars like glucose, fructose, and galactose are
important in the diet as energy sources.
Five-carbon sugars are components of ATP, DNA and RNA
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Carbohydrates: Disaccharides
Two simple sugars bound together by dehydration Examples: sucrose, lactose, maltose
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Carbohydrates: Polysaccharides
Long chains of many monosaccharides. Storage molecules for monosaccharides and form part ofcell surface markers
Glycogen formed by animals.
Starch and cellulose formed by plants Starch in food is used as a source of monosaccharides
Cellulose in food acts as fiber (bulk) in the diet
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Lipids: Fats Ingested and broken down by hydrolysis
Triglycerides: composed of glycerol and fatty acids Functions: protection, insulation, energy source
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Lipids: Phospholipids
Polar (hydrophilic) at one end; nonpolar (hydrophobic) at the
other.
Function: important structural component of cell membranes
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Lipids: Eicosanoids and
Fat-soluble Vitamins Eicosanoids: Derived from fatty acids.
Function: Important regulatory molecules
Include thromboxanes, leukotrienes, and
prostaglandins
Fat-soluble Vitamins: nonpolar molecules
essential for normal functioning.
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Lipids: Steroids
Cholesterol, bile salts, estrogen, testosterone. Carbon atoms arranged in four rings
Functions: physiological regulators and component of cell
membranes
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Enzymes Lower the activation energy necessary for a
reaction to occur; bring reactants into closeproximity
Three-dimensional shape contains an active sitewhere reactants attach.
Induced Fit Hypothesis: enzymes change shapeto accommodate the shape of specific reactants
Enzyme names usually end in ase and often havethe same word stem as the reactant; for example alipid is a reactant for lipase.
Cofactors: combine with active site and makenonfunctional enzymes functional
Organic cofactors called coenzymes
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Nucleic Acids DNA and RNA
Nucleotides Composed of a five-carbon sugar, a nitrogenous base, and a phosphate
Include the nucleic acids (DNA and RNA) and ATP
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DNA: Deoxyribonucleic acid
Genetic material of cells copied from one generation to next Composed of 2 strands of nucleotides
Each nucleotide contains one of the organic bases of adenine or guanine (which
are purines) and thymine or cystosine (which are pyrimidines).
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