PowerPoint Lecture Outlines to accompany

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Hole’s HumanAnatomy and Physiology

Tenth Edition

Shier Butler Lewis

Chapter 2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 2Chemical Basis of Life

Why study chemistry in an Anatomy and Physiology class?

- body functions depend on cellular functions

- cellular functions result from chemical changes

- biochemistry helps to explain physiological processes, and develop new drugs and methods for treating diseases

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Structure of Matter

Matter – anything that takes up space and has weight; composed of elements

Elements – composed of chemically identical atoms• bulk elements – required by the body in large amounts• trace elements – required by the body in small amounts

Atoms – smallest particle of an element

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Atomic Structure

Atoms - composed of subatomic particles:

• protons – carry a positive charge

• neutrons – carry no electrical charge• electrons – carry a negative charge

Nucleus• central part of atom• composed of protons and neutrons• electrons move around the nucleus 2-4

Atomic Number and Atomic Weight

Atomic Number • number of protons in the nucleus of one atom • each element has a unique atomic number• equals the number of electrons in the atom

Atomic Weight• the number of protons plus the number of neutrons in one atom • electrons do not contribute to the weight of the atom

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Isotopes

Isotopes• atoms with the same atomic numbers but with different atomic weights• atoms with the same number of protons and electrons but a different number of neutrons• oxygen often forms isotopes (O16, O17, O18)• unstable isotopes are radioactive; they emit subatomic particles

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Molecules and Compounds

Molecules – particle formed when two or more atoms chemically combine

Compound – particle formed when two or more atoms of different elements chemically combine

Molecular formulas – depict the elements present and the number of each atom present in the molecule

H2 C6H12O6 H2O

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Electrons

• found in regions of space called electron shells (energy shells)

• each shell can hold a limited number of electrons• for atoms with atomic numbers of 18 or less, the following rules apply:

• the first shell can hold up to 2 electrons• the second shell can hold up to 8 electrons• the third shell can hold up to 8 electrons

• lower shells are filled first• if the outermost shell is full, the atom is stable

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Ions

Ion• an atom that has gained or lost an electron(s)• an electrically charged atom• atoms form ions to become stable

Cation• a positively charged ion• formed when an atom loses an electron(s)

Anion• a negatively charged ion• formed when an atom gains an electron(s)

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Ionic Bond

• an attraction between a cation and an anion

Ionic Bond

• formed when electrons are transferred from one atom to another atom

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Covalent Bond

Formed when atoms share electrons

•Hydrogen atoms form single bonds•Oxygen atoms form two bonds•Nitrogen atoms form three bonds•Carbon atoms form four bonds

H ― HO = ON ≡ NO = C = O

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Structural Formula

Structural formulas show how atoms bond and are arranged in various molecules

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Polar Molecules

Polar Molecule• molecule with a slightly negative end and a slightly positive end• results when electrons are not shared equally in covalent bonds• water is an important polar molecule

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Hydrogen Bonds

Hydrogen Bond• a weak attraction between the positive end of one polar molecule and the negative end of another polar molecule• formed between water molecules• important for protein and nucleic acid structure

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Chemical Reactions

Chemical reactions occur when chemical bonds form or break among atoms, ions, or molecules

Reactants are substances being changed by the chemical reaction

Products are substances formed at the end of the chemical reaction

NaCl ’ Na+ + Cl-

Reactant Products2-15

Types of Chemical Reactions

Synthesis Reaction – chemical bonds are formed A + B ’ AB

Decomposition Reaction – chemical bonds are brokenAB ’ A + B

Exchange Reaction – chemical bonds are broken and formed AB + CD ’ AD + CB

Reversible Reaction – the products can change back to the reactants

A + B AB2-16

Acids, Bases, and Salts

Electrolytes – substances that release ions in water

Acids – electrolytes that release hydrogen ions in waterHCl H+ + Cl-

Bases – substances that release ions that can combine with hydrogen ions

NaOH Na+ + OH-

Salts – electrolytes formed by the reaction between an acid and a base

NaCl Na+ + Cl-

HCl + NaOH H2O + NaCl 2-17

Acid and Base Concentrations

pH scale - indicates the concentration of hydrogen ions insolution

Neutral – pH 7; indicates equal concentrations of H+ and OH-

Acidic – pH less than 7; indicates a greater concentration of H+

Basic or alkaline – pH greater than 7;indicates a greater concentration of OH-

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Organic Versus Inorganic

Organic molecules • contain C and H• usually larger than inorganic molecules• dissolve in water and organic liquids• carbohydrates, proteins, lipids, and nucleic acidsInorganic molecules • generally do not contain C• usually smaller than organic molecules• usually dissolve in water or react with water to release ions• water, oxygen, carbon dioxide, and inorganic salts 2-19

Inorganic Substances

Water • most abundant compound in living material• two-thirds of the weight of an adult human• major component of all body fluids• medium for most metabolic reactions• important role in transporting chemicals in the body• can absorb and transport heat

Oxygen (O2) • used by organelles to release energy from nutrients• necessary for survival 2-20

Inorganic Substances

Carbon dioxide (CO2)• waste product released during metabolic reactions• must be removed from the body

Inorganic salts• abundant in body fluids• sources of necessary ions (Na+, Cl-, K+, Ca2+, etc.)• play important roles in metabolic processes

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Organic SubstancesCarbohydrates

• provide energy to cells

• supply materials to build cell structures

• water-soluble• contain C, H, and O• ratio of H to O close to 2:1 (C6H12O6)• monosaccharides – glucose, fructose• disaccharides – sucrose, lactose• polysaccharides – glycogen, cellulose

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Organic SubstancesCarbohydrates

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Organic SubstancesLipids

• soluble in organic solvents• fats (triglycerides)

• used primarily for energy• contain C, H, and O but less O than carbohydrates (C57H110O6)• building blocks are 1 glycerol and 3 fatty acids per molecule• saturated and unsaturated

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Organic SubstancesLipids

• phospholipids

• building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per molecule

• hydrophilic and hydrophobic

• major component of cell membranes

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Organic Substances Lipids

• steroids• connected rings of carbon• component of cell membrane• used to synthesize hormones• cholesterol

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Organic SubstancesProteins

• structural material• energy source• hormones• receptors• enzymes• antibodies• building blocks are amino acids

• amino acids held together with peptide bonds

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Organic Substances Proteins

Four Levels of Structure

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Organic SubstancesNucleic Acids

• constitute genes• play role in protein synthesis• building blocks are nucleotides

• DNA (deoxyribonucleic acid) – double polynucleotide• RNA (ribonucleic acid) – single polynucleotide 2-29

Organic SubstancesNucleic Acids

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Clinical Applications

Radioactive Isotopes Reveal Physiology

• can be detected in the body using a scintillation counter

• injected into the body

• different types taken up by different organs

• can be used to destroy specific tissues• commonly used

• iodine-131 for thyroid function• thallium-201 for heart function• gallium-67 and cobalt-60 for cancer• others used to assess kidney functions, measure hormone levels and bone density changes 2-31