Chapter 2: Chemistry Part 1

Atoms Chemical Bonds Acids, Bases and the pH Scale

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Elements

The most fundamental different types of material that things (e.g., the body) are made of are called elements.Examples: Gold, iron, sodium, carbon, helium, potassium

Different elements have different properties (behaviors)

Table of known elements

Structure of Atoms

The smallest chemical units Composed of 3 particles:

Protons: + charged Neutrons: neutral Electrons: - charged

Regions of Atoms: Nucleus:

in center contains protons & neutrons

Electron Cloud organized into Shells/Orbitals: External to the nucleus

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What makes different types of atoms different?

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Different numbers of protons and electrons

Electron Shells

Electron shells/orbitals Surround the nucleus 1st shell: up to 2 e- 2nd shell: up to 8 e- 3rd shell: up to 8 e-

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Atoms - Electron Shells continued

Valence shell: Outermost e- shell Valence electrons: e- in the outermost shell

participate in chemical reactions/form bonds e- lost, gained, or shared to fill/empty the valence shell

Basis of chemical bonding

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Atoms - Isotopes

Are different forms of same atom Number of protons and electrons are same Number of neutrons different

Different isotopes are detectable and sometime emit radiation and can be used in imaging, research, and treatment of disease

e.g., Carbon IsotopesCarbon 12: 6 p+, 6 e-, 6 nCarbon 13: 6 p+, 6 e-, 7 nCarbon 14 : 6 p+, 6 e-, 8 n

* Carbon 12 is most common stable form, carbon 13 is naturally occurring and makes up just over 1%, C14 is radioactive

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1 2 3 4 5 6 7 8

Number of valance electrons

Ion Formation

Electrons are transferred Lost & gained e- transfer creates ions

cation (+ charged ) anion (- charged)

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11 e- 17 e-

10 e- 18 e-

Examples of Common ions and their Functions:

Relevance of Isotopes

Imaging: using radioactive (low risk) isotope (tracers/radiolabelling) injected into the body to create anatomical images E.g.NMR: imaging using isotopes

Clearance/processing: injecting molecules with uncommon isotopes to see how the molecule is used or how fast is it is processed.

Specific isotopes connected to specific molecules can test/image specific tissues, organs, or processes E.g. iodine for thyroid, cobalt for intestinal absorption of B vitamins

Radiopharmaceutics: using radioactive isotopes inside the body to destroy tumors or other abnormal tissue

Radioactive decay/dating: not very common in A&P but used to date very old things.

Chemical Bonds

Atoms join together through chemically bonding: Creates molecules Based on valence e- (number and shell) Atoms “want” valence shell to be empty or full Lose, gain, or share e- to empty of fill their

valance shell

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Chemical Bond Overview

Covalent Non-polar Polar

Ionichydrogen

Ions, + cation & - anion, are attracted to one another Opposite charges attract

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Ionic Bonding

Covalent Bonds

Valence electrons are shared Single, double, triple

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Type of Covalent Bonds

Nonpolar: electrons shared equally e.g. in H2 or O2

Polar: electrons shared unequally Creates molecules with + and – regions (poles) O, N, P commonly create

e.g., water/H20

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Free Radicles

Free radicals are atoms/molecules that have single unpaired electrons in valance shells.Highly reactive—damagingFree radical theory of agingThe/a hypothetical reason why anti-oxidants are good for your health

Ions dissociate (atoms unbind) when mixed in H2O

Polar molecules freely separate from one another and mix with water. H2O forms hydration spheres around ions and polar

molecules

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Ions, Polar Molecules and Water

Hydrophilic : soluble in water (interact w/ water) Polar or charged

e.g. ions, glucose, some amino acids Form hydration spheres

Hydrophobic : not soluble in water (lipid soluble) Nonpolar

e.g., fats, oils, cholesterol (lipids) cannot form hydration spheres

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Hydrophobic v. Hydrophilic

Polar (and charged)

HydrophilicWater soluble

nonpolar

HydrophobicNot water soluble

(i.e., lipid soluble)

Hydrogen Bonds Attraction between a H and a (partially) negatively charged

atom Oxygen, Nitrogen

H+ is part of a polar bond. e.g., between adjacent H20s

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Hydrogen Bonds Hydrogen bond can form between two different molecules:

this creates an attraction between the molecules that causes them to want to “hold onto each other”

does not combine the two molecules to create a new molecule

Within a molecule: causes the molecule to bend and twist into a 3-dimensional

shape

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Properties of Water Due to water molecules’ polarity and the H-bonds between water

molecules 1. Water is an excellent solvent

Many molecules dissolve in water creating a solution due to water’s polarity

2. Ability to absorb and retain heat (high heat capacity) evaporation of water is an excellent cooler excellent distributor of heat (via blood) water has a high thermal inertia that stabilizes Tb due to hydrogen bonds between water molecules

3. Surface tension due to hydrogen bonds between water molecules

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Acids and Bases Acids release protons (H+ /hydrogen ion) in a solution

proton donor Bases lower H+ levels of a solution (or generates OH-)

proton acceptor

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pH Scale pH scale runs from 0 to 14 (commonly)

Pure H2O = neutral: pH = 7

H+ = to OH- Acids have a pH < 7 (pH 0 - 7)

Acidic More H+ than pure water

Bases have a pH > 7 (pH 7 - 14) Basic/Alkaline H+ < pure water

Acid and Basic can be used in a relative sense E.g., 11 is more acidic then 13 even though 11 is in the basic end

of the pH scale Fill in: pH 5 is more ____ (acidic/basic) then pH 2.

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pH Scale(technically not linear as show in diagram)

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H2O

H2OH2O H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2OH2O

OH-

H+H2O

H+

H+ H+

OH-

H2CO3 + H2O H+ + HCO3-

H+

HCO3-

OH-

OH-

HCO3-

H+

H2O H+ + OH-

Neutral acidic

H2OH2O

H2O

1) NaOH + H2O Na + OH-

2) OH- + H+ H20

H2O

H2OH2O H2O

H2O

H2O

H2O

H2OOH-

H+

H+OH-

H2O H+ + OH-

Neutral Basic

H2O

H2OH2O H2O

H2O

H2O

H2O

H2OOH-

H+

H+OH-

Na+

OH-

H2O

Blood pH

Normal range of pH is 7.35 – 7.45Maintained by buffering actionAcidosis occurs if pH < 7.35Alkalosis occurs if pH > 7.45

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Loss of homeostasis

Buffers

Reduce changes in pH combining with or release H+s Buffers stabilize pH/minimize pH changes

e.g. the bicarbonate buffer system in blood:

H20 + C02 H2C03 H+ + HC03-

Too acidic – too many H+

H+ + HC03- H2C03

This removes H+, reducing acidity

Too alkaline (basic) – too few H+

H2C03 H+ + HC03-

This adds H+, reducing alkalinity2-21

Synthesis Reactions

smaller molecules larger moleculescreates a water molecule as it adds two other

molecules together

synthesis = dehydration synthesis (condensation) = anabolism

+ H2OHO

H+

Chemical Reactions:

Synthesis = building (adding together) Dehydration Synthesis = adds molecules and creates water

Example above two monosaccharides joined this way make a disaccharide

Dehydration Synthesis /Condensation

Splits water out of 2 monosaccharides An H+ and OH- removed

H+ + OH- = H2O

Example: two monosaccharides joined this way make a disaccharide

Decomposition Reactions

large molecules smaller moleculesa pre-existing water is split into H + OH which

are added to the fragments of the original molecule

decomposition = hydrolysis = catabolism

+ H2OHO

H+

Chemical Reactions:

Hydro + Lysis

water Breakdown/separate

Breaking water apart

Hydrolysis

Water and another molecule are split H2O is split, H+ added to one monosaccharide, OH- to other

Example, Polysaccharide hydrolyzed into disaccharides, then to monosaccharides

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Reversible Rnx

+ H2OHO

H+