Ch. 2 Chemistry of Life PDF

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Spring 2020 Semester; A&P I; Dr. Harold Olivey...

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ANATOMY & PHYSIOLOGY INSTRUCTOR: DR. HAROLD OLIVEY

Ch. 2 Chemistry of Life What the Matter? Everything in the universe can be classified as either energy or matter Matter: anything that takes up space and has mass Element: the simplest type of matter with unique chemical properties; composed of atoms of only one kind Atom: smallest particle of an element that chemical characteristics of that element

Composed of Atoms Subatomic particles Protons and neutrons are found in the nucleus; electrons occupy an electron cloud that surrounds the nucleus Protons = positive charge; weight is appx. 1 Dalton Neutrons = no charge; weight similar to protons Electrons = negative charge; weight 1/1836 Dalton Atomic number = proton number Atomic mass = protons, and neutrons

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Elements An element is all the atoms with the same atomic number (number of protons) Elements can be arranged in an orderly fashion based on their atomic number in the periodic table

Major elements in the body Oxygen- O (O2)

Carbon- C

Phosphorous- P

Hydrogen- H (H2)

Nitrogen- N (N2)

Calcium Ca

Potassium- K

Sodium- Na

Chlorine- Cl

Isotopes Are elements with similar numbers of protons but different numbers of neutrons Common isotopes 3H- tritium

14C

32P

Isotopes are often radioactive and can thus be used experimentally or clinically to label and measure things in the body

Electrons and Ions Can be viewed as surrounding the nucleus in specific shells or orbits The outermost electron shell determines the reactivity of the element or its chemical properties Some atoms can add an electron from another atom and some atoms can give up

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electrons Thus, some atoms can have more or fewer electrons than protons. These are known as ions Protons > electrons = cations (+) Protons < electrons = anion (-)

Atoms combine through chemical reactions Molecule= a chemical structure consisting of atoms held together by chemical bonds Compound= a chemical substance composed of atoms of two or more different elements Molecular weight is the sum of the atomic weights of the component atoms There are three types of bond: ionic, covalent and hydrogen

Ions and Ionic bonds A cation is an atom or compound with a positive charge An anion is an atom or compound with a negative charge Ionic bond = attraction between positive cations and negative anions. It is an “electric” bond A salt is an ionic compound where the cation is not hydrogen (H+) and the anion is not hydroxide (OH-)

Ionic bonds

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Step 1. Formation of ions Step 2. Attraction between opposite charges Step 3. Formation of an ionic compound

Covalent Bonds Atoms share electrons Single covalent bond- share 1 set of electrons Double covalent bond- shares 2 sets of electrons Triple covalent bond- shares 3 sets of electrons

Polar and Nonpolar Covalent Bonds Nonpolar covalent: Electrons shared equally because nuclei attract the electrons equally (CC, C-H) Polar covalent: Electrons not shared equally because one nucleus attracts the electrons more than the other does (e.g., O-C, O-H) This results in one side of the molecule having a more negative charge and another part of the molecule having a more positive charge

Hydrogen bonds Hydrogen bonds are formed when a partially positive H atom in a polar covalent bond is attracted to the partially negative atom (-) of another polar covalent bond Usually, the other atom is O or a N

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Weak forces that affect the shape and properties of compounds (cannot make molecules themselves)

Solutions and suspensions Solution is a uniform mixture of two or more substances Solvent is the medium in which molecules of solute are dispersed (more abundant substance) Solutes are molecules evenly dispersed (dissolved) in solvent Solute concentrations are expressed in Molar values Colloids are thick or gelatinous solutions usually of protein or other large molecules Suspensions are large molecules that are not in solution but will eventually settle out

Solutes and solvents Compounds that dissolve or interact readily with water are hydrophilic Compounds that do not dissolve or interact with water are hydrophobic Likewise, compounds that dissolve or interact readily with fat or oil are lipophilic and those that don’t are lipophobic

Water and its properties Water (H2O) is the most important constituent of the body. ⅔ of the body is composed of water

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Many compounds are readily soluble in water High specific heat capacity Lubricant Aqueous solutions are solutions where water is the solvent

pH - Acids and Bases pH is a measure of the concentration of free hydrogen ions (H+) in solution Neutral pH (7.0) pure water Acidic pH (lower than 7.0) Basic pH (higher than 7.0) alkaline Acids release hydrogen ions solution and lower pH (acid = ↑ H+ and ↓ pH) Bases remove H+ from solution and raise pH (base = ↓ H+ and ↑ pH)

Chemical reactions Occurs when reactants combine or split apart to generate one or more products Types of reactions Synthesis- A+B → AB Decomposition (hydrolysis)- AB → A+B Exchange- AB + CD →← AD + CB

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Metabolism Metabolism = The sum of all reactions in the body. Provides for the capture, storage, and release of energy Catabolism = the breakdown of complex molecules (releases energy) Anabolism = is synthesis of new molecules (uses energy)

Basic energy concepts Energy = the capacity to perform work Kinetic energy = is the energy of motion. It does work (active energy) Potential energy = is stored energy resulting from position or structure Energy conversions are not 100% efficient, resulting in release of heat

Enzymes, energy and chemical reactions Activation energy = is the amount of energy needed to begin a reaction Enzymes are catalysts Reduce the energy of activation without being permanently changed or used up Promote chemical reactions

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