Anatomy and physiology chap 2

Chemistry

The science of change: structure of atoms, basic chemical building blocks, atoms combine to form increasingly complex structures

Matter

Made up of atoms; atoms join together to form chemicals with different characteristics; chemical characteristics determine physiology at the molecular and cellular levels

Atoms

Building blocks of matter

Subatomic particles

protons, neutrons, electrons

Proton

Positive charge, 1 mass unit

Neutron

Neutral, 1 mass unit

Electron

Negative charge, low mass

Atomic structure

atomic number, nucleus, electron cloud

Atomic number

Number of protons

Nucleus

Contains protons and neutrons

Electron cloud

Contains electrons

Hydrogen-1

A typical hydrogen nucleus contains a proton and no neutrons, mass number:1

Hydrogen-2, deuterium

Nucleus contains a proton and a neutron, mass number: 2

Hydrogen-3, tritium

Nucleus contains a proton and two neutrons, mass number: 2

Oxygen, O (65)

A component of water and other compounds; gaseous form is essential for respiration

Carbon, C (18.6)

Found in all organic molecules

Hydrogen, H (9.7)

A component of water and most other compounds in the body

Nitrogen, N (3.2)

Found in proteins, nucleic acids, and other organic compounds

Calcium, Ca (1.8)

Found in bones and teeth; important for membrane function, nerve impulses, muscle contraction, and blood clotting

Elements

Determined by atomic number of an atom; most basic chemicals

Isotopes

Specific version of an element based on its mass number

Mass number

Number of proton plus the number of neutrons

Why only are the number of neutrons different?

Because the number of protons determines the elements

Atomic weight

Exact mass of all particles; measured in moles; average of the mass numbers of the isotopes

Electrons in the electron cloud

Determine the reactivity of an atom

Electron cloud

Contains shells, or energy levels, that hold a maximum number of electrons

Valence shell

Outermost shell that determines bonding

Chemical bonds

Involve the sharing, gaining, and losing of electrons in the valence shell; form molecules and/or compounds

Three types of chemical bonds

Ionic, covalent, hydrogen

Ionic bonds

Attraction between cations (electron donor) and anions (electron acceptor) then draws the two ions together

Covalent bonds

Strong electron bonds involving shared electrons

Hydrogen bonds

Weak polar bonds based on partial electrical attractions; bonds between adjacent molecules, not atoms, slightly positive and negative portions of polar molecules being attracted to one another

Molecules

Two or more atoms joined by strong bonds

Compounds

Two or more atoms OF DIFFERENT ELEMENTS joined by strong or weak bonds

Explain: H2= Molecule only, H2O= molecule and compound

Compounds are all molecules, but not all molecules are compounds

Electron donor

Loses one or more electrons and becomes a cation, with a positive charge

Electron acceptor

Gains those same electrons from the donor and becomes an anion, with a negative charge

Ion

A subscript plus or minus sign following the symbol of an element

Single covalent bond

Sharing one pair of electrons

Double covalent bond

Sharing two pairs of electrons

Triple covalent bond

Sharing three pairs of electrons

Nonpolar covalent bonds

Involve equal sharing of electrons because atoms involved in the bond have equal pull for the electrons

Polar covalent bonds

Involve unequal sharing of electrons because one of the atoms involved in the bond has a disproportionately strong pull on the electrons; ex: water

Hydrogen bonds between H2O molecules causes

Surface tension

Chemical reaction

Either new bonds are formed or existing bonds are broken; reactants, products, metabolism; in cells, cannot start without help

Reactants

Materials going into a reaction

Products

Materials coming out of a reaction

Metabolism

All of the reactions that are occurring at one time

Energy

Power to do work

Work

A change in mass or distance

Kinetic energy

Energy of motion

Potential energy

Stored energy

Chemical energy

Potential energy stored in chemical bonds

Types of chemical reactions

Decomposition (catabolism), synthesis (anabolism), exchange, reversible

Decomposition reaction (catabolism)

Breaks chemical bonds

Synthesis reaction (anabolism)

Forms chemical bonds

Exchange reaction

Involves decomposition first, then synthesis

Reversible reaction

At equilibrium the amounts of chemicals do not change even though the reactions are still occurring; seek equilibrium, balancing opposing reaction rates; add or remove reactants

Activation energy

The amount of energy needed to get a reaction started

Enzymes

Protein catalysts that lower the activation energy of chemical reactions; are not changed or used up in the reaction

Exergonic (Exothermic) Reactions

Produce more energy than they use; releases energy; reaction ends with lower energy than it started with

Endergonic (Endothermic) Reactions

Use more energy than they produce; absorbs energy; reaction ends with higher energy than it started with

Nutrients

Essential molecules obtained from food

Metabolites

Molecules made or broken down in the body

Inorganic compounds

Molecules not based on carbon and hydrogen; carbon dioxide, oxygen, water, and inorganic acids, bases, and salts

Water

Accounts for up to two-thirds of your total body weight

Solution

Uniform mixture of two or more substances; consists of a solvent, or a medium, in which atoms, ions, or molecules of another substance, called a solute, are individually dispersed

Solubility

Water’s ability to dissolve a solute in a solvent to make a solution

Reactivity

Most body chemistry occurs in water

High heat capacity

Water’s ability to absorb and retain heat

Lubrication

To moisten and reduce friction

Colloid

A solution of very large organic molecules; ex: blood plasma

Suspension

A solution in which particles settle (sediment); ex: whole blood

Concentration

The amount of solute in a solvent (mol/L, mg/mL)

PH

The concentration of hydrogen ions (H+) in a solution

Neutral pH

A balance of H+ and OH-; pure water= 7.0

Acidic

Lower than 7.0; high H+ concentration; low OH- concentration

Basic (or alkaline)

Higher than 7.0; low H+ concentration; high OH- concentration

pH of human blood

Ranges from 7.35 to 7.45

pH Scale

Has an inverse relationship with H+ concentration; more H+ ions means lower pH, fewer H+ ions means higher pH

Acid

A solute that adds hydrogen ions to a solution; proton donor; strong ones dissociate completely in solution

Base

A solute that removes hydrogen ions from a solution; proton acceptor; strong ones dissociate completely in solution

Weak acids and weak bases

Fail to dissociate completely; help to balance the pH

Salts

Solutes that dissociate into cations and anions other than hydrogen ions and hydroxide ions

Buffers

Weak acid/salt compounds; neutralize either strong acid or strong base; sodium bicarbonate is very important in humans

Antacids

Basic compounds that neutralize acid and form a salt; alka-seltzer, tums, rolaids, etc

Organic molecules

Contain H, C, and usually O; covalently bonded; contain functional groups that determine chemistry; carbohydrates, lipids, proteins (amino acids), nucleic acids

Amino group— NH2

Acts as a base, accepting H+, depending on pH; can form bonds with other molecules; ex: amino acids

Carboxyl group— COOH

Acts as an acid, releasing H+ to become R—COO-; ex: fatty acids, amino acids

Hydroxyl group— OH

May link molecules through dehydration synthesis (condensation); hydrogen bonding between hydroxyl groups and water molecules affects solubility; ex: carbohydrates, fatty acids, amino acids

Phosphate group— PO4

May link other molecules to form larger structures; may store energy in high-energy bonds; ex: phospholipids, nucleic acids, high-energy compounds

Carbohydrates

Contain carbon, hydrogen, and oxygen in a 1:2:1 ratio; monosaccharide, disaccharide, polysaccharide

Monosaccharide

Simple sugars with 3 to 7 carbon atoms; ex: glucose, fructose, galactose

Disaccharide

Two simple sugars condensed by dehydration synthesis; ex: sucrose, maltose

Polysaccharide

Many monosaccharide condensed by dehydration synthesis; ex: glycogen, starch, cellulose

Breakdown of sucrose into simple sugars by hydrolysis

Reverses the steps of dehydration synthesis; a complex molecule is broken down by the addition of a water molecule

Lipids

Mainly hydrophobic molecules such as fats, oils, and waxes; made mostly of carbon and hydrogen atoms; fatty acids, eicosanoids, glycerides, steroids, phospholipids and glycolipids

Fatty acids

Long chains of carbon and hydrogen with a carboxyl group (COOH) at one end; relatively nonpolar, except the carboxyl group; saturated and unsaturated

saturated fatty acid

With hydrogen, no covalent bonds

unsaturated fatty acid

One or more double bonds; monounsaturated, polyunsaturated