A&P I CH.2 Chemical Basis of Life

Matter

anything that has mass (weight) and takes up space

Elements

composed of chemically identical atoms

Bulk elements

required by the body in large amounts

Trace elements

required by the body in small amounts

Ultratrace elements

required by the body in very small amounts, often less than 0.01% of body mass.

Atoms

smallest particle of an element

Ion

particle that’s electrically charged because it has gained or lost one or more electrons (cations + anions)

Molecule

particle formed by the chemical union of two or more atoms

Proton (+)

carries a positive charge

Neutron

carries no electrical charge

Electron (-)

carries a negative charge

Nucleus

• central part of an atom

• composed of protons and neutrons

• electrons move around the nucleus

Atomic Number

• # of protons in nucleus of atom

• equals the # of electrons in the atom

Atomic Weight

• approximated by the # of protons + the # of neutrons

• electrons don’t contribute to the weight

Isotopes

• atoms with same atomic # but different atomic weights

• different # of neutrons

• radioactive isotopes are unstable, releasing energy or pieces of themselves (atomic radiation)

Compound

particle formed when 2 or more atoms of different elements combine

Bonding of Atoms: Ions

• form when atoms combine w/ other atoms

• electrons occupy electron shells

• for atoms w/ atomic #/s of 18 or less:

• the 1st shell can hold up to 2 electrons

• -2nd shell holds 8 electrons

• -3rd shell holds 8 electrons

Ionic Bonds

• an attraction between a cation and anion

• formed when electrons are transferred from one atom to another

Cation (Transfers)

• positively charged ion

• formed when an atom loses electrons

Anion (Recieves)

• a negatively charged ion

• formed when an atom gains electrons

Covalent Bonds

formed when atoms share electrons

• Hydrogen atoms form single bonds H - H

• Oxygen atoms form 2 bonds O = O

• Nitrogen atoms form 3 bonds

• Carbon atoms form 4 bonds O = C = O

Structural Formulas

show how atoms bond and are arranged in various molecules

Polar Molecules

• molecule with a slightly negative end and a slightly positive end

• results when electrons are not shared equally in covallent bonds

• water is an important polar molecule

Hydrogen Bonds (formed w/ H + FON)

• 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

Chemical Reactions

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

Reactants

are the starting materials of the reaction - the atoms, ions, or molecules

Products

are substances formed at the end of the chemical reaction

Synthesis Reaction (marriage)

more complex chemical structure is formed

Decomposition Reaction (divorce)

chemical bonds are broken to form a simpler chemical structure

Exchange Reaction (replacement)

chemical bonds are broken and new bondsa are formed

Reversible Reaction

the products can change back to the reactants

Electrolytes

substances that release ions in water

NaCl —> Na(+) + Cl(-)

Acids

substances that dissociate to release hydrogen ions in water

HCl + H(+) + Cl(-)

Bases

substances that release ions that can with hydrogen ions (OH-)

NaOH —> Na(+) + OH(-)

Salts

electrolytes formed by the reaction between an acid and a base

HCl + NaOH —> H2O + NaCl

pH scale

indicated the concentration of hydrogen ions in solution

Neutral

pH 7; indicates equal concentration 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(-)

Blood pH

• Normal blood pH is 7.35 - 7.45

• Alkalosis occurs when blood pH rises to 7.5 - 7.8

• Acidosis occurs when pH drops to 7.0 - 7.3

• Homeostatic mechanisms help regulate pH

• Buffers are chemical which act to resits pH changes

Organic Molecules

• contains C and H

• usually longer than inorganic molecules

• dissolve in water and organic liquids

• Carbohydrates, proteins, lipids, and nucleic acids

Inorganic Molecules

• generally do not contain C and H

• usually smaller than organic molecules

• usually dissociate in water, forming ions

• Water, oxygen, carbon dioxide, and inorganic salts

Inorganic Substance

Water

• most abundant compound in living material

• 2/3 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

• absorbs and transports heat

Inorganic Substance

Oxygen (O2)

• used by organelles to release energy from nutrients in order to drive cell’s metabolic activities

• necessary for survival

Inorganic Substance

Carbon Dioxide (CO2)

• waste product released during metabolic reactions

• must be removed from the body

Inorganic Substance

Salts

• abundant in body fluids

• sources of necessary ions [Na(+), Cl(-), K(+), Ca(+2), etc.)

• play important roles in metabolism

Organic Substance

Carbohydrates

• 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 (C6, H12, O6)

• Monosaccharides- glucose, fructose

• Polysaccharides- glycogen, cellulose

Organic Substance

Lipids

• soluble in organic solvents; insoluble in water

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1. fats (triglycerides)

• used primarily for energy; most common lipid in body

• contain C, H, and O but less O than carbohydrates (C57, H110, O6)

• building blocks are 1 glycerol and 3 fatty acids per molecule

• — saturated fatty acids have 1 single carbon to carbon ends

• — saturated fats contain 3 saturated fatty acids

• — unsaturated fatty acids have one more or more carbon to carbon double bond

• — unsaturated fats contain at least one unsaturared fatty acid (mostly liquid and come from plants)

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• Phospholipds

• — 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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• Steroids

• — 4 connected rings of carbon

• widely distributed in the body, various functions

• component of cell membrane

• used to synthesize hormones

• cholestrol

Organic Substance

Proteins

• structural material

• energy source

• hormones

• receptors

• enzymes

• antibodies

• protein building blocks are amino acids

• amino acid held together with peptide bonds

Organic Substance

Nucleic Acids

• encode amino acid sequences of proteins

• building blocks are nucleotides

• DNA (deoxyribonucleic acid)- double polynucleotide

• RNA (ribonucleic acid)- single polynucleotide