Chemical Basis of Life

Matter – Anything that occupies space and has mass Mass – The amount of matter in an object (kg) Weight – Gravitational force acting on an object of a given mass

Element – Simplest type of matter with unique chemical properties Atoms – Smallest particle of an element that has chemical characteristics of that element – Composed of subatomic particles

Subatomic particles – Neutrons: no electrical charge – Protons: positive charge – Electrons: negative charge Nucleus – Formed by protons and neutrons – Most of the volume of an atom

Atomic mass and Mass number Atomic number – Equals the number of protons – Equals the number electrons (in a neutral atom) – The element number in the periodic table Atomic mass (mass number) – Protons plus the neutrons – The lower number in the periodic table

Isotopes and Atomic mass Isotopes – 2+ forms of the same element but with a different neutron number – Denoted by using the symbol of element preceded by mass number as ( 1 H, 2 H)

Electrons and chemical bonding Ion – When an atom loses or gains electrons and becomes charged Cation: positively charged ion (losses electrons) Anion: negatively charged ion (gains electrons) Ionic bonding – Cations and anions are attracted to each other – A transfer of electrons

Covalent bonding Atoms share pairs of electrons – Single covalent: One pair is shared – Double covalent: Two atoms share 4 electrons Nonpolar covalent: equal sharing Polar covalent: unequal sharing

Molecules and compounds Molecules – 2+ atoms held by a covalent bond – Example: water Compounds – A substance composed of 2+ elements in a fixed ratio – Example: hydrogen molecules Molecular mass – Determined by adding up atomic masses of its atoms or ions Example: NaCl ( )

Intermolecular forces Result from weak electrostatic attractions between oppositely charged parts or molecules Weaker than forces producing chemical bonding

Examples of forces Hydrogen bonds – Water: positively charged hydrogen atoms bond with negatively charged oxygen atoms of other water molecules – Important in determining shape of complex molecules

Intermolecular forces Solubility: ability of one substance to dissolve the other – Solute is the material dissolved – Solvent is the media that does the dissolving

Intermolecular forces Electrolytes – Cations and anions that dissociate in water Nonelectrolytes – Molecules that do not dissociate form solutions that do not conduct electricity

Chemical Reactions Chemical reactions: Atoms, ions, molecules, or compounds that interact to form or break chemical bonds – Metabolism: all anabolic and catabolic reactions in the body Catabolism: Decomposition reactions Anabolism: growth, maintenance, and repair

Oxidation-reduction reaction Oxidation: – Loss of an electron by an atom Reduction – Gain of an electron by an atom Oxidation-reduction reactions – The complete or partial loss of an electron by one atom is accompanied by the gain of that electron by another atom – “LEO the lion says GER”

Speed of chemical reaction Activation energy – Minimum energy reactants must have to start a chemical reaction – Catalysts: substances that increase the rate of chemical reactions without being permanently changed or depleted – Enzymes: increase the rate of chemical reactions by lowering the activation energy

Water Inorganic Stabilizes body temperature Protection Necessary for many chemical reactions Mixing medium – Mixture: substance physically but not chemically combined

Acids and bases Acid: A proton donor or any substance that releases hydrogen ions Base: a proton acceptor or any other substance that binds to or accepts hydrogen Buffers: a solution of a conjugate acid-base pair in which acid or base component occur in similar concentrations

The pH scale Refers to the hydrogen ion concentration in a solution – Neutral: pH of 7 or equal hydrogen and hydroxide ions – Acidic: 0-7, greater concentration of hydrogen ions – Basic: 7-14, greater concentration of hydroxide ions (less Hydrogen ions)

Organic molecules

Carbohydrates – Carbon, hydrogen, oxygen Lipids – Carbon, hydrogen, oxygen Proteins – Carbon, hydrogen, oxygen, nitrogen Nucleic acids – Carbon, hydrogen, oxygen, phosphorus – DNA and RNA

Carbohydrates Monosaccharide – Simple sugars: glucose, fructose, galactose Disaccharides – Two simple sugars bound by a dehydration synthesis Polysaccharides – Long chains of many monosaccharide – Glycogen, starch, cellulose

Lipids Relatively insoluble in water Fats: ingested and broken down by hydrolysis Triglycerides: composed of glycerol and 3 fatty acids Phospholipids: found in plasma membranes Steroids: cholesterol, bile salts, estrogen, testosterone

Proteins Amino acids: building blocks of proteins Peptide bonds: covalent bonds forms between amino acids during protein synthesis Example: enzymes

Nucleic acids DNA: Deoxyribonucleic acid – Genetic material of cells copied from one generation to another – Composed of 2 strands of nucleotides Sugar, phosphate, and a base Adenine, thymine, guanine, cytosine RNA: ribonucleic acids – Single strand – Uracil replaces thymine

ATP Adenosine Triphosphate Energy currency of the body Made in the mitochondria during cellular respiration.