Biology Chapter6 The Chemistry of Life

Elements Element: A subs. That can’t be broken down into simpler chemical substances. 90 – 92 Naturally occurring elements. Only 25 are essential to living things Four (4) elements make up more than 96% of the human body. These four are Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

Symbol: One or Two letter abbreviation. Only the first letter is capitalized. Ex. Hydrogen (H), Chlorine (Cl), Sodium (Na) Trace elements: elements need in only very small amounts. Plants get trace elements from roots. Animals get trace elements from the foods they eat.

Atoms Atom: the smallest particle of an element that has the characteristics of that element. Atomic Structure: A.Nucleus: Center of the atom Protons: Positively charged particles Neutrons: No charge (neutral)

B.Shells ( energy levels) Electron Clouds: region around the atom that electrons move about. –Electrons: Negatively charged particles 1 st energy level: Hold up to 2 electron 2 nd energy level: Hold up to 8 electrons 3 rd energy level: Hold up to 18 electrons

An atom of fluorine has nine electrons. Its first energy level will hold 2 electrons. Its second energy level will hold 7 electrons.

Atoms: A free atom has NO charge. The number or protons = the number of electrons. Therefore they have no net charge. Ex. Oxygen atomic # 8 (O) Oxygen has (+8) protons and (-8) electrons. +8 and a -8 = No charge

Isotopes: Atoms of the same element that differ in the number of neutrons. Isotopes have a different atomic mass. Ex. Carbon -12, Carbon- 13; Carbon – 14 Carbon has an atomic # of 6. All have 6 protons; 6 electrons but differ in # of neutrons. Atomic Mass: Number of neutrons + protons

Compounds & Bonding Atoms combine with other atoms to become stable. This happens when its outermost energy level becomes full. Compound: Atoms of two or more elements that chemically combine. Water: HOH (hydrogen and oxygen) Chemical formula: tells the number and types of elements in the Compound. Ex H 2 O

2 Major types of Bonds Covalent (sharing of electrons) Ionic ( Transfer of electrons) Outermost level or electrons interact. The first carbon cpds. That scientists studied were called “organic” cpds. Because they came from living organisms.

Covalent Bonding Sharing of the outer most electrons. When two atoms share electrons, the force that binds them is called a COVALENT BOND Water is a covalent bond Molecule: group of atoms held together by covalent bonds and having no overall charge.

IONIC Bond Ionic: When atoms gain or lose electrons. Ion: When an atom gains or loses an electron it will carry a charge and be called an ion. Ex. When a chloride atom becomes a chloride ion when it gains an electron. The attractive force between two ions of opposite charge is known as an IONIC BOND. Ex. Sodium and Chlorine = Sodium Chloride is an ionic bond.

Chemical Reactions Metabolism: all the chemical reactions within an organism. Chemical equations are written so that the same number of atoms of each element appear on both sides of the arrow. In other words, The equations must always be written so that they are balanced. (Insert transparency of equations) Chemical reaction results in a new substance being formed. Ex. Burning paper

Mixtures and Solutions Mixture: a combination of subs. In which the individual components keep their own properties. Ex. A salad Solution: a mixture in which one subs. Is distributed evenly in another. Ex. Kool-aid Solutions are important bec. vital subs. are dissolved in water.

Acids & Bases Chemical reactions in organisms depend on pH of the environment. pH is a measure of the hydrogen ions that are released when a subs. Is dissolved in water. pH scale: Measures these ions. 7 is neutral, 7 base Acid: Any subs. That forms hydrogen ions in water. (closer to 0 the stronger the acid)

Base: Any substance that form hydroxide ions in water. (closer to 14 stronger the base.) BOOK - pH scale

Water & Diffusion Water: Perhaps the most important cpd. In living organisms. Metabolic process occur in water Transportation of dissolved subs. Makes up between 70 – 95 % of most organisms. Water is polar. Water dissolved many ionic and molecular cpds. Because of its polarity

Polar molecule: Molecule with unequal distribution of charges. When atoms in a covalent bond do not share electron equally. Because of this polarity water has unique characteristic. “capillary action” Capillary action allows water to move up the root system of plants. Water resists temperature changes. Water expands when it freezes

Diffusion Kinetic energy: Energy of motion All objects in motion have kinetic energy. Brownian Movement: is evidence of “random motion of molecules.” Characteristic of gas, liquids and some solids. Diffusion: Movement of water molecules from an area of higher concentration of water molecules to an area of lesser concentration of water molecules.

Diffusion: will continue until there is no concentration gradient. Slow process. Three key factors: 1. Concentration (primary controlling factor) 2. Temperature 3. Pressure More concentrated more rapidly diffusion occurs Increase in temp. = increase in diffusion Increase in pressure = increase in diffusion. Dynamic equilibrium: Continuous movement but no overall concentration changes.

Life Substances Carbon: it has four electrons available for bonding. They can bond with each other and form branched chains, straight chains, or rings. They can single, double or triple bond. This allows for a hugh number of carbon structures. Isomers: Cpds. With the same simple formula but different structural formulas. Glucose and fructose both have the same simple formula but differ in arrangement of atoms. Therefore they are isomers.

Polymers Polymers: large molecule formed when many smaller ones bond together. –Made of monomers –Macromolecules: Large molecules (thousands of carbons) –Usually form by covalent bonding Ex. CHO, nucleic acids, proteins Condensation is how polymers form or join. Glucose and fructose combine to form sucrose, they do so by condensation. (forming a polymer) Hydrolysis is how they are broken apart. Cellulose: glucose polymer that forms the cell walls of plants

Proteins are macromolecules. essential to all life. Protein: Large complex polymer with Carbon,Hydrogen,Oxygen,Nitrogen and usually sulfur Unlike CHO and fats proteins have NITROGEN. Proteins: biological catalysts. Enzyme: protein that changes the rate of a chemical reaction. Amino Acids: Building blocks of proteins Peptide Bond: Bond formed between amino acids

Carbohydrates An organic compound composed of Carbon, Hydrogen, and Oxygen. in a ratio of 2:1 (hydrogen to oxygen) for each carbon atom Monosaccharide: simple sugar (one sugar) Disaccharide: 2 monosaccharides (double/2sugars) Polysaccharide: More than 2 (many sugar) Glycogen: animal starch (polymer) Cellulose: plant starch - cell wall (polymer)

Lipids Organic cpds. With a higher proportion of hydrogen to oxygen atoms. Commonly called fats. Insoluble in water ( Do NOT dissolve) Energy storage, insulation, protective coverings Most lipids are attached to the 3- carbon molecule “glycerol” the most common type of lipid Unsaturated: double bonds Saturated: Single bonds

Nucleic Acids Organic compound Complex macromolecule that stores all genetic information. Made from smaller polymers called nucleotides. Carbon, hydrogen, oxygen, nitrogen, and phosphorus groups. Nucleotide: Smaller subunits that make up nucleic acids. Nitrogen Base, simple sugar, phosphate group. DNA: deoxyribonucleic acid (Master copy of the genetic code) codes for the production of proteins) RNA: ribonucleic acid (used for making the protein) DNA and RNA work together to produce proteins.

Formulas How do you represent 12 molecules of water? How do you Represent 1 molecule of sugar? How do you represent 1 molecule of oxygen with two atoms?

Answers 12 H 2 O = 12 molecules of water C 6 H 12 O 6 = 1 molecule of sugar O 2 = 1 molecule of oxygen with 2 atoms of oxygen

Bonding Diagrams Draw Magnesium Chloride. Draw Hydrogen Fluoride –Which atom forms an ion by the loss of electron? – How many electrons are in the third energy level of a Mg atom? –Which cpd. Is covalent boding? –Which cpd. Is ionic bonding? –SEE Diagrams on the Board

Magnesium Chloride Mg Cl

Critical Thinking Indicator Color at lower pH values pH range of colorColor at higher pH values Methyl RedRed4.4 – 6.0Yellow LitmusRed5.5 – 8.0Blue Bromothymol Blue Yellow6.0 – 7.6Blue Phenol RedYellow6.8 – 8.4Red PhenolphthaleinColorless8.3 – 10.0Red

Test Tube1 day2 days Egg + waterNo change Egg + HCLNo change Egg + pepsinLiquid slightly cloudy, egg white solid Liquid cloudy, egg white still solid Egg + pepsin + HCLLiquid cloudy, pieces of egg smaller Liquid very cloudy, almost no egg remains