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Basic Chemistry Review

Basic Chemistry Review. Matter. 1. Matter refers to anything that takes up space and has mass 2. All matter (living and nonliving) is composed of basic elements a. Elements cannot be broken down to substances with different chemical or physical properties

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Basic Chemistry Review

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  1. Basic Chemistry Review

  2. Matter • 1. Matter refers to anything that takes up space and has mass • 2. All matter (living and nonliving) is composed of basic elements • a. Elements cannot be broken down to substances with different chemical or physical properties • b. There are 92 naturally occurring elements • c. Six elements (C, H, N, O, P, S) make up 98% of most organisms

  3. Elements Contain Atoms • 1. Chemical and physical properties of atoms depend on the subatomic particles: • a. Different atoms contain specific numbers of protons, neutrons, and electrons • b. Protons (+ charge) and neutrons (neutral charge) are in nucleus of atoms; electrons (- charge) move around nucleus • 2. Isotopes = atoms with the same number of protons but differ in number of neutrons; e.g., a carbon atom has six protons but may have more or less than usual six neutrons • a. Isotopes used to determine age of fossils and in medical diagnostic and treatment procedures

  4. Chemical Properties of Atoms • 1. Since protons are positively charged & electrons are negatively charged they are attracted to each other • 2. Arrangement of atom's electrons is determined by total number of electrons and electron shell they occupy • a. Energy = capacity to do work • b. Electrons with least amount of potential energy are located in shell closest to nucleus; electrons having more potential energy are located in shells farther from nucleus

  5. c. How atoms react with one another is dependent upon number of electrons in outer shell • 1) Atoms with filled outer shells do not react with other atoms • 2) In atom with one shell, outer shell is filled when it contains two electrons • 3) For atoms with more than one shell, the outer shell is stable when it contains eight electrons • 4) Atoms with unfilled outer shells react with other atoms so each has stable outer shell • 5) Atoms can give up, accept, or share electrons in order to have a stable outer shell

  6. Atoms form Molecules and Compounds • A. Molecules = two or more atoms of same or different elements bonded together (e.g., O2) • B. Compound = molecule of two or more different elements bonded together (e.g., H2O)

  7. Types of Bonds • 1. Covalent bond - involves sharing of electron(s). Electrons possess energy; bonds that exist between atoms in molecules contain energy. • Sharing of a pair of electrons creates a single bond represented by single dash, e.g. water H2O is made of two single bonds H-O-H. Sharing two pairs of electrons is represented by two dashes, C=C • Know the number of covalent bonds each of the six most important elements can form. • Element# of covalent bonds:Hydrogen-1, Oxygen-2, Nitrogen-3, Carbon-4, Phosphorous-5, Sulfur-2

  8. Types of bonds • 2. Ionic bond - electrons are transferred from one atom to another, e.g. salt NaCl • 3. Hydrogen bond - weak attractive force between slightly positive hydrogen atom of one molecule and slightly negative atom in another or the same molecule • a. E.X.: in a water molecule the electrons spend more time orbiting the oxygen than the hydrogens, therefore the oxygen becomes slightly negative and the two hydrogens become slightly positive • b. Such polar molecules attract each other like magnets

  9. Oxidation - reduction: • 1. Oxidation =  the loss of electrons (or loss of hydrogen atoms), a molecule that loses an electron is oxidized • 2. Reduction = the gain of electrons (or gain of hydrogen atoms), a molecule that gains an electron is reduced

  10. Water • A. Life evolved in water • All living things are 70-90% water • Because water is a polar molecule, water molecules are hydrogen bonded to each other • a. hydrophilic molecules - polar molecules attracted to water molecules • b. hydrophobic molecules - non-polar molecules repelled by water

  11. Properties of Water • 1. Water resists temperature changes because hydrogen bonds between water molecules require a large amount of heat to break • a. Calorie = amount of heat energy required to raise temperature of one gram of water 1° C. This is about twice that of other liquids • b. Water has a high heat of vaporization - takes 540 calories to change water to a gas • c. When animals sweat, evaporation of the sweat takes away body heat, thus cooling the animal • d. Because water resists temperature changes the earth's surface temperature is moderate and organisms are protected from rapid temperature changes, this helps them maintain normal temperatures

  12. 2. Water is universal solvent, facilitates chemical reactions both outside of and within living systems • a. Water is a universal solvent because it dissolves a great number of solutes • b. Important because living organisms get and transport most of needed chemicals in water or water based solutions

  13. 3. Water molecules are cohesive and adhesive • Cohesion - like molecules cling to each other • Adhesion - ability to adhere to polar surfaces; water molecules have positive, negative poles. • Capillarity - the tendency for a liquid to move upward against pull of gravity through a narrow space, e.g. water rises up tree from roots to leaves through small tubes • 1) Adhesion of water to walls of vessels prevents water column from breaking apart • 2) Cohesion allows evaporation from leaves to pull water column from roots

  14. 4. Frozen water is less dense than liquid water  • a. Below 4° C, hydrogen bonding becomes more rigid but open, causing expansion • b. Because ice is less dense, it floats; therefore, bodies of water freeze from the top down • c. This means that ice floats and the bottoms of lakes and oceans are still available for life and also insulated during cold weather

  15. Acids and Bases • 1. Water dissociates - has a tendency to spontaneously break into hydrogen and hydroxide ions: • H20 ---> H+ (hydrogen) + OH- (hydroxide) • 2. Acid molecules dissociate in water, releasing hydrogen ions (H+) ions:  • Hydrochloric acid (HCl) is a strong acid: HCl ---> H+ + Cl – • 3. Bases are molecules that take up hydrogen ions or release hydroxide ions: • Sodium hydroxide (NaOH) is a strong base: NaOH ---> Na+ + OH-

  16. 4. pH scale, which ranges from 0 to 14, is used to indicate the strength of acids and bases • a. pH = a measure of hydrogen (H+) ion concentration in a solution • b. Low pH value indicates a high concentration of H+ ions (acids) • c. High pH value indicates a low concentration of H+ ions (bases) • d. pH value of 7 is neutral, i.e. the solution has an equal concentration of H+ and OH- ions • e. pH scale is logarithmic, i.e. a ten fold difference for each number • E.X.: pH 4 is 10 times more acidic than 5, and 100 times more acidic than 6

  17. 5. Buffers keep pH steady and within normal limits in living organisms, e.g. blood pH is 7.4 • a. Buffers stabilize pH of a solution by taking up excess hydrogen or hydroxide ions • b. Carbonic acid helps keep blood pH within normal limits

  18. Salts • Any compound that results from the chemical interaction of an acid and a base • Dissociate in solution to become ions • See common salts on page 47

  19. Organic Substances • Carbohydrates • Provide energy that cells require • Contribute to cell structure • Built by simple sugar molecules (monosaccharides)

  20. Lipids (Fat, Phospholipids, Steroids) • Supply energy, build cell parts • Basic building block of fat molecules is combination of glycerol and fatty acids

  21. Protein • Serve as structural materials, energy sources, hormones, cell surface receptors, and enzymes • Enzymes speed chemical reactions without being consumed • Amino acids are building blocks of proteins • Proteins vary in the number and types of amino acids contained and in their sequence • Amino acid chain of protein folds into a complex shape that is maintained by hydrogen bonds • Excessive heat, radiation, electricity, altered pH, or chemicals can alter proteins

  22. Nucleic Acids • Nitrogen base, pentose sugar, phosphate) • Genetic material and control cellular activities • Nucleic acid molecules composed of mucleotides: • Adenine A • Guanine G • Cytosine C • Uracil U • Thymine T • A & G are purines (large 2 ring bases) • C, U, & T are pyrimidines (small single ring bases)

  23. Important Nucleic Acids • DNA (deoxyribonucleic acid) • Double stranded polymer (double helix)-twisted ladder • Nucleotides building are A, G, C, and T • Pentose sugar is deoxyribose • Stores information that cell parts use to construct specific protein molecules “Blueprint” • Nucleotides held by hydrogen bonds • A always bonds to T • G always bonds to C

  24. RNA (ribonucleic acid) • Help synthesize protein • Pentose sugar is ribose • Single strands of nucleotides • A, G, C, & U (U replaces T) • A always bonds to U • G always bonds to C

  25. Three types of RNA • Transfer RNA (tRNA) • Small & clover leaf shaped • Translate messages from mRNA • Messenger RNA (mRNA) • Long nucleotides that resemble half-DNA molecules • Carry messages from DNA for building a polypeptide (amino acid chain)

  26. Ribosomal RNA (rRNA) • Forms ribosomes (site of protein synthesis) • Nucleolar organizer

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