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Ap chemistry fast review

ap chemistry fast review

CHEMISTRY - A QUICK REVIEW AND A STUDY GUIDE

A.) ELEMENT- (1) A SUBSTANCE THAT CAN'T BE DECOMPOSED INTO OTHER SUBSTANCES. (2) A SUBSTANCE WHERE ALL OF THE ATOMS HAVE THE SAME NUMBER OF PROTONS (ATOMIC NUMBER) ALTHOUGH THE NUMBER OF NEUTRONS MAY DIFFER (THE ATOMIC WEIGHTS MAY DIFFER). THE DIFFERENT ATOMIC WEIGHT VARIANTS OF AN ELEMENT ARE CALLED THE ISOTOPES OF THAT ELEMENT. (For example C12, C13, and C14 are all isotopes of carbon, all have 6 protons but each has a different number of neutrons).

PROTONS AND NEUTRONS ARE FOUND IN THE NUCLEUS OF THE ATOM WHILE THE ELECTRONS ARE LOCATED IN VARIOUS ORBITALS OR SHELLS WHICH SURROUND THE NUCLEUS. THESE ORBITALS HAVE SPECIFIC NUMBERS OF ELECTRONS WHICH THEY CAN ACCOMODATE. (HOW DO THE SHELLS DIFFER IN THEIR ELECTRON CAPACITY?)

IF AN ATOM IS NEUTRAL THEN IT HAS AN EQUAL NUMBER OF PROTONS AND ELECTRONS. NEUTRAL ATOMS ARE ESPECIALLY STABLE IF THEIR ORBITALS ARE FILLED TO CAPACITY. THIS IS THE THE CASE WITH THE NOBLE GASES.

HOWEVER THE ATOMS OF MOST ELEMENTS HAVE INCOMPLETELY FILLED FILLED ORBITALS AND THESE ATOMS FORM BONDS TO ACHIEVE STABILITY. (See pg. 25, table 2.2).

IONS AND IONIC BONDS

ELECTRONS ARE LOST OR GAINED IN THE UNFILLED SHELL. THE ATOM BECOMES CHARGED -- EITHER POSITIVE (CATION) OR NEGATIVE (ANION). (See pg. 27, fig. 2.2). CHARGED ATOMS (OR MOLECULES) OF OPPOSITE CHARGE ARE ATTRACTED TO EACH OTHER AND CAN FORM REVERSABLE, IONIC BONDS WITH EACH OTHER. IONIC COMPOUNDS DISSOLVED IN WATER CONDUCT ELECTRICITY VERY WELL. DISSOLVED IONS ARE THEREFORE CALLED ELECTROLYTES.

COVALENT BONDS

IN COVALENT BONDS, PAIRS OF ELECTRONS ARE SHARED BETWEEN ATOMS IN ORDER TO FILL THEIR OUTER SHELLS. (See pg. 28, figure 2.3).

HYDROGEN BONDS

COVALENTLY BONDED ATOMS MAY BE ELECTRICALLY NEUTRAL HOWEVER THE ELECTRONS MAY NOT BE EVENLY DISTRIBUTED ACROSS THE MOLECULE. SUCH MOLECULES WILL HAVE OPPOSITELY CHARGED AREAS WHICH CAN BE ATTRACTED TO OTHER CHARGED MOLECULES. A GOOD EXAMPLE OF THIS OCCURS BETWEEN WATER MOLECULES WHERE SUCH ELECTROSTATIC BONDS ARE CALLED HYDROGEN BONDS. (See page 29, figure 2.4).

HYDROPHOBIC BONDS

THIS NON-COVALENT BOND DESCRIBES THE INTERACTION OF NON-POLAR, HYDROPHOBIC MOLECULES WHEN THEY ARE PUT INTO WATER. HYDROPHOBIC BONDS ARE VERY IMPORTANT IN THE FORMATION OF MEMBRANES AND IN ENZYME-SUBSTRATE BINDING.

THE MOLECULES OF LIFE

WATER

HYDROGEN BONDS BETWEEN WATER MOLECULES CONTRIBUTES TO WATER'S HIGH BOILING POINT. WATER MOLECULES ACTUALLY REPEL EACH OTHER AT FREEZING; THIS MEANS THAT FROZEN WATER IS LESS DENSE THAN LIQUID WATER. ALSO, THE HYDROGEN BONDS CAN ABSORB AND HOLD ON TO ENERGY; THIS MAKES WATER A GOOD TEMPERATURE BUFFER (ie.: water changes temperature slowly).

THE POLAR NATURE OF WATER MOLECULES CONTRIBUTES TO WATER'S EXCELLENT SOLVENT PROPERTIES. (See page 34, figure 2.6).

WATER CAN IONIZE TO FORM HYDROGEN (+) IONS AND HYDROXYL (-) IONS. THE CONCENTRATION OF THESE IONS DETERMINES THE pH OF WATER OR OTHER SOLUTIONS. (See pgs. 35-36; figs. 2.7 and 2.8).

ORGANIC COMPOUNDS

ORGANIC MOLECULES CAN BE ACIDIC OR BASIC. THEY MAY HAVE OTHER CHARGED GROUPS ATTACHED. THEY CAN BE POLAR OR NON-POLAR. THEY CAN BE HYDROPHILLIC OR HYDROPHOBIC. (Page 37 gives a good overview of the chemistry of carbon. Moreover, table 2.3 summarizes the most important functional groups found on organic molecules.)

CARBOHYDRATES - SUGARS AND THEIR POLYMERS.

MONOSACCHARIDES - THE SIMPLE SUGARS. WE WILL BE MOST CONCERNED WITH THE PENTOSE AND THE HEXOSE SUGARS.

DISACCHARIDES - 2 COVALENTLY BONDED MONOSACCHARIDES. (See page 38).

POLYSACCHARIDES - POLYMERS OF MONOSACCHARIDES AND DISACCHARIDES. SOME, LIKE CHITIN AND CELLULOSE ARE STRUCTURAL POLYSACCARIDES. OTHERS, LIKE STARCH AND GLYCOGEN ARE FOOD STORAGE MOLECULES. INCIDENTALLY ALL FOUR OF THE POLYSACCHARIDE EXAMPLES ARE POLYMERS OF GLUCOSE. (See Lewis pg 46 for a good discussion of how these four polysaccharides are constructed.)

LIPIDS - THESE ARE NON-POLAR MOLECULES WHICH ARE INSOLUBLE IN WATER. (See pages 39-41).

LIPIDS COMPOSED OF GLYCEROL AND FATTY ACIDS: DEPENDING ON HOW MANY FATTY ACIDS ARE ATTACHED TO THE GLYCEROL, THESE MAY BE MONOGLYCERIDES, DIGLYCERIDES OR TRIGLYCERIDES. DEPENDING ON HOW MANY HYDROGENS ARE ATTACHED TO THE FATTY ACIDS (OR HOW MANY DOUBLE BONDS ARE PRESENT), THESE MAY BE SATURATED OR UNSATURATED. IF LIQUID, THESE LIPIDS ARE CALLED OILS; IF SOLID, THESE LIPIDS ARE CALLED FATS OR WAXES. PHOSPHOLIPIDS ARE A SPECIAL CLASS OF DIGLYCERIDE WHICH HAS A PHOSPHATE GROUP ATTACHED TO IT. PHOPHOLIPIDS ARE AN IMPORTANT COMPONENT OF MEMBRANES.

STEROIDS REPRESENT ANOTHER CLASS OF LIPIDS WHICH ARE STRUCTURALLY VERY DIFFERENT FROM THE GLYCERIDES DESCRIBED ABOVE. (See page 41).

PROTEINS - THESE LARGE MOLECULES ARE POLYMERS OF AMINO ACIDS. PROTEINS CONTAIN A SIGNIFICANT AMOUNT OF NITROGEN IN ADDITION TO THE CARBON, HYDROGEN AND OXYGEN THEY CONTAIN. PROTEINS SERVE MANY ESSENTIAL PURPOSES IN THE CELL. THEY CAN BE STRUCTURAL PROTEINS SUCH AS COLLAGEN AND KERATIN. MOST OTHER PROTEINS SUCH AS THE ENZYMES, THE ANTIBODIES, THE CELL SURFACE RECEPTORS AND THE VARIOUS CARRIER MOLECULES ARE ACTIVELY INVOLVED IN MANY OF THE BIOCHEMICAL REACTIONS OF THE CELL OR THE MULTICELLULAR ORGANISM. EACH OF THESE PROTEINS HAS THE ABILITY TO SPECIFICALLY RECOGNIZE AND BIND TO ITS UNIQUE SUBSTRATE.

PROTEINS OR POLYPEPTIDES ARE POLYMERS OF AMINO ACIDS. (See page 42, fig. 2.15 for a description of an amino acid. See page 43, table 2.4 for a listing of the twenty common amino acids -- note the R-groups). EACH DIFFERENT AMINO ACID HAS A UNIQUE R-GROUP WHICH GIVES EACH AMINO ACID AN UNIQUE CHEMISTRY. THE AMINO ACIDS ARE COVALENTLY LINKED TO EACH OTHER VIA PEPTIDE BONDS. (See page 44, fig. 2.17 for a description of peptide bond formation). ONCE POLYMERIZED, THE R-GROUPS OF THE VARIOUS AMINO ACIDS INTERACT WITH EACH OTHER AND WITH THE SOLUTION ENVIRONMENT THE PROTEIN FINDS ITSELF IN. THIS THEN CAUSES THE POLYPEPTIDE TO ASSUME A SHAPE OR CONFORMATION. THEREFORE THE AMINO ACID SEQUENCE DETERMINES THE CONFORMATION OF THE PROTEIN AND THIS IN TURN DETERMINES THE FUNCTION OF THE PROTEIN. (See page 45, fig. 2.18 for a description of the conformation levels of proteins).

IT IS IMPORTANT TO REMEMBER THAT PROTEIN SHAPE IS SENSITIVE TO pH, TEMPERATURE AND DISSOLVED SALTS. BY CHANGING THESE VARIABLES THE ACTIVITY OR FUNCTION OF THE PROTEIN WILL BE ALTERED. IF THE PROTEIN'S SHAPE IS ALTERED SO SEVERELY THAT THE PROTEIN NO LONGER FUNCTIONS, THE PROTEIN IS SAID TO BE DENATURED.

NUCLEIC ACIDS - BOTH DEOXYRIBONUCLEIC ACID (DNA) AND RIBONUCLEIC ACID (RNA) ARE POLYMERS OF NUCLEOTIDES. (See page 47, figs. 2.20 and 2.21 for a description of nucleotides).

NUCLEOTIDES HAVE THREE ESSENTIAL PARTS: (1) A SUGAR -- EITHER RIBOSE OR DEOXYRIBOSE; (2) A BASE -- EITHER A PURINE SUCH AS GUANINE (G) OR ADENINE (A) OR A PYRIMIDINE SUCH AS THYMINE (T), CYTOSINE (C) OR URACIL (U); AND (3) A PHOSPHATE GROUP.

NUCLEOTIDES CAN BE COVALENTLY LINKED INTO A SINGLE STRAND OF NUCLEIC ACID BY FORMING COVALENT BONDS BETWEEN THE PHOSPHATE GROUPS AND THE 3' OH GROUP OF THE SUGARS OF A SERIES OF NUCLEOTIDES. A SINGLE STRANDED PIECE OF NUCLEIC ACID CAN BASE-PAIR OR HYBRIDIZE WITH A COMPLEMENTARY PIECE OF NUCLEIC ACID BY FORMING NON-COVALENT HYDROGEN BONDS BETWEEN COMPLEMENTARY BASES. THE BIOCHEMICALLY COMPLEMENTARY BASES ARE A-T, A-U and G-C. DOUBLE STRANDED NUCLEIC ACIDS CAN BE MELTED INTO SINGLE STRANDS IN THE LABORATORY BY RAISING THE TEMPERATURE AND THEY WILL HYBRIDIZE AGAIN WHEN THE TEMPERATURE IS LOWERED. WITHIN THE CELL, MELTING AND REANNEALING IS DONE BY ENZYMES.

NOTE THAT ATP IS A NUCLEOTIDE AS IS cAMP.

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