Presentation is loading. Please wait.

Presentation is loading. Please wait.


Similar presentations

Presentation on theme: "CHEMISTRY PART 2."— Presentation transcript:


2 Chemical Bonds Electron shells, or energy levels, surround the nucleus of an atom Bonds are formed using the electrons in the outermost energy level Valence shell – outermost energy level containing chemically active electrons Octet rule – atoms usually react in a manner to have 8 electrons in their valence shell. (2 in first, 8 in second and third)

3 Chemically Inert and Reactive Elements
Inert elements have their outermost energy level fully occupied by electrons Figure 2.4a

4 Chemically Inert and Reactive Elements
Reactive elements do not have their outermost energy level fully occupied by electrons Figure 2.4b

5 Types of Chemical Bonds
Ionic Covalent Hydrogen

6 Ionic Bonds Ions are charged atoms resulting from the gain or loss of electrons Anions have gained one or more electrons Cations have lost one or more electrons Opposite charges on anions and cations hold them close together, forming ionic bonds

7 Formation of an Ionic Bond
Ionic compounds form crystals instead of individual molecules Example: NaCl (sodium chloride)

8 Formation of an Ionic Bond
Figure 2.5

9 Covalent Bonds Electrons are shared by two atoms
Electron sharing produces molecules

10 Covalent Bonds Figure 2.6a

11 Covalent Bonds Figure 2.6b

12 Covalent Bonds Figure 2.6c

13 Polar and Nonpolar Molecules
Electrons shared equally between atoms produce nonpolar molecules Unequal sharing of electrons produces polar molecules Atoms with 6 or 7 valence shell electrons are electronegative Atoms with 1 or 2 valence shell electrons are electropositive

14 Comparison of Ionic, Polar Covalent, and Nonpolar Covalent Bonds
Figure 2.8

15 Hydrogen Bonds Too weak to bind atoms together
Common in dipoles such as water Responsible for surface tension in water Important as intramolecular bonds, giving the molecule a three-dimensional shape Figure 2.9

16 Chemical Reactions Occur when chemical bonds are formed, rearranged, or broken Are written in symbolic form using chemical equations Chemical equations contain: Number and type of reacting substances, and products produced Relative amounts of reactants and products H + H  H2 (reactants) (product)

17 Patterns of Chemical Reactions
Combination reactions: Synthesis reactions which always involve bond formation A + B  AB Decomposition reactions: Molecules are broken down into smaller molecules AB  A + B Exchange reactions: Bonds are both made and broken AB + C  AC + B

18 Oxidation-Reduction (Redox) Reactions
Reactants losing electrons are electron donors and are oxidized Reactants taking up electrons are electron acceptors and become reduced

19 Energy Flow in Chemical Reactions
Exergonic reactions – reactions that release energy Endergonic reactions – reactions whose products contain more potential energy than did its reactants

20 Reversibility of Chemical Reactions
All chemical reactions are theoretically reversible A + B  AB AB  A + B If neither a forward nor reverse reaction is dominant, chemical equilibrium is reached

21 Factors Influencing Rate of Chemical Reactions
Temperature – chemical reactions proceed quicker at higher temperatures Particle size – the smaller the particle the faster the chemical reaction Concentration – higher reacting particle concentrations produce faster reactions Catalysts – increase the rate of a reaction without being chemically changed Enzymes – biological catalysts

22 Biochemistry Organic compounds Inorganic compounds
Contain carbon, are covalently bonded, and are often large Inorganic compounds Do not contain carbon Water, salts, and many acids and bases

23 Water High heat capacity – absorbs and releases large amounts of heat before changing temperature High heat of vaporization – changing from a liquid to a gas requires large amounts of heat Polar solvent properties – dissolves ionic substances, forms hydration layers around large charged molecules, and serves as the body’s major transport medium Reactivity – is an important part of hydrolysis and dehydration synthesis reactions Cushioning – resilient cushion around certain body organs

24 Salts Inorganic compounds
Contain cations other than H+ and anions other than OH– Are electrolytes; they conduct electrical currents

25 Acids and Bases Acids release H+ and are therefore proton donors
HCl  H+ + Cl – Bases release OH– and are proton receptors NaOH  Na+ + OH–

26 Acid-Base Concentration (pH)
Acidic solutions have higher H+ concentration and therefore a lower pH Alkaline solutions have lower H+ concentration and therefore a higher pH Neutral solutions have equal H+ and OH– concentrations

27 Acid-Base Concentration (pH)
Acidic: pH 0–6.99 Basic: pH 7.01–14 Neutral: pH 7.00 Figure 2.12

28 Buffers Systems that resist abrupt and large swings in the pH of body fluids Carbonic acid–bicarbonate system Carbonic acid dissociates reversibly releasing bicarbonate ions and protons The chemical equilibrium between carbonic acid and bicarbonate resists pH changes in the blood

29 Break

30 Organic Compounds Carbohydrates Lipids Proteins Nucleic Acids

31 Carbohydrates Contain carbon, hydrogen, and oxygen
Their major function is to supply a source of cellular food Examples: Monosaccharides or simple sugars Figure 2.13a

32 Carbohydrates Disaccharides or double sugars Figure 2.13b

33 Carbohydrates Polysaccharides or polymers of simple sugars
Figure 2.13c

34 Lipids Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates Examples: Neutral fats or triglycerides Phospholipids Steroids Eicosanoids

35 Neutral Fats (Triglycerides)
Composed of three fatty acids bonded to a glycerol molecule Figure 2.14a

36 Other Lipids Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group Figure 2.14b

37 Other Lipids Steroids – flat molecules with four interlocking hydrocarbon rings Eicosanoids – 20-carbon fatty acids found in cell membranes Figure 2.14c

38 Representative Lipids Found in the Body
Neutral fats – found in subcutaneous tissue and around organs Phospholipids – chief component of cell membranes Steroids – cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones Fat-soluble vitamins – vitamins A, E, and K Eicosanoids – prostaglandins, leukotriens, and thromboxanes Lipoproteins – transport fatty acids and cholesterol in the bloodstream

39 Amino Acids Building blocks of protein, containing an amino group and a carboxyl group Amino acid structure Figure 2.15

40 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Figure 2.16

41 Structural Levels of Proteins
Primary – amino acid sequence Secondary – alpha helices or beta pleated sheets Tertiary – superimposed folding of secondary structures Quaternary – polypeptide chains linked together in a specific manner

42 Structural Levels of Proteins
Figure 2.17

43 Fibrous and Globular Proteins
Fibrous proteins Extended and strandlike proteins Examples: keratin, elastin, collagen, and certain contractile fibers Globular proteins Compact, spherical proteins with tertiary and quaternary structures Examples: antibodies, hormones, and enzymes

44 Protein Denaturation Reversible unfolding of proteins due to drops in pH and/or increased temperature Figure 2.19a

45 Protein Denaturation Irreversibly denatured proteins cannot refold and are formed by extreme pH or temperature changes Figure 2.19b

46 Molecular Chaperones (Chaperonins)
Help other proteins to achieve their functional three-dimensional shape Maintain folding integrity Assist in translocation of proteins across membranes Promote the breakdown of damaged or denatured proteins

47 Characteristics of Enzymes
Most are globular proteins that act as biological catalysts Holoenzymes consist of an apoenzyme (protein) and a cofactor (usually an ion) Enzymes are chemically specific Frequently named for the type of reaction they catalyze Enzyme names usually end in -ase Lower activation energy

48 Characteristics of Enzymes
Figure 2.20

49 Mechanism of Enzyme Action
Enzyme binds with substrate Product is formed at a lower activation energy Product is released Figure 2.21

50 Nucleic Acids Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus Their structural unit, the nucleotide, is composed of N-containing base, a pentose sugar, and a phosphate group Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) Two major classes – DNA and RNA

51 Deoxyribonucleic Acid (DNA)
Double-stranded helical molecule found in the nucleus of the cell Replicates itself before the cell divides, ensuring genetic continuity Provides instructions for protein synthesis

52 Structure of DNA Figure 2.22a

53 Structure of DNA Figure 2.22b

54 Ribonucleic Acid (RNA)
Single-stranded molecule found in both the nucleus and the cytoplasm of a cell Uses the nitrogenous base uracil instead of thymine Three varieties of RNA: messenger RNA, transfer RNA, and ribosomal RNA

55 Adenosine Triphosphate (ATP)
Source of immediately usable energy for the cell Adenine-containing RNA nucleotide with three phosphate groups Figure 2.23

Download ppt "CHEMISTRY PART 2."

Similar presentations

Ads by Google