Copyright 2010, John Wiley & Sons, Inc. Chapter 2 Introductory Chemistry

Copyright 2010, John Wiley & Sons, Inc. Chemical Elements Fundamental unit in chemistry 112 elements total Use 1-2 letter symbols for each  Examples: C= carbon, Na = sodium, Cl = chorine. 26 elements present in human body  4 major ones (O, C, H, and N) make up 96%  8 others significant also. See Table 2.1.

Copyright 2010, John Wiley & Sons, Inc. Atoms Smallest unit of an element that retains characteristics of an element contains  Nucleus that has protons (+), neutrons (0)  Electrons (–) surrounding nucleus Total charge is neutral:  Protons # = electron # Atomic number = number of protons = number of electrons Mass number = number of protons + number of neutrons

Copyright 2010, John Wiley & Sons, Inc. Ions, Molecules and Compounds When an atom gives up or gains an electron, it becomes an ion When atoms share electrons, they form a molecule Two or more different atoms held together with chemical bonds = a compound Described by the molecular formula

Copyright 2010, John Wiley & Sons, Inc. Molecular Formula O 2 = oxygen  Molecule: has 2 atoms bound together H 2 O = water  Compound has 2 different atoms: H (hydrogen): 2 atoms O (oxygen): 1 atom Subscript indicates # of atoms of element

Copyright 2010, John Wiley & Sons, Inc. Molecules

Copyright 2010, John Wiley & Sons, Inc. Chemical Bonding Attraction between atoms to form attachments Electrons are grouped into shells  Number of electrons in outer shell determines type of bonding Types of bonds:  Ionic  Covalent  Hydrogen

Copyright 2010, John Wiley & Sons, Inc. Ionic Bonds Electron is donated or accepted from another atom  ion Typically occurs between atoms in which:  One has just 1 or 2 electrons in outer shells  Other has almost full outer shell (6 or 7 electrons) Electrons are negative (–) so:  If electron is accepted, atom  negative ion: anion  If electron is donated, atom  positive ion: cation Opposite charges attract  ionic bonding

Copyright 2010, John Wiley & Sons, Inc. Ionic Bonds

Copyright 2010, John Wiley & Sons, Inc. Covalent Bonds Sharing of electrons in outer shell  covalent bonds Typically occurs between atoms in which outer shells are about half full.  Example: bonds involving carbon (C) atoms (with 4 electrons in outer shell). These are organic compounds.

Copyright 2010, John Wiley & Sons, Inc. Covalent Bonds – single bond

Copyright 2010, John Wiley & Sons, Inc. Covalent Bonds – double bonds

Copyright 2010, John Wiley & Sons, Inc. Covalent Bonds – triple bonds

Copyright 2010, John Wiley & Sons, Inc. Covalent Bonds – 4 bonds

Copyright 2010, John Wiley & Sons, Inc. Hydrogen Bonds Form when a hydrogen atom (with a partial positive charge) attracts the partial negative charge of neighboring atoms, such as oxygen or nitrogen. Contribute strength and stability within large complex molecules such as  DNA  Proteins

Copyright 2010, John Wiley & Sons, Inc. Chemical Reactions Occur when bonds break and new bonds form Types:  Synthesis  Decomposition  Exchange  Reversible

Copyright 2010, John Wiley & Sons, Inc. Chemical Reactions: Synthesis Putting atoms together to form larger molecules A + B  AB Example: 2H 2 + O 2  2 H 2 O Synthesis in the body = anabolism

Copyright 2010, John Wiley & Sons, Inc. Chemical Reactions: Decomposition Splitting molecules apart AB  A + B Example: CH 4  C + 2H 2 Decomposition in the body = catabolism

Copyright 2010, John Wiley & Sons, Inc. Chemical Reactions: Exchange Involve both synthesis and decomposition AB + CD  AD + BC

Copyright 2010, John Wiley & Sons, Inc. Chemical Reactions: Reversible Can go in either direction: synthesis or decomposition or exchange Examples:  A + B ↔ AB  AB ↔ A + B  AB + CD ↔ AD + BC

Copyright 2010, John Wiley & Sons, Inc. Classes of Chemicals Inorganic  Structure: lack C-H bonds; structurally simple  Examples Water, carbon dioxide, bicarbonate, acids, bases, and salts Organic  Structure: All contain C-H bonds Structurally complex (include polymers composed of many units = monomers)  Classes: carbohydrates, lipids, proteins, nucleic acids

Copyright 2010, John Wiley & Sons, Inc. Inorganic Compounds: Water Characteristics of water  Most abundant chemical in human body  Good solvent and lubricant  Takes part in chemical reactions  Absorbs and releases heat slowly; regulates body temperature  Involved in digestion, circulation, and elimination of wastes

Copyright 2010, John Wiley & Sons, Inc. Acids, Bases and Salts Acid dissolves  H + (1 or more) Base dissolves  OH - (1 or more) Acid + base  salt  Example: HCl + NaOH  NaCl + H 2 O acid + base  salt + H 2 O

Copyright 2010, John Wiley & Sons, Inc. pH Concept The concentration of H + or OH – expressed on the pH scale pH scale: 0–14 pH 7.0: H + concentration = OH – concentration pH < 7.0 = more H + (acid)  The smaller the number, the more H + pH > 7.0 = more OH – (alkaline)  The larger the number, the more OH – Alkalosis Acidosis

Copyright 2010, John Wiley & Sons, Inc. Organic Compounds: Carbohydrates Most common sources of energy for humans Three major classes: mono-, di-, poly- Monosaccharide: simple sugar.  Glucose (blood sugar)  fructose (fruit sugar) Disaccharides: two bonded monosaccharides  formed by dehydration synthesis and broken down by hydrolysis  Glucose + fructose ↔ sucrose (table sugar)  Glucose + galactose ↔ lactose (milk sugar)  Glucose + glucose ↔ maltose

Copyright 2010, John Wiley & Sons, Inc. Disaccharide

Copyright 2010, John Wiley & Sons, Inc. Polysaccharides Monosaccharides (monomers) in long chains  Complex branching structures not usually soluble in water Examples  Glycogen: carbohydrate stored in animals (liver, muscles)  Starch: carbohydrate stored in plants (potatoes, rice, grains)  Cellulose: plant polymer ( indigestible fibers)

Copyright 2010, John Wiley & Sons, Inc. Polysaccharides

Copyright 2010, John Wiley & Sons, Inc. Organic Compounds - Lipids Characteristics  Insoluble in water = hydrophobic  Functions: protect, insulate, provide energy Classes  Triglycerides Most plentiful in diet and body Each composed of 3 fatty acids + 1 glycerol May be saturated, monounsaturated, or polyunsaturated  Phospholipids: form lipid bilayer in membranes  Steroids based on ring-structure of cholesterol  Fat-soluble vitamins: A, D, E, and K

Copyright 2010, John Wiley & Sons, Inc. Lipids: Triglycerides

Copyright 2010, John Wiley & Sons, Inc. Lipids: Phospholipids

Copyright 2010, John Wiley & Sons, Inc. Lipids: Steroids

Copyright 2010, John Wiley & Sons, Inc. Cholesterol Used to make steroid hormones  Estrogen, testosterone, cortisone Help make plasma membranes stiff Made in liver

Copyright 2010, John Wiley & Sons, Inc. Organic Compounds - Proteins Structure: composed of amino acids (monomers)  20 different amino acids Amino acid structure: central carbon with  Acid (carboxyl) group (COOH)  Amino group (NH 2 )  Side chain (varies among the 20 amino acids) Amino acids joined in long chains  By dehydration synthesis to form peptide bonds  dipeptide  tripeptide  polypeptide  Ultimately, form large, complex structures

Copyright 2010, John Wiley & Sons, Inc. Amino Acids

Copyright 2010, John Wiley & Sons, Inc. Length of AA chain Peptide – 2-9 AA’s Polypeptide – AA’s Protein – 100-thousands of AA’s

Copyright 2010, John Wiley & Sons, Inc. Protein Structure Primary (1 0 ) – sequence of AA’s Secondary (2 0 ) – twisting of AA’s due to H- bonding Tertiary (3 0 ) – folding of AA chain due to ionic bonds, disulfide bridges, & hydrophobic interactions Quaternary (4 0 ) – interactions between different AA chains * A protein must be in Quaternary structure to be functional!

Copyright 2010, John Wiley & Sons, Inc. Denaturation of Proteins: loss of 3- dimensional conformation (shape) Extreme pH Extreme T Harsh chemicals High salt concentrations

Copyright 2010, John Wiley & Sons, Inc. Functions of Proteins Structure – keratin in hair, nails & skin Transport – hemoglobin Chemical messengers – hormones, neurotransmitters Movement – actin & myosin in muscle Defense – antibodies Catalysts - enzymes

Copyright 2010, John Wiley & Sons, Inc. Enzymes Proteins that serve as chemical catalysts Highly specific: one enzyme works on a specific substrate  product Efficient: one enzyme used over and over Names  Most end in “-ase”  Many give clues to functions: sucrase, lipase, protease, dehydrogenase

Copyright 2010, John Wiley & Sons, Inc. Enzymes

Copyright 2010, John Wiley & Sons, Inc. Nucleic Acids DNA or RNA Each nucleotide (monomer) consists of  Sugar (5-C monosaccharide: ribose or deoxyribose)  Phosphate  Nitrogen-containing (nitrogeneous) base In DNA: adenine (A), guanine (G), cytosine (C), or thymine (T) In RNA - (A), (G), (C), or uracil (U) (which replaces T of DNA)

Copyright 2010, John Wiley & Sons, Inc. DNA Molecule

Copyright 2010, John Wiley & Sons, Inc. Nucleic Acids: DNA Nucleotides are connected into long chains bonded by hydrogen bonds between the bases:  C – G, or A – T Two chains form double helix (spiral ladder) Function: stores genetic information in genes (found in chromosomes) that:  Direct protein synthesis - regulate everyday activities of cells

Copyright 2010, John Wiley & Sons, Inc. Nucleic Acid: RNA single chain (one side of a ladder) Function:  correctly sequences amino acids - regulate everyday activities of cells

Copyright 2010, John Wiley & Sons, Inc. ATP – Adenosine TriPhosphate Function: the main energy-storing molecule in the body  ATP contains 3 phosphates  high-energy chemical bonds between terminal phosphate groups  ATP  ADP + phosphate + energy

Copyright 2010, John Wiley & Sons, Inc. Structure of ATP and ADP

Copyright 2010, John Wiley & Sons, Inc. End of Chapter 2 Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.

Copyright 2010, John Wiley & Sons, Inc. We Love DNA Made of nucleotides Sugar, Phosphate, and Base Bonded down one side Adenine and Thymine Make a lovely pair Cytosine without Guanine Would feel very bare