Copyright 2010, John Wiley & Sons, Inc. Chapter 2 Introductory Chemistry.
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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.
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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
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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
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Molecular Formula O2 = oxygen
Molecule: has 2 atoms bound together
H2O = water Compound has 2 different atoms:
H (hydrogen): 2 atoms O (oxygen): 1 atom
Subscript indicates # of atoms of element
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Molecules
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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
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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
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Ionic Bonds
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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.
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Covalent Bonds – single bond
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Covalent Bonds – double bonds
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Covalent Bonds – triple bonds
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Covalent Bonds – 4 bonds
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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
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Chemical Reactions Occur when bonds break and new bonds
form Types:
Synthesis Decomposition Exchange Reversible
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Chemical Reactions: Synthesis Putting atoms together to form larger
molecules A + B AB Example: 2H2 + O2 2 H2O Synthesis in the body = anabolism
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Chemical Reactions: Decomposition Splitting molecules apart AB A + B Example: CH4 C + 2H2 Decomposition in the body = catabolism
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Chemical Reactions: Exchange Involve both synthesis and decomposition AB + CD AD + BC
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Chemical Reactions: Reversible Can go in either direction: synthesis or
decomposition or exchange Examples:
A + B ↔ AB
AB ↔ A + B
AB + CD ↔ AD + BC
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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
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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
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Acids, Bases and Salts Acid dissolves H+ (1 or more) Base dissolves OH- (1 or more) Acid + base salt
Example: HCl + NaOH NaCl + H2O
acid + base salt + H2O
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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
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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
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Disaccharide
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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)
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Polysaccharides
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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
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Lipids: Triglycerides
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Lipids: Phospholipids
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Lipids: Steroids
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Cholesterol Used to make steroid hormones
Estrogen, testosterone, cortisone Help make plasma membranes stiff Made in liver
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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 (NH2) 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
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Amino Acids
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Length of AA chain
Peptide – 2-9 AA’s Polypeptide – 10-100 AA’s Protein – 100-thousands of AA’s
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Protein Structure
Primary (10) – sequence of AA’s Secondary (20) – twisting of AA’s due to H-
bonding Tertiary (30) – folding of AA chain due to ionic
bonds, disulfide bridges, & hydrophobic interactions
Quaternary (40) – interactions between different AA chains
* A protein must be in Quaternary structure to be functional!
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Denaturation of Proteins: loss of 3-dimensional conformation (shape) Extreme pH Extreme T Harsh chemicals High salt concentrations
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Functions of Proteins Structure – keratin in hair, nails & skin Transport – hemoglobin Chemical messengers – hormones,
neurotransmitters Movement – actin & myosin in muscle Defense – antibodies Catalysts - enzymes
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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
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Enzymes
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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)
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DNA Molecule
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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
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Nucleic Acid: RNA single chain (one side of a ladder) Function:
correctly sequences amino acids - regulate everyday activities of cells
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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
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Structure of ATP and ADP
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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.
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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
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