copyright 2010, john wiley & sons, inc. chapter 2 introductory chemistry

Copyright 2010, John Wiley & Sons, Inc.

Chapter 2

Introductory Chemistry


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.


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


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


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


Molecules


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


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


Ionic Bonds


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.


Covalent Bonds – single bond


Covalent Bonds – double bonds


Covalent Bonds – triple bonds


Covalent Bonds – 4 bonds


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


Chemical Reactions Occur when bonds break and new bonds

form Types:

Synthesis Decomposition Exchange Reversible


Chemical Reactions: Synthesis Putting atoms together to form larger

molecules A + B AB Example: 2H2 + O2 2 H2O Synthesis in the body = anabolism


Chemical Reactions: Decomposition Splitting molecules apart AB A + B Example: CH4 C + 2H2 Decomposition in the body = catabolism


Chemical Reactions: Exchange Involve both synthesis and decomposition AB + CD AD + BC


Chemical Reactions: Reversible Can go in either direction: synthesis or

decomposition or exchange Examples:

A + B ↔ AB

AB ↔ A + B

AB + CD ↔ AD + BC


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


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


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


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


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


Disaccharide


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)


Polysaccharides


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


Lipids: Triglycerides


Lipids: Phospholipids


Lipids: Steroids


Cholesterol Used to make steroid hormones

Estrogen, testosterone, cortisone Help make plasma membranes stiff Made in liver


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


Amino Acids


Length of AA chain

Peptide – 2-9 AA’s Polypeptide – 10-100 AA’s Protein – 100-thousands of AA’s


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!


Denaturation of Proteins: loss of 3-dimensional conformation (shape) Extreme pH Extreme T Harsh chemicals High salt concentrations


Functions of Proteins Structure – keratin in hair, nails & skin Transport – hemoglobin Chemical messengers – hormones,

neurotransmitters Movement – actin & myosin in muscle Defense – antibodies Catalysts - enzymes


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


Enzymes


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)


DNA Molecule


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


Nucleic Acid: RNA single chain (one side of a ladder) Function:

correctly sequences amino acids - regulate everyday activities of cells


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


Structure of ATP and ADP


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.


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

copyright 2010, john wiley & sons, inc. chapter 2 introductory chemistry

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