Copyright 2010, John Wiley & Sons, Inc.

 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.

 Smallest unit of an element that retains characteristics of an element
 Atom 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.

 When an atom gives up of 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.

 O
2

= oxygen
Molecule: has 2 atoms bound together
 H
2
O = water

Molecule has 2 atoms bound together

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.

Copyright 2010, John Wiley & Sons, Inc.

 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.

 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.

Copyright 2010, John Wiley & Sons, Inc.

 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.

Example: water
Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

 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.

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





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.

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

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

 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.

 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.

 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.




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.






The concentration of H + or OH
– the pH scale expressed on 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
–
Copyright 2010, John Wiley & Sons, Inc.

 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.

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

Copyright 2010, John Wiley & Sons, Inc.

 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.

Copyright 2010, John Wiley & Sons, Inc.

 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.

Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

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




Structure: composed of amino acids (monomers)

20 different amino acids (like alphabet)
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.

Copyright 2010, John Wiley & Sons, Inc.

 Functions (many)

Much of cell structure

Contraction: muscle fibers

Regulate body: hormones

Transport of O
2 in blood: hemoglobin

Defense: antibodies

Chemical catalysts: enzymes
Copyright 2010, John Wiley & Sons, Inc.

 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.

Copyright 2010, John Wiley & Sons, Inc.

 DNA or RNA
 Huge polymers composed of nucleotides
 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: adenine (A), guanine (G), cytosine (C), or uracil (U) (which replaces T of DNA)
Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

 Nucleotides are connected into long chains that are bonded by bases:

C – G, G – C, T – A, or A – T
 Two chains form double helix (spiral ladder)
 Function: stores DNA (genetic information) in genes (found in chromosomes) that:

Direct protein synthesis and therefore regulate everyday activities of cells

Carry this genetic information to the next generation of cells
Copyright 2010, John Wiley & Sons, Inc.

 Nucleotides are connected into a long, single chain (one side of a ladder)

In transcription, RNA (italics) positions next to
DNA: C – G, G – C, A - T, or U – A

In translation, t-RNA (italics) positions next to m-
RNA (italics) : C – G, G – C, A - U, or U - A
 Function:

Carries out protein synthesis by correctly sequencing amino acids, so helps to regulate everyday activities of cells
Copyright 2010, John Wiley & Sons, Inc.

 Structure: composed of chemicals similar to those in RNA: base (adenine), ribose, and phosphates
 Function: the main energy-storing molecule in the body

ATP contains 3 phosphates

Carries energy in high-energy chemical bonds between terminal phosphate groups

Energy released from those bonds when they break: ATP

ADP + phosphate + energy
Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

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