Slide 0 Copyright © 2005. Elsevier Inc. All Rights Reserved. Chapter 2 Chemistry of Life.

Slide 1Copyright © 2005. Elsevier Inc. All Rights Reserved.

Chapter 2Chapter 2

Chemistry of Life


Learning ObjectivesLearning Objectives

• Define the terms atom, element, molecule, and compound.

• Describe the structure of an atom.• Compare and contrast ionic and

covalent types of chemical bonding.

• Distinguish between organic and inorganic chemical compounds.


Learning Objectives (cont’d.)Learning Objectives (cont’d.)

• Discuss the chemical characteristics of water.

• Explain the concept of pH.• Discuss the structure and function

of the following types of organic molecules: carbohydrate, lipid, protein, and nucleic acid.


Chapter 2Lesson 2.1Chapter 2Lesson 2.1


Levels of Chemical OrganizationLevels of Chemical Organization

• Elements, molecules, and compounds Element—a pure substance; made up of

only one kind of atom Molecule—a group of atoms bound together

to form a larger chemical unit Compound—substances whose molecules

have more than one kind of element


Important Elements in the Human Body

Important Elements in the Human Body


Levels of Chemical OrganizationLevels of Chemical Organization

• Atoms Nucleus—central core of atom

Proton—positively charged particle in nucleus Neutron—noncharged particle in nucleus Atomic number—number of protons in the

nucleus; determines the type of atom


A Model of the AtomA Model of the Atom


Levels of Chemical Organization (cont’d.)

Levels of Chemical Organization (cont’d.)

Energy levels—regions surrounding atomic nucleus that contain electrons

electron—negatively charged particle may contain up to two electrons in the level

closest to the nucleus may contain up to eight electrons in the

remaining levels energy increases with distance from the

nucleus


Chemical BondingChemical Bonding

• Chemical bonds form to make atoms more stable. Outermost energy level of each atom is full. Atoms may share electrons, or donate or

borrow them to become stable.


Chemical Bonding (cont’d.)Chemical Bonding (cont’d.)

• Ionic bonds Ions form when an atom gains or loses

electrons in its outer energy level to become stable.

Positive ion—has lost electrons; indicated by superscript positive sign(s), as in Na+ or Ca+

Negative ion—has gained electrons; indicated by superscript negative sign(s), as in Cl–


Chemical Bonding (cont’d.)Chemical Bonding (cont’d.)

Ionic bonds form when positive and negative ions attract each other because of electrical attraction.

Electrolyte—molecule that dissociates (breaks apart) in water to form individual ions; an ionic compound


Ionic BondingIonic Bonding


Chemical BondingChemical Bonding

• Covalent bonds Covalent bonds form when atoms that share

their outer energy fill up and thus become stable.

Covalent bonds do not ordinarily dissociate in water.


Covalent BondingCovalent Bonding




Inorganic ChemistryInorganic Chemistry

• Organic molecules contain carbon–carbon covalent bonds and/or carbon-hydrogen covalent bonds; inorganic molecules do not.

• Examples of inorganic molecules: water and some acids, bases, and salts.


Inorganic Chemistry (cont’d.)Inorganic Chemistry (cont’d.)

• Water Water is a solvent (liquid into which solutes are

dissolved), forming aqueous solutions in the body

Water is involved in chemical reactions Dehydration synthesis—chemical reaction in

which water is removed from small molecules so they can be strung together to form a larger molecule

Hydrolysis—chemical reaction in which water is added to the subunits of a large molecule to break it apart into smaller molecules


Water-Based ChemistryWater-Based Chemistry


Acids, bases, and saltsAcids, bases, and salts

Water molecules dissociate to form equal amounts of H+ (hydrogen ion) and OH– (hydroxide ion).

Acid—substance that shifts the H+/OH– balance in favor of H+; opposite of base

Base—substance that shifts the H+/OH– balance against H+; also known as an alkaline; opposite of acid


Inorganic Chemistry Inorganic Chemistry

pH—mathematical expression of relative H+ concentration in an aqueous solution

7 is neutral (neither acid nor base) pH values above 7 are basic; pH values below

7 are acidic. Neutralization occurs when acids and bases

mix and form salts. Buffers are chemical systems that absorb

excess acids or bases and thus maintain a relatively stable pH.


The pH ScaleThe pH Scale




Organic ChemistryOrganic Chemistry

• Carbohydrates—sugars and complex carbohydrates Contain carbon (C), hydrogen (H), oxygen

(O) Made up of six carbon subunits called

monosaccharides or single sugars (e.g., glucose)

Disaccharide—double sugar made up of two monosaccharide units (e.g., sucrose, lactose)


Organic Chemistry (cont’d.)Organic Chemistry (cont’d.)

Polysaccharide—complex carbohydrate made up of many monosaccharide units (e.g., glycogen made up of many glucose units)

The function of carbohydrates is to store energy for later use.


CarbohydratesCarbohydrates



• Lipids—fats and oils Trigylcerides

Made up of one glycerol unit and three fatty acids

Store energy for later use


TriglycerideTriglyceride



Phospholipids Similar to triglyceride structure, except with

only two fatty acids, and with a phosphorus-containing group attached to glycerol

The head attracts water and the double tail repels water, thus forming stable double layers (bilayers) in water

Form membranes of cells


Phospholipids Phospholipids



Cholesterol Cholesterol molecules have a steroid

structure made up of multiple rings. Cholesterol stabilizes the phospholipid tails in

cellular membranes. It is converted into steroid hormones, such as

estrogen, testosterone, and cortisone by the body.



• Proteins very large molecules made up of amino

acids held together in long folded chains by peptide bonds

Structural proteins form structures of the body

Collagen is a fibrous protein that holds many tissues together.

Keratin forms tough waterproof fibers in the outer layer of the skin.



Functional proteins Participate in chemical processes (examples:

hormones, cell membrane channels and receptors, enzymes)

Enzymeso Catalysts help chemical reactions occur.o Lock-and-key—each enzyme fits a particular

molecule that it acts on as a key fits into a lock Proteins can combine with other organic molecules

to form glycoproteins or lipoproteins.


ProteinProtein



• Nucleic acids Made up of nucleotide units

sugar (ribose or deoxyribose) phosphate nitrogen base (adenine, thymine or uracil,

guanine, cytosine)

• By directing the formation of structural and functional proteins, nucleic acids ultimately direct overall body structure and function



DNA (deoxyribonucleic acid) used as the cell’s “master code” for

assembling proteins composed of deoxyribose (the sugar),

phosphate, and four bases: cytosine, guanine, adenine, and thymine

forms a double helix



RNA (ribonucleic acid) Used as a temporary “working copy” of a

gene (portion of the DNA code) Composed of ribose (the sugar), phosphate,

and four bases: adenine, uracil, cytosine, and guanine

Slide 0 Copyright © 2005. Elsevier Inc. All Rights Reserved. Chapter 2 Chemistry of Life.

Documents

nucleus slide

covalent bonding slide

ionic bonding slide

type of atom slide

ionic compound slide

chemistry of life slide

kind of element slide

human body slide