Copyright © 2010 Pearson Education, Inc. BASIC CHEMISTRY CH. 2.

Copyright © 2010 Pearson Education, Inc.

BASIC CHEMISTRY CH. 2


Matter

• Definition: Anything that has mass and occupies space

• States of matter:

1. Solid—

2. Liquid—

3. Gas—


Energy

• Definition: Capacity to do work or put matter into motion

• Types of energy:

• Kinetic—

• Potential—

• Electrical –


Energy Form Conversions

• Energy may be converted from one form to another

• Conversion is inefficient


Composition of Matter

• Elements

• Atoms


Atomic Structure

• Neutrons

• Protons

• Electrons

Copyright © 2010 Pearson Education, Inc. Figure 2.1

Helium atom Helium atom

Nucleus Nucleus

Proton Neutron Electroncloud

Electron


Identifying Elements

• Atoms of different elements contain different numbers of protons

• Compare hydrogen, helium and lithium


Proton

Neutron

Electron

Helium (He) Lithium (Li)Hydrogen (H)



• Atomic number =



• Mass number =

• Mass numbers of atoms of an element are not all identical

• Isotopes: Structural variations of elements; differ in the # of neutrons they contain


Proton

Neutron

Electron

Deuterium (2H) Tritium (3H)Hydrogen (1H)


Molecules and Compounds

• Molecule—(H2 or C6H12O6)

• Compound—(C6H12O6)


Chemical Bonds

• Electrons occupy up to seven electron shells (energy levels) around nucleus

• Octet rule:


Chemically Inert Elements

• Stable and unreactive

• Outermost energy level fully occupied or contains eight electrons

Copyright © 2010 Pearson Education, Inc. Figure 2.4a

Helium (He) Neon (Ne)

2e 2e8e

(a) Chemically inert elements

Valence shell complete


Chemically Reactive Elements

• Valence shell not fully occupied by electrons

• Tend to gain, lose, or share electrons (form bonds) with other atoms to achieve stability

Copyright © 2010 Pearson Education, Inc. Figure 2.4b

2e4e

2e8e

1e

(b) Chemically reactive elementsValence shell incomplete

Hydrogen (H) Carbon ©

1e

Oxygen (O)Sodium (Na)

2e6e


Types of Chemical Bonds

• Ionic

• Covalent

• Hydrogen


Ionic Bonds

• Ions are formed by transfer of valence shell electrons between atoms

• Anions (– charge)

• Cations (+ charge)

• Attraction of opposite charges results in: An ionic bond


Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl–)

Sodium chloride (NaCl)

+ –


Covalent Bonds

• Formed by sharing of two or more valence shell electrons

• Allows each atom to fill its valence shell at least part of the time


+

Hydrogenatoms

Carbonatom

Molecule ofmethane gas (CH4)

(a) Formation of four single covalent bonds:

or

Resulting moleculesReacting atoms


or

Oxygenatom

Oxygenatom

Molecule ofoxygen gas (O2)

(b) Formation of a double covalent bond:


+

Copyright © 2010 Pearson Education, Inc. Figure 2.7c

+ or

Nitrogenatom

Nitrogenatom

Molecule ofnitrogen gas (N2)

(c) Formation of a triple covalent bond:.



Covalent Bonds

• Sharing of electrons may be equal or unequal

• Equal sharing produces: Electrically balanced nonpolar molecules

• CO2


Covalent Bonds

• Unequal sharing by atoms with different electron-attracting abilities produces: polar molecules

• H2O

• Atoms with six or seven valence shell electrons are electronegative, e.g., oxygen


Hydrogen Bonds

• Attractive force between electropositive hydrogen of one molecule and an electronegative atom of another molecule

• Important in intramolecular bonds, holding a large molecule in a three-dimensional shape


(a) The slightly positive ends (+) of the watermolecules become aligned with the slightlynegative ends (–) of other water molecules.

+

–

–

–– –

+

+

+

+

+

Hydrogen bond

Figure 2.8


(b) High surface tension of water, due to hydrogen bonds.


Synthesis Reactions

• A + B AB

• Always involve bond formation

• Anabolic

• Endergonic


ExampleAmino acids are joined toForm protein.

(a) Synthesis reactions

Smaller particles are bondedtogether to form larger,

molecules.

Amino acidmolecules

Proteinmolecule


Decomposition Reactions

• AB A + B

• Reverse synthesis reactions

• Involve breaking of bonds

• Catabolic

• Exergonic


ExampleGlycogen is broken down to releaseglucose units.

Bonds are broken in largermolecules, resulting in smaller,

less complex molecules.

(b) Decomposition reactions

Glucosemolecules

Glycogen


Classes of Compounds

• Inorganic compounds

• Organic compounds


Water


Salts


Acids and Bases

• Both are electrolytes

• Acids :

• HCl H+ + Cl–


Acids and Bases

• Bases-

• NaOH Na+ + OH–


Acid-Base Concentration

• Acid solutions contain [H+]

• Basic solutions contain bases (e.g., OH–)


pH: Acid-Base Concentration

• pH =

• Neutral solutions:

• pH = 7


pH: Acid-Base Concentration

• Acidic solutions

• [H+], pH

• pH = 0–6.99

• Basic solutions

• [H+], pH

• pH= 7.01–14


Concentration(moles/liter)

[OH–]

100 10–14

10–1 10–13

10–2 10–12

10–3 10–11

10–4 10–10

10–5 10–9

10–6 10–8

10–7 10–7

10–8 10–6

10–9 10–5

10–10 10–4

10–11 10–3

10–12 10–2

10–13 10–1

[H+] pHExamples

1M Sodiumhydroxide (pH=14)

Oven cleaner, lye(pH=13.5)

Household ammonia(pH=10.5–11.5)

Neutral

Household bleach(pH=9.5)

Egg white (pH=8)

Blood (pH=7.4)

Milk (pH=6.3–6.6)

Black coffee (pH=5)

Wine (pH=2.5–3.5)

Lemon juice; gastricjuice (pH=2)

1M Hydrochloricacid (pH=0)10–14 100

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0


Carbohydrates

• Sugars and starches

• Three classes

• Monosaccharides

• Disaccharides

• Polysaccharides


Carbohydrates

• Functions

• Primary role:

• Structural molecules (ribose sugar in RNA)


Monosaccharides

• Simple sugars containing three to seven C atoms


ExampleHexose sugars (the hexoses shown

here are isomers)

ExamplePentose sugars

Glucose Fructose Galactose Deoxyribose Ribose

(a) MonosaccharidesMonomers of carbohydrates


Disaccharides

• Double sugars

• Too large to pass through cell membranes


PLAYPLAY Animation: Disaccharides

ExampleSucrose, maltose, and lactose

(these disaccharides are isomers)

Glucose Fructose Glucose Glucose Glucose

Sucrose Maltose Lactose

Galactose

(b) DisaccharidesConsist of two linked monosaccharides


Polysaccharides

• Three/more simple sugars, e.g., starch and glycogen

• Not very soluble


PLAYPLAY Animation: Polysaccharides

ExampleThis polysaccharide is a simplified representation of

glycogen, a polysaccharide formed from glucose units.

(c) PolysaccharidesLong branching chains (polymers) of linked monosaccharides

Glycogen


Lipids

• Insoluble in water

• Main types:

• Triglycerides

• Phospholipids

• Steroids


Triglycerides

• Defined as:

• Composed of:

• Main functions

• Energy storage

• Insulation

• Protection


Glycerol

+

3 fatty acid chains Triglyceride,or neutral fat

3 watermolecules

(a) Triglyceride formation


Phospholipids

• Modified triglycerides:

• “Head” and “tail” regions have different properties

• Important in cell membrane structure


Phosphorus-containing

group (polar“head”)

ExamplePhosphatidylcholine

Glycerolbackbone

2 fatty acid chains(nonpolar “tail”)

Polar“head”

Nonpolar“tail”

(schematicphospholipid)

(b) “Typical” structure of a phospholipid molecule

Two fatty acid chains and a phosphorus-containing group areattached to the glycerol backbone.


Steroids

• Steroids—interlocking four-ring structure

• Examples are cholesterol, vitamin D, steroid hormones, and bile salts


ExampleCholesterol (cholesterol is the

basis for all steroids formed in the body)

(c) Simplified structure of a steroid

Four interlocking hydrocarbon rings form a steroid.


Proteins

• Composed of amino acids


(a) Generalized structure of all amino acids.

(b) Glycine is the simplest

amino acid.

(c) Aspartic acid (an acidic amino acid)

has an acid group (—COOH) in the

R group.

(d) Lysine (a basic amino acid) has an amine group

(–NH2) in the R group.

(e) Cysteine (a basic amino acid)

has a sulfhydryl (–SH) group in the R group, which suggests that

this amino acid is likely to participate in

intramolecular bonding.

Aminegroup

Acidgroup


Structural Levels of Proteins

PLAYPLAY Animation: Introduction to Protein Structure


(a) Primary structure: The sequence of amino acids forms the polypeptide chain.

Amino acid Amino acid Amino acid Amino acid Amino acid

PLAYPLAY Animation: Primary Structure


-Helix: -Sheet:

(b) Secondary structure:The primary chain forms spirals (-helices) and sheets (-sheets).

PLAYPLAY Animation: Secondary Structure


(c) Tertiary structure:

PLAYPLAY Animation: Tertiary Structure

Copyright © 2010 Pearson Education, Inc. Figure 2.19d

(d) Quaternary structure: Two or more polypeptide chains, each with its own tertiary structure,

combine to form a functional protein.

PLAYPLAY Animation: Quaternary Structure


Protein Denaturation

• Shape change and disruption of active sites due to environmental changes

• A denatured protein is nonfunctional


Enzymes

• Biological catalysts

• Increase the speed of a reaction

• Allows for millions of reactions/minute


Substrates

Enzyme

Active site

+

Enzyme Function


Nucleic Acids

• DNA and RNA

• Building block = nucleotide


Deoxyribonucleic Acid (DNA)

• Four Nitrogen containing bases:

• adenine (A), guanine (G), cytosine (C), and thymine (T)

• Double-stranded, helical

• Replicates before cell division, ensuring genetic continuity

• Provides instructions for protein synthesis


Deoxyribosesugar

Phosphate

Sugar-phosphatebackbone

Adenine nucleotideHydrogen

bond

Thymine nucleotide

PhosphateSugar:

Deoxyribose PhosphateSugarThymine (T)Base:

Adenine (A)

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

(b)

(a)

(c) Computer-generated image of a DNA molecule


Ribonucleic Acid (RNA)

• Four bases:

• adenine (A), guanine (G), cytosine (C), and uracil (U)

• Single-stranded

PLAYPLAY Animation: DNA and RNA


Adenosine Triphosphate (ATP)

• Adenine-containing RNA nucleotide with two additional phosphate groups


Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP)

Adenosine monophosphate (AMP)

Adenosine

Adenine

Ribose

Phosphate groups

High-energy phosphatebonds can be hydrolyzed

to release energy.


Function of ATP

• Phosphorylation:

• The chemical energy contained in the high energy phosphate bonds can be used to perform cellular work


Solute

Membraneprotein

Relaxed smoothmuscle cell

Contracted smoothmuscle cell

+

+

+

Transport work

Mechanical work

Chemical work

(a)

(b)

(c)

Copyright © 2010 Pearson Education, Inc. BASIC CHEMISTRY CH. 2.

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