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PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College
C H A P T E R
Copyright © 2010 Pearson Education, Inc.
2 Chemistry Comes Alive: Part A
Copyright © 2010 Pearson Education, Inc.
Matter
• Anything that has mass and occupies space
• States of matter:
1. Solid—definite shape and volume
2. Liquid—definite volume, changeable shape
3. Gas—changeable shape and volume
Copyright © 2010 Pearson Education, Inc.
Energy
• Capacity to do work or put matter into motion
• Types of energy:
• Kinetic—energy in action
• Potential—stored (inactive) energy
PLAY Animation: Energy Concepts
Copyright © 2010 Pearson Education, Inc.
Forms of Energy
• Chemical energy—stored in bonds of chemical substances
• Electrical energy—results from movement of charged particles
• Mechanical energy—directly involved in moving matter
• Radiant or electromagnetic energy—exhibits wavelike properties (i.e., visible light, ultraviolet light, and X-rays)
Copyright © 2010 Pearson Education, Inc.
Energy Form Conversions
• Energy may be converted from one form to another
• Conversion is inefficient because some energy is “lost” as heat
Copyright © 2010 Pearson Education, Inc.
Composition of Matter
• Elements
• Cannot be broken down by ordinary chemical means
• Each has unique properties:
• Physical properties
• Are detectable with our senses, or are measurable
• Chemical properties
• How atoms interact (bond) with one another
Copyright © 2010 Pearson Education, Inc.
Composition of Matter
• Atoms
• Unique building blocks for each element
• Atomic symbol: one- or two-letter chemical shorthand for each element
Copyright © 2010 Pearson Education, Inc.
Major Elements of the Human Body
• Oxygen (O)
• Carbon (C)
• Hydrogen (H)
• Nitrogen (N)
About 96% of body mass
Copyright © 2010 Pearson Education, Inc.
Lesser Elements of the Human Body
• About 3.9% of body mass:
• Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), magnesium (Mg), iodine (I), and iron (Fe)
Copyright © 2010 Pearson Education, Inc.
Trace Elements of the Human Body
• < 0.01% of body mass:
• Part of enzymes, e.g., chromium (Cr), manganese (Mn), and zinc (Zn)
Copyright © 2010 Pearson Education, Inc.
Atomic Structure
• Determined by numbers of subatomic particles
• Nucleus consists of neutrons and protons
Copyright © 2010 Pearson Education, Inc.
Atomic Structure
• Neutrons
• No charge
• Mass = 1 atomic mass unit (amu)
• Protons
• Positive charge
• Mass = 1 amu
Copyright © 2010 Pearson Education, Inc.
Atomic Structure
• Electrons
• Orbit nucleus
• Equal in number to protons in atom
• Negative charge
• 1/2000 the mass of a proton (0 amu)
Copyright © 2010 Pearson Education, Inc.
Models of the Atom
• Orbital model: current model used by chemists
• Depicts probable regions of greatest electron density (an electron cloud)
• Useful for predicting chemical behavior of atoms
Copyright © 2010 Pearson Education, Inc.
Models of the Atom
• Planetary model—oversimplified, outdated model
• Incorrectly depicts fixed circular electron paths
• Useful for illustrations (as in the text)
Copyright © 2010 Pearson Education, Inc. Figure 2.1
(a) Planetary model (b) Orbital model
Helium atom
2 protons (p+)2 neutrons (n0)2 electrons (e–)
Helium atom
2 protons (p+)2 neutrons (n0)2 electrons (e–)
Nucleus Nucleus
Proton Neutron Electroncloud
Electron
Copyright © 2010 Pearson Education, Inc.
Identifying Elements
• Atoms of different elements contain different numbers of subatomic particles
• Compare hydrogen, helium and lithium (next slide)
Copyright © 2010 Pearson Education, Inc. Figure 2.2
ProtonNeutronElectron
Helium (He)(2p+; 2n0; 2e–)
Lithium (Li)(3p+; 4n0; 3e–)
Hydrogen (H)(1p+; 0n0; 1e–)
Copyright © 2010 Pearson Education, Inc.
Identifying Elements
• Atomic number = number of protons in nucleus
Copyright © 2010 Pearson Education, Inc.
Identifying Elements
• Mass number = mass of the protons and neutrons
• Mass numbers of atoms of an element are not all identical
• Isotopes are structural variations of elements that differ in the number of neutrons they contain
Copyright © 2010 Pearson Education, Inc.
Identifying Elements
• Atomic weight = average of mass numbers of all isotopes
Copyright © 2010 Pearson Education, Inc. Figure 2.3
ProtonNeutronElectron
Deuterium (2H)(1p+; 1n0; 1e–)
Tritium (3H)(1p+; 2n0; 1e–)
Hydrogen (1H)(1p+; 0n0; 1e–)
Copyright © 2010 Pearson Education, Inc.
Radioisotopes
• Spontaneous decay (radioactivity)
• Similar chemistry to stable isotopes
• Can be detected with scanners
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Radioisotopes
• Valuable tools for biological research and medicine
• Cause damage to living tissue:
• Useful against localized cancers
• Radon from uranium decay causes lung cancer
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Molecules and Compounds
• Most atoms combine chemically with other atoms to form molecules and compounds
• Molecule—two or more atoms bonded together (e.g., H2 or C6H12O6)
• Compound—two or more different kinds of atoms bonded together (e.g., C6H12O6)
Copyright © 2010 Pearson Education, Inc.
Mixtures
• Most matter exists as mixtures
• Two or more components physically intermixed
• Three types of mixtures
• Solutions
• Colloids
• Suspensions
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Solutions
• Homogeneous mixtures
• Usually transparent, e.g., atmospheric air or seawater
• Solvent
• Present in greatest amount, usually a liquid
• Solute(s)
• Present in smaller amounts
Copyright © 2010 Pearson Education, Inc.
Concentration of Solutions
• Expressed as• Percent, or parts per 100 parts
• Milligrams per deciliter (mg/dl)
• Molarity, or moles per liter (M)
• 1 mole = the atomic weight of an element or molecular weight (sum of atomic weights) of a compound in grams
• 1 mole of any substance contains 6.02 ×1023 molecules (Avogadro’s number)
Copyright © 2010 Pearson Education, Inc.
Colloids and Suspensions
• Colloids (emulsions)• Heterogeneous translucent mixtures, e.g.,
cytosol
• Large solute particles that do not settle out
• Undergo sol-gel transformations
• Suspensions:• Heterogeneous mixtures, e.g., blood
• Large visible solutes tend to settle out
Copyright © 2010 Pearson Education, Inc. Figure 2.4
Solution
Soluteparticles
Soluteparticles
Soluteparticles
Solute particles are verytiny, do not settle out or
scatter light.
ColloidSolute particles are larger
than in a solution and scatterlight; do not settle out.
SuspensionSolute particles are verylarge, settle out, and may
scatter light.
ExampleMineral water
ExampleGelatin
ExampleBlood
Copyright © 2010 Pearson Education, Inc.
Mixtures vs. Compounds
• Mixtures• No chemical bonding between components
• Can be separated physically, such as by straining or filtering
• Heterogeneous or homogeneous
• Compounds• Can be separated only by breaking bonds
• All are homogeneous
Copyright © 2010 Pearson Education, Inc.
Chemical Bonds
• Electrons occupy up to seven electron shells (energy levels) around nucleus
• Octet rule: Except for the first shell which is full with two electrons, atoms interact in a manner to have eight electrons in their outermost energy level (valence shell)
Copyright © 2010 Pearson Education, Inc.
Chemically Inert Elements
• Stable and unreactive
• Outermost energy level fully occupied or contains eight electrons
Copyright © 2010 Pearson Education, Inc. Figure 2.5a
Helium (He)(2p+; 2n0; 2e–)
Neon (Ne)(10p+; 10n0; 10e–)
2e 2e8e
(a) Chemically inert elements
Outermost energy level (valence shell) complete
Copyright © 2010 Pearson Education, Inc.
Chemically Reactive Elements
• Outermost energy level 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 2.5b
2e4e
2e8e
1e
(b) Chemically reactive elementsOutermost energy level (valence shell) incomplete
Hydrogen (H)(1p+; 0n0; 1e–)
Carbon (C)(6p+; 6n0; 6e–)
1e
Oxygen (O)(8p+; 8n0; 8e–) Sodium (Na)
(11p+; 12n0; 11e–)
2e6e
Copyright © 2010 Pearson Education, Inc.
Ionic Bonds
• Ions are formed by transfer of valence shell electrons between atoms
• Anions (– charge) have gained one or more electrons
• Cations (+ charge) have lost one or more electrons
• Attraction of opposite charges results in an ionic bond
Copyright © 2010 Pearson Education, Inc. Figure 2.6a-b
Sodium atom (Na)(11p+; 12n0; 11e–)
Chlorine atom (Cl)(17p+; 18n0; 17e–)
Sodium ion (Na+) Chloride ion (Cl–)
Sodium chloride (NaCl)
+ –
(a) Sodium gains stability by losing one electron, andchlorine becomes stable by gaining one electron.
(b) After electron transfer, the oppositelycharged ions formed attract each other.
Copyright © 2010 Pearson Education, Inc.
Formation of an Ionic Bond
• Ionic compounds form crystals instead of individual molecules
• NaCl (sodium chloride)
Copyright © 2010 Pearson Education, Inc. Figure 2.6c
CI–
Na+
(c) Large numbers of Na+ and Cl– ionsassociate to form salt (NaCl) crystals.
Copyright © 2010 Pearson Education, Inc.
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
Copyright © 2010 Pearson Education, Inc. Figure 2.7a
+
Hydrogenatoms
Carbonatom
Molecule ofmethane gas (CH4)
Structuralformulashows singlebonds.
(a) Formation of four single covalent bonds:carbon shares four electron pairs with fourhydrogen atoms.
or
Resulting moleculesReacting atoms
Copyright © 2010 Pearson Education, Inc. Figure 2.7b
or
Oxygenatom
Oxygenatom
Molecule ofoxygen gas (O2)
Structuralformulashowsdouble bond.(b) Formation of a double covalent bond: Two
oxygen atoms share two electron pairs.
Resulting moleculesReacting atoms
+
Copyright © 2010 Pearson Education, Inc. Figure 2.7c
+ or
Nitrogenatom
Nitrogenatom
Molecule ofnitrogen gas (N2)
Structuralformulashowstriple bond.(c) Formation of a triple covalent bond: Two
nitrogen atoms share three electron pairs.
Resulting moleculesReacting atoms
Copyright © 2010 Pearson Education, Inc.
Covalent Bonds
• Sharing of electrons may be equal or unequal
• Equal sharing produces electrically balanced nonpolar molecules
• CO2
Copyright © 2010 Pearson Education, Inc.
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
• Atoms with one or two valence shell electrons are electropositive, e.g., sodium
Copyright © 2010 Pearson Education, Inc.
Hydrogen Bonds
• Attractive force between electropositive hydrogen of one molecule and an electronegative atom of another molecule
• Common between dipoles such as water
• Also act as intramolecular bonds, holding a large molecule in a three-dimensional shape
PLAY Animation: Hydrogen Bonds
Copyright © 2010 Pearson Education, Inc.
(a) The slightly positive ends (δ+) of the watermolecules become aligned with the slightlynegative ends (δ–) of other water molecules.
δ+
δ–
δ–
δ–δ– δ–
δ+
δ+
δ+
δ+
δ+
Hydrogen bond(indicated bydotted line)
Figure 2.10a
Copyright © 2010 Pearson Education, Inc. Figure 2.10b
(b) A water strider can walk on a pond because of the highsurface tension of water, a result of the combinedstrength of its hydrogen bonds.
Copyright © 2010 Pearson Education, Inc.
Chemical Reactions
• Occur when chemical bonds are formed, rearranged, or broken
• Represented as chemical equations
• Chemical equations contain:
• Molecular formula for each reactant and product
• Relative amounts of reactants and products, which should balance
Copyright © 2010 Pearson Education, Inc.
Examples of Chemical Equations
H + H → H2 (hydrogen gas)
4H + C → CH4 (methane)
(reactants) (product)
Copyright © 2010 Pearson Education, Inc.
Patterns of Chemical Reactions
• Synthesis (combination) reactions
• Decomposition reactions
• Exchange reactions
Copyright © 2010 Pearson Education, Inc.
Synthesis Reactions
• A + B → AB
• Always involve bond formation
• Anabolic
Copyright © 2010 Pearson Education, Inc. Figure 2.11a
ExampleAmino acids are joined together toform a protein molecule.
(a) Synthesis reactionsSmaller particles are bonded
together to form larger,more complex molecules.
Amino acidmolecules
Proteinmolecule
Copyright © 2010 Pearson Education, Inc.
Decomposition Reactions
• AB → A + B
• Reverse synthesis reactions
• Involve breaking of bonds
• Catabolic
Copyright © 2010 Pearson Education, Inc. Figure 2.11b
ExampleGlycogen is broken down to releaseglucose units.
Bonds are broken in largermolecules, resulting in smaller,
less complex molecules.
(b) Decomposition reactions
Glucosemolecules
Glycogen
Copyright © 2010 Pearson Education, Inc.
Exchange Reactions
• AB + C → AC + B
• Also called displacement reactions
• Bonds are both made and broken
Copyright © 2010 Pearson Education, Inc. Figure 2.11c
ExampleATP transfers its terminal phosphategroup to glucose to form glucose-phosphate.
Bonds are both made and broken(also called displacement reactions).
(c) Exchange reactions
Glucose Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)Glucosephosphate
+
+
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Oxidation-Reduction (Redox) Reactions
• Decomposition reactions: Reactions in which fuel is broken down for energy
• Also called exchange reactions because electrons are exchanged or shared differently
• Electron donors lose electrons and are oxidized
• Electron acceptors receive electrons and become reduced
Copyright © 2010 Pearson Education, Inc.
Chemical Reactions
• All chemical reactions are either exergonic or endergonic
• Exergonic reactions—release energy
• Catabolic reactions
• Endergonic reactions—products contain more potential energy than did reactants
• Anabolic reactions
Copyright © 2010 Pearson Education, Inc.
Chemical Reactions
• All chemical reactions are theoretically reversible
• A + B → AB
• AB → A + B
• Chemical equilibrium occurs if neither a forward nor reverse reaction is dominant
• Many biological reactions are essentially irreversible due to
• Energy requirements
• Removal of products
Copyright © 2010 Pearson Education, Inc.
Rate of Chemical Reactions
• Rate of reaction is influenced by:
• ↑ temperature → ↑ rate
• ↓ particle size → ↑ rate
• ↑ concentration of reactant → ↑ rate
• Catalysts: ↑ rate without being chemically changed
• Enzymes are biological catalysts
PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College
C H A P T E R
Copyright © 2010 Pearson Education, Inc.
2 Chemistry Comes Alive: Part B
Copyright © 2010 Pearson Education, Inc.
Classes of Compounds
• Inorganic compounds
• Water, salts, and many acids and bases
• Do not contain carbon
• Organic compounds
• Carbohydrates, fats, proteins, and nucleic acids
• Contain carbon, usually large, and are covalently bonded
Copyright © 2010 Pearson Education, Inc.
Water
• 60%–80% of the volume of living cells
• Most important inorganic compound in living organisms because of its properties
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Properties of Water
• High heat capacity
• Absorbs and releases heat with little temperature change
• Prevents sudden changes in temperature
• High heat of vaporization
• Evaporation requires large amounts of heat
• Useful cooling mechanism
Copyright © 2010 Pearson Education, Inc.
Properties of Water
• Polar solvent properties
• Dissolves and dissociates ionic substances
• Forms hydration layers around large charged molecules, e.g., proteins (colloid formation)
• Body’s major transport medium
Copyright © 2010 Pearson Education, Inc. Figure 2.12
Water molecule
Ions in solutionSalt crystal
δ–
δ+
δ+
Copyright © 2010 Pearson Education, Inc.
Properties of Water
• Reactivity
• A necessary part of hydrolysis and dehydration synthesis reactions
• Cushioning
• Protects certain organs from physical trauma, e.g., cerebrospinal fluid
Copyright © 2010 Pearson Education, Inc.
Salts
• Ionic compounds that dissociate in water
• Contain cations other than H+ and anions other than OH–
• Ions (electrolytes) conduct electrical currents in solution
• Ions play specialized roles in body functions (e.g., sodium, potassium, calcium, and iron)
Copyright © 2010 Pearson Education, Inc.
Acids and Bases
• Both are electrolytes
• Acids are proton (hydrogen ion) donors (release H+ in solution)
• HCl → H+ + Cl–
Copyright © 2010 Pearson Education, Inc.
Acids and Bases
• Bases are proton acceptors (take up H+ from solution)
• NaOH → Na+ + OH–
• OH– accepts an available proton (H+)
• OH– + H+ → H2O
• Bicarbonate ion (HCO3–) and ammonia (NH3)
are important bases in the body
Copyright © 2010 Pearson Education, Inc.
Acid-Base Concentration
• Acid solutions contain [H+]
• As [H+] increases, acidity increases
• Alkaline solutions contain bases (e.g., OH–)
• As [H+] decreases (or as [OH–] increases), alkalinity increases
Copyright © 2010 Pearson Education, Inc.
pH: Acid-Base Concentration
• pH = the negative logarithm of [H+] in moles per liter
• Neutral solutions:
• Pure water is pH neutral (contains equal numbers of H+ and OH–)
• pH of pure water = pH 7: [H+] = 10 –7 M
• All neutral solutions are pH 7
Copyright © 2010 Pearson Education, Inc.
pH: Acid-Base Concentration
• Acidic solutions • ↑ [H+], ↓ pH
• Acidic pH: 0–6.99
• pH scale is logarithmic: a pH 5 solution has 10 times more H+ than a pH 6 solution
• Alkaline solutions • ↓ [H+], ↑ pH
• Alkaline (basic) pH: 7.01–14
Copyright © 2010 Pearson Education, Inc. Figure 2.13
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
Copyright © 2010 Pearson Education, Inc.
Acid-Base Homeostasis
• pH change interferes with cell function and may damage living tissue
• Slight change in pH can be fatal
• pH is regulated by kidneys, lungs, and buffers
Copyright © 2010 Pearson Education, Inc.
Buffers
• Mixture of compounds that resist pH changes
• Convert strong (completely dissociated) acids or bases into weak (slightly dissociated) ones
• Carbonic acid-bicarbonate system
Copyright © 2010 Pearson Education, Inc.
Organic Compounds
• Contain carbon (except CO2 and CO, which are inorganic)
• Unique to living systems
• Include carbohydrates, lipids, proteins, and nucleic acids
Copyright © 2010 Pearson Education, Inc.
Organic Compounds
• Many are polymers—chains of similar units (monomers or building blocks)
• Synthesized by dehydration synthesis
• Broken down by hydrolysis reactions
Copyright © 2010 Pearson Education, Inc. Figure 2.14
+
Glucose Fructose
Water isreleased
Monomers linked by covalent bond
Monomers linked by covalent bond
Water isconsumed
Sucrose
(a) Dehydration synthesis
Monomers are joined by removal of OH from one monomerand removal of H from the other at the site of bond formation.
+
(b) Hydrolysis
Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other.
(c) Example reactions
Dehydration synthesis of sucrose and its breakdown by hydrolysis
Monomer 1 Monomer 2
Monomer 1 Monomer 2
+
Copyright © 2010 Pearson Education, Inc.
Carbohydrates
• Sugars and starches
• Contain C, H, and O [(CH20)n]
• Three classes
• Monosaccharides
• Disaccharides
• Polysaccharides
Copyright © 2010 Pearson Education, Inc.
Carbohydrates
• Functions
• Major source of cellular fuel (e.g., glucose)
• Structural molecules (e.g., ribose sugar in RNA)
Copyright © 2010 Pearson Education, Inc.
Monosaccharides
• Simple sugars containing three to seven C atoms
• (CH20)n
Copyright © 2010 Pearson Education, Inc. Figure 2.15a
ExampleHexose sugars (the hexoses shown
here are isomers)
ExamplePentose sugars
Glucose Fructose Galactose Deoxyribose Ribose
(a) MonosaccharidesMonomers of carbohydrates
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Disaccharides
• Double sugars
• Too large to pass through cell membranes
Copyright © 2010 Pearson Education, Inc. Figure 2.15b
PLAY Animation: Disaccharides
ExampleSucrose, maltose, and lactose
(these disaccharides are isomers)
Glucose Fructose Glucose Glucose GlucoseSucrose Maltose Lactose
Galactose
(b) DisaccharidesConsist of two linked monosaccharides
Copyright © 2010 Pearson Education, Inc.
Polysaccharides
• Polymers of simple sugars, e.g., starch and glycogen
• Not very soluble
Copyright © 2010 Pearson Education, Inc. Figure 2.15c
PLAY 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
Copyright © 2010 Pearson Education, Inc.
Lipids
• Contain C, H, O (less than in carbohydrates), and sometimes P
• Insoluble in water
• Main types:• Neutral fats or triglycerides
• Phospholipids
• Steroids
• EicosanoidsPLAY Animation: Fats
Copyright © 2010 Pearson Education, Inc.
Triglycerides
• Neutral fats—solid fats and liquid oils
• Composed of three fatty acids bonded to a glycerol molecule
• Main functions
• Energy storage
• Insulation
• Protection
Copyright © 2010 Pearson Education, Inc. Figure 2.16a
Glycerol
+
3 fatty acid chains Triglyceride,or neutral fat
3 watermolecules
(a) Triglyceride formationThree fatty acid chains are bound to glycerol by
dehydration synthesis
Copyright © 2010 Pearson Education, Inc.
Saturation of Fatty Acids
• Saturated fatty acids• Single bonds between C atoms; maximum
number of H
• Solid animal fats, e.g., butter
• Unsaturated fatty acids• One or more double bonds between C atoms
• Reduced number of H atoms
• Plant oils, e.g., olive oil
Copyright © 2010 Pearson Education, Inc.
Phospholipids
• Modified triglycerides:
• Glycerol + two fatty acids and a phosphorus (P)-containing group
• “Head” and “tail” regions have different properties
• Important in cell membrane structure
Copyright © 2010 Pearson Education, Inc. Figure 2.16b
Phosphorus-containing
group (polar“head”)
ExamplePhosphatidylcholine
Glycerolbackbone
2 fatty acid chains(nonpolar “tail”)
Polar“head”
Nonpolar“tail”
(schematicphospholipid)
(b) “Typical” structure of a phospholipid moleculeTwo fatty acid chains and a phosphorus-containing group are
attached to the glycerol backbone.
Copyright © 2010 Pearson Education, Inc.
Steroids
• Steroids—interlocking four-ring structure
• Cholesterol, vitamin D, steroid hormones, and bile salts
Copyright © 2010 Pearson Education, Inc. Figure 2.16c
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.
Copyright © 2010 Pearson Education, Inc.
Eicosanoids
• Many different ones
• Derived from a fatty acid (arachidonic acid) in cell membranes
• Prostaglandins
Copyright © 2010 Pearson Education, Inc.
Other Lipids in the Body
• Other fat-soluble vitamins
• Vitamins A, E, and K
• Lipoproteins
• Transport fats in the blood
Copyright © 2010 Pearson Education, Inc.
Proteins
• Polymers of amino acids (20 types)
• Joined by peptide bonds
• Contain C, H, O, N, and sometimes S and P
Copyright © 2010 Pearson Education, Inc. Figure 2.17
(a) Generalizedstructure of allamino acids.
(b) Glycineis 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 likelyto participate in
intramolecular bonding.
Aminegroup
Acidgroup
Copyright © 2010 Pearson Education, Inc. Figure 2.18
Amino acid Amino acid Dipeptide
Dehydration synthesis:The acid group of one
amino acid is bonded to the amine group of the
next, with loss of a water molecule.
Hydrolysis: Peptide bonds linking amino acids together are
broken when water is added to the bond.
+
Peptidebond
Copyright © 2010 Pearson Education, Inc.
Structural Levels of Proteins
PLAY Animation: Introduction to Protein Structure
Copyright © 2010 Pearson Education, Inc. Figure 2.19a
(a) Primary structure:The sequence of amino acids forms the polypeptide chain.
Amino acid Amino acid Amino acid Amino acid Amino acid
PLAY Animation: Primary Structure
Copyright © 2010 Pearson Education, Inc. Figure 2.19b
α-Helix: The primary chain is coiledto form a spiral structure, which is
stabilized by hydrogen bonds.
β-Sheet: The primary chain “zig-zags” backand forth forming a “pleated” sheet. Adjacentstrands are held together by hydrogen bonds.
(b) Secondary structure:The primary chain forms spirals (α-helices) and sheets (β-sheets).
PLAY Animation: Secondary Structure
Copyright © 2010 Pearson Education, Inc. Figure 2.19c
Tertiary structure of prealbumin(transthyretin), a protein that
transports the thyroid hormonethyroxine in serum and cerebro-
spinal fluid.
(c) Tertiary structure:Superimposed on secondary structure. α-Helices and/or β-sheets are
folded up to form a compact globular molecule held together byintramolecular bonds.
PLAY Animation: Tertiary Structure
Copyright © 2010 Pearson Education, Inc. Figure 2.19d
Quaternary structure ofa functional prealbuminmolecule. Two identical
prealbumin subunitsjoin head to tail to form
the dimer.
(d) Quaternary structure:Two or more polypeptide chains, each with its own tertiary structure,
combine to form a functional protein.
PLAY Animation: Quaternary Structure
Copyright © 2010 Pearson Education, Inc.
Fibrous and Globular Proteins
• Fibrous (structural) proteins
• Strandlike, water insoluble, and stable
• Examples: keratin, elastin, collagen, and certain contractile fibers
Copyright © 2010 Pearson Education, Inc.
Fibrous and Globular Proteins
• Globular (functional) proteins
• Compact, spherical, water-soluble and sensitive to environmental changes
• Specific functional regions (active sites)
• Examples: antibodies, hormones, molecular chaperones, and enzymes
Copyright © 2010 Pearson Education, Inc.
Protein Denaturation
• Shape change and disruption of active sites due to environmental changes (e.g., decreased pH or increased temperature)
• Reversible in most cases, if normal conditions are restored
• Irreversible if extreme changes damage the structure beyond repair (e.g., cooking an egg)
Copyright © 2010 Pearson Education, Inc.
Molecular Chaperones (Chaperonins)
• Ensure quick and accurate folding and association of proteins
• Assist translocation of proteins and ions across membranes
• Promote breakdown of damaged or denatured proteins
• Help trigger the immune response
• Produced in response to stressful stimuli, e.g., O2 deprivation
Copyright © 2010 Pearson Education, Inc.
Enzymes
• Biological catalysts
• Lower the activation energy, increase the speed of a reaction (millions of reactions per minute!)
Copyright © 2010 Pearson Education, Inc. Figure 2.20
Activationenergy required
Less activationenergy required
WITHOUT ENZYME WITH ENZYME
Reactants
Product Product
Reactants
PLAY Animation: Enzymes
Copyright © 2010 Pearson Education, Inc.
Characteristics of Enzymes
• Often named for the reaction they catalyze; usually end in -ase (e.g., hydrolases, oxidases)
• Some functional enzymes (holoenzymes) consist of:
• Apoenzyme (protein)
• Cofactor (metal ion) or coenzyme (a vitamin)
Copyright © 2010 Pearson Education, Inc. Figure 2.21
Substrates (S)e.g., amino acids
Enzyme (E)
Enzyme-substratecomplex (E-S)
Enzyme (E)
Product (P)e.g., dipeptide
Energy isabsorbed;
bond isformed.
Water isreleased. Peptide
bond
Substrates bindat active site.
Enzyme changesshape to holdsubstrates in
proper position.
Internalrearrangements
leading tocatalysis occur.
Product isreleased. Enzymereturns to original
shape and isavailable to catalyzeanother reaction.
Active site
+ H2O
1 23
Copyright © 2010 Pearson Education, Inc. Figure 2.21, step 1
Substrates (S)e.g., amino acids
Enzyme (E)
Enzyme-substratecomplex (E-S)
Substrates bindat active site.
Enzyme changesshape to holdsubstrates in
proper position.
Active site
+
1
Copyright © 2010 Pearson Education, Inc. Figure 2.21, step 2
Substrates (S)e.g., amino acids
Enzyme (E)
Enzyme-substratecomplex (E-S)
Energy isabsorbed;
bond isformed.
Water isreleased.
Substrates bindat active site.
Enzyme changesshape to holdsubstrates in
proper position.
Internalrearrangements
leading tocatalysis occur.
Active site
+ H2O
1 2
Copyright © 2010 Pearson Education, Inc. Figure 2.21, step 3
Substrates (S)e.g., amino acids
Enzyme (E)
Enzyme-substratecomplex (E-S)
Enzyme (E)
Product (P)e.g., dipeptide
Energy isabsorbed;
bond isformed.
Water isreleased. Peptide
bond
Substrates bindat active site.
Enzyme changesshape to holdsubstrates in
proper position.
Internalrearrangements
leading tocatalysis occur.
Product isreleased. Enzymereturns to original
shape and isavailable to catalyzeanother reaction.
Active site
+ H2O
1 23
Copyright © 2010 Pearson Education, Inc.
Nucleic Acids
• DNA and RNA
• Largest molecules in the body
• Contain C, O, H, N, and P
• Building block = nucleotide, composed of N-containing base, a pentose sugar, and a phosphate group
Copyright © 2010 Pearson Education, Inc.
Deoxyribonucleic Acid (DNA)
• Four bases:
• adenine (A), guanine (G), cytosine (C), and thymine (T)
• Double-stranded helical molecule in the cell nucleus
• Provides instructions for protein synthesis
• Replicates before cell division, ensuring genetic continuity
Copyright © 2010 Pearson Education, Inc. Figure 2.22
Deoxyribosesugar
PhosphateSugar-phosphate
backbone
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
Copyright © 2010 Pearson Education, Inc.
Ribonucleic Acid (RNA)
• Four bases: • adenine (A), guanine (G), cytosine (C), and
uracil (U)
• Single-stranded molecule mostly active outside the nucleus
• Three varieties of RNA carry out the DNA orders for protein synthesis• messenger RNA, transfer RNA, and ribosomal
RNAPLAY Animation: DNA and RNA
Copyright © 2010 Pearson Education, Inc.
Adenosine Triphosphate (ATP)
• Adenine-containing RNA nucleotide with two additional phosphate groups
Copyright © 2010 Pearson Education, Inc. Figure 2.23
Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)
Adenosine monophosphate (AMP)
Adenosine
Adenine
Ribose
Phosphate groups
High-energy phosphatebonds can be hydrolyzed
to release energy.
Copyright © 2010 Pearson Education, Inc.
Function of ATP
• Phosphorylation:
• Terminal phosphates are enzymatically transferred to and energize other molecules
• Such “primed” molecules perform cellular work (life processes) using the phosphate bond energy
Copyright © 2010 Pearson Education, Inc. Figure 2.24
Solute
Membraneprotein
Relaxed smoothmuscle cell
Contracted smoothmuscle cell
+
+
+
Transport work: ATP phosphorylates transportproteins, activating them to transport solutes(ions, for example) across cell membranes.
Mechanical work: ATP phosphorylates contractile proteins in muscle cells so the
cells can shorten.
Chemical work: ATP phosphorylates key reactants, providing energy to drive
energy-absorbing chemical reactions.
(a)
(b)
(c)