powerlecture: chapter 2 molecules of life. learning objectives understand how protons, electrons,...

PowerLecture:PowerLecture:Chapter 2Chapter 2

Molecules of LifeMolecules of Life

Learning ObjectivesLearning Objectives

Understand how protons, electrons, and Understand how protons, electrons, and neutrons are arranged into atoms and ions.neutrons are arranged into atoms and ions.

Explain how the distribution of electrons in Explain how the distribution of electrons in an atom or ion determines the number and an atom or ion determines the number and kinds of chemical bonds that can be kinds of chemical bonds that can be formed.formed.

Know the various types of chemical bonds, Know the various types of chemical bonds, the circumstances under which each forms, the circumstances under which each forms, and the relative strengths of each type.and the relative strengths of each type.

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

Understand the essential chemistry of water Understand the essential chemistry of water and of some common substances dissolved and of some common substances dissolved in it.in it.

Understand how small organic molecules can Understand how small organic molecules can be assembled into large macromolecules by be assembled into large macromolecules by condensation. Understand how large condensation. Understand how large macromolecules can be broken apart into macromolecules can be broken apart into their basic sub units by hydrolysis. their basic sub units by hydrolysis.


Memorize the functional groups presented Memorize the functional groups presented and know the properties they confer when and know the properties they confer when attached to other molecules.attached to other molecules.

Know the general structure of a Know the general structure of a monosaccharide with six carbon atoms, monosaccharide with six carbon atoms, glycerol, a fatty acid, an amino acid, and a glycerol, a fatty acid, an amino acid, and a nucleotide. nucleotide.

Know the macromolecules into which these Know the macromolecules into which these essential building blocks can be assembled essential building blocks can be assembled by condensation. by condensation.


Know where these carbon compounds tend Know where these carbon compounds tend to be located in cells or organelles and the to be located in cells or organelles and the activities in which they participate. activities in which they participate.

Impacts/IssuesImpacts/Issues

It’s ElementalIt’s Elemental

It’s ElementalIt’s Elemental

Life depends on chemical reactions.Life depends on chemical reactions. An An elementelement is a fundamental form of matter is a fundamental form of matter

that has mass and takes up space.that has mass and takes up space. Organisms consist mostly of carbon, oxygen, Organisms consist mostly of carbon, oxygen,

hydrogen, and nitrogen.hydrogen, and nitrogen. Trace elementsTrace elements are needed only in small are needed only in small

quantities.quantities.

Elements in the Human Body Elements in the Human Body vs. Earth’s Crustvs. Earth’s Crust

Human Body

Oxygen 65%Carbon 18Hydrogen 10Nitrogen 3Calcium 2Phosphorus 1.1Potassium 0.35Sulfur 0.25Sodium 0.15Chlorine 0.15Magnesium 0.05Iron 0.004

Oxygen 46.6%Silicon 27.7Aluminum 8.1Iron 5.0Calcium 3.6Sodium 2.8Potassium 2.1Magnesium 1.5

Earth’s Crust

How Would You Vote?How Would You Vote?To conduct an instant in-class survey using a classroom response To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main system, access “JoinIn Clicker Content” from the PowerLecture main menu. menu.

Many communities add fluoride to drinking Many communities add fluoride to drinking water supplies. Do you want it in yours?water supplies. Do you want it in yours? a. Yes, screening lets people make informed a. Yes, screening lets people make informed

reproductive decisions about the risk to their reproductive decisions about the risk to their children.children.

b. No, therapies and medications b. No, therapies and medications for CF continue to improve; a for CF continue to improve; a person with CF can live a full life. person with CF can live a full life.

Section 1Section 1

Atoms, the Starting Point Atoms, the Starting Point

Atoms, the Starting PointAtoms, the Starting Point

Atoms are composed of smaller particles. Atoms are composed of smaller particles. An An atomatom is the smallest unit of matter that is is the smallest unit of matter that is

unique to a particular element.unique to a particular element. Atoms are composed of three particles:Atoms are composed of three particles:

• ProtonsProtons (p (p++) are part of the atomic nucleus and have ) are part of the atomic nucleus and have a positive charge. Their quantity is called the a positive charge. Their quantity is called the atomic atomic numbernumber ( (unique for each elementunique for each element).).

• ElectronsElectrons (e (e--) have a negative charge. Their quantity ) have a negative charge. Their quantity is equal to that of the protons. They move around the is equal to that of the protons. They move around the nucleus.nucleus.

• NeutronsNeutrons are also a part of the nucleus; they are are also a part of the nucleus; they are neutral. Protons plus neutrons = atomic mass neutral. Protons plus neutrons = atomic mass number.number.

Fig. 2.1, p. 16

Atoms, the Starting PointAtoms, the Starting Point

Electron activity is the basis for organization of Electron activity is the basis for organization of materials and the flow of energy in living things.materials and the flow of energy in living things.

Isotopes are varying forms of atoms.Isotopes are varying forms of atoms. Atoms with the same number of protons (e.g., Atoms with the same number of protons (e.g.,

carbon has six) but a different number of carbon has six) but a different number of neutrons (carbon can have six, seven, or eight) neutrons (carbon can have six, seven, or eight) are called are called isotopesisotopes (12C, 13C, 14C). (12C, 13C, 14C).

Some radioactive isotopes are unstable and Some radioactive isotopes are unstable and tend to decay into more stable atoms.tend to decay into more stable atoms.

• They can be used to date rocks and fossils.They can be used to date rocks and fossils.• Some can be used as tracers to follow the path of an Some can be used as tracers to follow the path of an

atom in a series of reactions or to diagnose disease.atom in a series of reactions or to diagnose disease.

Section 2Section 2

Medical Uses for Medical Uses for RadioisotopesRadioisotopes

Medical Uses for RadioisotopesMedical Uses for Radioisotopes

Radioisotopes have many important uses in Radioisotopes have many important uses in medicine.medicine.

TracersTracers are substances containing are substances containing radioisotopes that can be injected into patients radioisotopes that can be injected into patients to study tissues or tissue function.to study tissues or tissue function.

Radiation therapyRadiation therapy uses the radiation from uses the radiation from isotopes to destroy or impair the activity of cells isotopes to destroy or impair the activity of cells that do not work properly, such as cancer cells. that do not work properly, such as cancer cells.

For safety, clinicians usually use isotopes For safety, clinicians usually use isotopes with short with short half-liveshalf-lives (the time it takes the (the time it takes the isotope to decay to a more stable isotope). isotope to decay to a more stable isotope).

Example of Radioactive IodineExample of Radioactive Iodine

Figure 2.2Figure 2.2

Section 3Section 3

What Is a Chemical What Is a Chemical Bond?Bond?

What Is a Chemical Bond?What Is a Chemical Bond?

Interacting atoms: Electrons rule!Interacting atoms: Electrons rule! In chemical reactions, an atom can share In chemical reactions, an atom can share

electrons with another atom, accept extra electrons with another atom, accept extra electrons, or donate electrons.electrons, or donate electrons.

Electrons are attracted to protons, but are Electrons are attracted to protons, but are repelled by other electrons.repelled by other electrons.

Orbitals can be thought of as occupying shells Orbitals can be thought of as occupying shells around the nucleus, representing different around the nucleus, representing different energy levels.energy levels.

Electron ArrangementsElectron Arrangements



Chemical bonds join atoms.Chemical bonds join atoms. A A chemical bondchemical bond is a union between the is a union between the

electron structures of atoms.electron structures of atoms. Having a filled outer shell is the most stable Having a filled outer shell is the most stable

state for atoms.state for atoms.• The shell closest to the nucleus has one orbital The shell closest to the nucleus has one orbital

holding a maximum of two electrons.holding a maximum of two electrons.• The next shell can have four orbitals with two The next shell can have four orbitals with two

electrons each for a total of eight electrons.electrons each for a total of eight electrons.• Atoms with “unfilled” orbitals in their outermost shell Atoms with “unfilled” orbitals in their outermost shell

tend to be reactive with other atoms—they want to tend to be reactive with other atoms—they want to “fill” their outer shell with the maximal eight electrons “fill” their outer shell with the maximal eight electrons allowed.allowed.

Shell ModelShell Model



Atoms can combine into molecules.Atoms can combine into molecules. MoleculesMolecules may contain more than one atom of may contain more than one atom of

the same element; Nthe same element; N22 for example. for example. CompoundsCompounds consist of two or more elements consist of two or more elements

in strict proportions.in strict proportions. A A mixturemixture is an intermingling of molecules in is an intermingling of molecules in

varying proportions.varying proportions.

Section 4Section 4

Important Bonds in Important Bonds in Biological MoleculesBiological Molecules

Important Bonds in Biological Molecules Important Bonds in Biological Molecules

An ionic bond joins atoms that have An ionic bond joins atoms that have opposite charges.opposite charges.

When an atom loses or gains one or more When an atom loses or gains one or more electrons, it becomes positively or negatively electrons, it becomes positively or negatively charged—an ion.charged—an ion.

In an In an ionic bondionic bond, (+) and (–) ions are linked by , (+) and (–) ions are linked by mutual attraction of opposite charges, for mutual attraction of opposite charges, for example, NaCl.example, NaCl.

Example of an Ionic BondExample of an Ionic Bond

Figure 2.7aFigure 2.7a


Electrons are shared in a covalent bond.Electrons are shared in a covalent bond. A A covalent bondcovalent bond holds together two atoms that holds together two atoms that

share one or more pairs of electrons.share one or more pairs of electrons. In a In a nonpolarnonpolar covalent bond, atoms share covalent bond, atoms share

electrons equally; H2 is an example.electrons equally; H2 is an example. In a In a polarpolar covalent bond, because atoms share covalent bond, because atoms share

the electron unequally, there is a slight differ the electron unequally, there is a slight differ ence in charge (electronegativity) between the ence in charge (electronegativity) between the two atoms participating in the bond; water is an two atoms participating in the bond; water is an example.example.

Examples of Covalent BondsExamples of Covalent Bonds

Figure 2.7bFigure 2.7b


A hydrogen bond is a weak bond between A hydrogen bond is a weak bond between polar molecules.polar molecules.

In a In a hydrogen bondhydrogen bond, a slightly negative atom , a slightly negative atom of a polar molecule interacts weakly with a of a polar molecule interacts weakly with a hydro gen atom already taking part in a polar hydro gen atom already taking part in a polar covalent bond.covalent bond.

These bonds impart structure to liquid water These bonds impart structure to liquid water and stabilize nucleic acids and other large and stabilize nucleic acids and other large molecules.molecules.

Example of a Hydrogen BondExample of a Hydrogen Bond

Figure 2.7cFigure 2.7c

Section 5Section 5

AntioxidantsAntioxidants


Free radicalsFree radicals are formed by the process of are formed by the process of oxidation.oxidation.

Oxidation is the process whereby an atom or Oxidation is the process whereby an atom or molecule loses one or more electrons.molecule loses one or more electrons.

Oxidation can produce free radicals that may Oxidation can produce free radicals that may “steal” electrons from other molecules.“steal” electrons from other molecules.

In large numbers, free radicals can damage In large numbers, free radicals can damage other molecules in a cell, such as DNA.other molecules in a cell, such as DNA.


AntioxidantsAntioxidants are chemicals that can give up are chemicals that can give up an electron to a free radical before it does an electron to a free radical before it does damage to a DNA molecule. damage to a DNA molecule.


Section 6Section 6

Life Depends on WaterLife Depends on Water

Figure 2.9cFigure 2.9c


Hydrogen bonding makes water liquid.Hydrogen bonding makes water liquid. Water is a polar molecule Water is a polar molecule

because of a slightly negative because of a slightly negative

charge at the oxygen end and charge at the oxygen end and

a slightly positive charge at a slightly positive charge at

the hydrogen end. the hydrogen end. Water molecules can form Water molecules can form

hydrogen bonds with each hydrogen bonds with each

other.other.

Figure 2.9a-bFigure 2.9a-b


Polar substances are Polar substances are

hydrophilichydrophilic (water loving); (water loving);

nonpolar ones are nonpolar ones are

hydrophobichydrophobic (water (water

dreading) and are repelled dreading) and are repelled

by water.by water.


Water can absorb and hold heat.Water can absorb and hold heat. Water tends to stabilize temperature because it Water tends to stabilize temperature because it

has a high has a high heatheat capacitycapacity—the ability to absorb —the ability to absorb considerable heat before its temperature considerable heat before its temperature changes. changes.

This is an important property in evaporative and This is an important property in evaporative and freezing processes.freezing processes.


Water is a biological solvent.Water is a biological solvent. The solvent properties of water The solvent properties of water

are greatest with respect to are greatest with respect to

polar molecules because polar molecules because

““spheres of hydration” are spheres of hydration” are

formed around the solute formed around the solute

(dissolved) molecules.(dissolved) molecules. For example, the NaFor example, the Na++ of salt of salt

attracts the negative end of water molecules, attracts the negative end of water molecules, while the Clwhile the Cl- - attracts the positive end.attracts the positive end.


Section 7Section 7

Acids, Bases, and Acids, Bases, and Buffers: Body Fluids Buffers: Body Fluids

in Fluxin Flux

Acids, Bases, and BuffersAcids, Bases, and Buffers

The pH scale indicates the concentration of The pH scale indicates the concentration of hydrogen ions.hydrogen ions.

pH is a measure of the HpH is a measure of the H++ concentration in a concentration in a solution; the greater the Hsolution; the greater the H++ the lower the value the lower the value on the pH scale.on the pH scale.

The scale extends from 0 (acidic) to 7 (neutral) The scale extends from 0 (acidic) to 7 (neutral) to 14 (basic).to 14 (basic).


The pH ScaleThe pH Scale


Acids give up HAcids give up H++ and bases accept H and bases accept H++.. A substance that releases hydrogen ions (HA substance that releases hydrogen ions (H++) in ) in

solution is an solution is an acidacid—for example, HCl.—for example, HCl. Substances that release ions such as (OHSubstances that release ions such as (OH --) that ) that

can combine with hydrogen ions are called can combine with hydrogen ions are called basesbases (example: baking soda). (example: baking soda).

High concentrations of High concentrations of strong acids or bases strong acids or bases can disrupt living can disrupt living systems both internal systems both internal and external to the body.and external to the body.



Buffers protect against shifts in pH. Buffers protect against shifts in pH. Buffer molecules combine with, or release, HBuffer molecules combine with, or release, H++

to prevent drastic changes in pH.to prevent drastic changes in pH. Bicarbonate is one of the body’s major buffers.Bicarbonate is one of the body’s major buffers.


A salt releases other kinds of ions.A salt releases other kinds of ions. A salt is an ionic compound formed when an A salt is an ionic compound formed when an

acid reacts with a base; example: HCl + NaOH acid reacts with a base; example: HCl + NaOH NaCl + H NaCl + H22O.O.

Many salts dissolve into ions that have key Many salts dissolve into ions that have key functions in the body; for example, Na, K, and functions in the body; for example, Na, K, and Ca in nerve and muscles.Ca in nerve and muscles.

Section 8Section 8



Biological molecules contain carbon.Biological molecules contain carbon. Only living cells synthesize the molecules Only living cells synthesize the molecules

characteristic of life—carbohydrates, lipids, characteristic of life—carbohydrates, lipids, proteins, and nucleic acids.proteins, and nucleic acids.

These molecules are These molecules are organic compoundsorganic compounds, , meaning they consist of atoms of carbon and meaning they consist of atoms of carbon and one or more other elements, held together by one or more other elements, held together by covalent bonds.covalent bonds.


Carbon’s key feature: versatile bonding.Carbon’s key feature: versatile bonding. Living organisms are mostly oxygen, hydrogen, Living organisms are mostly oxygen, hydrogen,

and carbon.and carbon. Much of the hydrogen and oxygen are linked as Much of the hydrogen and oxygen are linked as

water.water. Carbon can form four covalent bonds with other Carbon can form four covalent bonds with other

atoms to form organic molecules of several atoms to form organic molecules of several configurations.configurations.


Functional groups affect the chemical Functional groups affect the chemical behavior of organic compounds.behavior of organic compounds.

By definition a hydrocarbon has only hydrogen By definition a hydrocarbon has only hydrogen atoms attached to a carbon backbone.atoms attached to a carbon backbone.

FunctionalFunctional groupsgroups—atoms or groups of atoms —atoms or groups of atoms covalently bonded to a carbon backbone—covalently bonded to a carbon backbone—convey distinct properties, such as solubility, to convey distinct properties, such as solubility, to the complete molecule.the complete molecule.

Examples of Examples of Functional GroupsFunctional Groups



Cells have chemical tools to assemble and Cells have chemical tools to assemble and break apart biological molecules.break apart biological molecules.

EnzymesEnzymes speed up specific metabolic speed up specific metabolic reactions.reactions.

In In condensation reactionscondensation reactions, one molecule is , one molecule is stripped of its Hstripped of its H++; another is stripped of its OH; another is stripped of its OH--..

• The two molecule fragments join to form a new The two molecule fragments join to form a new compound; the Hcompound; the H++ and OH and OH-- form water (dehydration form water (dehydration synthesis).synthesis).

• Cells use series of condensation reactions to build Cells use series of condensation reactions to build polymers out of smaller monomers.polymers out of smaller monomers.

Examples of Condensation ReactionsExamples of Condensation Reactions



In In hydrolysis reactionshydrolysis reactions, the reverse happens: , the reverse happens: one molecule is split by the addition of Hone molecule is split by the addition of H++ and and OHOH-- (from water) to yield the individual (from water) to yield the individual components. components.

Figure 2.14bFigure 2.14b

Section 9Section 9

Carbohydrates: Plentiful Carbohydrates: Plentiful and Variedand Varied

Carbohydrates: Plentiful and VariedCarbohydrates: Plentiful and Varied

A A carbohydratecarbohydrate can be a simple sugar or a can be a simple sugar or a larger molecule composed of sugar units.larger molecule composed of sugar units.

Carbohydrates are the most abundant Carbohydrates are the most abundant biological molecules.biological molecules.

Carbohydrates serve as energy sources or Carbohydrates serve as energy sources or have structural roles.have structural roles.


Simple sugars—the simplest Simple sugars—the simplest carbohydrates.carbohydrates.

A A monosaccharidemonosaccharide—one sugar unit—is the —one sugar unit—is the simplest carbohydrate.simplest carbohydrate.

Sugars are soluble in water and may be sweet-Sugars are soluble in water and may be sweet-tasting.tasting.

Ribose and deoxyribose (five-carbon Ribose and deoxyribose (five-carbon backbones) are building blocks for nucleic backbones) are building blocks for nucleic acids.acids.

Glucose (six-carbon backbone) is a primary Glucose (six-carbon backbone) is a primary energy source and precursor of many organic energy source and precursor of many organic molecules.molecules.


Oligosaccharides are short chains of sugar Oligosaccharides are short chains of sugar units.units.

An An oligosaccharideoligosaccharide is a short chain resulting is a short chain resulting from the covalent bonding of two or three from the covalent bonding of two or three monosaccharides.monosaccharides.

Lactose (milk sugar) is glucose plus galactose; Lactose (milk sugar) is glucose plus galactose; sucrose (table sugar) is glucose plus fructose.sucrose (table sugar) is glucose plus fructose.

Oligosaccharides are used to modify protein Oligosaccharides are used to modify protein structure and have a role in the body’s defense structure and have a role in the body’s defense against disease.against disease.

Formation of a Formation of a Sucrose Sucrose MoleculeMolecule



Polysaccharides are sugar chains that store Polysaccharides are sugar chains that store energy.energy.

A A polysaccharidepolysaccharide consists of many sugar units consists of many sugar units (same or different) covalently linked.(same or different) covalently linked.

Glycogen is a storage form of glucose found in Glycogen is a storage form of glucose found in animal tissues.animal tissues.

Starch (energy storage in plants) and cellulose Starch (energy storage in plants) and cellulose (structure of plant cell walls) are made of (structure of plant cell walls) are made of glucose units but in different bonding glucose units but in different bonding arrangements.arrangements.

Examples of PolysaccharidesExamples of Polysaccharides


Section 10Section 10

Lipids: Fats and Their Lipids: Fats and Their Chemical KinChemical Kin

Lipids: Fats and Their Chemical Kin Lipids: Fats and Their Chemical Kin

LipidsLipids are composed mostly of nonpolar are composed mostly of nonpolar hydrocarbon and are hydrophobic.hydrocarbon and are hydrophobic.

Fats are energy-storing lipids.Fats are energy-storing lipids. FatsFats are lipids that have one, two, or three fatty are lipids that have one, two, or three fatty

acids attached to glycerol.acids attached to glycerol. A A fatty acidfatty acid is a long, unbranched hydrocarbon is a long, unbranched hydrocarbon

with a carboxyl group (—COOH) at one end.with a carboxyl group (—COOH) at one end. • SaturatedSaturated fatty acids have only single C—C bonds fatty acids have only single C—C bonds

in their tails, are solids at room temperature, and are in their tails, are solids at room temperature, and are

derived from animal sources.derived from animal sources.

Lipids: Fats and Their Chemical KinLipids: Fats and Their Chemical Kin

• UnsaturatedUnsaturated fatty acids have one or more double fatty acids have one or more double

bonds between the carbons that form “kinks” in the bonds between the carbons that form “kinks” in the tails; they tend to come from plants and are liquid at tails; they tend to come from plants and are liquid at room temperature.room temperature.



TriglyceridesTriglycerides have three fatty acids attached to have three fatty acids attached to one glycerol.one glycerol.

• They are the body’s most abundant lipids.They are the body’s most abundant lipids. • On a per-weight basis, these molecules yield twice On a per-weight basis, these molecules yield twice

as much energy as carbohydrates. as much energy as carbohydrates. Trans fatty acidsTrans fatty acids are partially saturated are partially saturated

(hydrogenated) lipids implicated in some types (hydrogenated) lipids implicated in some types of heart disease.of heart disease.

Formation of a TriglycerideFormation of a Triglyceride



Phospholipids are key building blocks of cell Phospholipids are key building blocks of cell membranes.membranes.

A A phospholipidphospholipid has a has a

glycerol backbone, two glycerol backbone, two

fatty acids, a phosphate fatty acids, a phosphate

group, and a small group, and a small

hydrophilic group.hydrophilic group. They are important They are important

components of cell components of cell

membranes.membranes.Figure 2.19a-cFigure 2.19a-c


Sterols are building blocks of cholesterol Sterols are building blocks of cholesterol and steroids.and steroids.

Steroids have a backbone of four carbon rings, Steroids have a backbone of four carbon rings, but no fatty acids.but no fatty acids.

CholesterolCholesterol is an is an

essential component essential component

of cell membranes in of cell membranes in

animals and can be animals and can be

modified to form sex modified to form sex

hormones.hormones.Figure 2.19d-eFigure 2.19d-e


Proteins: Biological Proteins: Biological Molecules with Molecules with

Many RolesMany Roles

ProteinsProteins

Because they are the most diverse of the Because they are the most diverse of the large biological molecules, proteins function large biological molecules, proteins function as enzymes, in cell movements, as storage as enzymes, in cell movements, as storage and transport agents, as hormones, as and transport agents, as hormones, as antidisease agents, and as structural antidisease agents, and as structural material throughout the body. material throughout the body.


ProteinsProteins

Proteins are built from amino acids.Proteins are built from amino acids. Amino acidsAmino acids are small organic molecules with are small organic molecules with

an amino group, an acid group, a hydrogen an amino group, an acid group, a hydrogen atom, and one of 20 varying “R” groups.atom, and one of 20 varying “R” groups.

They form large polymers called proteins.They form large polymers called proteins.Figures 2.20 and 2.21Figures 2.20 and 2.21

ProteinsProteins

The sequence of amino acids is a protein’s The sequence of amino acids is a protein’s primary structure. primary structure.

Primary structurePrimary structure is defined as the chain is defined as the chain (polypeptide) of amino acids.(polypeptide) of amino acids.

The amino acids are linked together in a The amino acids are linked together in a definite sequence by peptide bonds between an definite sequence by peptide bonds between an amino group of one and an acid group of amino group of one and an acid group of another.another.

The final shape and function of any given The final shape and function of any given protein is determined by its primary structure.protein is determined by its primary structure.

Formation of Formation of Peptide Bonds Peptide Bonds

in Proteinsin Proteins



A Protein’s Function A Protein’s Function Depends on Its ShapeDepends on Its Shape

Primary structure determines the shape and Primary structure determines the shape and function of proteins by positioning different function of proteins by positioning different amino acids so that hydrogen bonds can amino acids so that hydrogen bonds can form between them and by putting R groups form between them and by putting R groups in positions that force them to interact.in positions that force them to interact.



Many proteins fold two or three times.Many proteins fold two or three times. Secondary structureSecondary structure is the helical coil or is the helical coil or

sheetlike array that will result from hydrogen sheetlike array that will result from hydrogen bonding of side groups on the amino acid bonding of side groups on the amino acid chains.chains.

Tertiary structureTertiary structure is caused by interactions is caused by interactions among R groups, resulting in a complex three-among R groups, resulting in a complex three-dimensional shape.dimensional shape.


Figure 2.23b-cFigure 2.23b-c

Fig. 2.23, p. 34

one peptide group

coil, helix sheet

coiled coils

primary structure

a

secondary structure

b

tertiary structure

c

Stepped Art

Proteins can have more than one Proteins can have more than one polypeptide chain.polypeptide chain.

Hemoglobin, the oxygen-carrying protein in the Hemoglobin, the oxygen-carrying protein in the blood, is an example of a protein with blood, is an example of a protein with quaternaryquaternary structurestructure—the complexing of two —the complexing of two or more polypeptide chains to form globular or or more polypeptide chains to form globular or fibrous proteins.fibrous proteins.

Hemoglobin has four polypeptide chains Hemoglobin has four polypeptide chains (globins), each coiled and folded with a heme (globins), each coiled and folded with a heme group at the center.group at the center.


Glycoproteins have sugars attached; Glycoproteins have sugars attached; lipoproteins have lipids.lipoproteins have lipids.

Certain proteins combine with triglycerides, Certain proteins combine with triglycerides, cholesterol, and phospholipids to form cholesterol, and phospholipids to form lipoproteinslipoproteins for transport in the body. for transport in the body.

GlycoproteinsGlycoproteins form when oligosaccharides are form when oligosaccharides are added to proteins.added to proteins.


Disrupting a protein’s shape denatures it.Disrupting a protein’s shape denatures it. High temperatures or chemicals can cause the High temperatures or chemicals can cause the

three-dimensional shape to be disrupted.three-dimensional shape to be disrupted. Normal functioning is lost upon denaturation, Normal functioning is lost upon denaturation,

which is often irreversible.which is often irreversible.




Nucleotides and Nucleotides and

Nucleic Acids Nucleic Acids

Nucleotides and Nucleic AcidsNucleotides and Nucleic Acids

Nucleotides: energy carriers and other Nucleotides: energy carriers and other roles.roles.

Each Each nucleotidenucleotide has a five-carbon sugar has a five-carbon sugar (ribose or deoxyribose), a nitrogen-containing (ribose or deoxyribose), a nitrogen-containing base, and a phosphate group.base, and a phosphate group.

ATP molecules link cellular reactions that ATP molecules link cellular reactions that transfer energy.transfer energy.

Other nucleotides include the Other nucleotides include the coenzymescoenzymes, , which accept and transfer hydrogen atoms and which accept and transfer hydrogen atoms and electrons during cellular reactions, and electrons during cellular reactions, and chemical messengerschemical messengers

Nucleotides and Nucleic AcidsNucleotides and Nucleic Acids

Nucleic acids include DNA and RNA.Nucleic acids include DNA and RNA. In In nucleic acidsnucleic acids, nucleotides are bonded , nucleotides are bonded

together to form large single- or double-together to form large single- or double-stranded molecules.stranded molecules.

DNADNA (deoxyribonucleic acid) is double- (deoxyribonucleic acid) is double-stranded; genetic messages are encoded in its stranded; genetic messages are encoded in its base sequences.base sequences.

RNARNA (ribonucleic acid) is single-stranded; it (ribonucleic acid) is single-stranded; it functions in the assembly of proteins.functions in the assembly of proteins.


Food Production and a Food Production and a Chemical Arms RaceChemical Arms Race

Food Production and Food Production and a Chemical Arms Racea Chemical Arms Race

Nearly half of the food grown each year Nearly half of the food grown each year around the world is lost to disease or around the world is lost to disease or insects.insects.

Natural plant defenses have been Natural plant defenses have been augmented by the development of synthetic augmented by the development of synthetic toxins designed to kill pests and increase toxins designed to kill pests and increase crop yields.crop yields.

Herbicides kill unwanted plants (weeds).Herbicides kill unwanted plants (weeds). Insecticides kill insects.Insecticides kill insects. Fungicides kill or inhibit the growth of harmful Fungicides kill or inhibit the growth of harmful

mold or fungi.mold or fungi.

Food Production and Food Production and a Chemical Arms Racea Chemical Arms Race

Synthetic chemicals are not without Synthetic chemicals are not without dangers; some kill “good” insects and plants dangers; some kill “good” insects and plants while others harm humans through while others harm humans through exposure.exposure.

powerlecture: chapter 2 molecules of life. learning objectives understand how protons, electrons,...

Documents

carbon atoms

number of protons

stable atoms

starting point atoms

varying forms of atoms

atomic number unique

atomic mass number

carbon compounds