The Chemical Basis of LifeThe Chemical Basis of Life

BASIC CHEMISTRYBASIC CHEMISTRY• ATOMIC STRUCTUREATOMIC STRUCTURE

– NUCLEUSNUCLEUS• PROTONSPROTONS – ATOMIC MASS = 1 – ATOMIC MASS = 1• NEUTRONSNEUTRONS – ATOMIC MASS = 1 – ATOMIC MASS = 1

– ELECTRONSELECTRONS • NOT ENOUGH MASS FOR US TO NOT ENOUGH MASS FOR US TO

CONSIDER.CONSIDER.

Atomic StructureAtomic Structure

(-)

(+)

Chemical Chemical ElementsElements• All matter on Earth is composed of All matter on Earth is composed of

combinations of chemical elements.combinations of chemical elements.• Elements cannot be broken down by Elements cannot be broken down by

chemical processes into simpler chemical processes into simpler substances.substances.

• There are over 90 naturally-occurring There are over 90 naturally-occurring chemical elements.chemical elements.

• The most common chemical elements in The most common chemical elements in living things are: living things are: – S, P, O, N, C, HS, P, O, N, C, H

Periodic TablePeriodic Table

MOLECULESMOLECULES and and COMPOUNDSCOMPOUNDS

• MADE OF MORE THAN ONE KIND MADE OF MORE THAN ONE KIND OF ATOM HELD TOGETHER BY A OF ATOM HELD TOGETHER BY A CHEMICAL BOND.CHEMICAL BOND.

• FAMILIAR ONES INCLUDE WATER, FAMILIAR ONES INCLUDE WATER, SUGAR, FAT, PROTEIN, SUGAR, FAT, PROTEIN, CARBOHYDRATE, SALT.CARBOHYDRATE, SALT.

WHY DO SOME ATOMS COMBINE TO WHY DO SOME ATOMS COMBINE TO FORM COMPOUNDS AND FORM COMPOUNDS AND

MOLECULES?MOLECULES?

• An Atom’s ability to combine with other An Atom’s ability to combine with other atoms relies on its number of electrons atoms relies on its number of electrons in its outer shell (energy level): the in its outer shell (energy level): the outer shell needs to be full for the atom outer shell needs to be full for the atom to become stable (stable atoms do not to become stable (stable atoms do not combine with other atoms).combine with other atoms).

• For our purposes, the first shell contains For our purposes, the first shell contains 2 electrons, and each successive shell 2 electrons, and each successive shell contains up to 8 electrons. contains up to 8 electrons.

Electron Energy Levels:Electron Energy Levels:

First energy level holds up to 2 electrons

Second energy level holds up to 8 electrons

Third energy level holds up to 8 electrons

Stable atoms:Stable atoms:• Some atoms already have a full Some atoms already have a full

outer energy level. outer energy level. • These atoms do not react with These atoms do not react with

other atoms to form molecules.other atoms to form molecules.• These include the inert or noble These include the inert or noble

gases: helium, argon, neon, gases: helium, argon, neon, krypton, xenon, and radon.krypton, xenon, and radon.

If an atom is not stable:If an atom is not stable:• It will combine with other atomsIt will combine with other atoms• Some will give up or gain electrons.Some will give up or gain electrons.

– These form These form ionic bondsionic bonds– Each member is an ionEach member is an ion– The opposite electrical charges attract each The opposite electrical charges attract each

otherother• Some will share electrons between Some will share electrons between

them.them.– The force holding them together is called a The force holding them together is called a

covalent bondcovalent bond..

Ionic BondsIonic Bonds

NaCl = salt

POLAR MOLECULESPOLAR MOLECULES• BECAUSE OF THE WAY SOME BECAUSE OF THE WAY SOME

MOLECULES COMBINE, THEY MOLECULES COMBINE, THEY CONTAIN DIFFERENT ELECTRICAL CONTAIN DIFFERENT ELECTRICAL CHARGES AT OPPOSITE ENDS. CHARGES AT OPPOSITE ENDS.

• THIS CREATES ATTRACTION TO THIS CREATES ATTRACTION TO OPPOSITE CHARGES ON OTHER OPPOSITE CHARGES ON OTHER MOLECULESMOLECULES

Polar MoleculesPolar Molecules

Positive end

HYDROGEN BONDSHYDROGEN BONDS• HOLD TOGETHER MOLECULES HOLD TOGETHER MOLECULES

THAT CONTAIN HYDROGEN.THAT CONTAIN HYDROGEN.• IMPORTANT IN WATER MOLECULES IMPORTANT IN WATER MOLECULES

AND MANY MOLECULES IN LIVING AND MANY MOLECULES IN LIVING ORGANISMS.ORGANISMS.

• WEAKER THAN IONIC OR WEAKER THAN IONIC OR COVALENT BONDS.COVALENT BONDS.

• THESE HOLD DNA TOGETHERTHESE HOLD DNA TOGETHER

CHEMICAL REACTIONCHEMICAL REACTION• ONE OR MORE SUBSTANCES IS ONE OR MORE SUBSTANCES IS

CHANGED INTO NEW SUBSTANCES CHANGED INTO NEW SUBSTANCES BY BREAKING OR FORMING BY BREAKING OR FORMING CHEMICAL BONDS.CHEMICAL BONDS.

• EX: EX: – 6CO6CO22 + 6H + 6H220 0 C C66HH1212OO66 + 6O + 6O22

– WHAT IS THE ABOVE EQUATION AND WHAT IS THE ABOVE EQUATION AND WHAT DOES IT MEAN?WHAT DOES IT MEAN?

ALL CHEMICAL REACTIONS ALL CHEMICAL REACTIONS INVOLVE ENERGYINVOLVE ENERGY

• WHEN BONDS WHEN BONDS FORM,FORM,ENERGY IS ENERGY IS STOREDSTORED

• WHEN BONDSWHEN BONDSBREAK, BREAK, ENERGY IS ENERGY IS RELEASEDRELEASED

ATP = energy carrier of a cell

ORGANIC COMPOUNDSORGANIC COMPOUNDS• COMPOUNDS THAT CONTAIN COMPOUNDS THAT CONTAIN

CARBONCARBON, , HYDROGENHYDROGEN AND AND OXYGENOXYGEN IN DEFINITE PROPORTIONS. IN DEFINITE PROPORTIONS.

• USUALLY ASSOCIATED WITH LIVING USUALLY ASSOCIATED WITH LIVING THINGSTHINGS

CARBOHYDRATESCARBOHYDRATES• BUILDING BLOCKS = SIMPLE SUGARS BUILDING BLOCKS = SIMPLE SUGARS

((MONOSACCHARIDESMONOSACCHARIDES).).• MONOSACCHARIDES INCLUDE MONOSACCHARIDES INCLUDE

– GLUCOSEGLUCOSE– FRUCTOSEFRUCTOSE ISOMERS ISOMERS– GALACTOSEGALACTOSEALL THREE HAVE THE SAME MOLECULAR ALL THREE HAVE THE SAME MOLECULAR

FORMULA, BUT DIFFERENT STRUCTURE:FORMULA, BUT DIFFERENT STRUCTURE:CC66HH12120066

THESE MOLECULES ARE THE MOST COMMON THESE MOLECULES ARE THE MOST COMMON SOURCE OF ENERGYSOURCE OF ENERGY FOR LIVING THINGS. FOR LIVING THINGS.

Isomers – can you tell the Isomers – can you tell the difference?difference?

glucose

C6H12O6

MORE COMPLEX CARBSMORE COMPLEX CARBS• DISACCHARIDESDISACCHARIDES

– MADE UP OF TWO MONOSACCHARIDES MADE UP OF TWO MONOSACCHARIDES CHEMICALLY COMBINED. CHEMICALLY COMBINED.

– GLUCOSE + GLUCOSE = GLUCOSE + GLUCOSE = MALTOSEMALTOSE– GLUCOSE + GALACTOSE = GLUCOSE + GALACTOSE = LACTOSELACTOSE

• THIS IS MILK SUGARTHIS IS MILK SUGAR– GLUCOSE + FRUCTOSE = GLUCOSE + FRUCTOSE = SUCROSESUCROSE

• THIS IS TABLE SUGARTHIS IS TABLE SUGAR• These molecules These molecules store energystore energy for later use for later use

THE MOST COMPLEX THE MOST COMPLEX CARBSCARBS

• STARCHSTARCH – MADE UP OF MANY GLUCOSE UNITS – MADE UP OF MANY GLUCOSE UNITS COMBINED.COMBINED.– PLANT LONG-TERM PLANT LONG-TERM FOOD STORAGEFOOD STORAGE

• GLYCOGENGLYCOGEN – MADE OF MANY GLUCOSE UNITS – MADE OF MANY GLUCOSE UNITS COMBINEDCOMBINED– ANIMAL ANIMAL STORAGESTORAGE IN LIVER AND MUSCLES IN LIVER AND MUSCLES

• CELLULOSECELLULOSE – MADE OF MANY GLUCOSE UNITS – MADE OF MANY GLUCOSE UNITS COMBINED.COMBINED.– PLANT PLANT CELL WALLSCELL WALLS; ; FIBERFIBER

• CHITINCHITIN – – PROTECTIVEPROTECTIVE COVERINGS IN INSECTS AND COVERINGS IN INSECTS AND OTHER ARTHROPODS; ALSO IN FUNGUS CELL WALLSOTHER ARTHROPODS; ALSO IN FUNGUS CELL WALLS

DEHYDRATION SYNTHESISDEHYDRATION SYNTHESIS

• In order for two molecules to join In order for two molecules to join together, each molecule must break off together, each molecule must break off atoms to provide a bonding place. atoms to provide a bonding place.

• Most organic molecules do this by losing Most organic molecules do this by losing a a hydrogenhydrogen atom from one molecule and atom from one molecule and a a hydroxylhydroxyl group from the other. group from the other.

• These two join to form These two join to form waterwater, and allow , and allow the molecules to make a bond. the molecules to make a bond.

Dehydration SynthesisDehydration Synthesis

disaccharideC6H12O6 + C6H12O6 C12H22O11 + H2O

HydrolysisHydrolysis • In order to break down a large In order to break down a large

molecule to make smaller molecule to make smaller molecules, a molecule of water has molecules, a molecule of water has to be added.to be added.

• This fills in the spots where the This fills in the spots where the bond broke – one molecule gets a bond broke – one molecule gets a hydrogen atom, the other gets the hydrogen atom, the other gets the hydroxyl group. hydroxyl group.

HydrolysisHydrolysisADD WATER

POLYSACCHARIDE

MONOSACCHARIDES

TO A

AND FORM MANY

Dehydration Synthesis and Dehydration Synthesis and Hydrolysis store and release Hydrolysis store and release

energy energy • Dehydration synthesis stores Dehydration synthesis stores

energy by forming bonds.energy by forming bonds.– As in the formation of polysaccharides As in the formation of polysaccharides

from monosacharidesfrom monosacharides• Hydrolysis releases energy by Hydrolysis releases energy by

breaking bonds.breaking bonds.

LipidsLipids: : fats, oils, waxes, fats, oils, waxes, phospholipids, steroidsphospholipids, steroids

• Used for Used for longer-term storage of energylonger-term storage of energy• FatsFats – in animals – in animals• OilsOils – in plants – in plants• WaxesWaxes – water repellent (In your ears, – water repellent (In your ears,

beeswax, coat plant leaves), waterproof beeswax, coat plant leaves), waterproof bird feathers. bird feathers.

• SteroidsSteroids – in animal cell membranes and – in animal cell membranes and some hormones.some hormones.

• PhospholipidsPhospholipids – make up parts of cell – make up parts of cell membranesmembranes

A common fat = A common fat = TriglycerideTriglyceride

• Composed of one Composed of one glycerolglycerol and three and three fatty acidsfatty acids, joined together by , joined together by dehydration synthesis:dehydration synthesis:

GLYCEROL

3FATTYACIDS

Saturated and unsaturated fats:Saturated and unsaturated fats:• Saturated fatsSaturated fats have no C=C bonds have no C=C bonds

within the fatty acidswithin the fatty acids– These are considered unhealthy – they clog These are considered unhealthy – they clog

up the coronary (heart) arteries.up the coronary (heart) arteries.– These are solid at room temperature.These are solid at room temperature.– From animals.From animals.

• Unsaturated fatsUnsaturated fats have at least one C=C have at least one C=C bond in one of its fatty acidsbond in one of its fatty acids– These are considered healthier.These are considered healthier.– Plant oils are usually unsaturated.Plant oils are usually unsaturated.– Liquid at room temperature. Liquid at room temperature.

PROTEINSPROTEINS• Important for movement, structure, Important for movement, structure,

regulation, transport, nutrition, and regulation, transport, nutrition, and defense.defense.

• Composed of building blocks called Composed of building blocks called amino acidsamino acids

• Humans cannot make these from Humans cannot make these from scratch – we must eat foods with scratch – we must eat foods with proteins, then use the amino acids to proteins, then use the amino acids to make our own proteins.make our own proteins.

Amino AcidsAmino Acids• There are 20 different aa’s There are 20 different aa’s • They are combined in various numbers and They are combined in various numbers and

orders to produce a great number of different orders to produce a great number of different proteins. proteins.

• Each aa has an Each aa has an amino groupamino group, an , an acid group acid group (carboxyl(carboxyl), and a ), and a variable groupvariable group (there are 20 (there are 20 different variable groups).different variable groups).

• Amino acids attach to each other by Amino acids attach to each other by dehydration synthesis forming a peptide bond dehydration synthesis forming a peptide bond between the amino group of one aa and the between the amino group of one aa and the acid group of the other aa.acid group of the other aa.

• Change the number or arrangement of the aa’s Change the number or arrangement of the aa’s and the protein isand the protein is changed. changed.

Amino acidsAmino acidsAcid group

Amino group

Three different R groups:

Dipeptide – two aa’s joined by a Dipeptide – two aa’s joined by a peptide bond.peptide bond.

PolypeptidePolypeptide

EnzymesEnzymes – Special Proteins – Special Proteins

• Change the rate of chemical Change the rate of chemical reactions without being used up reactions without being used up themselves (themselves (biological catalystbiological catalyst).).

• Can be used over and over.Can be used over and over.• Action is very specific – Action is very specific –

each enzyme will only each enzyme will only work on one particular substance work on one particular substance (the substrate).(the substrate).

HOW DOES AN ENZYME HOW DOES AN ENZYME WORK?WORK?

• LOCK AND KEY LOCK AND KEY MODELMODEL

• INDUCED FIT INDUCED FIT MODELMODEL

Nucleic AcidsNucleic Acids• Molecules of heredity.Molecules of heredity.• DNA – deoxyribonucleic acidDNA – deoxyribonucleic acid

– makes up chromosomes (GENES)makes up chromosomes (GENES)– Contains the genetic code Contains the genetic code

• Determines the organism’s traitsDetermines the organism’s traits• Contains the code for making proteinsContains the code for making proteins

Which control the cell’s activities Which control the cell’s activities • RNARNA – ribonucleic acid– ribonucleic acid

– Helps DNA make proteinsHelps DNA make proteins

MetabolismMetabolism• All the chemical reactions that take All the chemical reactions that take

place in the organismplace in the organism• These reactions need to be These reactions need to be

balanced to keep the organism balanced to keep the organism alivealive– The balance is called The balance is called homeostasishomeostasis

Water and SolutionsWater and Solutions• HH22OO• Forms solutions easily – all life’s Forms solutions easily – all life’s

chemical reactions take place in chemical reactions take place in solutions. solutions.

• SolutionSolution – two or more substances are – two or more substances are mixed together that they cannot be mixed together that they cannot be distinguished. distinguished. – Ex- sugar + water or salt + waterEx- sugar + water or salt + water

• Sugar or salt is the Sugar or salt is the solutesolute• Water is the Water is the solventsolvent

Salt + Water Solution:Salt + Water Solution:

Acids and BasesAcids and Bases• Form when an ionic compound is Form when an ionic compound is

mixed with water to form a mixed with water to form a solution. solution.

• AcidAcid – releases H – releases H++ (hydrogen) ions (hydrogen) ions (like HCl = hydrochloric acid)(like HCl = hydrochloric acid)

• BaseBase – releases OH – releases OH-- (hydroxide) (hydroxide) ions ions (like NaOH = sodium hydroxide)(like NaOH = sodium hydroxide)

pH scalepH scale• Standard measurement of the H+ Standard measurement of the H+

ions in a solutionions in a solution• Ranges from 0 – 14Ranges from 0 – 14• 7 is neutral 7 is neutral

– Water has an equal number of H+ and Water has an equal number of H+ and OH- ions, so there is no excess of OH- ions, so there is no excess of either ion.either ion.

pH scalepH scale• Acids are less than 7Acids are less than 7• Bases are more than 7Bases are more than 7• The further away from 7, the The further away from 7, the

stronger the acid or basestronger the acid or base• Most chemical reactions in humans Most chemical reactions in humans

take place between 6+8take place between 6+8– However, stomach acid is 2-3However, stomach acid is 2-3– Enzymes are pH specificEnzymes are pH specific