BiochemistryBiochemistryChapter 3Chapter 3

WaterWaterSec 3-1Sec 3-1

Polarity (1)Polarity (1) Many of water’s Many of water’s

biological biological functions stem functions stem from its chemical from its chemical structure.structure.

The hydrogen The hydrogen and oxygen and oxygen atoms share atoms share electrons to form electrons to form covalent bonds.covalent bonds.

Polarity (2)Polarity (2) The oxygen atom The oxygen atom

pulls the shared pulls the shared electrons toward its electrons toward its nucleus away from nucleus away from the hydrogen the hydrogen nucleus, so the nucleus, so the electrical charge is electrical charge is unevenly distributed.unevenly distributed.

Because of this Because of this uneven pattern of uneven pattern of charge, water is charge, water is called a called a polar polar compoundcompound..

Polarity (3)Polarity (3) The polar nature of The polar nature of

water makes water water makes water very effective in very effective in dissolving many dissolving many other substances.other substances.

Water dissolves Water dissolves other polar other polar substances, substances, including sugars and including sugars and some proteins, as some proteins, as well as ionic well as ionic compounds.compounds.

Hydrogen Bonding (1)Hydrogen Bonding (1)

The polar nature of The polar nature of water also causes water also causes water molecules to water molecules to be attracted to one be attracted to one another.another.

The type of The type of attraction that holds attraction that holds two water molecules two water molecules together is called a together is called a hydrogen bondhydrogen bond..

Hydrogen Bonding (2)Hydrogen Bonding (2)

A hydrogen bond A hydrogen bond tends to form tends to form between a hydrogen between a hydrogen atom in one atom in one molecule and the molecule and the region of negative region of negative charge on another charge on another molecule.molecule.

A hydrogen bond is a A hydrogen bond is a weak bond that can weak bond that can easily be broken.easily be broken.

Hydrogen Bonds (3)Hydrogen Bonds (3) The hydrogen bonds in The hydrogen bonds in

water exert a significant water exert a significant attractive force, causing attractive force, causing water to cling to itself water to cling to itself and to other and to other substances.substances.

An attractive force An attractive force between particles of the between particles of the same kind is known as same kind is known as cohesioncohesion..

AdhesionAdhesion is the is the attractive force between attractive force between unlike substances.unlike substances.

Hydrogen Bonding (4)Hydrogen Bonding (4) Water must gain or Water must gain or

lose a relatively lose a relatively large amount of large amount of energy for its energy for its temperature to temperature to change its state.change its state.

When water is When water is heated, most of the heated, most of the thermal energy that thermal energy that the water initially the water initially absorbs breaks the absorbs breaks the hydrogen bonds.hydrogen bonds.

Complete Complete Reading Guide and Review 3-1Reading Guide and Review 3-1

Carbon CompoundsCarbon Compounds

Sec 3-2Sec 3-2

Compounds of LifeCompounds of Life Organic compoundsOrganic compounds

contain carbon atoms contain carbon atoms that are covalently that are covalently bonded to other bonded to other carbon atoms and to carbon atoms and to other elements.other elements.

Inorganic compounds Inorganic compounds are the compounds are the compounds used to create used to create organic compounds organic compounds and don’t contain and don’t contain carbon, except carbon, except carbon dioxide.carbon dioxide.

Carbon Bonding (1)Carbon Bonding (1)

A carbon atom has A carbon atom has four electrons in its four electrons in its outermost energy outermost energy level.level.

A carbon atom A carbon atom readily forms four readily forms four covalent bonds with covalent bonds with other elements as other elements as well as with other well as with other carbon atoms.carbon atoms.

Carbon Bonding (2)Carbon Bonding (2) The tendency of carbon The tendency of carbon

to bond with itself to bond with itself results in an enormous results in an enormous variety of organic variety of organic compounds in many compounds in many different shape, different shape, including straight including straight chains, branched chains, branched chains, and ringschains, and rings

These structures form These structures form the backbone of many the backbone of many different kinds of different kinds of organic molecules.organic molecules.

Functional GroupsFunctional Groups

In most organic In most organic compounds, clusters of compounds, clusters of atoms, called atoms, called functional functional groupsgroups, influence the , influence the properties of the properties of the molecules they molecules they compose.compose.

The functional group is The functional group is the structural building the structural building block that determines block that determines the characteristics of the characteristics of the compound.the compound.

Large Carbon Molecules (1)Large Carbon Molecules (1) In many carbon In many carbon

compounds, the compounds, the molecules are built up molecules are built up form smaller, simpler form smaller, simpler molecules known as molecules known as monomersmonomers..

Monomers can bond to Monomers can bond to one another to form one another to form complex molecules complex molecules known as known as polymerspolymers..

Large polymers are Large polymers are called called macromoleculesmacromolecules..

Large Carbon Molecules (2)Large Carbon Molecules (2)

Monomers link to form polymers through a Monomers link to form polymers through a chemical reaction called a chemical reaction called a condensation condensation reaction reaction or or dehydration synthesisdehydration synthesis..

Large Carbon Molecules (3)Large Carbon Molecules (3)

The breakdown of some complex molecules, The breakdown of some complex molecules, such as polymers, occurs through a process such as polymers, occurs through a process known as known as hydrolysishydrolysis..

Energy Currency (1)Energy Currency (1) Life process require a constant supply of energy.Life process require a constant supply of energy. Most cellular energy is stored in a chemical Most cellular energy is stored in a chemical

compound known as compound known as adenosine triphosphateadenosine triphosphate, , more commonly abbreviated as more commonly abbreviated as ATPATP..

Energy Currency (2)Energy Currency (2) The covalent bond that holds the last phosphate The covalent bond that holds the last phosphate

group to the rest of the molecule is easily broken.group to the rest of the molecule is easily broken. When this bond is broken, much more energy is When this bond is broken, much more energy is

released than was required to break the bondreleased than was required to break the bond This conversion of energy is used by the cell to This conversion of energy is used by the cell to

drive the chemical reactions that enable an drive the chemical reactions that enable an organism to function.organism to function.

Complete Complete Reading Guide and Review 3-2Reading Guide and Review 3-2

Molecules of LifeMolecules of Life

Sec 3-3Sec 3-3

Organic CompoundsOrganic Compounds

There are four main There are four main classes of organic classes of organic compounds are compounds are essential to life essential to life processes.processes.– CarbohydratesCarbohydrates– LipidsLipids– ProteinsProteins– Nucleic AcidsNucleic Acids

Carbohydrates (1)Carbohydrates (1)

CarbohydratesCarbohydrates are are organic compounds organic compounds composed of carbon, composed of carbon, hydrogen, and hydrogen, and oxygenoxygen

The ratio of hydrogen The ratio of hydrogen to oxygen is 2:1to oxygen is 2:1

The monomer of a The monomer of a carbohydrates is a carbohydrates is a monosaccharidemonosaccharide..

Carbohydrates (2)Carbohydrates (2)

The general formula The general formula for a for a monosaccharide monosaccharide is written as (CHis written as (CH22O)O)nn, , where n is any whole where n is any whole number from 3 to 8.number from 3 to 8.

The most common The most common monosaccharides are monosaccharides are glucose, fructose, and glucose, fructose, and galactose.galactose.

Carbohydrate (3)Carbohydrate (3) Glucose, fructose, and galactose have the same Glucose, fructose, and galactose have the same

molecular formula, Cmolecular formula, C66HH1212OO66 but they have different but they have different structures and different properties.structures and different properties.

Compounds like these sugars, with a single Compounds like these sugars, with a single chemical formula but different forms, are called chemical formula but different forms, are called isomersisomers..

Carbohydrates (4)Carbohydrates (4)

Two monosaccharides Two monosaccharides can combine in a can combine in a condensation reaction condensation reaction to form a double to form a double sugar, or sugar, or disaccharidedisaccharide..

A A polysaccharidepolysaccharide is a is a complex molecule complex molecule composed of three or composed of three or more more monosaccharides.monosaccharides.

Proteins (1)Proteins (1)

ProteinsProteins are organic are organic compounds mainly compounds mainly composed mainly of composed mainly of carbon, hydrogen, carbon, hydrogen, oxygen, and oxygen, and nitrogen.nitrogen.

Proteins are made Proteins are made up of the monomers up of the monomers of of amino acidsamino acids..

Proteins (2)Proteins (2) There are 20 different There are 20 different

amino acids.amino acids. Amino acids all have the Amino acids all have the

same basic structure; a same basic structure; a central carbon atom central carbon atom covalently bonded to covalently bonded to four other atoms or four other atoms or functional groups.functional groups.

A single hydrogen atom, A single hydrogen atom, a carboxyl group, an a carboxyl group, an amino group and a amino group and a functional group called functional group called the R groupthe R group

The main difference The main difference between the amino between the amino acids is the difference in acids is the difference in the R-group.the R-group.

Proteins (3)Proteins (3)

In a condensation In a condensation reaction, two amino reaction, two amino acids form a covalent acids form a covalent bond, called a bond, called a peptide bondpeptide bond to form to form a a dipeptidedipeptide..

Amino acids can Amino acids can bond to each other bond to each other one at a time, one at a time, forming a very long forming a very long chain called a chain called a polypeptidepolypeptide..

Proteins (4)Proteins (4)

Proteins are Proteins are composed of one or composed of one or more polypeptides.more polypeptides.

Protein shape can Protein shape can also be influenced also be influenced by conditions such by conditions such as temperatures or as temperatures or the type of solvent the type of solvent in which the protein in which the protein is dissolved.is dissolved.

Proteins (5)Proteins (5) Most enzymes are proteins.Most enzymes are proteins. Enzyme reactions depend on a physical fit between Enzyme reactions depend on a physical fit between

the enzyme molecule and its the enzyme molecule and its substratesubstrate, the , the reactant being catalyzed.reactant being catalyzed.

The enzyme and substrate have shapes that allow The enzyme and substrate have shapes that allow them to fit together like a lock and key.them to fit together like a lock and key.

Lipids (1)Lipids (1) Lipids Lipids are large, are large,

nonpolar organic nonpolar organic molecules that do molecules that do not dissolve in not dissolve in water.water.

Lipid molecules Lipid molecules have a higher ratio have a higher ratio of carbon and of carbon and hydrogen atoms to hydrogen atoms to oxygen atoms than oxygen atoms than carbohydrates.carbohydrates.

Lipids (2)Lipids (2)

Lipids store energy Lipids store energy efficiently.efficiently.

Lipid molecules have Lipid molecules have large numbers of large numbers of carbon-hydrogen carbon-hydrogen bonds, which store bonds, which store more energy than the more energy than the carbon-oxygen bonds carbon-oxygen bonds common in other common in other organic compounds.organic compounds.

Lipids (3)Lipids (3)

Fatty acids are Fatty acids are unbranched carbon unbranched carbon chains that make up chains that make up most lipids.most lipids.

A fatty acid contains a A fatty acid contains a long, straight carbon long, straight carbon chain with a carboxyl chain with a carboxyl group attached to one group attached to one end.end.

Lipids (4)Lipids (4) The two ends of the fatty-acid molecule have very different The two ends of the fatty-acid molecule have very different

properties.properties. The carboxyl end is polar and is attracted to water The carboxyl end is polar and is attracted to water

molecules so it is said to be molecules so it is said to be hydrophilic hydrophilic which means which means “water loving”.“water loving”.

The hydrocarbon end of the fatty-acid molecule is nonpolar The hydrocarbon end of the fatty-acid molecule is nonpolar does not interact with water molecules and is said to be does not interact with water molecules and is said to be hydrophobichydrophobic, or “water fearing”., or “water fearing”.

Lipids (5)Lipids (5)

Lipids are divided into Lipids are divided into categories according categories according to their structure.to their structure.(a) A (a) A triglyceridetriglyceride is is

composed of three composed of three molecules of fatty acid molecules of fatty acid joined to one molecule joined to one molecule of the alcohol glycerol.of the alcohol glycerol.

Lipids (6)Lipids (6)(b) (b) PhospholipidsPhospholipids have have

two, rather than three, two, rather than three, fatty acids joined by a fatty acids joined by a molecule of glycerol.molecule of glycerol.

– The cell membrane is The cell membrane is composed of two layers composed of two layers of phospholipids, which of phospholipids, which are referred to as the are referred to as the lipid bilayer.lipid bilayer.

– The inability of lipids to The inability of lipids to dissolve in water allows dissolve in water allows the membrane to form a the membrane to form a barrier between the barrier between the inside and outside the inside and outside the cell.cell.

Lipids (7)Lipids (7)

(c) A (c) A waxwax is a type of structural lipid. is a type of structural lipid.- A wax molecule consists of a long fatty-acid chain joined A wax molecule consists of a long fatty-acid chain joined

to a long alcohol chain.to a long alcohol chain.- Waxes are highly waterproof, and in plants, wax forms a Waxes are highly waterproof, and in plants, wax forms a

protective coating on the outer surfaces.protective coating on the outer surfaces.

Lipids (8)Lipids (8)

Unlike most other lipids Unlike most other lipids steroidsteroid molecules are molecules are composed of four fused composed of four fused carbon rings with various carbon rings with various functional groups attached functional groups attached to them.to them.

Many animal hormones, Many animal hormones, such as the male hormone such as the male hormone testosteronetestosterone, are steroid , are steroid compounds.compounds.

One of the most familiar One of the most familiar steroids in humans is steroids in humans is cholesterolcholesterol..

Nucleic Acids (1)Nucleic Acids (1)

Nucleic acidsNucleic acids are are very large and very large and complex organic complex organic molecules that store molecules that store important important information in the information in the cell.cell.

Nucleic acids use a Nucleic acids use a system of four system of four compounds to store compounds to store hereditary hereditary information.information.

Nucleic Acids (2)Nucleic Acids (2) Deoxyribonucleic Deoxyribonucleic

acidacid, or , or DNADNA, , contains information contains information that is essential for that is essential for almost all cell almost all cell activities, including activities, including cell division.cell division.

Ribonucleic acidRibonucleic acid, or , or RNARNA, stores and , stores and transfers information transfers information that is essential for that is essential for the manufacturing of the manufacturing of proteins.proteins.

Nucleic Acids (3)Nucleic Acids (3) Both DNA and RNA are polymers, composed of Both DNA and RNA are polymers, composed of

thousands of linked monomers called thousands of linked monomers called nucleotidesnucleotides.. Each nucleotide is made up of a phosphate group, a Each nucleotide is made up of a phosphate group, a

five-carbon sugar, a ring-shaped nitrogen base.five-carbon sugar, a ring-shaped nitrogen base.

Complete Complete Reading Guide and Review 3-3Reading Guide and Review 3-3