Honors BiologyHonors BiologyThe molecules of The molecules of CellsCellsChapter 3Chapter 3

Life’s molecular diversity Life’s molecular diversity is based on the is based on the properties of carbonproperties of carbon

Most compounds in living organisms are Most compounds in living organisms are organic – composed of carbon bonded to organic – composed of carbon bonded to other elements. Functions of organic other elements. Functions of organic compounds:compounds: Main structural components of cells and Main structural components of cells and

tissuestissues Participate in and regulate many chemical Participate in and regulate many chemical

reactionsreactions Provide energyProvide energy

By sharing electrons, carbon can bond to By sharing electrons, carbon can bond to four other atoms.four other atoms.

This allows for branching in up to four This allows for branching in up to four directions.directions.

A chain of carbon atoms is called a A chain of carbon atoms is called a carbon skeleton.carbon skeleton. Carbon skeletons can be branched or Carbon skeletons can be branched or

unbranched.unbranched. Therefore, different compounds with the Therefore, different compounds with the

same molecular formula but different same molecular formula but different properties can be produced.properties can be produced. These structures are called ISOMERS.These structures are called ISOMERS.

Carbon skeletons can vary in:Carbon skeletons can vary in: LengthLength BranchingBranching Double bondsDouble bonds RingsRings

An organic compound has unique An organic compound has unique properties that depend upon:properties that depend upon: The size and shape of the molecule andThe size and shape of the molecule and The groups of atoms (functional groups) The groups of atoms (functional groups)

attached to it.attached to it. A functional group affects a biological molecule’s A functional group affects a biological molecule’s

function in a characteristic way.function in a characteristic way. Compounds that contain functional groups are Compounds that contain functional groups are

hydrophilic (water-loving)hydrophilic (water-loving)

Cells make a huge number of large Cells make a huge number of large molecules from a small set of small molecules from a small set of small moleculesmolecules

Four classes of biological molecules:Four classes of biological molecules:

CarbohydratesCarbohydrates

LipidsLipids

ProteinsProteins

Nucleic AcidsNucleic Acids

The four classes of biological molecules The four classes of biological molecules contain very large moleculescontain very large molecules They are often called macromolecules They are often called macromolecules

because of their large sizebecause of their large size They may also be called polymers when They may also be called polymers when

they are made from identical building blocks they are made from identical building blocks strung togetherstrung together

The building blocks of polymers are called The building blocks of polymers are called monomers.monomers.

Dehydration synthesis (condensation) is Dehydration synthesis (condensation) is the linking of monomers by the removal the linking of monomers by the removal of water. This reaction builds polymers.of water. This reaction builds polymers.

Hydrolysis (“to break, with water”) breaks Hydrolysis (“to break, with water”) breaks down polymers to monomers by adding down polymers to monomers by adding water.water.

A good example of hydrolysis is when A good example of hydrolysis is when you digest your food!you digest your food!

CarbohydratesCarbohydrates

Serve as fuel and structural components Serve as fuel and structural components for cellsfor cells

General structure: contain carbon, General structure: contain carbon, hydrogen and oxygen in a ratio of abouthydrogen and oxygen in a ratio of about

1:2:11:2:1

Classification of Classification of CarbohydratesCarbohydrates

Monosaccharides: contain one type of Monosaccharides: contain one type of sugar unitsugar unit

Disaccharides: contain two types of Disaccharides: contain two types of sugar unitssugar units

Polysaccharides: contain many sugar Polysaccharides: contain many sugar unitsunits

MonosaccharidesMonosaccharides

Also known as simple sugarsAlso known as simple sugars Example: glucose is an important fuel Example: glucose is an important fuel

molecule in living cellsmolecule in living cells Monosaccharides are also used as raw Monosaccharides are also used as raw

materials to manufacture other organic materials to manufacture other organic moleculesmolecules

Monosaccharides are the monomers for Monosaccharides are the monomers for disaccharides and polysaccharides.disaccharides and polysaccharides.

PolysaccharidesPolysaccharides

Composed of repeating monosaccharide Composed of repeating monosaccharide unitsunits

They can function in the cell as a storage They can function in the cell as a storage molecule or as a structural compoundmolecule or as a structural compound

Storage PolysaccharidesStorage Polysaccharides

Starch – storage polysaccharide of plantsStarch – storage polysaccharide of plants Glycogen – storage polysaccharide of Glycogen – storage polysaccharide of

animalsanimals

Structural Structural PolysaccharidesPolysaccharides

Cellulose is a polymer of glucose that Cellulose is a polymer of glucose that forms plant cell walls.forms plant cell walls.

Chitin is a polysaccharide that is a Chitin is a polysaccharide that is a structural component of the exoskeleton structural component of the exoskeleton of insects and crustaceans. (also used in of insects and crustaceans. (also used in surgical thread for stitches that dissolve!)surgical thread for stitches that dissolve!)

Lipids (fats)Lipids (fats)

Lipids are water insoluble (hydrophobic – Lipids are water insoluble (hydrophobic – “water fearing”) compounds that are “water fearing”) compounds that are made from glycerol and fatty acids.made from glycerol and fatty acids.

They contain twice as much energy as a They contain twice as much energy as a polysaccharide, so their main function is polysaccharide, so their main function is long-term energy storage.long-term energy storage.

Lipids differ from other organic Lipids differ from other organic compounds in that they are neither huge compounds in that they are neither huge macromolecules nor polymers.macromolecules nor polymers.

Three types of lipids:Three types of lipids: FatFat PhospholipidsPhospholipids SteroidsSteroids

Types of Fats:Types of Fats: Unsaturated – corn oil, olive oil, and other Unsaturated – corn oil, olive oil, and other

vegetable oils. Liquid at room temperature.vegetable oils. Liquid at room temperature. Saturated – have the maximum number of Saturated – have the maximum number of

hydrogens. Examples include beef fat and hydrogens. Examples include beef fat and butter. Solid at room temperature.butter. Solid at room temperature.

Trans fat – made by adding hydrogen to Trans fat – made by adding hydrogen to unsaturated fats. Associated with health unsaturated fats. Associated with health risks.risks.

Phospholipids – a modified fat that is the Phospholipids – a modified fat that is the main structural component of cell main structural component of cell membranes.membranes.

Steroids – cholesterol is a common Steroids – cholesterol is a common component of cell membranes. Animal component of cell membranes. Animal cells use it as a precursor for making cells use it as a precursor for making other steroids, including hormones.other steroids, including hormones.

ProteinsProteins

A protein is a polymer built from various A protein is a polymer built from various combinations of 20 amino acid combinations of 20 amino acid monomers.monomers.

Proteins are essential to the Proteins are essential to the structures and functions of lifestructures and functions of life

StructuralStructural proteins provide associations proteins provide associations between body parts.between body parts.

ContractileContractile proteins are found within proteins are found within muscle.muscle.

DefensiveDefensive proteins include antibodies of proteins include antibodies of the immune system.the immune system.

SignalSignal proteins are best exemplified by proteins are best exemplified by the hormonesthe hormones

ReceptorReceptor proteins serve as ‘antenna’ for proteins serve as ‘antenna’ for outside signalsoutside signals

TransportTransport proteins carry oxygen. proteins carry oxygen. EnzymesEnzymes regulate the chemical regulate the chemical

reactions within cells.reactions within cells.

Proteins are made from amino Proteins are made from amino acids linked by peptide bondsacids linked by peptide bonds

This is done by means of an enzyme-This is done by means of an enzyme-mediated dehydration synthesis.mediated dehydration synthesis.

A polypeptide chain contains hundreds or A polypeptide chain contains hundreds or thousands of amino acids.thousands of amino acids. The amino acid sequence causes the The amino acid sequence causes the

polypeptide to assume a particular shapepolypeptide to assume a particular shape The shape of a protein determines its The shape of a protein determines its

specific function.specific function.

Levels of protein Levels of protein organizationorganization

Primary structure Primary structure – unique sequence of – unique sequence of amino acidsamino acids Correct amino acid sequence is determined Correct amino acid sequence is determined

by the cell’s genetic informationby the cell’s genetic information The slightest change in this sequence The slightest change in this sequence

affects the protein’s ability to function. affects the protein’s ability to function.

SecondarySecondary structure – coiling or folding structure – coiling or folding of the peptide chainof the peptide chain Coiling results in a helical structure called an Coiling results in a helical structure called an

alpha helixalpha helix Folding may lead to a structure called a beta Folding may lead to a structure called a beta

pleated sheet.pleated sheet.

TertiaryTertiary structure – overall 3-D shape structure – overall 3-D shape

QuaternaryQuaternary structure – how the structure – how the polypeptides fit together in a moleculepolypeptides fit together in a molecule

Protein structure Protein structure determines functiondetermines function

Changes in protein structure can affect Changes in protein structure can affect functionfunction

Mutations can disrupt the biological Mutations can disrupt the biological activity of a proteinactivity of a protein

Denaturation can cause the protein to Denaturation can cause the protein to become inactivebecome inactive

Nucleic acids are information-Nucleic acids are information-rich polymersrich polymers

Two classes – RNA and DNATwo classes – RNA and DNA

Nucleic acids store information that Nucleic acids store information that codes for proteins, which govern the codes for proteins, which govern the structure and function of the organismstructure and function of the organism

Composition of nucleic Composition of nucleic acidsacids

Monomers are nucleotidesMonomers are nucleotides Each nucleotide is composed of:Each nucleotide is composed of:

Nitrogenous baseNitrogenous base 5-carbon sugar5-carbon sugar Phosphate groupPhosphate group