Chapter 5 Chapter 5

The Structure and Function ofThe Structure and Function of

Large Biological MoleculesLarge Biological Molecules

Focus on:Focus on:

� Elements in each large biological molecule.

� How these molecules are linked and unlinked.

� Examples and functions of each type of molecule.

MacromoleculesMacromolecules

� Large molecules formed by joining many subunits together.

� Also known as “polymers”.

MonomerMonomer

� A building block of a polymer.

AP Biology

Condensation Synthesis Condensation Synthesis oror

Dehydration SynthesisDehydration Synthesis� The chemical reaction that joins monomers into polymers.

� Covalent bonds are formed by the removal of a water molecule between the monomers.

HydrolysisHydrolysis

� Reverse of condensation synthesis.

� Hydro- water

� Lysis - to split

� Breaks polymers into monomers by adding water.

Four Main Types of Macromolecules Four Main Types of Macromolecules

or Large Biological Moleculesor Large Biological Molecules

� Carbohydrates

� Lipids

� Protein

� Nucleic acids

For each Macromolecule know the For each Macromolecule know the

following:following:� Elements it contains

� Monomer units and structures

� Examples

� Uses or roles

CarbohydratesCarbohydrates

� Used for fuel, building materials, and receptors.

� Made of C,H,O

� General formula is CH2O

� C:O ratio is 1:1

Types Of CarbohydratesTypes Of Carbohydrates

� Monosaccharides

� Disaccharides

�Oligosaccharides

� Polysaccharides

MonosaccharidesMonosaccharides

� Mono - single

� Saccharide - sugar

� Simple sugars.

� 3 to 7 carbons.

� Can be in linear or ring forms.

MonosaccharidesMonosaccharides

� Can be “Aldoses” or “Ketoses” depending on the location of the carbonyl group.

ExamplesExamples

� Glucose

� Galactose

� Ribose

� Fructose

-- OSEOSE

�Word ending common for many carbohydrates.

DisaccharidesDisaccharides

� Sugar formed by joining two monosaccharides through a “glycosidiclinkage”.

ExamplesExamples

� Maltose = glucose + glucose

� Lactose = glucose + galactose

� Sucrose = glucose + fructose

OligosaccharidesOligosaccharides

� 2 - 10 joined simple sugars.

� Used in cell membranes.

PolysaccharidesPolysaccharides

� Many joined simple sugars.

� Used for storage or structure.

� Examples:

◦ Starch

◦ Cellulose

◦ Glycogen

α α glucose and glucose and ββ glucoseglucose

StarchStarch

� Made of 1-4 linkages of α glucose.

� Linkage makes the molecule form a helix.

� Fuel storage in plants.

α α glucoseglucose

CelluloseCellulose

� Made of 1-4 linkages of β glucose.

� Linkage makes the molecule form a straight line.

� Used for structure in plant cell walls.

ββ glucoseglucose

CommentComment

� Most organisms can digest starch (1- 4 α linkage), but very few can digest cellulose (1- 4 β linkage).

� Another example of the link between structure and function.

GlycogenGlycogen

� “Animal starch”

� Similar to starch, but has more 1-6 linkages or branches.

� Found in the liver and muscle cells.

Glycogen

Starch

LipidsLipids

� Diverse hydrophobic molecules

� Made of C,H,O

� No general formula

� C:O ratio is very high in C

� Not strictly speaking a macromolecule like the others

Fats and OilsFats and Oils

� Fats - solid at room temperature.

�Oils - liquid at room temperature.

Fats and OilsFats and Oils

� Made of two kinds of smaller molecules.

◦ Fatty Acids

◦ Glycerol

Fatty AcidsFatty Acids

� A long carbon chain (12-18 C) with a -COOH (acid) on one end and a -CH3(fat) at the other.

Acid Fat

Neutral Fats or Neutral Fats or TriacylglycerolsTriacylglycerols

� Three fatty acids joined to one glycerol.

� Joined by an “ester” linkage between the -COOH of the fatty acid and the -OH of the alcohol.

Saturated FatsSaturated Fats

Unsaturated FatsUnsaturated Fats� Saturated - no double bonds.

� Unsaturated - one or more C=C bonds. Can accept more Hydrogens.

� Double bonds cause “kinks” in the molecule’s shape.

QuestionQuestion

�Why do fats usually contain saturated fatty acids and oils usually contain unsaturated fatty acids?

�The double bonds push the molecules apart, lowering the density, which lowers the melting point.

FatsFats

� Differ in which fatty acids are used.

� Used for energy storage, cushions for organs, insulation.

Question ?Question ?

�Which has more energy, a kg of fat or a kg of starch?

� Fat - there are more C-H bonds which provide more energy per mass.

PhospholipidsPhospholipids

� Similar to fats, but have only two fatty acids.

� The third -OH of glycerol is joined to a phosphate containing molecule.

ResultResult

� Phospholipids have a hydrophobic tail, but a hydrophilic head.

� Self-assembles into micelles or bilayers, an important part of cell membranes.

SteroidsSteroids

� Lipids with four fused rings.

� Differ in the functional groups attached to the rings.

� Examples:

◦ cholesterol

◦ sex hormones

ProteinsProteins

� The molecular tools of the cell.

� Made of C,H,O,N, and sometimes S.

� No general formula.

Uses Of ProteinsUses Of Proteins

� Structure� Enzymes� Antibodies� Transport� Movement� Receptors� Hormones

ProteinsProteins

� Polypeptide chains of Amino Acids linked by peptide bonds.

Amino AcidsAmino Acids

� All have a Carbon with four attachments:

� -COOH (acid)

� -NH2 (amine)

� -H

� -R (some other side group)

R groupsR groups

� 20 different kinds:

◦ Nonpolar - 9 AA

◦ Polar - 6 AA

◦ Electrically Charged

� Acidic - 2 AA

� Basic - 3 AA

Amino AcidsAmino Acids

Amino AcidsAmino Acids

R groupsR groups

� Contain the S when present in a protein. ◦ Cysteine or Cys◦ Methionine or Met

� The properties of the R groups determine the properties of the protein.

Polypeptide ChainsPolypeptide Chains

� Formed by dehydration synthesis between the carboxyl group of one AA and the amino group of the second AA.

� Produce an backbone of: (N-C-C)X

Levels Of Protein StructureLevels Of Protein Structure

�Organizing the polypeptide into its 3-D functional shape.

◦ Primary

◦ Secondary

◦ Tertiary

◦ Quaternary

PrimaryPrimary

� Sequence of amino acids in the polypeptide chain.

� Many different sequences are possible with 20 AAs.

SecondarySecondary� 3-D structure formed by hydrogen bonding between parts of the peptide backbone.

�Two main secondary structures:◦ α helix

◦ pleated sheets

TertiaryTertiary

� Bonding between the R groups.

� Examples:

◦ hydrophobic interactions

◦ ionic bonding

◦ Disulfide bridges (covalent bond)

QuaternaryQuaternary

�When two or more polypeptides unite to form a functional protein.

� Example: hemoglobin

Is Protein Structure Important?Is Protein Structure Important?

Denaturing Of A ProteinDenaturing Of A Protein

� Events that cause a protein to lose structure (and function).

� Example:

◦ pH shifts

◦ high salt concentrations

◦ heat

Chaperone ProteinsChaperone Proteins

� Large protein complexes that help fold other proteins into their correct shape.

�Often used when cells are stressed to keep proteins intact and functioning.

CommentComment

� Many other amino acids are possible (change the R group)

�Whole new group of proteins with new properties can be made

� Genetic engineering can use bacteria to make these new proteins

Nucleic AcidsNucleic Acids

� Informational polymers

� Made of C,H,O,N and P

� No general formula

� Examples: DNA and RNA

Nucleic AcidsNucleic Acids

� Polymers of nucleotides

� Nucleotides have three parts:

◦ nitrogenous base

◦ pentose sugar

◦ phosphate

Nitrogenous BasesNitrogenous Bases

� Rings of C and N

� The N atoms tend to take up H+ (base).

� Two types:

◦ Pyrimidines (single ring)

◦ Purines (double rings)

Pentose SugarPentose Sugar

� 5-C sugar

� Ribose - RNA

� Deoxyribose – DNA

� RNA and DNA differ in a –OH group on the 2nd carbon.

Nucleosides and NucleotidesNucleosides and Nucleotides

� Nucleoside = base + sugar

� Nucleotide = has the trio of base + sugar + Pi

DNADNA

� Deoxyribonucleic Acid.

� Makes up genes.

� Genetic information for life.

RNARNA

� Ribonucleic Acid.

� Structure and protein synthesis.

� Genetic information for a few viruses only.

� Control mechanisms for genes.

DNA and RNADNA and RNA

� More will be said about DNA and RNA in future lessons.

SummarySummary

�Role of hydrolysis and dehydration synthesis

� For each macromolecule, know the following:◦ Elements and monomers

◦ Structures

◦ Functions

◦ Examples