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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