Chapter 5 The Structure and Function of Macromolecules

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Chapter 5 The Structure and Function of
Macromolecules
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Macromolecules

• Large molecules formed by joining many subunits
  together.
• Also known as polymers.

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Monomer

• A building block of a polymer.

AP Biology
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Condensation Synthesis or Dehydration Synthesis

• The chemical reaction that joins monomers into
  polymers.
• Covalent bonds are formed by the removal of a
  water molecule between the monomers.

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Hydrolysis

• Reverse of condensation synthesis.
• Hydro- water
• Lysis - to split
• Breaks polymers into monomers by adding water.

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Four Main Types Of Macromolecules

• Carbohydrates
• Lipids
• Protein
• Nucleic acids

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Carbohydrates

• Used for fuel, building materials, and receptors.
• Made of C,H,O
• General formula is CH2O
• CO ratio is 11

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Types Of Carbohydrates

• Monosaccharides
• Disaccharides
• Oligosaccharides
• Polysaccharides

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Monosaccharides

• Mono - single
• Saccharide - sugar
• Simple sugars.
• 3 to 7 carbons.
• Can be in linear or ring forms.

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Monosaccharides

• Can be Aldoses or Ketoses depending on the
  location of the carbonyl group.

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Examples

• Glucose
• Galactose
• Ribose
• Fructose

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- OSE

• Word ending common for many carbohydrates.

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Disaccharides

• Sugar formed by joining two monosaccharides
  through a glycosidic linkage.

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Examples

• Maltose glucose glucose
• Lactose glucose galactose
• Sucrose glucose fructose

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Oligosaccharides

• 2 - 10 joined simple sugars.
• Used in cell membranes.

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Polysaccharides

• Many joined simple sugars.
• Used for storage or structure.
• Examples
• Starch
• Cellulose
• Glycogen

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a glucose and b glucose
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Starch

• Made of 1-4 linkages of a glucose.
• Linkage makes the molecule form a helix.
• Fuel storage in plants.

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a glucose
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Cellulose

• Made of 1-4 linkages of b glucose.
• Linkage makes the molecule form a straight line.
• Used for structure in plant cell walls.

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b glucose
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Comment

• Most organisms can digest starch (1- 4 a
  linkage), but very few can digest cellulose (1- 4
  b linkage).
• Another example of the link between structure and
  function.

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Glycogen

• Animal starch
• Similar to starch, but has more 1-6 linkages or
  branches.
• Found in the liver and muscle cells.

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Starch
Glycogen
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Lipids

• Diverse hydrophobic molecules.
• Made of C,H,O
• No general formula.
• CO ratio is very high in C.

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Fats and Oils

• Fats - solid at room temperature.
• Oils - liquid at room temperature.

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Fats and Oils

• Made of two kinds of smaller molecules.
• Fatty Acids
• Glycerol

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Fatty Acids

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

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Acid
Fat
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Neutral Fats or Triacylglycerols

• 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.

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Saturated FatsUnsaturated Fats

• Saturated - no double bonds.
• Unsaturated - one or more CC bonds. Can accept
  more Hydrogens.
• Double bonds cause kinks in the molecules
  shape.

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Question

• Why do fats usually contain saturated fatty acids
  and oils usually contain unsaturated fatty acids?
• The double bond pushes the molecules apart,
  lowering the density, which lowers the melting
  point.

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Fats

• Differ in which fatty acids are used.
• Used for energy storage, cushions for organs,
  insulation.

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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.

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Phospholipids

• Similar to fats, but have only two fatty acids.
• The third -OH of glycerol is joined to a
  phosphate containing molecule.

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Result

• Phospholipids have a hydrophobic tail, but a
  hydrophilic head.
• Self-assembles into micells or bilayers, an
  important part of cell membranes.

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Steroids

• Lipids with four fused rings.
• Differ in the functional groups attached to the
  rings.
• Examples
• cholesterol
• sex hormones

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Proteins

• The molecular tools of the cell.
• Made of C,H,O,N, and sometimes S.
• No general formula.

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Uses Of Proteins
Movie

• Structure
• Enzymes
• Antibodies
• Transport
• Movement
• Receptors
• Hormones

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Proteins

• Polypeptide chains of Amino Acids linked by
  peptide bonds.

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Amino Acids

• All have a Carbon with four attachments
• -COOH (acid)
• -NH2 (amine)
• -H
• -R (some other side group)

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R groups

• 20 different kinds
• Nonpolar - 9 AA
• Polar - 6 AA
• Electrically Charged
• Acidic - 2 AA
• Basic - 3 AA

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Amino Acids
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Amino Acids
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R 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.

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Polypeptide 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

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Levels Of Protein Structure

• Organizing the polypeptide into its 3-D
  functional shape.
• Primary
• Secondary
• Tertiary
• Quaternary

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Primary

• Sequence of amino acids in the
  polypeptide chain.
• Many different sequences are
  possible with 20
  AAs.

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Secondary

• 3-D structure formed by hydrogen bonding between
  the R groups.
• Two main secondary structures
• a helix
• pleated sheets

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Tertiary

• Bonding between the R groups.
• Examples
• hydrophobic interactions
• ionic bonding
• Disulfide bridges (covalent
  bond)

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Quaternary

• When two or more polypeptides unite to form a
  functional protein.
• Example hemoglobin

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Is Protein Structure Important?
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Denaturing Of A Protein

• Events that cause a protein to lose structure
  (and function).
• Example
• pH shifts
• high salt concentrations
• heat

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Nucleic Acids

• Informational polymers
• Made of C,H,O,N and P
• No general formula
• Examples DNA and RNA

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Nucleic Acids

• Polymers of nucleotides
• Nucleotides have three parts
• nitrogenous base
• pentose sugar
• phosphate

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Nitrogenous Bases

• Rings of C and N
• The N atoms tend to take up H (base).
• Two types
• Pyrimidines (single ring)
• Purines (double rings)

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Pentose Sugar

• 5-C sugar
• Ribose - RNA
• Deoxyribose DNA
• RNA and DNA differ in a OH group on the
  3rd carbon.

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Nucleosides and Nucleotides

• Nucleoside base sugar
• Nucleotide base sugar Pi

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DNA

• Deoxyribonucleic Acid.
• Makes up genes.
• Genetic information source for most
  life.

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RNA

• Ribonucleic Acid.
• Structure and protein synthesis.
• Genetic information for a few viruses only.

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DNA and RNA

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

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Summary

• For each macromolecule, know the following
• Elements and monomers
• Structures
• Functions