The Structure and Function of Macromolecules

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The Structure and Function of Macromolecules

• Chapter 5
• AP Biology

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Polymer Principles

• Very large molecules macromolecules
• Most macromolecules are polymers
• chains of identical or similar building
  blocksmonomers

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Polymer Principles, continued

• Formation Condensation Reactions
• monomers to polymers
• water is releaseddehydration
• Disassembly Hydrolysisrequires H2O

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Example of Condensation Reaction
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Hydrolysis of Sucrose
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Polymer Principles, continued

• Various polymers are built from a small set of
  monomers
• Each class of polymer
• formed from a specific set of monomers
• Limited monomer types
• Unique arrangements possible
• Due to specific arrangement of monomers into
  polymers.

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Monomer Characteristics

• Very small
• Mostly soluble in water
• Pass in/out of cells easily
• some organisms (autotrophs) synthesize monomers
• other organisms get monomers from "food"
  (heterotrophs)

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Monomer-Polymer Characteristics

• Monomer-polymer pattern
• extremely efficient and flexible
• Few monomers needed
• less than 30 common monomers in cells
• Thousands of kinds of polymers made

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Polymer Characteristics

• Polymer diversity results from
• Different monomer used
• Different sequence of monomers
• e.g English alphabet and different words possible
• Different patterns of branching
• glycogen is more branched than starch
• Polymers can be broken down into monomers and
  re-used to make different polymerscellular
  recycling.

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Polymer Characteristics Summary

• Extremely large?do not enter or leave cells
  except by special mechanisms.
• Synthesized by condensation reactions
  (dehydration synthesis)
• Broken down by hydrolysis (digestion)
• Great diversity possible from only a few kinds of
  monomers
• Cellular recyclingmonomer subunits reused to
  make different polymers

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Organic Compounds

• Four major classes in cells (Note cells are the
  basic unit of life)
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids

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Examples of Organic Molecules

• Carbohydrate
• Protein

• Lipid

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Examples of Organic Molecules, continued

• Nucleic Acid (building block nucleotidenitrogen
  base, phosphate group, and sugar)

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Functional Groups contribute to diversity of
molecules
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Formation of Polymers

• Joining monomers to each other
• Series of chemical reactions
• To form long chain molecules
• Formation reaction
• condensation reaction or
• dehydration synthesis reaction

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Formation of Polysaccharides
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Formation of Polypeptides(and Proteins)
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CARBOHYDRATES--FUEL AND BUILDING MATERIAL

• Sugars smallest carbohydrates
• Fuel and carbon sources
• Monosaccharidessimplest carbohydrates
• Used directly for fuel
• Converted to other types of organic molecules
• Used as monomers for polymers.
• Disaccharides
• Two monosaccharides
• Connected by a glycosidic linkage

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Polysaccharides

• Polysaccharides
• Polymers of sugars
• Have storage and structural roles
• Monosaccharide monomers of polysaccharides
  connected by glycosidic linkages
• Starch (plants) and glycogen (animals)
• storage polymers of glucose.
• Cellulose
• important structural polymer of glucose
• in plant cell walls.
• Starch, glycogen, and cellulose differ in the
  positions and orientations of their glycosidic
  linkages.

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LIPIDS--DIVERSE HYDROPHOBIC MOLECULES

• Fats store large amounts of energy
• Fats (triacylglycerols)
• Glycerol molecule joined to three fatty acids
• Dehydration reactions
• Saturated Fatty Acids
• Have maximum number of hydrogen atoms
• Unsaturated Fatty Acids (in oils)
• Have one double bonds in hydrocarbon chains.

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Lipids, continued

• Phospholipids
• Major components of cell membranes
• Contrast with fats--no third fatty acid linked to
  glycerol
• Have a negatively charged phosphate group
• may be joined to another small hydrophilic
  molecule
• Head" of phospholipid is hydrophilic.

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Lipids, continued

• Steroids
• Cholesterol
• Certain hormonesprogesterone, testosterone,
  estradiol
• Steroids have basic four fused rings of carbon
  atoms structure.

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PROTEINS--MANY STRUCTURES, MANY FUNCTIONS

• Protein
• One or more polypeptide chains
• Folded into a specific three-dimensional
  conformation

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Polypeptides

• Polymer of amino acids
• Connected in a specific sequence
• Constructed from 20 different amino acids (aa)
• Each aa has characteristic side chain (R group).
• Carboxyl and amino groups of adjacent aa link
  together (peptide bonds)

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Protein Function and Structure

• Function linked to conformation
• Primary Structure unique sequence of aa
• Secondary Structure folding or coiling into
  repeating configurations
• Mainly helix and b pleated sheet
• Due to hydrogen bonding of parts of polypeptide
  backbone.

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Protein Structure, continued

• Tertiary Structure overall three-dimensional
  shape of polypeptide
• Due to aa side chain interactions
• Proteins of more than one polypeptide chain
  (subunits) have a quaternary level of structure.
• Structure and function of protein are sensitive
  to physical and chemical conditions.
• Protein shape ultimately determined by primary
  structure, but in the cell, proteins called
  chaperonins may help the folding process.

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NUCLEIC ACIDS--INFORMATIONAL POLYMERS

• Nucleic acids store and transmit hereditary
  information
• DNA stores info for protein synthesis
• RNA (specifically, mRNA) carries genetic info to
  protein-synthesizing machinery.

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Nucleic Acid Strands

• Polymer of nucleotides
• Each nucleotide monomer pentose covalently
  bonded to a phosphate group and to one of four
  different nitrogenous bases (Adenine, Guanine,
  Cytosine, and Thymine or Uracil).
• RNA has ribose as its pentose
• DNA has deoxyribose.
• RNA has U and DNA has T

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Nucleic Acid Strand Formation

• Nucleotides join and form a sugar-phosphate
  backbone
• Nitrogenous bases project from backbone
• Sequence of bases along a gene specifies aa
  sequence of a particular protein

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Nucleic Acids and Inheritance

• Inheritance based on replication of the DNA
  double helix
• DNA helical, double-stranded macromolecule with
  bases projecting into the interior of the
  molecule.
• A always hydrogen-bonds to T
• C always hydrogen-bonds to G
• Nucleotide sequences of the two strands are
  complementary.

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DNA and Evolution

• DNA and proteins useful for evolution measures.
• Molecular comparisons help biologists sort out
  the evolutionary connections among species.

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Quiz

• What kind of chemical reaction is needed to form
  a polymer from individual monomers?
  __________________
• What kind of reaction is needed to break a
  polymer into its constituent monomers?
  ______________
• What are the monomers needed to build sucrose?
  _____________

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• 4. What is starch? _______________
• 5. What is glycogen? _____________
• 6. What kind of chemical bond is responsible for
  the secondary structure of proteins? ___________
• 7. What determines the primary structure of
  proteins? ___________
• 8. All proteins contain carbon, hydrogen, oxygen
  and what other element? ______