The Structure and Function of Macromolecules

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The Structure and Function of Macromolecules

• Chapter 5

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• Macromolecules - larger molecules made from
  smaller ones.
• 4 major classes of macromolecules carbohydrates,
  lipids, proteins, and nucleic acids.
• 3 of these are polymers because they are made
  from individual building blocks called monomers.

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• Monomers - joined together through condensation
  or dehydration reaction (form macromolecules)
• Requires energy uses covalent bonds (links
  together monomers)
• Water produced.

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Water produced as by-product
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• Hydrolysis breaks polymers into monomers.
• Water added to polymer breaks bonds, creates
  monomers (i.e. digestive process in animals)

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Carbohydrates

• 1Carbohydrates - sugars (monomers) and polymers.
• AMonosaccharides - simple sugars.
• BDisaccharides - double sugars (monosaccharides
  linked together)
• CPolysaccharides - polymers of monosaccharides.
• Sugars named with ose.

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• Monosaccharides needed for cellular work.
• Help to synthesize other macromolecules.
• 2 monosaccharides joined by glycosidic linkage to
  form disaccharide via dehydration.

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• Maltose - 2 glucose molecules.
• Sucrose - 1 glucose, 1 fructose.

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• Polysaccharides - energy storage.
• Starch - energy storage polysaccharide for
  plants.
• Starch stored in plants plastids.
• Herbivores access starch for energy.

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• Animals store energy as glycogen.
• Humans - in liver and muscles.
• Cellulose polysaccharide plant cell walls.
• Many herbivores cannot digest cellulose (develop
  relationships with microbes)

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• Chitin - polysaccharide - makes up exoskeleton of
  arthropods (like crustaceans).
• Chitin - found in fungi functions as structural
  support.

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Chitin is used in surgery
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Lipids

• Lipids - no polymers (exception)
• Lipids nonpolar (no affinity for water)
• Fat made from glycerol and fatty acids.
• Glycerol - 3 carbon molecule with hydroxyl group
  and fatty acid consists of carboxyl group
  attached to long carbon skeleton.

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• The 3 fatty acids in a fat can be same or
  different.
• No carbon-carbon double bonds, molecule is
  saturated fatty acid (hydrogen at every possible
  position)
• Form bad fats - solid at room temperature
  (butter, lard)

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No double-double bonds
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• 1 carbon-carbon double bonds - molecule is
  unsaturated fatty acid - formed by removal of
  hydrogen atoms from carbon skeleton.
• Form good fats - liquid at room temperature (oils)

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• Purpose of fat - energy storage.
• Gram of fat stores 2X as much energy as gram of
  polysaccharide.
• Fat also cushions vital organs.
• Layer of fat can also function as insulation.

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• Phospholipids - 2 fatty acids attached to
  glycerol, phosphate group at 3rd position.
• Fatty acid tails are hydrophobic, phosphate group
  and attachments form hydrophilic head.
• When phospholipids added to water, self-assemble
  with hydrophobic tails pointing toward center,
  hydrophilic heads on outside.

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• Phospholipids in cell form bilayer major
  component of cell membrane.

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Hydrophilic
Hydrophobic
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• Steroids - lipids with carbon skeleton consisting
  of 4 fused carbon rings.
• Cholesterol - component in animal cell membranes.
• Cholesterol also forms hormones (i.e.
  testosterone, estrogen)

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Cholesterol
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Proteins

• Proteins - support, storage, transport, defenses,
  and enzymes.
• Made in ribosomes in cell.
• Proteins - amino acids linked together to form
  polymer.
• 20 different amino acids that can be linked
  together to form thousands of different proteins.

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• Amino acids link - polypeptides - combine to form
  proteins.
• Amino acids made of hydrogen atom, carboxyl
  group, amino group, variable R group (or side
  chain).
• R group makes amino acids different from one
  another.
• R groups have different properties (i.e.
  hydrophobic) - form amino acids with different
  properties.

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• Amino acids joined by peptide bonds when
  dehydration reaction removes hydroxyl group from
  carboxyl end of 1 amino acid and hydrogen from
  amino group of another.

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• Shape of protein determines function.
• Shapes - 3 dimensional - determined by sequence
  of amino acids.

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• Primary structure of protein - linear sequence of
  amino acids determined by genetics problem in
  sequence can cause problem in ending protein
  created.

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• Secondary structure - hydrogen bonds at regular
  intervals along polypeptide backbone.
• Two shapes are usually formed alpha coils or
  beta sheets.

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• Tertiary structure determined by variety of
  interactions among R groups and between R groups
  and polypeptide backbone.
• Interactions include hydrogen bonds, van der
  Waals forces, and ionic bonds.
• Disulfide bridges help stabilize form.

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• Quarternary structure - joining of 2 polypeptide
  subunits.
• Collagen and hemoglobin examples.

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• Proteins shape can change due to environment.
• pH, temperature, or salinity (salt
  concentrations) change - protein can denature
  (starts to fall apart)
• Some proteins can return to functional shape
  after denaturation, others cannot, especially in
  crowded environment of cell.

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Nucleic acids

• Amino acid sequence of polypeptide programmed by
  a gene (regions of DNA, polymer of nucleic acids)
• 2 types of nucleic acids ribonucleic acid (RNA)
  and deoxyribonucleic acid (DNA).

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• DNA gives information so RNA can create proteins.
• Flow of genetic information - DNA -gt RNA -gt
  protein.
• Protein synthesis occurs in ribosomes.

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• Monomers of nucleic acids - nucleotides.
• Nucleotides made up of 3 parts nitrogen base,
  five-carbon sugar, and phosphate group.
• Nitrogen bases, rings of carbon and nitrogen,
  come in 2 types purines and pyrimidines.

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• Pyrimidines - cytosine (C), thymine (T), and
  uracil (U in RNA only).
• Purines - adenine (A) and guanine (G).
• Pyrimidines - single six-membered ring purines -
  five-membered ring.

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• In RNA - sugar is ribose DNA - sugar is
  deoxyribose.
• Difference between sugars is lack of oxygen atom
  on carbon two in deoxyribose.

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• Nitrogen base sequence is different for different
  genes.
• Genes are normally hundreds to thousands of
  nucleotides long.
• The number of possible combinations of the four
  DNA bases is limitless.

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• RNA single-stranded - linear shape.
• DNA forms double helix.
• Sugar and phosphate forms backbone of double
  helix while nitrogen bases form connection
  between backbones.

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• Adenine (A) always pairs with thymine (T) guanine
  (G) with cytosine (C).
• Due to six and five membered rings shapes are
  compatible.
• Know sequence of one side of double helix -
  figure out other.
• Two strands are complementary.

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http//www.emunix.emich.edu/rwinning/genetics/pic
s/dna2.gif
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• DNA used to show evolutionary similarities
  between species.
• Two species that appear to be closely-related
  based on fossil and molecular evidence also more
  similar in DNA and protein sequences than more
  distantly related species.

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