Structure and Function of Macromolecules

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Structure and Function of Macromolecules
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Monomers, Polymers, and Macromolecules

• Monomers repeating units that serve as
  building blocks for polymers
• Polymers long molecule consisting of many
  similar or identical building blocks linked by
  covalent bonds
• Macromolecules groups of polymers covalently
  bonded 4 classes of organic macromolecules to
  be studied
• 1. Carbohydrates 3. Proteins
• 2. LiPIDs 4. Nucleic Acids

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How to the monomers link up/break back into
monomers?

• Condensation reaction (specifically, dehydration
  synthesis)
• two molecules covalently bond and lose a water
  molecule in the process
• (THIS TAKES ENERGY TO DO!!!)
• Hydrolysis
• polymers are disassembled to monomers by
  adding a water molecule back
• (ex. Digestion of food)

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Figure 5.2 The synthesis and breakdown of
polymers
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Key to diversity of polymers from limited
monomers available

• ARRANGEMENT variation in the linear sequence
  the units follow
• (think of the number of words possible from
  our 26 letter alphabet)
• Molecular logic of life is simple but elegant
  and ORDERLY!!!

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Organic Compounds and Building Blocks

• Carbohydrates made up of linked
  monosaccharides
• Lipids -- CATEGORY DOES NOT INCLUDE POLYMERS
  (grouping based on insolubility)
• Triglycerides (glycerol and 3 fatty
  acids)
• Phospholipids
• Steroids

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• Proteins made up of amino acids
• Nucleic Acids made up nucleotides

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Carbohydrates fuel and building material

• Exist as three types
• 1. monosaccharides
• 2. disaccharides
• 3. polysaccharides (macromolecule stage)
• Made up of C, H, and O
• Has carbonyl group and multiple hydroxyl groups
  (location of carbonyl determines if is an aldose
  or a ketose
• Names end in ose
• Size of carbon skeleton determines category

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Figure 5.3 The structure and classification of
some monosaccharides
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In aqueous solns, most sugars form rings
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Monosaccharides

• Are major sources of energy for cells
• Ex. Glucose cellular respiration
• Are simple enough to serve as raw materials for
  synthesis of other small organic molecules such
  as amino and fatty acids
• Most common glucose, fructose, galactose

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Glucose, Fructose, Galactose

• Glucose made during photosynthesis
• main source of energy for plants and
  animals
• Fructose found naturally in fruits
• is the sweetest of monosacc
• Galactose found in milk
• is usually in association with glucose
  or fructose
• All three have same molecular formula but
  differstructurally so are ISOMERS

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Disaccharides

• Consists of two monosaccharides joined by a
  GLYCOSIDIC LINKAGE a covalent bond resulting
  from dehydration synthesis
• Ex. Maltose 2 glucoses joined
• Sucrose glucose and fructose
• Lactose glucose and galactose

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Figure 5.5 Examples of disaccharide synthesis
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Figure 5.5x Glucose monomer and disaccharides
Glucose monomer
Sucrose
Maltose
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Polysaccharides

• These are the polymers of sugars the true
  macromolecules of the carbs
• Serve as storage material that is hydrolyzed as
  needed in body or as structural units that
  support bodies of orgs

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Storage Polysaccharides Starch and Glycogen

• Starch found in plants
• made up of glucose monomers in alpha
  configuration
• has a helical shape
• can be unbranched (amylose) or branched
  (amylopectin)
• stored as granules in plants in the
  PLASTIDS
• (these granules are stockpiles of glucose for
  later use carb BANK)
• You can find starch in potatoes and grains

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• Glycogen found in animals
• extensively branched group of glucose
  units
• stored in liver and muscle cells
• glycogen bank is depleted within 24
  hours needs replentishing

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Figure 5.6 Storage polysaccharides
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Structural Polysaccharides

• Cellulose major component of plant cell
  walls
• most abundant organic compound on Earth
• polymer of glucose, but all glucose
  molecules are in the beta configuration
• thus, cellulose is always straight, and
  this provides for strength (Ex. Lumber)

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Figure 5.7a Starch and cellulose structures 
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Figure 5.7b,c Starch and cellulose structures 
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Figure 5.7x Starch and cellulose molecular
models
? Glucose
? Glucose
Cellulose
Starch
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Figure 5.8 The arrangement of cellulose in plant
cell walls
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Cellulose and the diet

• Few orgs possess the enzymes to digest cellulose
• Cellulose passes through the digestive tract and
  is eliminated in feces
• BUT, the fibrils of cellulose abrade the wall of
  the digestive tract and stimulate secretion of
  mucus which is necessary for smooth food passage
  so though cellulose is not nutritious, it is
  necessary
• Orgs that can digest cows (with help of
  bacteria), termites (with help of microbes), some
  fungi

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Figure 5.x2 Cellulose digestion cow
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Figure 5.x1 Cellulose digestion termite and
Trichonympha
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Chitin

• Another structural polysaccharide
• Used by arthropods to build their exoskeletons
• Pure chitin in leathery, but when encrusted with
  calcium carbonate it hardens into shell form
• Also used by fungi in their cell walls (instead
  of cellulose)
• Similar to cellulose, but the glucose monomer has
  a nitrogen containing appendage

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Figure 5.9 Chitin, a structural polysaccharide
exoskeleton and surgical thread
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Chemical Identification of Carbohydrates

• Benedicts Test Identifies the presence of a
  MONOSACCHARIDE by changing from blue to orange in
  the presence of heat
• Iodine Test Identifies the presence of a
  POLYSACCHARIDE by changing from yellow to
  purple/black
• Process of Elimination If there is no reaction
  with either the Benedicts or Iodine Tests, then
  a DISACCHARIDE is present.