Nerve activates contraction

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CHAPTER 5 THE STRUCTURE AND FUNCTION OF
MACROMOLECULES

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Polymers

• Polymers
• Similar or same building blocks repeated.
• Building block monomer
• Covalent bonds!

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Polymer formation Dehydration reaction

• One monomer provides a hydroxyl group
• the other provides a hydrogen
• Releases water.
• Process requires energy is aided by enzymes.

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Breakdown of polymers Hydrolysis

• covalent bond between two monomers is broken
  with the help of water
• E.g. digestive process, catalyzed by enzymes.

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There are four major varieties of macromolecules
seen in all living things

• Polymers of size 100,000 daltons or more called
  macromolecules
• Carbohydrates
• Proteins
• Lipids
• Nucleic acids

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Carbohydrates - Fuel and Building Material

• Sugars,smallest carbohydrates, serve as fuel and
  or source of energy for all living things
• 2. Polysaccharides, the polymers of sugars, have
  storage and structural roles

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Carbohydrates

• Carbohydrates can be studied as
• Monosaccharides simple sugars.
• Disaccharides, double sugars 2 monosaccharides
  joined by a condensation reaction.
• Polysaccharides polymers of monosaccharides.

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Sugars, the smallest carbohydrates serve as a
source of fuel and carbon sources

• Monosaccharides generally have molecular formulas
  that are in general multiple of CH2O.
• For example,
• Molecular formula of glucose 6CH2O or C6H12O6
• Most names for sugars end in -ose. glucose,
  fructose, maltose etc.

glucose
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Monosaccharides
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• Monosaccharides are represented as
• linear skeleton in a solid state,
• form rings in aqueous solutions.

Fig. 5.5
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• Functions of monosaccharides
• glucose is a major fuel for cellular work.
• Serve as raw material for the synthesis of other
  monomers, including those of amino acids and
  fatty acids.

Energy to think comes from glucose
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• Dissaccharides
• Maltose, malt sugar, is formed by joining two
  glucose molecules.
• Sucrose, table sugar, is formed by joining
  glucose and fructose and is the major transport
  form of sugars in plants.

Fig. 5.5a
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Polysaccharides

• polymers of hundreds to thousands of
  monosaccharides
• glycogen, starch, cellulose, chitin
• Functions of polysaccharides
• Serve as energy storage macromolecule
• serve as building materials for the cell or whole
  organism.

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Cellulose

• The architecture or how the monomers are linked
  are very important
• Can give different characteristic to polymer

Chitin
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Compare Cellulose and Chitin
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• Cellulose in diet
• Cellulose cannot be digested in human intestine
  because of lack of enzyme cellulase
• thus eliminated in feces as insoluble fiber.
• However it stimulates the secretion of mucus.
• -Facilitates defecation

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• How do cows or termites ( herbivores) digest
  plants ?
• They also do not have enzyme cellulase
• Herbivores have symbiotic relationships with
  microbes in their digestive tract,
• Microbes have the enzyme cellulase
• Breaks the cellulose and releases glucose.

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Lipids - Diverse Hydrophobic Molecules

• Fats store large amounts of energy
• Phospholipids are major components of cell
  membranes
• 3. Steroids include cholesterol and certain
  hormones

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• Lipids
• an exception among macromolecules because they
  are not repeating units of monomers
• All hydrophobic
• b/c structures are dominated by nonpolar
  covalent bonds.
• 3 types
• Fats
• Phospholipids
• Steroids

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Fats

• A fat consists of two kinds of
• glycerol fatty acids.

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Glycerol consists of a three carbon skeleton
with a hydroxyl group attached to each. A
fatty acid consists of a carboxyl group attached
to a long carbon skeleton, often 16 to 18 carbons
long.
Fig. 5.10a
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• Non-polar, long hydrocarbon skeleton make fats
  hydrophobic.
• In a fat, three fatty acids are joined to
  glycerol creating a triacylglycerol.

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• The three fatty acids in a fat can be the same or
  different.
• Fatty acids may vary
• 1) length (number of carbons)
• 2) number and locations of double bonds (if any).

Fig. 5.11a
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The presence or absence of a double bond
determines the shape of the fatty acid.
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• A diet rich in saturated fats may contribute to
  cardiovascular disease (atherosclerosis) through
  plaque deposits.

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• Functions of fat
• Source of energy
• Fat also functions to cushion vital organs.
• layer of fats can also function as insulation.
• E.g. This subcutaneous layer is especially thick
  in whales, seals, and most other marine mammals

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Phosopholipids

• Phospholipids 2 fatty acids attached to glycerol
  phosphate group at the third position.
• The phosphate group carries a negative charge
• (Additional smaller groups may be attached to the
  phosphate group)

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Phospholipid Bilayer
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• When phospholipids are added to water,
• they self assemble into 2 possible structures
• 1) Micelles
• 2) Bilayers

Fig. 5.13a
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• The phospholipid bilayer forms a barrier between
  the cell and the external environment.
• Major component of membranes.

Fig. 5.12b
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• Steroids are lipids
• carbon skeleton made of four fused carbon rings.
• Variation in steroids achieved by different
  functional groups

Fig. 5.14
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• Cholesterol, an important steroid, is a component
  in animal cell membranes.
• Cholesterol is also the precursor for sex
  hormones

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Proteins - Many Structures, Many Functions
A polypeptide is a polymer of amino acids
connected in a specific sequence A protein can be
one or many polypeptides coming together. A
proteins function depends on its specific
conformation
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• Proteins have multiple functions in cell.
• Such as
• structural support
• storage
• transport of other substances
• intercellular signaling
• Cellular movement muscular movement
• defense against foreign substances
• Enzymes!
• Humans have tens of thousands of different
  proteins, each with their own structure and
  function.

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• Monomers of polypeptides are amino acids.
• AAs consist of 4 components attached to a
  central carbon, the alpha carbon.
• 1) hydrogen atom
• 2) carboxyl group
• 3) amino group
• 4) variable R group (or side chain).

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• Variable R group creates 20 different amino acids
• The physical and chemical characteristics of the
  R group determine the unique characteristics of a
  particular amino acid.

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• Hydrophobic or nonpolar amino acids.

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• Polar or hydrophilic amino acids

Fig. 5.15b
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• Acidic and basic amino acids

Fig. 5.15c
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What is anEssential Amino Acid?

• We need 20 amino acids to build all the proteins
  we will need for life.
• 8 of those amino acids our body cannot
  synthesize.
• These must be obtained through diet.
• Phe, Met, Trp, Lys, Ala, Val, Leu, Iso

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• Two amino acids react with another by the process
  of dehydration
• To form a polymer .
• The bond that keeps the two amino acids together
  is called peptide bond

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• Repeating the process over and over creates a
  long polypeptide chain.
• At one end is an amino acid with a free amino
  group the (the N-terminus) and
• at the other is an amino acid with a free
  carboxyl group the (the C-terminus).

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• The folding of a protein from a chain of amino
  acids occurs spontaneously.
• Three levels of structure
• primary
• secondary
• tertiary structure
• (are used to organize the folding within a
  single polypeptide.)
• Quaternary structure arises when two or more
  polypeptides join to form a protein.

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• The primary structure of a protein is its unique
  sequence of amino acids.

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• Sickle cell anemia
• single change in amino acid changes the primary
  structure compromises function of the protein
  hemoglobin.

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• Secondary structure
• due to hydrogen bonds at regular intervals along
  the polypeptide backbone.
• 2 types
• 1) coils (an alpha helix) as in hair or
• 2) folds (beta pleated sheets) as in silk

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Biosteel

• Protein in spider web is toughest material known
  to man.
• Materials sci. wants to mass produce
• Implications light weight bullet proof vests,
  medical sutures, fishing line,
• Use transgenic goat.
• The Science paper, titled "Spider Silk Fibers
  Spun from Soluble Recombinant Silk Produced in
  Mammalian Cells" (Lazaris et al., 2002-01-18.
  Science. Vol. 295472-476)
• http//www.eurekalert.org/pub_releases/2002-01/nbi
  -nau011102.php

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• Tertiary structure
• variety of interactions among R groups and
  between R groups and the polypeptide backbone.
• These interactions include
• Covalent bonds
• hydrogen bonds
• ionic bonds
• hydrophobic interactions
• van der Waals interactions.

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disulfide bridges, strong covalent bonds that
form between the sulfhydryl groups (SH) of
cysteine monomers, stabilize the structure.

• disulfide bridges, strong covalent bonds that
  form between the sulfhydryl groups (SH) of
  cysteine monomers, stabilize the structure.

Fig. 5.22
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• Quaternary structure
• aggregation of two or more polypeptide subunits.
• Examples
• 1)Collagen fibrous protein of 3 polypeptides
  that are supercoiled like a rope.
• This provides the structural strength for their
  role in
• connective tissue.
• 2) Hemoglobin is a globular protein with two
  copies of two kinds of polypeptides.

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Fig. 5.24
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• Environment influences protein structure
• pH, salt concentration, temperature, or other
  factors can unravel or denature a protein.
• These forces disrupt the hydrogen bonds, ionic
  bonds, and disulfide bridges that maintain the
  proteins shape.

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Nucleic Acids - Informational Polymers

• 1. Nucleic acids store and transmit hereditary
  information
• Two types RNA, DNA

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• Nucleic acids are polymers of monomers called
  nucleotides.
• 3 Parts
• nitrogenous base
• pentose sugar
• phosphate group.

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• Nitrogen bases
• purines and pyrimidines.
• Pyrimidines
• single ring.
• cytosine (C), thymine (T), and uracil (U)
• Purine 2 rings
• adenine (A) and guanine (G).

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• Difference between the sugars is the lack of an
  oxygen atom on carbon two in deoxyribose.
• DNA deoxyribose
• RNA ribose

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There are two types of nucleic acids

• Deoxyribose nucleic acid (DNA)
• Contains information to make a polypeptide
• ribonucleic acid (RNA)
• Intermediary info. carrying molecule.

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Thus

• The types of nucleic acid molecules can be
  distinguished based on
• Nitrogenous bases they have
• Pentose sugar
• of strands they possess
• size

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• Compare DNA and RNA

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Fig. 5.30