Organic Molecules of Life

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Organic Molecules of Life

• Wednesday, July 9

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Macromolecules

• Highly organized molecules that can assume
  intricate shapes and perform complex tasks with
  great precision and efficacy
• Polymers composed of a large number of
  low-molecular weight building blocks (monomers)
• Constantly broken down (hydrolysis) and rebuilt
  (dehydration), necessitating a supply of
  precursors

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Figure 5.2 The synthesis and breakdown of
polymers
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Families of Biological Molecules

• Carbohydrates (sugars, saccharides)
• Lipids (fatty acids)
• Proteins (amino acids)
• Nucleic Acids (will cover in genetics unit 3)

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Carbohydrates

• Functions stores of chemical energy
• durable building materials
• Structure (CH2O)n where n 3-7
• Classification
• Number of Carbons
• N 3 (triose), 4 (tetrose), 5 (pentose), 6
  (hexose), 7 (heptose)
• Position of carbonyl group
• Internal ketose Terminal aldose
• Linking saccharides together sugars are joined
  together by covalent glycosidic bonds

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Figure 5.3 The structure and classification of
some monosaccharides
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Figure 5.4 Linear and ring forms of glucose
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Sterioisomerism
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Carbohydrates

• Functions stores of chemical energy
• durable building materials
• Structure (CH2O)n where n 3-7
• Classification
• Number of Carbons
• N 3 (triose), 4 (tetrose), 5 (pentose), 6
  (hexose), 7 (heptose)
• Position of carbonyl group
• Internal ketose Terminal aldose
• Linking saccharides together sugars are joined
  together by covalent glycosidic bonds

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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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Extending the sugar chains

• Oligosaccharides
• Additional saccharides can be attached to create
  a small chain of sugars
• These usually are attached to
• Lipids glycolipids
• Proteins glycoproteins
• Polysaccharides
• Long chain of sugar units
• Storage Polysaccharides (easily digested)
• Glycogen and Starch
• Structural Polysaccharides (tough and durable)
• Cellulose, Chitin, and Glycosaminoglycans (GAGs)

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Figure 5.6 Storage polysaccharides
Polymers of glucose stored in a highly
concentrated form
Plant energy
Unbranched polymer
Branched polymer
Animal energy
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Figure 5.7x Starch and cellulose molecular
models
? Glucose
? Glucose
Cellulose
Starch
Cellulose (plant cell walls, cotton textiles)
Multicellular organisms lack the enzyme
(cellulase) needed to degrade cellulose.
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Figure 5.7b,c Starch and cellulose structures 
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Figure 5.8 The arrangement of cellulose in plant
cell walls
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Figure 5.x1 Cellulose digestion termite,
Trichonympha, sheep, cow
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Figure 5.9 Chitin
Exoskeleton
Surgical Thread
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Lipids

• Properties nonpolar dissolve in organic
  solvents, insoluable in water
• Functional types of lipids
• Fats
• Steroids
• Phospholipids

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Fats

• Functions extremely concentrated storage fuel
  (lack water) found in adipocytes
• Structure triacylglycerol (3 fatty acids lined
  by ester bonds to a glycerol molecule)
• Fatty acids long unbranched hydrocarbon chains
  with a single terminal carboxyl group
• Length 14 20 carbons
• Double bonds lack (saturated), contain
  (unsaturated)
• Amphipathic contains both hydrophobic and
  hydrophillic regions

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Figure 5.10 The synthesis and structure of a
triacylglycerol
Hydrophobic region
Hydrophillic region
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Figure 5.11 Saturated and unsaturated fatty
acids 
Oil
Butter
Melting Temperature (Tm) the temp at which
lipids become liquid (melt) - length the
longer the chain, the more interactions that
occur, causing a stronger bond - double bonds
double bonds cause a kink in the chain,
preventing them from packing
together well Increasing Tm increase chain
length, increase saturation (less double
bonds) Decreasing Tm decrease chain length,
increase double bonds
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Phospholipids

• Functions plasma cell membranes
• Structure diacylglycerol with a phosphate group
  (phosphotidic acid) covalently bound to a polar
  group
• Choline
• Serine
• Ethanolamine
• Inositol

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Figure 5.12 The structure of a phospholipid
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Figure 5.13 Two structures formed by
self-assembly of phospholipids in aqueous
environments   
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Steroids

• Functions
• Cholesterol important component of cell
  membranes
• Testosterone/Estrogen hormones
• Structure
• Four-ringed hydrocarbon skeleton

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Figure 5.14 Structure of Cholesterol
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Proteins

• Functions carry out virtually all cellular
  activities
• Structure built from amino acids

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Amino Acids

• 20 amino acids
• Carboxyl Group -- aCH Amino Group
• Polypeptide chain amino acids are joined to
  form long, unbranched chains linked by peptide
  bonds
• Functional Groups (R side chain)
• Polar and Charged
• Polar and Uncharged
• Nonpolar

R
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Nonpolar Amino Acids
Hydrophobic R group consist of C and H atoms,
forming the inner core of soluble proteins,
buried away from the aqueous medium
Glycine is unique small amphipathic, resides at
sites where polypeptides come in close
contact Proline is unique creates kinks in
polypeptides, disrupting secondary structure
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Polar Uncharged Amino Acids
Hydrophillic R groups tend to have partial
charge allowing them to participate in chemical
reactions, for hydrogen bonds, associate with
water
Cysteine is unique can form a covalent bond
with another cysteine to form a disulfide link
(C-S-S-C)
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Polar Charged Amino Acids
Hydrophillic R groups tend to be fully charged
allowing them to act as acids and bases,
participating in chemical reactions and ionic
bonds
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Figure 5.16 Making a polypeptide chain
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Structural Levels

• Primary structure specific linear amino acid
  sequence
• Secondary structure conformation (3D
  arrangement, spatial organization) of parts of
  the polypeptide chain
• a-helix cylindrical twisting spiral
• ß-pleated sheet several polypeptides lying
  parallel to one another
• Tertiary structure conformation of the entire
  protein
• Fibrous highly elongated shape
• Structural proteins collagens, elastins, and
  keratin
• Globular compact shape
• Most proteins within the cell myoglobin
• Quaternary structure many proteins contain more
  than one polypeptide chain (subunit) linked by
  disulfide or noncovalent bonds

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Figure 5.18 The primary structure of a protein
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Figure 5.19 A single amino acid substitution in
a protein causes sickle-cell disease
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Structural Levels

• Primary structure specific linear amino acid
  sequence
• Secondary structure conformation (3D
  arrangement, spatial organization) of parts of
  the polypeptide chain
• a-helix cylindrical twisting spiral
• ß-pleated sheet several polypeptides lying
  parallel to one another
• Tertiary structure conformation of the entire
  protein
• Fibrous highly elongated shape
• Structural proteins collagens, elastins, and
  keratin
• Globular compact shape
• Most proteins within the cell myoglobin
• Quaternary structure many proteins contain more
  than one polypeptide chain (subunit) linked by
  disulfide or noncovalent bonds

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Figure 5.20 The secondary structure of a protein
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Structural Levels

• Primary structure specific linear amino acid
  sequence
• Secondary structure conformation (3D
  arrangement, spatial organization) of parts of
  the polypeptide chain
• a-helix cylindrical twisting spiral
• ß-pleated sheet several polypeptides lying
  parallel to one another
• Tertiary structure conformation of the entire
  protein
• Fibrous highly elongated shape
• Structural proteins collagens, elastins, and
  keratin
• Globular compact shape
• Most proteins within the cell myoglobin
• Quaternary structure many proteins contain more
  than one polypeptide chain (subunit) linked by
  disulfide or noncovalent bonds

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Figure 5.22 Examples of interactions
contributing to the tertiary structure of a
protein
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Figure 5.17 Conformation of a protein, the
enzyme lysozyme
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Structural Levels

• Primary structure specific linear amino acid
  sequence
• Secondary structure conformation (3D
  arrangement, spatial organization) of parts of
  the polypeptide chain
• a-helix cylindrical twisting spiral
• ß-pleated sheet several polypeptides lying
  parallel to one another
• Tertiary structure conformation of the entire
  protein
• Fibrous highly elongated shape
• Structural proteins collagens, elastins, and
  keratin
• Globular compact shape
• Most proteins within the cell myoglobin
• Quaternary structure many proteins contain more
  than one polypeptide chain (subunit) linked by
  disulfide or noncovalent bonds

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Figure 5.23 The quaternary structure of proteins
Heteropolymer
Homotrimer
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Figure 5.24 Review the four levels of protein
structure
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Figure 5.26 Chaperon proteins help to fold
proteins correctly
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Figure 5.25 Denaturation and renaturation of a
protein
pH, heat