Main types of organic molecules

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Main types of organic molecules

• Carbohydrates
• Proteins
• Nucleic acids
• Lipids

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Typical composition of organisms by mass
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CARBOHYDRATES

• carbon chain with equal numbers of OH and H and a
  few carbonyl
• general formula "CH2O"
• Includesmonosaccharides (simple sugars) and
  polysaccharides (complex carbohydrates)

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Monosaccharides

• Simple sugars small chains or ring structure,
  with H, OH, and one O
• Triose, tetrose, pentose, hexose sugars name
  depends on number of carbons in the chain
• Sugars may be aldose or ketose depending on
  whether aldehyde or ketone

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The structure and classification of some
monosaccharides
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Monosaccharides, continued

• Important as fuel for energy metabolism
  (glycolysis, cellular respiration)
• Building blocks (monomers) for polysaccharides
  such as starch, cellulose
• Monosaccharide example glucose

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Glucose

• An aldose hexose C6H12O6
• Primary fuel for cells
• Linear and ring forms (structural isomers)

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Polysaccharides

• polymers (chains) of monosaccharides
• condensation reactions link monosaccharides
• hydrolysis reactions separate them

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Polymers

• Large molecules built from chains of smaller
  molecules (monomers)
• Important polymers include
• Polysaccharides (polymers of ring-form hexose
  sugars)
• Proteins (polymers of amino acids
• Nucleic acids (polymers of nucleotides)

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Condensation reactions make polymers from monomers
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Hydrolysis reactions take polymers apart
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Example of a condensation (or dehydration)
synthesis the disaccharide maltose formed from
two glucose monomers by 1-4 linkage
By the waynames for short chains Mono-, di-,
tri-, tetra-, penta-, etc. and oligo-
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Functions of polysaccharides

• Fuel storage - small molecules such as glucose
  affect the osmotic concentration of body fluids
  must be sequestered to store in large quantities
• Structural long molecules used to toughen and
  support cells and tissues

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Glucose storage polysaccharides

• starch in plants and glycogen in animals
• Both are polymers of the glucose isomer a-glucose
• Helical filaments, differ in branching pattern.

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Alpha-glucose
a and ß glucose are structural isomers of glucose
Beta-glucose
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Storage polysaccharides
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Structural polysaccharides

• Cellulose is a polymer of ß-glucose.
• Plant cell-walls
• Most abundant (greatest mass quantity) of any
  organic molecule on earth
• Straight chains cross-linked by hydrogen bonds.

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The arrangement of cellulose in plant cell walls
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Starch and cellulose structures 
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Structural polysaccharides, continued

• Chitin
• cell walls of fungi, exoskeletons of arthropods
• Tough, resistant to digestion
• Similar to cellulose but with acetylamino
  attached to each glucose
• Chitinase - enzyme to break down chitin produced
  by certain microorganisms and plants but not
  animals

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Cellulose
Chitin
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LIPIDS

• Diverse molecules, grouped mainly because of
  hydrophobicity
• Mostly hydrocarbon few polar functional groups
• Types of lipids include fatty acids,
  triglycerides, waxes, phospholipids, and steroids

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Fatty acids

• Carboxyl group at one end of a long hydrocarbon
  tail
• ionized at physiological pH

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A fatty acid
The sodium salt of a fatty acid (soap)
amphipathic
Na
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How Soap works
Na
Na
Na
Na
Na
Na
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Triacylglycerol (fats and oils)

• Three fatty acids joined to glycerol.
• Important energy stores in animals- hydrocarbons
  to be used as metabolic fuel.
• Fats are H-saturated, have higher melting
  temperature
• Oils are H-unsaturated, so have lower melting
  temperature

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Saturated and unsaturated fatty acids
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Unsaturated fat
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Triacylglycerol synthesis
1. Dehydration linkage of a fatty acid to
glycerol
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Triacylglycerol synthesis
2. Completed triacylglycerol molecule
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Phospholipids

• Two fatty acids plus hydrophilic phosphate head
  attached to glycerol
• Amphipathic molecules ionized, hydrophilic
  head and hydrocarbon, hydrophobic tails
• important structural functions

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The structure of a phospholipid
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Phospholipid functions

• Cell membranes phospholipid bilayer

Water outside cell
Water inside cell
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Phospholipid functions

• Lung surfactant interface between air and moist
  surface
• Breakfast cereal additive?

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Steroids

• Another class of lipids, but structurally
  unrelated to FA and triglycerides
• Example cholesterol is a component of cell
  membranes
• also precursor of steroid hormones, including
  androgens and estrogens