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• Macromolecules


  Large polymers
• Polymer


  A long molecule consisting of many similar building blocks
• Monomers


  The repeating units that serve as building blocks
• Examples of polymers


  • Carbohydrates
  • Proteins
  • Nucleic acids
• Enzymes


  • Specialized macromolecules that speed up chemical reactions
  • Make or break down polymers
• Dehydration reaction


  Two monomers bond together through the loss of a water molecule
• Hydrolysis


  Polymers are disassembled to monomers by a reaction that is essentially the reverse of the dehydration reaction
• A cell has thousands of different macromolecules
• Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species
• A huge variety of polymers can be built from a small set of monomers
• Carbohydrates


  • Sugars
  • Polymers of sugars
• Monosaccharides


  The simplest carbohydrates, simple sugars
• Polysaccharides


  Carbohydrate macromolecules, polymers composed of many sugar building blocks
• Disaccharide


  Formed when a dehydration reaction joins two monosaccharides
• Glycosidic linkage


  The covalent bond between two monosaccharides in a disaccharide
• Glycoside


  A substance containing a glycosidic bond
• Storage polysaccharides


  • Starch
  • Glycogen
• Starch


  • A storage polysaccharide of plants, consists of glucose monomers
  • Plants store surplus starch as granules within chloroplasts and other plastids
  • Simplest form is amylose
• Glycogen


  • A storage polysaccharide in animals, stored mainly in liver and muscle cells
  • Hydrolysis of glycogen releases glucose when the demand for sugar increases
• Cellulose


  • A major component of the tough wall of plant cells
  • A polymer of glucose, but the glycosidic linkages differ from starch
• Alpha (α) and beta (β) ring forms of glucose


  The difference in the glycosidic linkages of starch and cellulose is based on these two ring forms
• Enzymes that digest starch by hydrolyzing α linkages can't hydrolyze β linkages in cellulose
• The cellulose in human food passes through the digestive tract as "insoluble fiber"
• Some microbes use enzymes to digest cellulose, and many herbivores have symbiotic relationships with these microbes
• Chitin


  • Another structural polysaccharide, found in the exoskeleton of arthropods and the cell walls of many fungi
  • Made of N-Acetyl glucosamine, a different glucose (C8H13O5N)n
• Lipids


  • A class of large biological molecules that does not include true polymers
  • The unifying feature is that they mix poorly, if at all, with water
• Most biologically important lipids


  • Fats
  • Phospholipids
  • Steroids
• Fats


  • Constructed from glycerol and fatty acids
  • Three fatty acids joined to glycerol by an ester linkage, creating a triacylglycerol or triglyceride
• Saturated fatty acids


  Have the maximum number of hydrogen atoms possible and no double bonds
• Unsaturated fatty acids


  Have one or more double bonds
• Fats made from saturated fatty acids are called saturated fats and are solid at room temperature, while fats made from unsaturated fatty acids are called unsaturated fats or oils and are liquid at room temperature
• A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits
• Hydrogenation


  The process of converting unsaturated fats to saturated fats by adding hydrogen
• Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds, which may contribute more than saturated fats to cardiovascular disease
• Phospholipids


  • Have two fatty acids and a phosphate group attached to glycerol
  • The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head
• When phospholipids are added to water, they self-assemble into double-layered sheets called bilayers
• At the surface of a cell, phospholipids are also arranged in a bilayer, with the hydrophobic tails pointing toward the interior
• Steroids


  • Lipids characterized by a carbon skeleton consisting of four fused rings
  • Cholesterol is a type of steroid that is a component in animal cell membranes and a precursor from which other steroids are synthesized
• A high level of cholesterol in the blood may contribute to cardiovascular disease
• Proteins


  Biologically functional molecules that consist of one or more polypeptides