Bio

• Carbohydrates


  Play a number of important roles in cells
• Roles of carbohydrates


  1. Used as an energy source for living organisms, including humans

  2. Oligosaccharides play a key role in processes that take place on the surfaces of cells, particularly in cell-cell interactions and immune recognition

  3. Polysaccharides are essential structural components of plants and bacteria
• Cellulose is a major component of grass and trees
• Other polysaccharides are major components of bacterial cell walls
• Monosaccharides

  Consist of only a single sugar molecule and are commonly called simple sugars
• Monosaccharides

  • Can have a carbon backbone of three to seven carbons
  • The simplest one is of 3C called trioses, 4C-tetrose, 5C-pentose, 6C-hexose, 7C-heptose
  • The most common monosaccharide is the hexose glucose
  • Other common hexoses are fructose, found in fruits, and galactose, which is found in milk
• Monomers


  The smaller units that are used to build longer carbohydrate chains
• Monosaccharides


  • Glucose
  • Fructose
• Disaccharides


  Made by joining only two monosaccharides together by a dehydration reaction
• Disaccharides


  • Maltose
  • Sucrose
  • Lactose
• Maltose formation


  1. Dehydration reaction between two glucose molecules

  2. Glycosidic bond formed
• Sucrose


  Disaccharide formed by joining glucose and fructose
• Lactose


  Disaccharide formed by joining glucose and galactose
• Sucrose is commonly known as table sugar, ordinarily derived from sugarcane and sugar beets
• Formation of maltose :glucose-a-1,4-glucose
• Formation of lactose:

  glactose-B-1,4-glucose
• Formation of sucrose:

  glucose-a-1,2-fructose
• Polysaccharides


  • Long polymers of glucose monomers
  • Examples: starch, glycogen, cellulose
• Starch

  Long polymer of glucose found in plants, used to store glucose for energy
• Glycogen


  Long polymer of glucose found in animals, used to store glucose for energy
• Starch and glycogen

  Have slightly different structures, with starch having fewer side branches
• Cellulose


  Commonly called fiber, found in plant cell walls
• Cellulose


  • Glucose units joined by β-linkages, different from starch/glycogen (α-linkages)
  • Humans/animals cannot digest cellulose due to lack of cellulase enzymes
  • Cellulose passes through digestive tract as fiber/roughage
  • Cellulose is an important dietary component and helps keep digestive system healthy
• Humans and animals lack the enzymes (cellulases) that hydrolyze cellulose to glucose
• Cellulose is a structural polymer, while starch is an energy-storage polymer
• Cellulose


  • Found in certain bacteria, including those in digestive tracts of insects and grazing animals
  • Allows cows and horses to live on grass and hay, but not humans
• Lipids

  Diverse in structure and function, but do not dissolve in water due to lack of hydrophilic polar groups
• Lipid groups


  • Open-chain compounds with polar head groups and long nonpolar tails (fatty acids, triacylglycerols, sphingolipids, phosphoglycerides, glycolipids)
  • Fused ring compounds (steroids, including cholesterol)
• Lipids

  • Contain more energy per gram than other biological molecules (carbohydrates)
  • Function as energy storage molecules in animals and plants
  • Phospholipids form cell membranes to separate cells from environment and create inner compartments
  • Steroids include sex hormones
• Cellulose


  Commonly called fiber, found in cell walls
• Cellulose


  • Glucose units joined by β-linkages, different from starch or glycogen (α-linkages)
  • Humans and animals lack the enzymes (cellulases) to hydrolyze cellulose to glucose
  • Cellulose largely passes through digestive tract as fiber
• Cellulose is an important component of our diet and helps keep our digestive system healthy
• Lipids


  Diverse in structure and function, but do not dissolve in water due to lack of hydrophilic polar groups
• Lipid groups


  • Open-chain compounds with polar head groups and long nonpolar tails (e.g. fatty acids, triacylglycerols, sphingolipids, phosphoacylglycerols, glycolipids)
  • Fused ring compounds (steroids, e.g. cholesterol)
• Lipids


  • Contain more energy per gram than other biological molecules (e.g. carbohydrates)
  • Function as energy storage molecules in animals and plants
  • Phospholipids form membrane so that the cell is separated from it‘s environment
  • Steroids include sex hormones
• Fatty acid

  A carbon-hydrogen chain (nonpolar tail) that ends with the acidic group - COOH (polar head)
• Most of the fatty acids in cells contain an even number of carbons atom per molecule, usually 16 or 18, although smaller ones with fewer carbons are also known
• Fatty acids

  • Amphipathic compounds: the carboxyl group is hydrophilic and the hydrocarbon tail is hydrophobic
  • The carboxyl group can ionize under the proper conditions
• Types of fatty acids

  • Saturated fatty acids (no double bonds between the carbon atoms)
  • Unsaturated fatty acids (double bonds in the carbon chain wherever the number of hydrogens is less than two per carbon)