Biological Science

• Carbohydrate


  CHO includes both sugars and polymers of sugars
• Carbohydrates


  • Consists of C, H, O
• Monosaccharides


  Simplest carbs, also called simple sugars, with the formula (CH2O)n

  
• Disaccharides


  "Double sugars" consisting of 2 monosaccharides joined by condensation
• Polysaccharides


  Polymers made up of hundreds and thousands of monosaccharides either in the form of linear or branch, broken down through hydrolysis

  
• Monosaccharides


  • glucose, fructose, galactose

  
• Disaccharides


  • sucrose, maltose, lactose

  
• Polysaccharides


  • starch, glycogen, cellulose

  
• Monosaccharides


  • Consist of 3 - 7 carbon atoms

  
• Aldoses


  Monosaccharides with a terminal carbonyl group

  
• Ketoses


  Monosaccharides with an internal carbonyl group

  
• Monosaccharide classification


  Heptose, hexose, pentose, tetrose, triose (7 to 3 carbons)

  
• Glucose


  An aldohexose, have 6 carbons in a straight chain, ending in an aldehyde group
• Monosaccharides have molecular formulae that are multiples of CH2O

  
• Glucose and galactose are different due to the special arrangement around a symmetric carbon

  
• Monosaccharides especially glucose are major nutrients for cells
• In cellular respiration cells extract energy stored in glucose molecules
• Carbon skeleton of monosaccharides serves as raw material for the synthesis of small organic molecules like amino acids and fatty acids

  
• Unused glucose is generally incorporated as monomers into disaccharides or polysaccharides

  
• Ribose with five carbons are building blocks for RNA and DNA molecules
• Fructose


  Ketose sugar, and fruit sugar, 1.5 times sweeter than sucrose but have low Glycemic Index

  
• Isomers


  Same molecular formula but different structures and properties
• Enantiomers


  Mirror images of each other with different properties
• Alpha and beta glucose


  2 most common isomers, similar ring structures and only the hydrogen (H) and hydroxyl (OH) groups on C1 are different

  
• Alpha glucose molecules can combine to form starch, beta glucose can form cellulose</b>

  
• Disaccharides


  2 monosaccharides join together via condensation reaction that releases water and requires energy to form a glycosidic bond

  
• Polysaccharides


  Many monosaccharides linked together by glycosidic bonds, general formula (C6H10O5)n, insoluble and not sweet

  
• Starch and glycogen


  • Provide energy storage
• Cellulose


  • Provides plant support and rigidity
• Amylose


  Linear polymer of glucose, linked by α 1-4 bonds

  
• Amylopectin


  Branched polymer of glucose, branch out in α 1-6, every 24 to 30 units

  
• Glycogen


  Almost same structure as amylopectin but have more branches than them, every 8-12 glucose

  
• Cellulose


  • Made from beta d-glucose polymer, found in plant cell walls

  
• Chitin


  • Also made with beta d-glucose, found in insect shells

  
• Bacterial cell wall


  • Made of n-acetylglucosamine and n-acetylmuramic acid and they repeat
• Lipids


  Also macromolecules, not soluble in water (covalent bond) but in soluble organic solvent like ether, 3 families - fat (triglycerides, triacylglycerols), phospholipids and steroids
• Triglycerides


  In 2 forms - fats (solid at room temp) and oils (liquid at room temp), formed from condensation process of glycerol and fatty acids

  
• Saturated vs Unsaturated fatty acids

  Presence of double bond affects how packed the fatty acids are, temperature affects saturation, addition of hydrogen (hydrogenation) will remove the double bond which make the plant oil solid
• Functions of fat


  • Long-term energy storage, cushion for vital organs, insulation
• Phospholipids


  Only two tails, the last tail is attached to the phosphate group, have hydrophilic and hydrophobic tails, form a ball-like form when in contact with aqueous or water, main function is major component in plasma membrane