Biochemistry

• Biochemistry

  The study of chemicals, chemical reactions, or processes that occur in living organisms
• Four types of organic molecules essential to human functioning

  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids
• Bioenergetics


  The transformation of energy in living organisms, the study of energy changes during biochemical reactions inside the body
• Endergonic reactions


  • Energy consumption, absorb energy from surroundings, increase internal energy
• Exergonic reactions


  • Energy releasing, release energy as heat or work, decrease internal energy
• Metabolism


  A set of chemical reactions that interconnect in a series of pathways
• Hydrolysis of ATP is an exergonic reaction
• Photosynthesis in plants is an endergonic reaction where energy is stored in glucose
• Cellular respiration in animals is an exergonic reaction where energy stored in glucose is released
• Carbohydrates


  Saccharides or sugars, the most abundant organic molecules in nature

  
• Saccharide


  Derived from the Greek word "sakcharon" meaning "sugar"
• Carbohydrates


  • Chemically are polyhydroxy aldehydes or ketones
  • Compounds of carbon, hydrogen and oxygen
  • General formula is CH2O

  
• Examples of carbohydrates


  • Ribose
  • Glucose
  • Sucrose

  
• Monosaccharides


  Consist of 3-6 carbon atoms, the most abundant is glucose

  
• Five important monosaccharides


  • Glucose
  • Fructose
  • Galactose
  • Ribose
  • Xylose

  
• Monosaccharides


  • Can be classified into two families: Aldoses (carbonyl C at one end) and Ketoses (carbonyl C in middle)

  
• Oligosaccharides


  Contain 2-20 monosaccharide units linked by glycosidic bonds

  
• Polysaccharides


  Complex sugar polymers with more than 20 monosaccharide units, often over 1000 units

  
• Three important polysaccharides


  • Starch
  • Glycogen
  • Cellulose

  
• Stereoisomerism


  Isomers with the same atomic connectivity but differ in spatial arrangement
• Enantiomers


  D and L-sugars, mirror images of each other. D-sugars are utilized by humans.
• Anomerism


  Sugars exist in ring form, carbon 1 becomes asymmetric and is called anomeric carbon. Differ as alpha (α) and beta (β) forms.

  
• Epimerism


  Variations in configuration of H and OH around a single carbon atom. Eg. Mannose is a C2-epimer of glucose, galactose is a C4-epimer of glucose.

  
• Optical activity


  Ability to rotate plane polarized light. Dextrorotatory (+) rotates to the right, levorotatory (-) rotates to the left.
• Monosaccharides


  The simplest sugar in nature, with three carbons

  
• Glyceraldehyde and Dihydroxyacetone


  The simplest monosaccharides

  
• Glucose


  A monosaccharide or simple sugar, produced by plants

  
• Fructose


  A monosaccharide known for its sweetness in fruit and corn syrup
• Galactose


  Similar to glucose in structure, differing only in the position of one hydroxyl group

  
• Ribose


  A five-carbon aldose found in the backbone of RNA (ribonucleic acid)
• Monosaccharides (Classification by Carbon Atoms)


  • Triose (C3H6O3)
  • Tetroses (C4H8O4)
  • Pentoses (C5H10O5)
  • Hexoses (C6H12O6)

  
• Oligosaccharides (Disaccharides)


  Contain two covalently linked monosaccharide units

  
• Homodisaccharides


  Both the monosaccharide units are the same
• Heterodisaccharides


  The monosaccharide units are different
• Sucrose


  A non-reducing disaccharide of glucose and fructose, formed only in plants

  
• Lactose


  A reducing disaccharide of glucose and galactose, present naturally only in milk

  
• More than half of the world's adults are lactose intolerant
• Lactose intolerance


  The inability to metabolize lactose due to the absence or lowered availability of the enzyme lactase
• Lactose intolerance


  1. Lactose remains uncleaved and passes into the colon

  2. Intestinal bacteria switch to lactose metabolism, producing gases

  3. Causes abdominal symptoms like stomach cramps, bloating, and flatulence
• Maltose


  Malt sugar or maltobiose, connected through α1-4 glycosidic linkage, produced from starch by the activity of the enzyme β-amylase