Th03L03 Carbohydrates

1. Usually n=3, 4, 5 or 6
   1. Triose (n=3) e.g. glyceraldehyde, dihydroxyacetone
   2. Pentose (n=5
      1. 2-deoxyribose, ribose
   3. Hexoses (n=6)
      1. Glucose, fructose

1. Located in the middle of the ketose molecule and end of the aldose molecule

1. Aldose and ketone
   1. Aldose
      1. contains the aldehyde groups (-CH=O)
      2. Adloses with three or more carbon isomers exhibit stereoisomerism
         1. same molecule that differs in dimensional orientations of their atoms in space affecting properties of the molecule
   2. Ketone
      1. contains the fructose groups
2. Different molecules with same chemical formula
3. Galactose, mannose and glucose

1. Isomeric forms
2. D-sugar is most common biologically

1. In aqueous solution, the aldehyde or ketone group tend to react with a hydroxyl group of the same molecule, closing the molecule into a ring structure

1. Hydroxyl group (-OH) of the carbon that carriers the aldehyde or ketone group can rapidly change from one position to another
2. Alpha form: hydroxyl group is facing up
3. Beta form: hydroxyl group is facing down

1. Digestion of alpha-amylase results in the random hydrolysis of internal alpha 1>4 linkages in the glycogen molecule
2. Pancreatic alpha-amylase mixture of mono and disaccharides continues hydrolysis of internal linkages
3. Maltase produces glucose and can be absorbed into intestinal mucosal cells
4. In the liver, glucose phosphorylase hydrolyses terminal alpha (1>4) to produce glucose-1- phosphate

Nota:

• Normally lactose is broken down into galactose and glucose              When lactose remains undigested, it can be digested by bacteria in the large intestine producing excess CO2 and other metabolites > bloating and diarrhoea   

1. glucose + fructose

1. glucose + glucose

1. glucose + galactose

1. Stored form
2. Linear glucose polymer (alpha 1>4)
3. Alpha (1>6) branches

1. Gycosyltransferase via a dehydration (condensation) reaction