1. Structure and metabolism
Carbohydrate
Structure and metabolism

2. Definition CHO (Hydrated carbon)
CHO are aldehyde or ketone (=O) compounds with multiple hydroxy (-OH) groups
General formula (CH2O)n
Monosaccharides and Disaccharides are called sugars, they end by – OSE e.g. glucose, lactose etc.

3. Functional groups C-OH, hydroxyl group C=O, carbonyl group OH
C=O, carboxyl group

4. Functions Provision of energy Storage of energy
Major component in nucleic acid structure
Structural functions, cell wall (bacteria and plants)
Cell membrane (Signal transduction – adhesion, cell-cell interaction and etc)
Others e.g. mucin

5. Glucose
Figure 4.6 Mannose and galactose are epimers of glucose

6. Classification Monosaccharides (simplest unit)
Disaccharides: 2 monosaccharides linked by covalent glycosidic bond e.g. sucrose
Oligosaccharides: 3 – 10 monomers
Polysaccharides: more than 10 could be linear or branched

7. Monosaccharides (simplest unit)
A . Aldose b. Ketose
Trioses [3]
Tetroses [4]
Pentoses [5]
Hexoses [6]
Heptoses [7]
Nonoses [9]

10. Hexoses [C6] (Isomers)
Isomers; are sugars have the same chemical formula (CH2O)n, but have different structures
Enantiomers (mirror images; L or D) (position of OH on asymmetric carbons furthest from =O group)
Anomers: OH above () or below () plane around anomeric C (C to which attached the =O) e.g. C1 in glucose, C2 in fructose
Epimers: they differ in orientation (right or left) of one OH around asymmetric C (C2 to C5)

11. Enantiomers have identical chemical and physical properties except for their ability to rotate plane-polarized light by equal amounts but in opposite directions.

12. Figure 4.7 Formation of ring structures in sugars

14. Monosacchrides form cyclic structure (ring) in solution (=O react with -OH in the same molecule)
Formed Glu ring is called pyranose (pyran like)
In this case the C1 is called anomeric C
If the OH attached to C1 above the ring plane, we say -anomer, if below is -anomer
In solution -and - interchange (mutarotation)
Keto sugars form (furan like) furanoses

15. Figure 4.6 Mannose and galactose are epimers of glucose

17. Bonds (linkage)
Monosaccharides interact with each other or other compound through glycosidic bonds
Glycosidic bond is covalent bond between the anomeric C (in glucose C1) and C of another compound
The glycosidic bond can be O- or N- glycosidic bond

19. Disaccharides

20. Polysaccharides 1. Cellulose: Found in plant cell walls
Composed of glucose units
linear structure
1-4 linkages
Insoluble
Humans can not hydrolyze the 1-4 bonds, so not digestible in humans
Important in our diet – decrease constipation and colon cancer

21. Cellulose Structure
Figure 4.9 The β1,4 glycosidic bonds in cellulose

22. Polysaccharides 2. Starches Plant origin
Polysaccharides of long chain polymers of - D-glucose
Have un-branched chains (amylose; 20%); glucose units linked by -1-4 links
In branched chains part (amylopectin; 80%); in addition to -1-4 links there are -1-6 links at branch points

23. Figure 4.10 The structures of amylose and Amylopectin

24. Polysaccharides 3. Glycogen Animal origin (animal starch)
Storage form of CHO in human cells, found as glycogen granules (also contain enzymes of synthesis & degradation)
Polysaccharides of long chain polymers of - D-glucose
Similar to amylopectin of starch but much more branched
Multiple Branches; to provide many non-reducing ends for quick release of glucose

25. Polysaccharides
Most tissues contain glycogen, But liver (10%wt), and muscles (2%wt), store most of body glycogen
The muscle glycogen is for local use of the muscles, it CAN NOT be released in blood
Liver glycogen is to maintain blood glucose

26. Polysaccharides 4. Inulin
Is plant starch, found in tuber and root of certain plants
A polymer of fructose
The linkage is (2-1)
Soluble in warm water
Has been used to measure renal glomerular filtration rate

27. Reducing sugars
The free anomeric C (aldhyde or keto group ) of the open-chain form of sugar can reduce Cu2+ (cupric) to Cu+ (cuprous) in alkaline solutions (Fehling or Benedict test)
Examples of reducing sugars are: glucose, galactose, fructose, maltose, and lactose
Non-reducing sugars: sucrose, cellobiose

28. Glycoproteins and proteoglycans
Oligosaccharides or small polysacch. covalently linked to protein via N- or O- glycosidic bonds
Examples: blood groups, signal molecules

29. Glycoproteins and proteoglycans
Large protein polysaccharides complex (ground substance of connective tissue)
The polysaccharides: are high MW, polyanionic glycosaminoglycans (repeated units of disaccharide, one of them is always amino sugar – glucosamine or galactosamine and the other is uronic acid)

31. Digestion & absorption
Digest.: Break of glycosidic bonds of di- oligo- and polysaccharides by different enzymes
Enzymes are glycosidases
In mouth: salivary -amylase, act on - 1,4 glycosidic bonds in starch/glycogen
In intestine: pancreatic -amylase, like salivary but work at lower pH (stomach acids)
Both produce disaccharides e.g. maltose, isomaltose

35. Absorption
Small intestine mucosal brush border secret disacchridases (break disaccharides), releasing monosaccharides, which are absorbed
Deficiency e.g. lactase, lead to lactose intolerance; lactose acted upon by bacteria causing diarrhea, distension and dehydration

37. Transport of glucose in the cell
A. Na+-dependent:
- Needs energy (Na+/K+ ATPase)
- Carrier binds both Glu and Na+ transport them inside cells (against concentration gradient), then pump Na+ out in exchange with K+, using ATP as source for energy.
B. Na+-independent facilitated transport:
mediated by glucose transporters (GLUT to 14) located in cell membrane.

38. Glucose transporters Transporter Tissue location GLUT1
Brain, kidney, colon, RBC, placenta
GLUT2
Liver, pancreatic B cell, small intestine, kidney
GLUT3
Brain, kidney, placenta
GLUT4
Heart, skeletal muscles, adipose tissue
GLUT5
Small intestine

39. Figure 4. 14 How a glucose transporter (GLUT) works
Figure 4.14 How a glucose transporter (GLUT) works. Note the conformational change upon binding glucose