1. Carbohydrates

2. Carbohydrates Types of Carbohydrates Classification of Monosaccharides
D and L Notations from Fischer Projections
Structures of Some Important Monosaccharides

3. Carbohydrates Carbohydrates are:
A major source of energy from our diet.
Composed of the elements C, H and O.
Also called saccharides, which means “sugars”.
Produced by photosynthesis in plants.

4. Photosynthesis and Respiration
Photosynthesis in plants requires CO2, H2O, and energy from the sun and produces carbohydrates, such as glucose
[C6H12O6 = C(H2O)6].
In respiration, glucose is oxidized in living cells to produce CO2, H2O, and energy.

5. Types of Carbohydrates
Monosaccharides are the simplest carbohydrates.
Disaccharides consist of two monosaccharides.
Polysaccharides contain many monosaccharides.

6. Classification of Monosaccharides
1) Functional group:
Aldoses are monosaccharides with an aldehyde group and many hydroxyl (-OH) groups.
Ketoses are monosaccharides with a ketone group and many hydroxyl (-OH) groups.
Aldose
Aldose
Ketose

7. Monosaccharides 2) Number of carbon atoms:
A triose has three carbons; a Tetrose has four carbons; a pentose has five carbons; and a hexose has six carbons.
Triose
Tetrose
Hexose

11. Note Numerous Chiral Carbons2 |
1—C—3 4
3—C—1
The two simplest sugars
Note Numerous Chiral Carbons

12. Fischer Projections Is used to represent carbohydrates.
Places the most oxidized group at the top.
Uses horizontal lines for bonds that come forward.
Uses vertical lines for bonds that go back.

13. D and L isomers
By convention, the letter L is assigned to the structure with the —OH on the left.
The letter D is assigned to the structure with —OH on the right.

14. D and L isomers
The —OH on the chiral atom farthest from the carbonyl group is used to assign the D or L configuration.
The D form is usually the isomer found in nature.

15. D-Glucose Found in grape, corn syrup, and honey.
An aldohexose with the formula C6H12O6
Known as blood sugar in the body.

16. Blood Glucose Level
In the body, glucose has a normal concentration of mg/dL.
In a glucose tolerance test, blood glucose is measured for several hours after ingesting glucose.

17. D-Fructose Is a ketohexose with formula of C6H12O6.
Is the sweetest carbohydrate.
Is found in fruit, juices and honey.
Converts to glucose in the body.

18. D-Galactose Is not found free in nature.
Is obtained from lactose, a disaccharide.
Is important in cellular membranes.

19. Cyclic Structures
Monosaccharides with 5-6 carbon atoms form cyclic structures
The hydroxyl group on C-5 reacts with the aldehyde group or ketone group

20. Sugars Prefer To Be Cyclic

21. Haworth Structure for D-Isomers
The cyclic structure of a D-isomer has the final CH2OH group located above the ring.

22. Haworth Structure for D-Glucose
The new –OH on C1 has two possibilities: down for  anomer, up for  anomer

23. Cyclic Haworth Structures
Stable cyclic when the C=O group and the -OH are part of the same molecule.
The cyclic structure of a D-isomer has the last CH2OH group located above the ring.

24. Haworth Structure for D-Glucose 
-D-Glucose
-D-Glucose

25. Glucose Anomers

27. Mutarotation
A small amount of open chain is in equilibrium with the cyclic forms.
The most stable form of glucose is β-D-glucose.
-D-glucose D-glucose (open) β-D-glucose
(36%) (trace) (64%)

28. -D-Glucose In nature, open chain forms are rare.
All 5 forms coexist with the pyranose forms occurring 99% of the time, Furanose about 0.5% each and a trace of open chain.
 and  are “anomers” and differ in configuration at the new chiral center formed in the cycle