1. Carbohydrates

2. Carbohydrates Composed of the elements C, H, O
They are hydrates of carbon
Carbon + H2O
Empirical formula: CH2O
C:H:O ratio is 1:2:1
Contain many hydroxyl groups
Contain either an aldehyde or ketone
Polar (= hydrophilic)

3. Types of carbohydrates:
Monosaccharide
Disaccharides
Polysaccharides

4. Monosaccharide Contain 3 - 7 carbon atoms Empirical formula: (C1H2O1)n
if n=3:    C3H6O3
if n=5:    C5H10O5
if n=6:    C6H12O6

5. Monosaccharides Standard empirical formula (CH2O)n
Glucose = C6H12O6
Fructose = C6H12O6
Ribose = C5H10O5
Glyceraldehyde = C3H6O3
Contain hydroxyl & carbonyl groups
Can switch between linear / ring
Main fuel molecules for cells
Over 200 types of monosaccharides
Carbon numbers of 5 and 6 are most common

6. Naming Monosaccharides
Most common: 3, 5, 6 Carbons
3 Carbons – Triose
5 Carbons – Pentose
6 Carbons – Hexose
The ending -ose denotes a carbohydrate.
Simple sugars (monosaccharides) contain one aldehyde or ketone
If has a ketone group, it can be called a ketose
If has an aldehyde group, it can be called an aldose

8. Trioses
Glyceraldehyde is a triose and an aldose, thus it is a aldotriose.
Dihydroxyacetone is a triose and a ketose, thus it is a ketotriose.

9. Pentoses deoxyribose ribose
Ribose and deoxyribose are both pentoses and aldoses, or aldopentoses.
Ribose and deoxyribose differ around carbon #2.
deoxyribose
ribose

10. Hexoses
Glucose is an aldohexose
Fructose is a ketohexose

11. Glucose and fructose are structural isomers
They have identical molecular formulas
But the atoms arranged differently.
Fructose is a ketohexose
Glucose is an aldohexose
See previous slide

12. Glucose and galactose are stereoisomers= (enantiomers)
Both are aldohexoses.
They have identical molecular formulas,
But Carbon #4 are mirror images of each other

13. Enantiomers (= Stereoisomers)

14. Hexoses In solution a hexose will form a ring.
To assume this structure:
Carbon 1 forms a covalent bond with the oxygen on carbon 5;
The doubled bonded oxygen on carbon 1 accepts a hydrogen atom and is reduced to an alcohol (-OH).

15. Glucose Ring FormationOH
β -glucose OH

16. α - and β -glucose
α -Glucose (alpha): -OH is on the opposite side of the ring as the -CH2OH.
β -Glucose (beta): -OH is on the same side of the ring as the -CH2OH.
Remember β “balloon up”
See previous slide

17. Disaccharides
Two (2) monosaccharide rings joined by a glycoside linkage (a.k.a. glycosidic bond)
mono + mono ---> mono--mono + H20                                   (disaccharide)
Look familiar??
Formed by a condensation rxn.
Examples of disaccharides
maltose, sucrose, lactose

18. Disaccharides
Sucrose

19. Hydrolysis of Disaccharides
Maltose 1. Maltose + H2O -*--> glucose + glucose 2. * = enzyme; in this case maltase 3. Enzymes end in -ase
Sucrose 1. Sucrose + H2O -*-> glucose + fructose 2. * = sucrase
Hydrolysis of Lactose 1. Lactose + H2O -*-> galactose + glucose 2. * = lactase

20. Polysaccharides
Repeating units of simple sugars (monosaccharides) joined by glycoside linkages.
The sugar is usually glucose.

21. Cellulose Is a homopolymer of glucose. Joined by β -glycoside linkages
Is a structural polysaccharide in plant cell walls.
What enzyme would digest cellulose? (Cellulase)

22. Polysaccharide structures
Amylose (starch) alpha-glycoside linkages
Cellulose beta-glycoside linkages

23. Plant Starch Is also a homopolymer of glucose.
Joined by α -glycoside linkages
Is a storage polysaccharide; 2 forms:             - amylose (unbranched)             - amylopectin (branched)
See previous slide for amylose
What enzyme would digest amylose? (Amylase)

24. Amylopectin Structure

25. Animal starch Glycogen – animal storage polysaccharide
Is also a homopolymer of glucose
Joined by a-glycoside linkages
Same as amylopectin, but more highly branched

26. Structure of Glycogen

27. Chitin Is a homopolymer of N-acetyl glycosamine
Joined by b-glycoside linkages
Is a structural polysaccharide found in fungal cell walls and in the exoskeleton of arthropods.

28. Chitin

29. Other Polysaccharides
Chondroitin - Major polysaccharide of cartilage.
Heparin - Anticoagulant; prevents blood clots.
Hyaluronic acid - "glue" between animal cells