Carbohydrates

Lecture Two

Carbohydrates
Dr. Khalidah Merzah

Carbohydrates

Most abundant class of biological molecules on Earth
• Originally produced through CO2 fixation during photosynthesis
Roles of Carbohydrates
• Energy storage (glycogen, starch)
• Structural components (cellulose, chitin)
• Cellular recognition
• Carbohydrate derivatives include
DNA, RNA, co-factors, glycoproteins, glycolipids
Carbohydrates
• Monosaccharides (simple sugars) cannot be broken down into simpler sugars under mild conditions

• Oligosaccharides = "a few" - usually2 to 10

• Polysaccharides are polymers of the simple sugars


Monosaccharides
• Polyhydroxy ketones (ketoses) and aldehydes (aldoses)

• Aldoses and ketoses contain aldehyde and ketone functions, respectively

• Ketose named for “equivalent aldose” + “ul” inserted

• Triose, tetrose, etc. denotes number of carbons

• Empirical formula = (CH2O)n












Reducing Sugars
When in the uncyclized form, monosaccharides act as reducing agents.
• Free carbonyl group from aldoses or ketoses can reduce Cu2+ and Ag+ ions to insoluble products

Monosaccharide structures you need to know

• Glucose
• Fructose
• Ribulose
• Glyceraldehyde
• Dihydroxyacetone

Carbohydrates: oligo- and polysaccharides

Polysaccharides