CARBOHYDRATES
description
Transcript of CARBOHYDRATES
CARBOHYDRATES
Carbohydrates• Important energy source for cell
• Monosaccharides – monomers for sugars
• Disaccharides – 2 sugars linked by glycosidic covalent bond
• Polysaccharide – many sugars (100-1000’s)
• All sugars have a C1H2O1 formula.
Monomers: Monosaccharides
• Glucose
• Fructose
• Galactose
Glucose(an aldose)
Fructose(a ketose)
Glucose = Aldose
1
23
4
5
6
1
2
34
5
6
=Ketose
Structuralformula
Abbreviatedstructure
Simplifiedstructure
GalactoseGlucose
2 forms of glucose
Alpha-Glucose Beta-Glucose
• When alpha-glucose molecules are joined chemically to form a polymer starch is formed.
• When beta-glucose molecules are joined to form a polymer cellulose is formed.
Alpha-Glucose
Starch: Alpha-glucose is the monomer unit in starch.
• As a result of the bond angles in the alpha acetal linkage, starch (amylose) actually forms a spiral structure.
Beta-Glucose
• Cellulose: Beta glucose is the monomer unit in cellulose.
• As a result of the bond angles in the beta acetal linkage, cellulose is mostly a linear chain.
Disaccharides
• Lactose
• Maltose
• Sucrose
Disaccharides
• Two monosaccharides (monomers) can bond to form a disaccharide in a dehydration reaction– An example is a glucose monomer bonding to a
fructose monomer to form sucrose, a common disaccharide
Glucose Glucose
Glucose Glucose
Maltose
Fig. 5-5
(b) Dehydration reaction in the synthesis of sucrose
Glucose Fructose Sucrose
MaltoseGlucoseGlucose
(a) Dehydration reaction in the synthesis of maltose
1–4glycosidic
linkage
1–2glycosidic
linkage
Polysaccharides
• Polysaccharides are polymers of monosaccharides (long chains of sugar)– They can function in the cell as a storage molecule
or as a structural compound
Polysaccharide
• Starch – plant energy storage
• Glycogen- animal energy storage
• Cellulose- cell wall of plants
• Chitin – cell wall of fungi
All composed of glucoses
Starch granules inpotato tuber cells
Glycogengranulesin muscletissue
Cellulose fibrils ina plant cell wall
Cellulosemolecules
Glucosemonomer
GLYCOGEN
CELLULOSE
Hydrogen bonds
STARCH
Polysaccharides
• Polysaccharides are hydrophilic (water-loving)– Cotton fibers, such as those in bath towels, are
water absorbent
To get to the energy, you must break the bonds connecting the glucoses.
But those starch bonds are very hard to break…
What’s in spit?