Microsoft PowerPoint - Ch8.pptBiological Function
Outline
Carbohydrates
• Compounds that have aldehyde or ketone functional groups and multiple hydroxyl groups
C OH
• Proteins • Nucleic acids • Lipids • Carbohydrates
Carbohydrates Serve Many Different Functions
• As fuel and chemical stores • Structural functions • Components of the nucleic acids • Markers for molecular recognition
Outline
Monosaccharides
• Compounds with single aldehyde or ketone unit and multiple hydroxyl group (CH2O)n
n = 3~7 for most naturally occurring monosaccharides
n = 1: formaldehyde n = 2: Glycoaldehyde
Glycoaldehyde and Glycolic Acid
Monosaccharides Containing Three Carbons (Trioses)
• n = 3
The Family of D-aldoses Containing From Three to Six Carbons
Triose
Tetroses
Pentoses
Hexoses
The Family of D-Ketoses Containing fro Three to Six Carbons
Triose
Tetroses
Pentoses
Hexoses
ul
Cyclization Reaction
Haworth projection form
Haworth projection form
Cyclization Reaction
OR”Ketone Alcohol
Haworth projection form
Reactions of monosaccharides
Oxidation-Reduction
RC
H
Esterification
Important Phosphate Esters of Carbohydrates
Amino Derivatives (1/2)
Amino Derivatives (2/2)
Combining Two Monosaccharide Molecules
Disaccharide
Disaccharide
The Formation of an N-glycosidic Bond Between β-D-glucose and an
Amine
Outline
Structural Features
• The identity of the monomeric units. • The sequence of monosaccharide residues • The types of glycosidic bonds linking the
units • The approximate length of the chain • The degree of branching
Terms
Polysaccharides
• Large polymeric oligosaccharides • Play vital roles in energy storage and in
maintaining the structural integrity of an organism.
• If all of the monosaccharides are the same,these polymers are called homopolymers.
• In animal cells: Glycogen • In plants: Starch
– Amylose: the unbranched type – Amylopectin: the branched type
Storage Polysaccharides
Glycogen granules in liver cells
Branch Point in Glycogen
Once in 10 units (glycogen) Once in 30 units (starch)
Starch and Glycogen
• A mixture of two types of polymeric glucose – Amylose – Amylopectin
The Structure of Amylose
• An unbranched polymer of glucose • MW: a few thousand to 500,000
Amylopectin
• A main backbone composed of glucose units linked by α(1 4) glycosidic bonds
• Brances connected to the backbone via α(1 6) glycosidic bonds
• Fig8.19a • The salivary enzyme: α-amylase
– Catalyzes the hydrolysis of O-glycosidic bonds – Yielding the disaccharide maltose and oligosaccharide
products
The Chemical Structure of Glycogen
• Has more numerous α(1 6) branches and a much higher average molecular weight.
• Glycogen phosphorylase
• Tightly coiled helical structures
Structural Polysaccharides
glucose units together by β(1 4) glycosidic linkages
• Cellulase : catalyze the hydrolysis of the β(1 4) glycosidic bonds in cellulose
Cellulose • One of the most abundant organic compounds in
the biosphere. • The major structural polymer of plants • Consists of linear chains of glucose units
Two Parallel Cellulose
• The monomeric unit of the plant cell wall polysaccharide, pectin
Chitin
The Structural Unit of Hyaluronic Acid
• Mucopolysaccharides: provide a thin, viscous, jellylike coating to cells.
The Structure of Chondroitin Sulfate
• A component of the extracellular matrix
Peptidoglycans • Form the cell walls of bacteria
Outline
Glycoproteins
• These proteins are involved in many biological functions – Immunological protection – Cell-cell recognition events – Blood clotting – Host-pathogen interactions
Glycoprotein Structure
• Carbohydrate portion of a glycoprotein usually constitute 1% to 30% of the total weight.
Monosaccharides in glycoproteins
Examples of Oligosaccharide Units in Glycoproteins
ABO Blood Groups
Exercises