Carbohydrates Flashcards
General Formula of Carbohydrates
Cx(H2O)y
Carbohydrate Functional Groups
Contains C=O (Aldehyde or Ketone group) and many -OH functional groups
Aldehyde and Ketone
Aldehyde: R-C=O-H
Ketone: R-C=O-R
Classification of Carbohydrates
- Size of base carbon chain
- No. of sugar units
- Location of C=O
- Stereochemistry
Types of Carbohydrates
Monosaccharides: single sugar unit
Disaccharides: 2 sugar units
Oligosaccharides: 2-10 sugar units
Polysaccharides: >10 sugar units
Carbohydrate Chains
Bridging of oxygen atoms to form glycosidic bonds
Carbohydrate Functions
- Energy Metabolism
- Structure
- Precursor of DNA & RNA
- Cell Surface Marker
Energy Metabolism
Fuel & Storage
Carbohydrate Fuel
Glucose & it’s derivatives produce energy for immediate use by the organism
Carbohydrate Storage
Starch is stored by plants while glycogen is stored in the liver & muscles of animals for later use
Carbohydrate Structural Use
- Scaffolding of bacterial and plant cell wall
- Exoskeleton shell of arthropods
- Lubricative coating for cells
Carbohydrate Precursors of DNA & RNA
- Serves a chemical structural role
- Polar sites for the catalytic processes of RNA
Ribose & Deoxyribose sugars
- Monosaccharides
- Vital for the synthesis of nucleic acids RNA & DNA
Carbohydrates Cell Surface Markers (4 pts) [1]
- Markers for recognition by other biomolecules when carbohydrates covalently bond with other proteins & complex lipids
- Immune protection/ recognition
Carbohydrates Cell Surface Markers (4 pts) [2]
- Cell-Cell Recognition
- Host Pathogen Interaction
Monosaccharides
- Hydrogen bonding with OH groups
- High mp
- Water-soluble
- Insoluble in non-polar solvents
- Optical isomers are D-Sugars
- Sweet tasting
- Chiral
- Cyclic structure
D-Sugar and L-Sugar
D-Sugar: OH on the right
L-Sugar: OH on the left
*Locate chiral centre furthest from C=O
α & β glucose
α glucose: opposite sides
β glucose: same side
*Ring form
Carbohydrate Chemical features
- Have at least 1, often >2 asymmetric centres
- Exists in either linear or ring structure
- Able to form polymers via glycosidic bonds
- Able to form multiple H bonds with H2O
Glucose & Monosaccharide reactions
- Redox
- Esterification
- Amino Derivative
- Glycoside Formation
Testing for Reducing Sugars
Benedict's Test 1. Add Benedict's solution to test solution 2. Gently heat to boil Red Precipitate: Reducing Sugar present *Colour varies with sugar concentration
Esterification
Esters formed when hydroxyl groups (alcohols) react with acids
β-Maltose
-α-D-glucose and β-D-glucose, α (1 -> 4) linkage.
Polysaccharides
- Carbohydrate Polymers
- Storage Polysaccharides
- Structural Polysaccharides
- Structural Peptidoglycans
Cellobiose
- β-D-glucose and β-D-glucose, β (1 -> 4) linkage.
- Unuseable since we lack enzymes to hydrolyze
Lactose
-β-D-galactose and β-D-glucose, β (1 -> 4) linkage
Sucrose
α-glucose and β-fructose, α (1 -> 2) linkage
