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Bio chapter 2: Carbohydrates - Coggle Diagram
Bio chapter 2: Carbohydrates
structure of monomers
ring: ring structure is the preomdinant form as it is more energetically stable
eg. glucose ring form is created when the oxygen on carbon number 5 links with the carbon comprising carbonyl group and transfers its hydrogen to the carbonyl oxygen to create a hydroxyl group
ring structure is the form incorporated into disaccharides and polysaccharides
anomeric carbon (carbon that is bonded to 2 oxygen atoms OCO)
hydroxyl group that is bonded to the anomeric carbon can either lie:
BELOW the plane ring (a-glucose)
ABOVE the plane of the ring (b-glucose)
ABBA (alpha below beta above)
straight- chain
monosaccharides
:
colourless, crystalline solides that are freely soluble in water bu insoluble in non polar solvents
eg glucose (most common and key energy source for cells
cells use polysaccharides composed only of glucose units
FORMATION AND BREAKAGE OF GLYCOSIDIC BOND
glycosidic bond is formed when two monosaccharides form a dissacharide, this process is Called
condensation
and a molecule of water is lost
hydrolysis
is when a disaccharide is broken down into its constituent monosaccharides, one molecule of water is added via: - incubation with dilute acid at 100 degrees or incubation with an enzyme
polysaccharides
storage polysaccharides
starch
:
commonly found in plant tissues
serves as carbon source
consist of only a-glucose monomers, starch consist of both unbranched amylose and branched amylopectin
starch is stored in plant cells as starch grains either within chloroplasts, or within the amyloplasts which are specialised plastids for starch storage
amylose
:
exists as an unbranched chain that consists of hundreds to thousands of a-glucose rescues joined by a (1,4) glycosidic bonds
amylose forms a helical structure that is compact; 6 glucose per turn in the helix
since it is bulky, amylose is poorly soluble in water and thus does not exert osmotic influence In the cell
amylopectin
:
also contains a(1,4) AND a(1,6) glycosidic bonds, making it unbranched
branch points occur at every 12-30 residues and average branch length is between 24 - 30 residues
many branch ends allow larger number of enzymes to act on it simultaneoulsy
extensive branching cause amylopectin to be compact
STRUCTURE TO FUNCTION:
Starch is a large molecule: since it is insoulble, does not affect water potential within cells and living organisms
amylose molecules are local in shape: compact
amylopectin molecules are highly branched due to presence of a(1,6) glycosidic bonds: amylopectin is compact and a large number of free ends available for hydrolysis by amylase at any one time
glycogen
:
major form of storage polysaccharide in animals
found mainly in the liver and skeletal muscle in the form of cytoplasmic granules
-consists only of a-glucose
has similar structure to amylopectin but it is more extensively brnached
the a(1,6)glycosidic bonds occur every 8-12 glucose units
thus it is more compact than amylopectin
STRUCTURE TO FUNCTION:
glycogen is a large molecule: insoluble, does not affect water potential within cells and living organisms
glycogen is highly branded due to presence of a(1,6)glycosidic bonds: highly compact, large number of free ends available for hydrolysis by amylase at any one time
structural polysaccharides
cellulose
:
found in plant cell walls, make up 50% of cell wall
made up of b-glucose, hence b glycosidic bond is formed between monomers
inorder to obtain b(1,4)glycosidic bonds in cellulose, alternate monomers are inverted
hence cellulose forms a long unbranched chain
POLYMER made up of 10,000 b-glucose molecules forming a long unbranched chains
many chains run parallel to each other and their
hydroxyl oxygen (OH) project outwards
from each chain
1
. extensive
hydrogen bonds
form between protruding OH groups of niehgbouring chains, allowing the establishment of rigid cross links between chains
2
. cross linked cellulose chains
ASSOCIATE
in groups to form microfibrils, which consist of 60-70 cellulose chains and can attain a diameter of up to 25 nm
3
. microfibrils then associate with other, non cellulose polyssacharides, and are arranged in larger bundles to form macrofibrils, which are laid down in the cell wall
PROPERTIES OF CELLULOSE CELL WALL:
1. High tensile strength:
confers cellulose considerable stability, making it a valuable structural material
cellulose fibres are laid down in different orientations in different layer of plant cell wall, Thye permit the cell wall to withstand forces exerted in all directions
2. full permeability to water and solutes
: important for the proper functioning of plant cells
3. important food source for animals,
algae, bacteria and fungi, all of which processes the envy,e cellulase that catalyses the digestion of cellulose to glucose
STRUCTURE TO FUNCTION:
Cellulose is a large molecule: insoluble and makes a good structural material
b-glucose units are linked by b(1,4) glycosidic bonds, which has a different MOLECULAR SHAPE from a(1,4)glycosidic bond found in amylose and amylopectin:
few organisms produce cellulase
amylase can only hydrolyse a(1,4)glycosidic bonds
cellulose is stable
alternate inverted b-glucose units linked by b(1,4)glycosidic bonds allow cellulose to form long, unbranched and straight chains; extensive hydrogen bonds form between parallel chains; straight parallel chains can be grouped into microfibrils, which eventually cluster into macrofibrils: cellulose provide high tensile strength for structural support