Carbohydrates Flashcards
What is Amylose?
Amylose chains are unbranched and consists of a-glucose linked by a(1,4) glycosidic bonds
What is Amylopectin?
-Amylopectin chains are branched. In the main chain, a-glucose are linked by a(1,4) glycosidic bonds but branch point are linked by a(1,6) glycosidic bonds
Why is starch insoluble?
most of the hydrophilic hydroxyl groups of the glucose residues project into the interior of the helices, thus starch is hydrophobic and is hence insoluble in water. Starch can be stored in large quantities without greatly affecting the water potential of cells.
Why does starch have a compact shape?
most of the hydrophilic hydroxyl groups project into the interior of the helices, so the chains are not cross linked to form bundles. Individual chains can be fold into a very compact shape. Hence glucose monomers can be stored in large quantities within the limited space in cells.
Why is starch easily broken down
presence of many branch points and chains are not cross linked to form big bundles. Starch can be easily broken down by hydrolytic enzymes to glucose.
What is cellulose?
Cellulose contains b glucose linked together by b(1,4) glycosidic bonds. Adjacent units are orientated 180 degrees with respect to each other.
Why does cellulose have great tensile strength?
due to the 180d rotation of each adjacent glucose residues with respect to each other, large number of hydroxyl groups project outwards from each cellulose molecule in all directions, thus forming many hydrogen bonds between parallel chains to form a microfibril. Association of many microfibril to form macrofibrils. Hence cellulose have great tensile strength and plant cells are prevented from bursting when placed in solutions of higher water potential.
Why is cellulose insoluble in water?
long chains of b-glucose molecules and cross linkages between parallel chains result in high molecular weight and crystalline structure. Hence cellulose in insoluble in water.
Why is cellulose permeable?
large intermolecular spaces between macrofibrils makes cellulose highly permeable and allow for passage of water and solute molecules through cell wall.
