Starch And Cellulose

Question 1

What do starch and cellulose have in common

Answer 1

Both polysaccharides in plants, act as storage molecules as they produce no osmotic effect, made up of monosaccharides joined by glycosidic bonds

Question 2

What are the two forms of starch

Answer 2

Amylose and amylopectin

Question 3

What is amylose

Answer 3

Straight chain (no branches), forms a coil

Question 4

What is amylopectin

Answer 4

Straight chain with branches at regular intervals

Question 5

Bonds in cellulose

Answer 5

Beta glucose molecules joined together by b-1,4 glycosidic links releasing a water molecule in a condensation reaction. Alternate b-glucose molecules are rotated through 180 degrees

Question 6

Properties of cellulose

Answer 6

-make cell walls strong
-chains can be very long with 1000-10000 glucose molecules, resulting in cellulose molecule forming a very long straight unbranched chain
-hydroxyl groups project from both sides of the chain

Question 7

What does the strength of cellulose cell wall come from

Answer 7

-comes from cellulose microfibrils
-bundles of 60 straight unbranched cellulose can lie parallel to form cellulose microfibrils held together by hydrogen bonds between hydroxyl groups in neighbouring chains to produce a strong structure

Question 8

Which are stronger the glycosidic bonds in cellulose chains or the hydrogen bonds between chains

Answer 8

The covalent glycosidic bonds are stronger between glucose molecules

Question 9

How are microfibrils stuck together

Answer 9

Stuck together by a polysaccharide ‘glue’ made from short branched polysaccharides called hemicellulose and pectins

Question 10

What are hemicelluloses

Answer 10

Polymers of other sugars not glucose eg xylose

Question 11

What are pectins

Answer 11

Polymers of a sugar acid (galacturonic acid)