Polysaccharides

Question 1

What are polysaccharides

Answer 1

Large, complex polymers, which are made up of 100s of monosaccharide units, which are their monomers, joined by glycosidic bonds.

These long molecules can be branched or unbranched

Question 2

What are polysaccharides formed

Answer 2

large number of monosaccharide units are joined together by glycosidic bonds, where water is produced (A Condensation reaction)

Question 3

What is the main source of energy in the cell

Answer 3

Glucose

Question 4

What is the problem with glucose storage in cells

Answer 4

Glucose is soluble in water and so it would increase the concentration of the cell contents and draw in water by osmosis which would expand the cell

Question 5

How does the cell over come this problem

Answer 5

Stores glucose as a polysaccharide, e.g. starch

Question 6

What 4 advantages does storing glucose as starch provide

Answer 6

Starch is insoluble so there is not osmotic effect

Cannot diffuse out of the cell

Is a compact molecule and can be stored iin a small space

Carries alot of energy in its CC and CH bonds

Question 7

What is starch

Answer 7

Starch is made up primarily of alpha glucose molecules bound together by glycosidic bonds forming two polymers

1. Amylose
2. Amylopectin

Question 8

What are the two types of polymer found in starch

Answer 8

Amylose

Amylopectin

Question 9

What is amylose

Answer 9

A linear Unbranched molecule with a alpha 1, 4 - glycosidic bond forming between the first carbon atom (C1) on one glucose monomer and fourth carbon atom on the adjacent one.

This is repeated forming a chain which coils into a helix

Question 10

What is amylopectin

Answer 10

A chain of glucose monomers joined with alpha 1, 4 - glycosidic bond

They are cross linked with alpha 1, 6-glycosidic bonds and fit inside amylose

They usually have branches

Question 11

Where is amylopectin found

Answer 11

Inside Amylose

Question 12

What test do you use to detect the presence of starch

Answer 12

Iodine-potassium iodide test

Question 13

What is the test

Answer 13

Iodine solution (iodine dissolved in an aqueous solution of potassium iodide reacts with the starch Turning the colour from orange brown to blue black The depth of the change in colour gives the relative concentration of starch

Question 14

Is the Iodine-potassium iodide test therefore qualitative or quantitative

Answer 14

Qualitative

Question 15

What other test can you think of that is used to measure reducing sugars

Answer 15

Benedicts test

Question 16

Is benedictus test qualitative or quantitative

Answer 16

Qualitative

Question 17

What makes this starch test unreliable

Answer 17

If the temperature goes above 35 degrees centigrade or the PH is very low

Question 18

What makes starch a good food store

Answer 18

Can be readily hydrolised into alpha glucose which soluable and can be easily transported to where energy is needed.