1.4 Starch, Glycogen and Cellulose

Question 1

How are starch molecules bonded?

Answer 1

They are bonded by glyosidic bonds formed by condensation reactions between chains of alpha-glucose monosachharides

Question 2

Structure of starch and how it relates to its function.

Answer 2

• Branched form has many ends so it can be acted on by multiple enzymes at a time, meaning glucose monomers are released very rapidly
• Insoluble and therefore doesn’t affect water potential, water isn’t drawn into cells by osmosis
• Large and insoluble, can’t diffuse out of cells
• It is compact, lot of energy can be stored in a small place

Question 3

Where is starch never found in? and what similar polysaccharide serves the same role?

Answer 3

Never found in animal cells
Glycogen

Question 4

Relate the structure to the roles/functions of glycogen.

Answer 4

• Insoluble, doesn’t draw water into cell via osmosis
• It is compact, so lots of energy can be stored in a small space
• Highly branched so that it can be simultaneously acted on by multiple enzymes which breaks it down into glucose, this is used in respiration.

Question 5

What is the monomer that builds up cellulose?

Answer 5

Beta-Glucose

Question 6

Is cellulose a branched or unbranched, and coiled or straight chained?

Answer 6

Unbranched
Straight

Question 7

When cellulose molecules are grouped together they form ___________ which are arranged in parallel groups called ______.

Answer 7

Microfibrils
Fibres

Question 8

Where can cellulose be found?

Answer 8

Plant cell wall

Question 9

Relate the structure of cellulose to its roles.

Answer 9

-molecules run parallel to each other and are cross linked by hydrogen bonds which add collective strength
- molecules grouped in microfibrils and form fibres which provide more strength
-very strong, provides rigidity to the plant cell and prevents the cell from bursting as water enters via osmosis

Question 10

Why is it important for the stems and leaves to maintain a turgid state?

Answer 10

so that they can provide the maximum surface area for photosynthesis.