1.4 - Starch, glycogen and cellulose

Question 1

How is cellulose adapted to its function?

Answer 1

• made up of B-glucose - forms long straight, unbranched chains
• cellulose molecular chains run parallel to each other, also crosslinked by hydrogen which adds collective strength
• Molecules are grouped to form microfibrils which form fibres which provides more strength

Question 2

Purpose of the cellulose cell wall

Answer 2

• provides rigidity to the plant cells
• prevents it from bursting due to osmosis
  which therefore is turgid and provides the maximum SA for photosynthesis

Question 3

how are fibres formed?

Answer 3

cellulose molecules are grouped together to form microfibrils and are arranged in parallel groups

Question 4

arrangement of the glucose chains

Answer 4

Question 5

Hydrogen bonds within bonding of monomers

Answer 5

Adds very little strength to the molecule and the sheer overall number of them makes them a considerable contribution to strengthening cellulose

Question 6

Difference between cellulose and starch

Answer 6

made from beta glucose monomers and therefore has straight unbranched chains which run parallel to one another - allowing hydrogen bonds and it froms cross linkages between adjacent chains

Question 7

how is glycogen suitable for storage?

Answer 7

• Insoluble - doesn’t affect water potential
  doesn’t diffuse out of cells
• compact, a lot can be stored in a small space
• more highly branched than starch - has more ends that can be acted on simultaneously by enzymes
  can be broken down rapidly to form glucose monomers which is used in respiration

Question 8

structure of glycogen

Answer 8

• similar to starch but has shorter chains and more highly branched
  stored mainly in muscles and liver
• relatively small mass however as there’s more fats (energy reserve for animals)

Question 9

Adaptations of starch’s structure

Answer 9

• It’s insoluble and therefore it doesn’t affect water potential (osmosis doesn’t occur)
• large and insoluble so it doesn’t diffuse
• compact - a lot can be stored in a small space
• when hydrolysed, froms a-glucose - both easily transported and readily used in respiration
• branched form has many ends
  can be acted upon enzymes simultaneously, glucose monomers are released rapidly

Question 10

Role of starch

Answer 10

Storage

Question 11

What is starch made up of? And what is its structure?

Answer 11

made up of alpha glucose monosaccharides linked by glycosidic bonds formed through condensation reactions and it can be branched or unbranched - this can be wound into a tight coil which makes it very compact

Question 12

What is starch and where and how much is found in plants?

Answer 12

A polysaccharide found in many parts of a plant in from of small grains and mainly large quantities in seeds and storage organs and is the main energy source in most diets