Starch, glycogen and cellulose Flashcards
What is the test for starch and how does it work?
Detected by adding iodine solution and starch is present, the colour will change from brown to dark black.
What is starch?
Starch is a polysaccharide which is found in plants in forms for small grains.
Large amounts are found in seeds and storage grains.
Why is starch important?
An important component of food and major energy source in most diets.
What is starch made up of?
Chains of alpha glucose monosaccharides linked by glycosidic bonds formed by condensation reactions.
The chain may be branched or unbranched.
How is starch’s structure suitable for its role?
- Insoluble so it doesn’t affect the water potential and water is not drawn in by osmosis.
- Large and insoluble so it can’t diffuse out.
- Compact so a lot can fit into a small space.
- When hydrolysed, it forms alpha glucose so it can be easily transported and to be used for respiration.
- It can be in branched or unbranched forms when it’s branched, it can be acted upon by enzymes which allow glucose monomers to be released rapidly.
Where is glycogen found and what is it?
It serves the same role as starch but it’s found in animals and bacteria. It’s the major carbohydrate storage product for animals.
What is the structure of glycogen?
Its structure is very similar to starch but it has a SHORTER chain and more highly branched.
Where is glycogen stored?
In animals, it’s usually stored in the muscles and liver.
How does its structure of glycogen fit for its role?
- Insoluble so it does not affect water potential so it does not draw water in by osmosis. Also as it’s insoluble, it doesn’t diffuse out of cells.
- Compact so a lot can fit into small space.
- More highly branched than starch so even more ends to be acted upon by enzymes. So it can be more rapidly broken down to form glucose monomers to be used in respiration. ( It’s important bc animals to have a higher metabolic rate than plant so it needs a higher respiratory rate)
What is cellulose and how is it different to starch and glycogen?
Cellulose is an insoluble substance and it provides structural support for plants.
It differs from starch and glycogen because S+G is made from alpha glucose whereas C is made from beta glucose.
What is a complex sugar?
Complex sugars are polysaccharides made up of monosaccharides such as starch, cellulose, and glycogen. Each of them is made up of glucose molecules combined together.
insoluble in water, have high molecular weight and do not have a sweet taste.
What sort of chain does cellulose form?
Straight, unbranched chains.
These run parallel to one another and it allows hydrogen bonds to form cross-linkages between adjacent chains.
Is hydrogen a strong bond?
Individual hydrogen bond is very weak but when there’s a lot of them, it adds to the strength.
What are microfibrils?
Cellulose molecules grouped together. Then they would be arranged into parallel groups to form fibers.
Why is cellulose important?
Gives rigidity to the plant cell.
It prevents the cell from bursting as water enters by osmosis.
