The Variety of Life (UNIT 2) Flashcards
What is starch?
A Polysaccharide.
Where is starch found?
In many parts of a plant in the form of small grains. Large amounts occur in seeds, storage organs.
What is starch made up of?
Alpha-glucose monosaccharides linked by glycosidic bonds formed in condensation reactions.
How is a starch molecule made compact?
Unbranched chain wound into a tight coil.
What is the main role of starch?
Energy storage.
Why is starch suited for energy storage?
- INSOLUBLE- does not tend to draw water into cells by osmosis.
- Does not easily diffuse out of cells.
- COMPACT- a lot stored in a small space
- When HYDROLYSED forms alpha-glucose, which is easily transported and readily used in respiration.
Where is starch never found?
Animal cells.
How is glycogen different to starch?
SHORTER CHAINS AND MORE HIGHLY BRANCHED.
Why is glycogen sometimes called “animal starch”?
Major carbohydrate storage product of animals.
How is glycogen stored in animals?
As small granules found mainly in the muscles and the liver.
Why is glycogen more readily hydrolysed than starch?
Shorter chains.
What is the main difference between cellulose and starch or glycogen?
Cellulose is made of monomers of beta-glucose.
How does beta-glucose affect the structure of cellulose?
In the beta-glucose units, the positions of the -H group and the -OH group on a single carbon atom are reversed. -OH above rather than below the ring. This means that to form glycosidic links, each beta-glucose molecule must be rotated by 180 degrees compared to its neighbour. Result: -CH2OH group on each beta-glucose molecule alternates between being above and below the chain.
What shape does cellulose chains make?
Straight chains, unbranched.
These run parallel to one another, allowing hydrogen bonds to form cross linkages between adjacent chains.
Amount of hydrogen bonds makes cellulose very strong.
What are microfibrils?
Groups of cellulose molecules.
What are fibres?
Parallel groups of microfibrils (Groups of cellulose molecules)
What is cellulose used for and why is it good?
Major component in pant cell walls. Provides rigidity to plant cells. Prevents cell from bursting as water enters by osmosis. Exerts inwards pressure that stops any further influx of water. As a result, living plant cells are turgid and push against one another
Describe the structure of haemoglobin.
PRIMARY- Consists of 4 polypeptide chains.
SECONDARY- in which each of these polypeptides chains is coiled into a helix
TERTIARY STRUCTURE- in which each polypeptide chain is folded into a precise shape-
IMPORTANT FACTOR IN ITS ABILITY TO CARRY O2.
QUATERNARY STRUCTURE- all for polypeptides are linked togehter to form an almost spherical molecule. Each polypeptide is associated with a HAEM group- contains ferrous (Fe2+) ion. Each Fe2+ ion can combine with a single oxygen molecule, making a total of four O2 molecules that can be carried by a single haemoglobin molecule in humans.
What is the role of haemoglobin?
To transport oxygen
To be efficient at transporting oxygen haemoglobin must…
- Readily associate with O2 at surface where gass exchange takes place.
- Readily dissociate from oxygen at those tissues requiring it.
What property of haemoglobin allows it to readily associate and dissociate with oxygen?
it changes its affinity for oxygen under different conditions.
How does haemoglobin change its affinity for oxygen?
Its shape change in the presence of certain substances, e.g. CO2. In the presence of CO2, the new shape of the haemoglobin binds MORE LOOSELY to oxygen. As a result haemoglobin releases its oxygen. i.e. in tissues due to higher levels of CO2