Carbohydrates 2: Energy storage
- Created by: Lois
- Created on: 07-04-13 09:39
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- Carbohydrates 2: Energy storage
- Energy & structure
- Glucose molecules contain a large number of bonds that can be broken to form simpler molecules
- The braking of glucose into simpler molecules of water and CO2 in respiration releases energy, which is used to make ATP
- The breaking down of glucose in living organisms takes place in a series of many steps, each of which are driven by a specific enzyme
- Animals & plants have enzymes that break alpha-glucose only, plant & animal enzymes cannot break down beta-glucose due to its different arrangement of the H and OH
- So alpha-glucose can be respired whereas beta-glucose cannot
- Glucose molecules contain a large number of bonds that can be broken to form simpler molecules
- Carbohydrate polymers - stores of potential energy
- Two alpha-glucose molecules bonded together form a disaccharide called maltose
- The same condensation reaction can be carried out over and over again eventually forming amylose
- The glycosidic bond between all the glucose subunits occurs between C1 of one molecule and C4 of the next, so is often called 1,4-glycosidic bond
- The long chains of amylose coil into a spring because of the shape of the glucose molecules & the formation of the the glycosidic bonds
- this makes amylose quite compact, iodine molecules can become trapped in the 'coils'of the spring
- this causes iodine (in potassium iodine solution) to change colour from yellow/browm to blue/ black - starch test
- this makes amylose quite compact, iodine molecules can become trapped in the 'coils'of the spring
- The long chains of amylose coil into a spring because of the shape of the glucose molecules & the formation of the the glycosidic bonds
- The glycosidic bond between all the glucose subunits occurs between C1 of one molecule and C4 of the next, so is often called 1,4-glycosidic bond
- The same condensation reaction can be carried out over and over again eventually forming amylose
- not water soluible
- Two alpha-glucose molecules bonded together form a disaccharide called maltose
- Starch - the energy-storage polysaccharide in plants
- Starch consists of a mixture of long, straight-chain amylose molecules & branched amylopectin
- Starch in plants is a mixture of amylose and amylopectin - stored in chloroplasts & elsewhere in membrane-bound starch grains
- Starch can be broken down to glucose molecules, which may then be respired to releasde energy
- Glycogen - the energy-storage polysaccharide in animals
- Glycogen is sometimes referred to as animal starch, it is identical to starch in that it is made up of alpha-glucose subunits; can also be broken down to release glucose to be respired
- Differs from starch by having the 1-4 linked glucose chains in glycogen shorter with many more branches
- Glycogen is more compact than starch & forms glycogen granules in animal cells e.g. liver & muscle cells
- Features of the energy-storage molecules starch & glycogen
- Dont dissolve - so stored glucose dopes not affect water potential of the cell - vital in both plants & animals, as glucose stored as free molecules would dissolve & dramatically reduce water potential
- Hold glucose molecules in chains so that they can easily be 'broken off' to provide glucose for respiration when required
- Energy & structure
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