04-07-2012, 02:55 PM
Investigation of the effect of temperature on enzyme
activities
Investigation of the effect .pdf (Size: 25.21 KB / Downloads: 266)
Starch is a mixture of two polysaccharides, amylose and
amylopectin. The relative amounts of the two
polysaccharides vary widely in different types of starch.
Amylose molecules consist of long straight chains of
glucose units. Amylopectin has a complicated branched
structure. The two polysaccharides combine with iodine to
give the characteristic blue-black colour of the standard
iodine test.
Through the process of hydrolysis, amylase degrades starch
by splitting the long glucose chains into smaller
intermediates, finally producing a complex mixture
containing predominantly maltose, but with some glucose
and some small branched oligosaccharides. This mixture
does not react with iodine to give blue-black colour.
Amylases are found in almost all plants, animals and
microorganisms. Large amounts of amylase occur in
germinating cereals, and in the pancreas and saliva of
higher animals.
Initial measurement of enzyme activity
1. Put 2 cm3 of 1% starch solution and 2 cm3 of pH 4.7
acetate buffer into a test tube.
2. Use a dropper to add one drop of iodine solution to
each cavity of a spot plate.
3. Use a graduated pipette to add 1 cm3 of the enzyme
extract to the test tube, and start the stopwatch at the
same time. Shake the tube vigorously, quickly transfer
one drop of the reaction mixture onto one of the iodine
samples and stir with a glass rod.
The effect of temperature on amylase activity
1. Use a dropper to add one drop of iodine solution to
each cavity of seven spot plates.
2. Label 7 test tubes from 1A to 7A.
3. Use graduated pipettes to add 2 cm3 of pH 4.7 acetate
buffer and 1 cm3 of diluted enzyme extract to each
tube.
4. Label another 7 test tubes from 1B to 7B. Use a
graduated pipette to add 2 cm3 of 1% starch solution to
each tube.
5. Place the above tubes in water baths maintained at
different temperatures for 5 minutes as shown below.