The effect of pH on amylase activity HO KP (2008)
How does the degree of acidity / alkalinity affect the rate of enzymatic reaction ? pH
Amylase is • a digestive enzyme that helps break down starch • found in (a) saliva • (b) some digestive • juices
Sprouting mung beans is a rich source of amylase and other enzymes. (Shall we remove the seed coat ?)
Sit down, hold the mortar and pestle tight.Press on the seedlings to release (釋放) cell sap. Grind for a few minutes. A mistake
The mortar must be put on a heat-proof mat or wet cloth to reduce wear. X A mistake
Mortar Pestle Make an enzyme extract – use only a few ml of water for grinding
Get the top portion of the mung bean 綠豆enzyme extract by using a clean dropper. Filtering may be done by a muslin cloth.
No need to have so much ! Enzyme extract Less than a few ml of extract is required.
Agar (瓊脂), (大菜糕) dissolves in hot water Preparing for the starch - agar suspension
Petri dish Solidified starch agar Starch(substrate) is mixed with agar (a jelly like semi-solid)
The reaction : 不是 substance, substrate 指 enzyme reaction 的 reactant.
Which chemical provides for an acidic medium ? Hydrochloric acid Which chemical provides for an alkaline medium ? Sodium carbonate
C3 C1 C2 C5 C6 C4 Into each of six cavities, Prepare a mixture of “ enzyme + pH medium ”
Dropper – Hold it vertically ! White cavity tile Or use a spotting tile
Make sure that each drop of chemical is of the same size. Why is this important ? Use clean dropper.
Soak the paper disc into the reaction mixture for at least 30 seconds. Do not dip the forceps into the reaction mixtures. If so, clean the forceps every time !
Put six labels on the side of the Petri dish, in sequence.(Not on the lid 蓋)
At this stage, the “ enzyme - soaked paper discs ” may be put onto the starch agar plate by a pair of clean forceps.
Soak the 6 paper disc(s) in the 6 respective solutions for 30seconds. Label the six positions on the starch-agar plate. Transfer轉移 the disc(s) onto the starch-agar plate by using cleanforceps. Wash the forceps after every transfer to avoid contamination.
Class, name The set-up just before putting into the incubator. Remember to label the group name on the lid.
Incubator 恆溫器 Label your name Incubation time : 60 – 120 min. Incubation temperature – at about 37 deg C
Do this step after the plate has been put into the incubator. Clearly label each of the conditions Find out the pH of each mixture !!!
Use brown Iodine solution to test for starch. Pour in a little to cover the agar surface.
Look against light Measure the diameter of the clear zone and write down the degree of clearing
For each condition, measure (1) the diameter of the clear zone, and (2) how clear the spot is.