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The effect of pH on amylase activity HO KP (2008) - PowerPoint PPT Presentation


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The effect of pH on amylase activity HO KP (2008). How does the degree of acidity / alkalinity affect the rate of enzymatic reaction ?. pH. Germinating Mung bean – source of the enzyme AMYLASE. Amylase is a digestive enzyme that helps break down starch found in (a) saliva

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Presentation Transcript
slide4

Amylase is

  • a digestive enzyme that helps break down starch
  • found in (a) saliva
  • (b) some digestive
  • juices
slide5

Sprouting mung beans is a rich source of amylase and other enzymes. (Shall we remove the seed coat ?)

slide10

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

slide12

Mortar

Pestle

Make an enzyme extract – use only a few ml of water for grinding

slide15

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.

slide16

No need to have so much !

Enzyme extract

Less than a few ml of extract is required.

slide18

Agar (瓊脂),

(大菜糕)

dissolves in hot water

Preparing for the starch - agar suspension

slide19

Petri dish

Solidified starch agar

Starch(substrate) is mixed with agar (a jelly like semi-solid)

slide20

The reaction :

不是 substance, substrate 指 enzyme reaction 的 reactant.

slide23

Which chemical provides for an acidic medium ?

Hydrochloric acid

Which chemical provides for an alkaline medium ?

Sodium carbonate

slide26

C3

C1

C2

C5

C6

C4

Into each of six cavities,

Prepare a mixture of “ enzyme + pH medium ”

slide28

Dropper – Hold it vertically !

White cavity tile

Or use a spotting tile

slide29

Make sure that each drop of chemical is of the same size.

Why is this important ?

Use clean dropper.

slide32

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 !

slide35

At this stage, the “ enzyme - soaked paper discs ” may be put onto the starch agar plate by a pair of clean forceps.

slide39

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.

slide40

Class, name

The set-up just before putting into the incubator. Remember to label the group name on the lid.

slide42

Incubator

恆溫器

Label your name

Incubation time : 60 – 120 min.

Incubation temperature – at about 37 deg C

slide43

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 !!!

slide47

Look against light

Measure the diameter of the clear zone and write down the degree of clearing

slide53

What are your experimental findings ?

What conclusion can you draw ?

slide56

No. 2

The diameter of the clear zoneindicates the degree of enzyme activity.

slide57

No. 3

The diameter of the clear zone in

:

C5> C1 > C3 > C4 > C2 > C6

descending order

slide58

No. 4

Comparing C1 and C6,

It shows that mung bean extract[with enzyme(s)] can digest starch on the agar plate but distilled water alone can not. (If the tap water is slightly alkaline, a little digestion may occur, or the effect is due to contamination.)

slide59

No. 5

Comparing [treatments]C3 and C5, it can be concluded thatdigestion of starch is higher when the enzyme(s) work(s) under an alkaline pH, rather than with an alkali alone.

slide60

No. 6

C6 is a control experiment to let us know that starch does not break down by itself.

slide61

No. 7

The enzyme (or enzymes) in mung bean extract works better under an alkaline condition rather than an acidic condition. Acid inhibits抑制 the activity of amylase.

slide62

No. 8

  • Yes.
  • Yes.
slide63

No. 9

  • The apparatus must be well cleanedbecause enzyme is easily damaged by a small amount of some chemicals.
  • The drop size of reactants must be the same.
  • Forcepsmust be washed after each dip into the reaction mixtures.
  • Each setup must be clearly labelled.
slide64

No. 10

It is to provide a suitable (or best / optimal) temperature for the enzyme.

slide65

NO. 11

At 100 deg C,

Enzymes would be denatured, clear zones could not be seen.

slide66

NO. 12

The pH of the reaction medium affects enzyme activity – amylase works better under an alkaline condition.