What is an enzyme and testing leaves for starch Flashcards
(18 cards)
What is the first stage in the testing leaves for starch practical?
De-starch the plant
This is optional but recommended for controlled experiments.
Why is it recommended to de-starch the plant before the starch test?
To ensure any starch already present in the leaves is used up
This confirms that any starch found after the experiment was produced during the test period.
What is the purpose of boiling the leaf in water?
To kill the leaf and stop all chemical reactions
This also breaks down the cell walls, facilitating the entry of subsequent chemicals.
How long should the leaf be boiled in water?
About 30 seconds to 2 minutes
What is the next step after boiling the leaf in water?
Boil the leaf in ethanol
Why is the leaf boiled in ethanol?
To remove chlorophyll and decolorize the leaf
This allows any color change with iodine to be seen clearly.
What safety precaution should be taken when boiling the leaf in ethanol?
Never heat ethanol over a flame
What is the purpose of rinsing the leaf in cold water?
To soften the leaf and wash off any remaining ethanol
What should be done after rinsing the leaf in cold water?
Add iodine solution
What does iodine solution indicate when added to the leaf?
Turns blue-black in the presence of starch
What is the significance of the color change with iodine?
It shows where photosynthesis has occurred
What is the overall purpose of the starch testing practical?
To demonstrate that starch is made in leaves during photosynthesis
Define an enzyme.
A biological catalyst that speeds up reactions without being used up
How do enzymes work?
By binding to their target molecule (substrate) at the active site
What effect does enzyme binding have on chemical reactions?
Lowers the activation energy needed for the reaction
What happens after the reaction catalyzed by an enzyme?
The enzyme releases the product and can be reused
True or False: Enzymes are changed during the reactions they catalyze.
False
At what temperature do enzymes typically allow reactions to occur?
At body temperature
