Practical 4 - Investigation of the digestion of starch agar using germinating seeds Flashcards
What are there large quantities of in the endosperm of seeds such as maize?
Starch
Where is starch stored in seeds such as maize?
In the endosperm
Where is starch stored in broad beans?
In the cotyledons
What are there large quantities in the cotyledons of broad beans?
Starch
Explain what happens during the germination of a seed
The starch is broken down by the enzyme amylase into maltose which is transported in the phloem to the growing points in the plumule and radical
Which enzyme is starch broken by?
Amylase
What does amylase break starch down into?
Maltose
What is maltose transported in?
The phloem
What is maltose transported in the phloem to?
The growing points in the plumule and radical
Apparatus
Soaked maize seeds
Starch agar plates
White tile
Water bath
Scalpel
Iodine-potassium iodide solution
Boiling tube
Method
Method
1. Cut the maize seed in half.
2. Place one half cut surface down onto the starch agar.
3. Place the other half of the maize seed into the boiling tube add water and place in a water bath at 80°C for 10 minutes. This will denature any enzymes present.
4. Place this half of the maize seed onto another starch agar plate cut surface down.
This will act as a control.
5. Incubate both plates at 25 °C overnight.
6. Remove the maize seeds and flood each plate with iodine-potassium iodide solution.
7. Observe and record any difference between the two plates.
8. Calculate the area of any ‘clear’ zone on the plates.
Why do we place one half of the maize seed into a water bath?
Denatures enzymes = acts as a control
Observations of the results
For the non-boiled seed, there is a lighter patch surrounding where the seed was in the iodine
This isn’t apparent on the seed that was boiled and there’s no clear gap in the iodine
Area of the clear zone + why
pir^2
Approximately a circle
Why is there no clear area in he iodine for the control?
Since he enzymes have denatured so there’s no digestion of starch
Why is there a clear zone for the non-boiled seed?
Since enzymes have been released, which digest the starch
How can we compare how different faces effect the germination of plants
By measuring the diameter of the clear zones in the starch
What does flooding the plate with iodine do?
Makes it clear where the clear zones are where the enzymes have digested he starch/starch has been hydrolysed
What do seeds release as they germinate?
Amylase
What does amylase do to starch agar?
Digests it
What does amylase digest?
Starch agar
What digests starch agar?
Amylase
What factors can we investigate that affect the germination of plants by comparing the diameter of different clear zones?
-use different varieties of seed (keep other variables the same)
-use different temperatures
-use different oxygen partial pressures
-initially soak the seeds for different times
-use different light intensities
Why can we use different light intensities as a factor to compare germination in different plants in this practical?
Since some seeds need light to germinate
