Test a leaf for starch

Mandatory Junior Cert Experiment for science

Category:

Science & Technology

Tags:

• leaf
• starch
• junior
• cert
• iodine

[scienceteacher09]

The glucose is converted into starch and stored in the leaf. The plant is put in the dark to use up all the starch, then it's put back in the light and starts to store the glucose as starch again. It's in the light for at least 24 hours so the starch builds up (except for the covered leaves). If we tired to test for starch shortly after removing it from the dark, you're right the enzymes would be destroyed by the heat and the experiment would not work.

[Y0300857]

why is alcohol needed?

[scienceteacher09]

It removes the chlorophyll so the change in colour of the iodine solution is visible

[chemical2009d]

thanks for video, but I need to ask you about why did you wear glasses in this experiment

[scienceteacher09]

Splashes, the health and safety brigade insist on glasses if there's even a small chance of a splash.

[thinktoomuchto]

Also, my first thought was that the red pigment was an anthocyanin but the absorption reading threw me off...

[lilmrskux]

this is gay nobody at my school in 3rd form wud want to do that

[AnjaliPtv]

@ultramanlll its to open the cell walls to the alcohol can get to the chlorophyll and then the starch :)

[ultramanlll]

what is the purpose of killing the leave? to stop photosynthesis? reply pls

[OughtaBeFun]

You gotta answer me, yo?!

[OughtaBeFun]

We are testing for starch and photosynthesising only gives glucose, isn't it? So, we need enzymes to convert Glucose to Starch. So, wouldn't *boiling* the leaves kill the enzymes that convert Glucose to Starch??

[tumpitua]

@sexyslim819 photosynthesis takes place only in the presence of sunlight, but the leaf which is covered by foil does not absorb carbon dioxide, and hence starch is not present in it

most probably you got it, perhaps xD

[nomorefunds]

@chemical2009d You should always wear protective eyewear in the lab.