Question

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Q. a leaf is boiled in methylated spirit using iodine for starch test in order to

°°° - : options : -°°°

✒ a) dissolve starch
✒ b) dissolve chlorophyll
✒ c) soften the leaf
✒ d) make it react with iodine

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Answer 1

Answer:

b) dissolve chlorophyll .

Explanation :

To stop all the metabolic activity occurring in leaf and it is also dipped in alcohol or any other Chemical to to dissolve chlorophyll otherwise it will snythesis food.

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Answer 2

ᴬᴺˢᵂᴱᴿ ⃗

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b) Dissolve chlorophyll

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Explanation :

• In the starch test, we do an iodine test, A positive test would give a colour change to blue-black.

chlorophyll present in the leaves would mask this observations,

• Methylated spirit contain "Alcohol Methanol" and "Ethanol"

• Chlorophyll dissolve in Organic solvents (alcohol)

• so when leaf is heated in alcohol they decolorize as alcohol extracts the chlorophyll of the leaf and thus leaf becomes pale yellow.

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Q. ᵂᴴʸ ᴵˢ ᵀᴴᴱ ᴸᴱᴬᶠ ᴮᴼᴵᴸᴱᴰ ᴵᴺ ᴹᴱᵀᴴʸᴸᴬᵀᴱᴰ ˢᴾᴵᴿᴵᵀ ᴰᵁᴿᴵᴺᴳ ᵀᴴᴱ ˢᵀᴬᴿᶜᴴ ᵀᴱˢᵀ ?

→ᵈᵘʳᶦⁿᵍ ˢᵗᵃʳᶜʰ ᵗᵉˢᵗ ᵗʰᵉ ˡᵉᵃᶠ ᵇᵒᶦˡᵉᵈ ᶦⁿ ʷᵃᵗᵉʳ ᵗᵒ ᵏᶦˡˡ ᵗʰᵉ ᶜᵉˡˡˢ.

→ ᵀᴴᴱ ᴸᴱᴬᶠ ᴵˢ ᴮᴼᴵᴸᴱᴰ ᴵᴺ ᴹᴱᵀᴴʸᴸᴬᵀᴱᴰ ˢᴾᴵᴿᴵᵀ ᵀᴵᴸᴸ ᴵᵀ ᴮᴱᶜᴼᴹᴱˢ ᴾᴬᴸᴱ ᵂᴴᴵᵀᴱ/ʸᵉˡˡᵒʷ ᵈᵘᵉ ᵗᵒ ʳᵉᵐᵒᵛᵃˡ ᵒᶠ ᶜʰˡᵒʳᵒᵖʰʸˡˡ.

→ ᵀᴴᴱ ᴸᴱᴬᶠ ᴮᴱᶜᴼᴹᴱˢ ᴴᴬᴿᴰ ᴬᴺᴰ ᴮᴿᴵᵀᵀᴸᴱ.

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♦ Effects on leaf after test ;

•→ when we boil the leaf in the alcohol we are testing it for starch as this would remove chlorophyll from the green leaf.

•→ Deolourish leaf is treated with iodine and blue black colour is obtained which confirms the presence of starch in green portion of the leaf.