Turn on thread page Beta
    • Thread Starter
    Offline

    3
    ReputationRep:
    Hi! I've been working my butt off with :adore: chemistry and I've been brainstorming a few question but there was a question I just wasnt sure how to answer :s: -

    "One enantiomer of limonene smells of oranges and the other smells of lemons. How do you think your nose is able to distinguish between the two molecules, given the that structures of the two enantiomers are so alike?"

    I said that it was because the double bond on the carbon ring was on the 1st and 2nd carbon in one enantiomer and on the other enantiomer, the double bond was on the 2nd and 3rd carbon. please help :confused: My explanation doesnt even make sense :bawling:
    Offline

    2
    ReputationRep:
    The nose is able to sense which enantiomer it is and one causes a lemon smell and the other an orange smell, i think its about that simple
    Offline

    20
    ReputationRep:
    Moving this to the correct forum - but basically it's to do with receptor structure; there are two different, specific receptors for these molecules in the nose, and each enantiomer will only fit in one.
    • Community Assistant
    • Study Helper
    Offline

    17
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Da Mouse)
    Hi! I've been working my butt off with :adore: chemistry and I've been brainstorming a few question but there was a question I just wasnt sure how to answer :s: -

    "One enantiomer of limonene smells of oranges and the other smells of lemons. How do you think your nose is able to distinguish between the two molecules, given the that structures of the two enantiomers are so alike?"

    I said that it was because the double bond on the carbon ring was on the 1st and 2nd carbon in one enantiomer and on the other enantiomer, the double bond was on the 2nd and 3rd carbon. please help :confused: My explanation doesnt even make sense :bawling:
    Enantiomers are optically active molecules - that is they have mirror images which are non superimposible.

    Basically it is like your left hand and your right hand - all the dimensions are the same but the two objects are non-superimposible (the right hand could not exactly fit into the identical space that your right hand occupies)

    The nose contains receptors that are also optically active shapes i.e. one type of receptor will accomodate one type of limonene only.

    Taking the hands analogy, it's like the receptors in the nose being gloves for the hands. Only the left hand fits correctly into the left glove - only one of the two limonene enantiomers fits correctly into the available receptor.

    So one of the limonene enantiomers triggers a different response to the other. The brain identifies this as 'orange' or 'lemon'.
    • Thread Starter
    Offline

    3
    ReputationRep:
    thanx! I'm gonna try and use my diddy brain and caste back my dim memoreeeeeese of GCSE bio :s: thanx again for helping!
    Offline

    14
    ReputationRep:
    (Original post by Da Mouse)
    Hi! I've been working my butt off with :adore: chemistry and I've been brainstorming a few question but there was a question I just wasnt sure how to answer :s: -

    "One enantiomer of limonene smells of oranges and the other smells of lemons. How do you think your nose is able to distinguish between the two molecules, given the that structures of the two enantiomers are so alike?"

    I said that it was because the double bond on the carbon ring was on the 1st and 2nd carbon in one enantiomer and on the other enantiomer, the double bond was on the 2nd and 3rd carbon. please help :confused: My explanation doesnt even make sense :bawling:
    One stereo-isomer of limonene is (S)-(-)-limonene (left) and is responsible for the orange smell. Its partner, (R)-(+)-limonene (right), produces the lemon smell

    The molecules differ in their spatial orientation but the most important difference is how they react with chiral molecules. In the case of limonene it is determined by how they react with the olfactory receptors in the nose.

    The fact that chiral molecules produce different smells in humans infers that the olfactory receptors in the human nose are chiral also. This means that they can tell the difference between left and right-handed molecules.

    Marcus
 
 
 
Turn on thread page Beta
Updated: July 14, 2005

2,945

students online now

800,000+

Exam discussions

Find your exam discussion here

Poll
Should predicted grades be removed from the uni application process

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.