12

First of all, you assumption seems to be incorrect. Plants in same part of the world can twine in opposite directions. Little seems to be known exactly. Gravity has nothing to do with plant's chirality (or "handedness") or spiraling: How plants do this is still unknown. Darwin proposed that it was "autonomously induced." This came to be known as the ...


10

Having had a self-sown pumpkin grow in my back yard I can tell you what happened with the tendril in your picture. The tendril started growing straight, with a couple of branches. When one of the tendril branches touched something (looks like the middle one in your picture), the tip began to curl as it grew, in order to latch onto it. Shortly after, the ...


7

tendril coiling occurs via asymmetric contraction of an internal fiber ribbon of specialized cells. Under tension, both extracted fiber ribbons and old tendrils exhibit twistless overwinding rather than unwinding, with an initially soft response followed by strong strain-stiffening at large extensions. Source: Gerbode et al. 2012, Science, How the Cucumber ...


7

The current thinking amongst biophysicists is that if we all woke up tomorrow to find that someone had edited the book of life so as to exchange all of the L-'s and D-'s (and made similar mirroring changes to all of the molecules that any protein interacts with), everything would be exactly the same. Milton, et al. (Science, 1992) lent supporting empirical ...


6

As you say yourself, biological molecules are usually available in both chiralic possibilities, yet nature uses only one of the two possibilities. At some point in our molecular evolution (and at a very early one) L-amino acids were stochastically "chosen" over their D-equivalents (I think that the choices would have been equiprobable). There is no reason ...


4

One aspect of the basic biochemistry needed to approach this question is the fact that the enzymes that catalyse cellular reactions show various levels of specificity towards their substrates (reactants), including stereo-specificity. This is illustrated below (an ill-favoured thing, but mine own). The first example shows that the specificity of proteases ...


3

First off, quick clarification: "chiral" simply means distinct from its mirror image. All current life is chiral, in that it is made up of molecules which have a "handedness". What you're asking about is life which is made up of molecules of the opposite handedness (which I'll term "mirror chiral"). Such a lifeform is theoretically possible - chemical and ...


3

There is no reason to expect to find opposing chiral life today even if it did exist during the early stages of life's evolution. Everything not incorporated into more recent organisms has been lost, selective process will destroy early life as better adapted life evolves. Remember the earliest forms of life will be very flimsy compared to what comes later ...


3

As far as I know, there isn't too much we know about why life is "left-handed". So far the prevailing hypothesis is that in space there may be a tendency for amino-acids to favor one chiral-state over another, and there's some very smart people who are testing this, as opposed to the 50:50 shot here on Earth. To answer your question, however, the general ...


3

Hypothetically if an alien species were found , and if they contained similar biochemical polymers (DNA with A,T,C,G , Protein with 20 Amino acids etc) then we MAY be able to conclude that they share an origin with us. (Just similar chirality does not necessitates the theory of same origin) Does the chirality of a single compound more or less determine the ...


2

Antibodies are proteins and proteins are made up of L-amino acids, which have at least 1 chiral centre. Therefore proteins contain chiral centres. So yes antibodies have chirality.


2

As Nicolai has mentioned in his answer, change of chirality (L and D) of amino acids will drastically change the way a protein folds. I searched online to find if a solved structure of D only form of any protein. However, there were none. But, both right handed and left handed DNA are known. This difference does not happen because of the chirality difference ...


2

No. One can make no generalization about the effect of the change in chirality in a ligand in the protein to which it normally binds. As the simple diagram below shows, as far as interaction with the ligand binding site is concerned there is no essential difference between a enantiomer of the normal ligand and a modified version of it: Both may be able to ...


2

There a few things you have to take care of with chirality in biological systems: First note, that for amino acids we usually use L and D instead of r and s nomencalture. In chemistry the difference between chiral enantionemeres is usually really just a difference in light polarisation like you described, otherwise they can be thought of as identical, ...


1

I took a 30 second look at the book you mentioned. The authors just made this up, just like 95% of the book. The authors are not wrong, they didn't want to write something useful and made a mistake, they're just bullshitting: They're making stuff up, letting it sound a tiny bit scientific and try to sell a lot of books. If you want to know more about ...


1

The best reading for the topic is "a comparison of chirality patterns of climbing plants in Peru and Brazil" from "assymetry in plants" which sais that: The mechanical or physiological basis for dextral versus sinistral orientation of circumnutation among apically twining plants has not been determined, despite several papers on the topic in recent years ((...


1

This question is a matter of discussions, but I'd like to mention that there's basically two viewpoints. The first viewpoint is that the symmetry breaking is global (in other words, there's a reason why exactly L-amino acids; if there are other planets with Life, L-amino acids should be "used" on all of them or at least on the major number of them). The ...


1

Microscopic chirality is not at all necessary to explain curly hair (or other objects). All that is required is flexibility. Once hair gets long enough, it collides with itself, and is pushed off to one side or another, forming a chiral curl. For some anecdotal evidence against microscopic chirality, find someone with large diameter hanging curls in their ...


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