Which of the following amino acids does not have an L-enantiomer? (A) Cysteine (B) Threonine (C)

Which of the following amino acids does not have an...

Key Concepts

Enantiomers

Enantiomers are pairs of molecules that are mirror images of each other, often designated as L- and D- forms in biochemistry. Most amino acids in living organisms are found as L-enantiomers, which is crucial for protein structure and function.

Achirality

Achirality describes molecules that do not possess a chiral center, usually due to having two identical substituents. In the context of amino acids, glycine is unique because it is achiral, meaning it does not have distinct L- and D- forms.

Chirality

Chirality refers to a property of a molecule that makes it non-superimposable on its mirror image. In amino acids, this is determined by the carbon atom bonded to four different groups, leading to distinct mirror-image forms known as enantiomers.

Transcript

00:01 Okay, this problem is asking us, which of these amino acids does not have an l anantimer? okay, so what is an l anantimer? that is best explained if we just discuss what is an ananthiomor in the first place.

00:10 So, for example, an an anantomor is a compound.

00:13 Let's just say we have something like this, in which we have a hydrogen in the front, and then, for example, a bromine in the back, and then i have this ethel group here, and i have a methyl group right there, and that is all revolving around this carbon, right? so anytime i have an an anantir, that means that i have a chiral center.

00:28 And this is going to be my chiral center, that carbon, because it has four different attachments, right? connected to that carbon, we have a hydrogen, a bromine, an ethyl group, and a methyl group.

00:36 Okay, so because i have four different attachments, if i are to draw a, the reverse of this, this compound, i would have something like this, in which i have a hydrogen in the back this time, and then the bromine in the front.

00:48 Okay, so these are not going to be the same exact molecules.

00:50 They're going to be anantomers of each other.

00:52 Okay, and we don't really have to focus on l for now because the l -slash -d anantimer, that's not really relevant for this, because all.

00:58 All eukaryotic amino acids are l, except for one, and that's the one that we're going to discuss right now.

01:04 So, for example, cysteine.

01:06 Okay, so cysteine, does this have a chiral center? because if it does, that means that it has an l an antimer.

01:11 Okay, so do i have a carol center here? the answer is yes, because i'll do this part in red, this is my carol center, right? because that carbon has four different attachments.

01:19 It has the attachment to a carboxylok acid group, it has the attachment to an immune group, it has the attachment to the sulfur group, and then it has the attachment to this implied hydrogen.

01:27 Okay, so because it has four different attachments, that means that it has a chiro center, that means that it has an anantomir, specifically the l anantamor...

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