Amino Acid Configuration and Chirality

The video explores the stereochemistry of amino acids, focusing on R&S and D&L classifications. It explains how to determine chirality using the Cahn-Ingold-Prelog system and provides examples with alanine, phenylalanine, and cysteine. The video also covers Fischer projections and the logic behind L and R amino acids, emphasizing that cysteine is the only L amino acid with R stereochemistry.

What is the main difference between R&S and D&L configurations in amino acids?

• R&S are used for sugars, D&L for amino acids.

• R&S are for achiral molecules, D&L for chiral molecules.

• R&S refer to absolute configuration, D&L to relative configuration.

• R&S are used in biological contexts, D&L in chemical contexts.

In a Fischer projection, where is the carbonyl group typically placed?

• At the bottom

• On the left

• On the right

• At the top

What is the configuration of L-phenylalanine?

• D

• S

• R

• L

Which amino acid is the only L amino acid with R stereochemistry?

• Glycine

• Alanine

• Methionine

• Cysteine

What is the configuration of R-alanine in a Fischer projection?

• R

• L

• D

• S

Which atom is given the highest priority when determining chirality in amino acids?

• Nitrogen

• Sulfur

• Hydrogen

• Carbon

What determines whether an amino acid is D or L in a Fischer projection?

• The position of the R group

• The position of the hydrogen atom

• The position of the carbonyl group

• The position of the amine group

How can you quickly determine if an amino acid is D or L based on its R or S configuration?

• All L amino acids are S unless they are cysteine

• All S amino acids are L

• All R amino acids are D

• All D amino acids are R unless they are glycine

What is the priority order of atoms when ranking substituents in amino acids?

• Nitrogen, Sulfur, Oxygen, Carbon, Hydrogen

• Sulfur, Oxygen, Nitrogen, Carbon, Hydrogen

• Carbon, Nitrogen, Oxygen, Sulfur, Hydrogen

• Oxygen, Sulfur, Nitrogen, Carbon, Hydrogen

Which amino acid is achiral due to having two identical substituents?

• Cysteine

• Alanine

• Phenylalanine

• Glycine