Change in environmental condition is not necessary for natural selection.

TLS Online TPP Program

#Id: 7675

#Unit 1. Molecules and their Interaction Relevant to Biology

Isoleucine and Threonine have two chiral carbons so exists in multiple RS configuration.

TLS Online TPP Program

#Id: 7676

#Unit 1. Molecules and their Interaction Relevant to Biology

A dihedral angle is determined by 4 atoms. These 4 determine Phi (φ). Here, the angle is 0º.

TLS Online TPP Program

#Id: 7677

#Unit 1. Molecules and their Interaction Relevant to Biology

Clockwise rotation gives dihedral angles from 0º to 180º.

180º is the same as counter-clockwise rotation to -180º.

TLS Online TPP Program

#Id: 7678

#Unit 1. Molecules and their Interaction Relevant to Biology

Counter-clockwise rotation starting at 0º gives negative dihedral angles from -1º through

90º ending at -180º (the same dihedral angle  as +180º).

TLS Online TPP Program

#Id: 7679

#Unit 1. Molecules and their Interaction Relevant to Biology

Because they cannot rotate, each peptide bond holds 6 atoms in a plane.

However, most possible angles of Phi (φ) and Psi (ψ) are impossible due to clashes

between atoms. These balls are much smaller than the atoms they represent.

TLS Online TPP Program

#Id: 7680

#Unit 1. Molecules and their Interaction Relevant to Biology