Original antigenic sin

Tendency to focus an immune attack on those structures that were present during the original.

This means that our immune systems effectively ignore the subtle changes occurring each year in pathogens

TLS Online TPP Program

#Id: 7738

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following are true for an element?

(i) Atomic number = number of protons + number of electrons

(ii) Mass number = number of protons + number of neutrons

(iii) Atomic number = number of protons = number of neutrons

(iv) Atomic number = number of protons = number of electrons

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (ii) and (iv)

TLS Online TPP Program

#Id: 7739

#Unit 1. Molecules and their Interaction Relevant to Biology

Atoms are characterised by:

Radius

Ionization energy

Electron affinity

Electronegativity

Metallic character

Oxidation potential

TLS Online TPP Program

#Id: 7740

#Unit 1. Molecules and their Interaction Relevant to Biology

Atomic radii: The atomic radii of an atom depends on its position in the periodic table.

We can never determine the atomic radius of an atom because there is never a zero probability of finding an electron, and thus never a distinct boundary to the atom.

All that we can measure is the distance between two nuclei (internuclear distance).

TLS Online TPP Program

#Id: 7741

#Unit 1. Molecules and their Interaction Relevant to Biology

Atomic radii: The atomic radii of an atom depends on its position in the periodic table.

We can never determine the atomic radius of an atom because there is never a zero probability of finding an electron, and thus never a distinct boundary to the atom.

All that we can measure is the distance between two nuclei (internuclear distance).

TLS Online TPP Program

#Id: 7742

#Unit 1. Molecules and their Interaction Relevant to Biology

Atomic radii: The atomic radii of an atom depends on its position in the periodic table.

We can never determine the atomic radius of an atom because there is never a zero probability of finding an electron, and thus never a distinct boundary to the atom.

All that we can measure is the distance between two nuclei (internuclear distance).

TLS Online TPP Program

#Id: 7743

#Unit 1. Molecules and their Interaction Relevant to Biology

A covalent radius is one-half the distance between the nuclei of two identical atoms.