Question

Which statements regarding weak bonds are true?

A) Represent the bonds that hold water molecules together in liquid state

B) Are what hold the three-dimensional structures of proteins, nuleic acis, and lipid membranes together

C) sre ofter electrostatic (Involving charges particles or regions) in natre

D A&B

E) A B & C

Answer 1

ANSWER

E (A, B& C) is the answer for the above question.

All the above bonds listed in the statements A, B & C are belonging to Non-covalent interactions. Even though non-covalent interactions are weak, they play a very important role in stabilization of structure of biomolecules and also in facilitating the interactions between biomolecules within a cell.

Explanation

For Statement A

Water is a polar solvent because hydrogen and oxygen atoms have substantially different electronegativities. Since electrons are shared unequally, the -O-H bonds are dipolar and partial positive and negative charges occur on H and O. Hence the bonds that hold water molecules together in liquid state are weak.

For statements B & C

Most of the bonds in the biomolecules are found to be non-covalent bonds. The Non-covalent interactions are weak electrical bonds between molecules that hold atoms together but do not involve significant overlapping of electrons.

Different types of non-covalent interactions include ionic (electrostatic) bonds, H-bonds, hydrophobic bonds and van der Waals interactions.

Ionic bonds (electrostatic bonds)

In this type of interaction, the atoms involved are positively or negatively charged (called ions). These ions are held together by electrostatic force of attraction between the charged atoms or ions holds them together.

A cell contains a large number of compounds with both acidic and basic groups. In the aqueous environment of the cell and under appropriate conditions these groups ionize and become charged.

The acidic groups acquire negative charge, whereas the basic groups acquire positive charge. The electrostatic forces of attraction between these charged ions hold them together and are called ionic bonds.

Such bonds play an important role in stabilizing the three dimensional structure of proteins, in protein-protein and protein-nucleic acid interactions etc,.

Hydrogen bonds

            H-bonds are non-covalent bonds occurring between the H atom of a dipolar molecule such as water, and the unshared electron pair of another atom (i.e., O or N).

            These bonds represent the primary way in which water molecules interact with themselves and many types of biomolecules.

Hydrophobic interactions

These interactions occur when nonpolar hydrophobic molecules or groups in the molecules are forced to aggregate by polar water molecules.

When molecules with nonpolar hydrophobic groups are added to water, the groups aggregate to minimize exposure to water and are held together by a lattice of hydrogen bonded water molecules.

Van der Waals interactions

These attractive interactions arise due to momentary unequal electron density around an atom leading to charge separation and consequently, resulting in molecules with opposite charges.

As the electrons are orbiting around the nucleus of an atom, at any given point of time, the electron density on one side of the atom may be greater than the other.

This momentary asymmetric distribution of electrons may create a transient separation of charges and dipoles in the molecules (one part of the molecule has a small positive and other part a small negative charge).

This transient dipole molecule can induce a similar charge separation in a nearby molecule. When two such appropriately oriented dipolar molecules come close together, they experience weak attractive forces that hold the two molecules together are called van der Waals interactions.