Chemical Properties of Biological Molecules
Facts
- W & C did not suggested the structure of DNA molecule, but they did not prove that double helices would form spontaneously outside the biological system. However, if you keep a set of two single helices at 1mM concentration, 25 degree C, 99% would form a double helix
- Resonance structure: A same molecule can be written in two different ways based on the bonding possibilities (alternative arrangements)
- Covalent Bonds : Sharing of more than 1 electron between the atoms - Stronger
- Types of Non-covalent bonds
- Electrostatic interactions: Charged group of one atom attracts other other. Coulomb's law defines/measures the energy outcome due to electrostatic interactions
- Hydrogen bonds : Fundamentally electrostatic interaction. Donar and acceptar of the electron between hydrogen and the adjacent molecule. Weaker. All the water's special properties are due to the presence of hydrogen bonding in it.
- Van der Waals interactions: The charge in the atom is dynamic with time. Atoms (depending on the charge they repel/attract) gets attracted until they reach Van der Waals distance. Meaning, Van der walls is the distance at which the atoms get attracted/repeled.
- Hydrophobic interactions
- Laws of thermodynamics
- Zeroth law of thermodynamics: If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This law helps define the notion of temperature.
- First law of thermodynamics: When energy passes, as Work (thermodynamics)|work, as heat, or with matter, into or out from a system, the system's internal energy changes in accord with the law of conservation of energy. Equivalently, perpetual motion machines of the first kind are impossible.
- Second law of thermodynamics: In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases. Equivalently, perpetual motion machines of the second kind are impossible.
- Third law of thermodynamics: The entropy of a system approaches a constant value as the temperature approaches absolute zero. With the exception of non-crystalline solids (glasses) the entropy of a system at absolute zero is typically close to zero, and is equal to the natural logarithm of the product of the quantum ground states.