Biochemistry Review

Flashcards on Biochemistry and the properties of water.

Biochemistry

Explains life in terms of atomic structures of biological molecules and the chemical changes they undergo when they interact with other biological and non-biological molecules.

Non-polar molecules

Molecules with predominantly C-H and C-C bonds (e.g. Saturated hydrocarbons) that tend to be non-reactive.

Polar functional groups

Give biological molecules their structural and functional properties.

includes: carboxyl, carbonyl, alcohol, amino, thiol/sulfhydryl, phosphate/phosphoryl

Electronegativity

A measure of the ability of an atom in a molecule to attract electrons to itself.

Biomolecule reactivity

Found in functional groups that have polar bonds.

Water properties

Explained by its structure and the ability of the O to form additional bonds with H2O and other molecules.

Hydrogen bond

An electrostatic attraction between polarized molecules containing O-H, N-H, or F-H.

Hydrogen-bonded matrix in water

Gives rise to its high melting and boiling points relative to its low molecular weight.

Water exists as

A Hydrogen-bonded network with an average of 4 H-bonds per molecule in ice and 3.4 in liquid.

H-bonds strength

Strongest when linear i.e. the two heavy atoms and the shared H are in a line.

Weak Interaction

H-bonding (free energy = 8-21 kJ/mol) as compared to covalent bonding.

These are stable, but since they’re weak, they’re able to move

Breaking H-bonds

Requires the addition of enthalpy.

Gibbs free energy equation

G = H - T S

Hydrophilic molecules

Water will dissolve polar and charged molecules.

Electrostatic Interactions

Attraction between oppositely charged ions: free energy up to 50 kJ /mol

Salts such as sodium chloride (NaCl)

Easily solubilized because water hydrates and stabilizes Na+ and Cl+ ions via Electrostatic interactions.

van der Waals Interaction

A short range, very weak attraction, free energy ~ 4 kJ / mol.

Hydrophobic Effect

The entropy of water is reduced, disfavouring dissolution of hydrocarbons in water.

Amphipathic molecules

Contain both polar and non-polar groups. E.g. detergents, lipids, proteins.

Detergent micelle

Hydrocarbons interact with each other via vdW forces to form a hydrophobic core, while the hydrophilic groups associate with water.

Micelles of fatty acids

Form with a hydrophobic core and hydrophilic exterior.

carboxyl

carbonyl

alcohol