Small Molecules and The Chemistry of Life

Who is the instructor for the 'Small Molecules and The Chemistry of Life' study unit?

Prof. Rebamang Mosa from the Department of Biochemistry, Genetics and Microbiology.

What percentage of the tissue of most living organisms is made up of the six elements highlighted in the periodic table (H, C, N, O, P, S)?

Typically 98% (except for skeletons).

What is the difference between a polar and a non-polar covalent bond based on electronegativity?

Non-polar covalent bonds occur between atoms of equal electronegativities, while polar covalent bonds occur between atoms of greatly different electronegativities.

What are the common bond energies for Covalent, Ionic, and Hydrogen bonds?

Covalent bonds have the highest energy at $50-110\,kcal/mol$, while Ionic and Hydrogen bonds are both lower with ranges of $3-7\,kcal/mol$.

How do hydrophobic interactions differ from van der Waals forces?

Hydrophobic interactions involve the interaction of non-polar substances in the presence of polar substances like water, while van der Waals forces are electrical attractions between the electrons of non-polar substances.

What is the primary reason water molecules are considered cohesive?

Water molecules are held together by hydrogen bonds (H-bonds).

Why is ice less dense than liquid water?

Water expands on freezing because hydrogen bonds hold the molecules relatively far from each other in a rigid ice crystal.

What is the molar ratio of Carbon, Hydrogen, and Oxygen in carbohydrates?

The molar ratio is $1:2:1$.

Define the mathematical relationship for pH in terms of hydrogen ion concentration.

$$pH = -\log[H^+]$$

In pure water at neutral pH, what is the concentration of hydrogen ions $[H^+]$?

$$1 \times 10^{-7}\,M$$

If solution X has a pH of 4 and solution Y has a pH of 7, how much greater is the $[H^+]$ in solution X?

The $[H^+]$ in solution X is $1,000$ times (or $10^3$) greater than in solution Y.

What is the function of a buffer in a biological system?

A buffer resists large pH changes when an acid or base is added.

Distinguish between structural isomers and optical isomers.