The Chemistry of Life
Why Chemistry Matters in Biology
Atoms to cells
Biology is governed by chemistry: the structure of atoms determines bonding, bonding determines molecular shape, and molecular shape determines function. Living systems rely on a small set of elements, especially , , , , , and .
Core idea
In biology, function usually follows structure. Even small changes in molecular structure can strongly change activity.
Bonding and polarity
Covalent bonds share electrons, while ionic interactions depend on charge attraction. Polar molecules interact well with water, while nonpolar molecules tend to cluster together. These properties influence membrane formation, protein folding, and solubility.
Which interaction is most directly responsible for the hydrophobic effect in water-based systems?
Nonpolar molecules aggregate in water because this reduces the energy cost of disturbing water's hydrogen-bond network.
Correct answer: Nonpolar molecules clustering to reduce disruption of water's hydrogen-bond network
Why are hydrogen bonds important in biology?
Hydrogen bonds are weak individually but powerful in groups, helping molecules recognize and stabilize one another.
Correct answer: They help stabilize structures and mediate interactions such as DNA base pairing and protein folding.
Common biological elements
| Element | Main role |
|---|---|
| Carbon | Backbone of organic molecules |
| Oxygen | Polarity and oxidation reactions |
| Nitrogen | Amino acids and nucleic acids |
| Phosphorus | ATP and nucleic acids |
| Sulfur | Disulfide bonds and some amino acids |
Acids, bases, and buffers
The of a solution affects ionization states of molecules. Buffers resist changes in by donating or accepting protons. Enzyme activity, membrane transport, and protein structure are all sensitive to .
A buffer is most useful because it:
Buffers minimize changes in pH by reversibly binding or releasing .
Correct answer: Resists large pH changes when acids or bases are added