Can I "see" a single molecule?
Single molecules are incredibly small, making them hard to detect without sophisticated technology. However, certain molecules can fluoresce, a processes by which the molecule emits light. These molecules have very interesting chemical structures that enable this process. If the color of the molecule is right and the molecule is "bright", the eye is sensitive enough to detect the light emitted a single molecule.
Beyond memorizing facts and taking practice tests, what else can I do to study for the biology and chemistry sections of the MCAT?
Read at least two scientific papers per week. Learning to handle complex scientific experiments, process foreign terminology and digest details are key to conquering the MCAT. These skills are only built through practice and cannot be memorized or learned from a study book. Also, there are a many monumental and really interesting research studies to read about.
How does the cell membrane form?
The outer lipid membrane of the cell, also known as the plasma membrane, is a fascinating, self-organizing, self-healing macromolecular structure composed of lipids and proteins. Phospholipids, molecules with hydrophillic phosphate-containing head groups and hydrophobic tails, are driven by the fundamental rules of thermodynamics, entropy and enthalpy, to order themselves into continuous, fluid sheets known as a lipid monolayer. Two sheets will associate due to the same principles of energy minimization to form a lipid bilayer. The center of the bilayer is composed of the hydrophibic carbon chain tails of the phospholipids and excludes water. Proteins that contain extensive hydrophobic amino acids on their surface interact favorably with the lipid tails and will insert into the bilayer, again due to the rules of thermodynamics. To add to the complexity but elegance of the plasma membrane, the exact composition of the membrane is highly regulated but adaptable to the needs of the cells.