Key concepts in biology study guide

The progression of microscope technology, particularly the advent of electron microscopy, has fundamentally transformed our ability to visualise and comprehend cellular structures. Early light microscopes, while groundbreaking, were limited by the wavelength of visible light, restricting their resolution and magnification. This meant that only larger organelles, such as the nucleus, could be clearly observed, and many finer details remained elusive. Electron microscopes, however, employ beams of electrons instead of light. Since electrons possess a much shorter wavelength than visible light, electron microscopes can achieve significantly higher resolution and magnification. This technological leap has allowed scientists to resolve intricate sub-cellular structures like mitochondria, endoplasmic reticulum, ribosomes, and lysosomes. By revealing these previously unseen components, electron microscopy has been crucial in elucidating their specific shapes, arrangements, and ultimately, their diverse and vital roles within the cell, greatly advancing our understanding of cellular function.

Osmosis is the net movement of water molecules through a partially permeable membrane from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution). When studying osmosis in living tissues, such as potato cylinders, we often measure changes in mass. If the tissue gains mass, it has absorbed water via osmosis. If it loses mass, it has lost water. To quantify these changes, we calculate the percentage change in mass. This involves finding the difference between the final and initial masses, dividing by the initial mass, and then multiplying by 100. This percentage allows for a standardised comparison between experiments, regardless of the initial mass of the sample.