Page 2: Prokaryotic Cell Structure and Microscopy
This page delves into the structure of prokaryotic cells, specifically bacterial cells, and introduces the concept of microscopy in cell biology.
Prokaryotic Cell Structure
Definition: Prokaryotic cells are simpler than eukaryotic cells and are typically found in bacteria.
Key components of prokaryotic cells include:
- Chromosomal DNA: A single, long, circular chromosome that controls the cell's activities and replication. It floats freely in the cytoplasm, not enclosed in a nucleus.
- Plasmids: Small loops of extra DNA that contain genes for things like drug resistance and can be passed between bacteria.
- Cell membrane and cell wall: Provide structure and protection for the cell.
Highlight: The difference between prokaryotic and eukaryotic cell structure is significant. Prokaryotic cells lack a true nucleus and many organelles found in eukaryotic cells.
Microscopy
The page then transitions to discussing microscopes and their importance in cell biology.
Definition: Microscopes use lenses to magnify images and increase the resolution of an image, allowing scientists to see more detail.
Key points about microscopes:
- Light microscopes allow visualization of nuclei and chloroplasts.
- Electron microscopes provide much higher magnification and resolution, enabling scientists to see smaller structures like the internal structure of mitochondria, plasmids, or viruses.
Vocabulary: Resolution in microscopy refers to how well a microscope can distinguish between two points that are close together.
Example: While a light microscope might allow you to see the overall shape of a mitochondrion, an electron microscope would let you see its internal cristae structures.
The page concludes by comparing transmission electron microscopes to light microscopes:
- Transmission electron microscopes offer higher magnification and resolution.
- However, they are not portable, are expensive, and require complex specimen preparation.
- Unlike light microscopes, electron microscopes cannot be used to observe living tissue.
Highlight: The maximum resolution of an electron microscope is significantly higher than that of a light microscope, allowing for the observation of much smaller structures.
This information is crucial for students studying OCR Gateway Combined Science topics related to cell biology and microscopy, providing a comprehensive overview of cell structures and the tools used to study them.
