Cell Structure and Microscopy
This section covers the fundamental differences between eukaryotic and prokaryotic cells, their structures, and microscopy techniques used to study them.
Eukaryotic vs Prokaryotic Cells
Eukaryotic cells are complex cells found in animals and plants, while prokaryotic cells are simpler, single-celled organisms like bacteria.
Definition: Eukaryotes are organisms with complex cells containing a nucleus and other membrane-bound organelles, while prokaryotes are simpler organisms lacking these features.
Animal Cells (Eukaryotic)
Animal cells contain several key structures:
- Nucleus: Controls cell activities and contains genetic material
- Cytoplasm: Site of chemical reactions
- Cell membrane: Controls what enters and exits the cell
- Mitochondria: Site of aerobic respiration
- Ribosomes: Where proteins are synthesized
Plant Cells (Eukaryotic)
Plant cells share structures with animal cells but also have additional features:
- Rigid cell wall made of cellulose
- Permanent vacuole containing cell sap
- Chloroplasts for photosynthesis
Highlight: Chloroplasts contain chlorophyll, which absorbs light for photosynthesis.
Bacterial Cells (Prokaryotic)
Bacterial cells have a simpler structure:
- No nucleus; instead, a single strand of DNA floats freely in the cytoplasm
- Small rings of DNA called plasmids
- Cell membrane and cell wall
Microscopy
Microscopy is essential for studying cells. Two main types of microscopes are used:
- Light microscopes: Use light and lenses to form an image
- Electron microscopes: Use electrons for higher resolution and more detailed images
Example: An onion cell viewed under a microscope with 100x magnification appears 7.5mm wide. To calculate its real width:
Real size = Image size / Magnification
Real size = 7.5 / 100 = 0.075 mm = 75 ฮผm
Vocabulary: Magnification is the ratio of image size to real size.