Microscopes and Magnification

This page covers different types of microscopes and how to calculate magnification.

Light microscopes:

• Developed in the mid-17th century
• Offer up to 2000x magnification
• Key components: eyepiece, objective lens, stage, slide, light source, fine and coarse focus

Electron microscopes:

• Developed in the 1930s
• Use a beam of electrons instead of light
• Offer up to 2,000,000x magnification
• Two types: Transmission Electron Microscope (TEM) for 2D images and Scanning Electron Microscope (SEM) for 3D images

Vocabulary: Resolution - The ability to distinguish between two separate points in an image.

Example: To calculate magnification using a light microscope, multiply the magnification of the eyepiece by the magnification of the objective lens.

Highlight: The magnification formula in biology is crucial for determining the actual size of microscopic objects: Magnification = Image size / Actual size

Cell Structure and Types

This page introduces the fundamental differences between eukaryotic and prokaryotic cells.

Eukaryotic cells are larger and more complex, typically found in animals and plants. They contain a nucleus and various organelles such as mitochondria, ribosomes, and chloroplasts (in plant cells). The eukaryotic cell diagram shows key structures like the cell membrane, cytoplasm, and nucleus.

Prokaryotic cells, on the other hand, are smaller and simpler, typically found in bacteria. They lack a true nucleus and most organelles found in eukaryotic cells. The prokaryotic cell diagram illustrates their basic structure, including the cell wall, flagella, and free-floating DNA.

Highlight: Electron microscopes offer higher magnification and resolution compared to light microscopes, allowing for detailed study of cell ultrastructure.

Vocabulary: Cytoplasm - The gel-like substance within cells where most chemical reactions occur.

Example: An onion tissue examined under a microscope using iodine stain demonstrates the typical plant cell structure, including the cell wall and large central vacuole.

Cell Division and Stem Cells

This page covers the cell cycle, mitosis, and the importance of stem cells.

Stages of the cell cycle:

1. Growth phase
2. DNA replication
3. Mitosis (nuclear division)
4. Cytokinesis (cell division)

Stem cells:

• Unspecialized cells that can develop into various cell types
• Two main types: embryonic stem cells and adult stem cells
• Used in therapeutic cloning and treating various diseases

Vocabulary: Chromosomes - Long, coiled strands of DNA found in the nucleus of a cell, containing genes.

Highlight: Humans have 23 pairs (46 total) of chromosomes.

Example: Adult stem cells from bone marrow can be used to treat conditions like Crohn's disease and paralysis.

Quote: "Stem cells are cells that aren't specialised yet and can turn into any type of cell."