Microscopes: How We See What We Can't See: Crash Course Biology #22

Summary

In this episode of Crash Course Biology, Dr. Sammy takes us on a journey through the fascinating world of microscopes. From Antonie van Leeuwenhoek's groundbreaking discovery of bacteria to modern advancements in microscopy, we explore how these tools have evolved. We learn about light microscopes, electron microscopes, and scanning probes, each with unique capabilities for magnifying the microscopic world. With detailed insights into how scientists use these technologies to understand cells, molecules, and even viruses, this episode showcases the power of curiosity and scientific progress.

Takeaways

• 😀 Antonie van Leeuwenhoek made a groundbreaking discovery in 1683 when he observed tiny living organisms in his mouth, which led to the identification of bacteria.
• 😀 Leuwenhoek's curiosity and invention of a simple microscope helped reveal the unseen world of microorganisms, sparking scientific exploration.
• 😀 The term 'animacules' was coined by Leuwenhoek to describe the tiny organisms he observed, though the name didn't stick.
• 😀 Modern microscopes have advanced significantly from Leuwenhoek's time, providing better magnification, resolution, and contrast for viewing small structures.
• 😀 Light microscopes, also known as optical microscopes, have been in use since the 1600s and work by magnifying objects using light.
• 😀 Light microscopes can magnify specimens up to 2,000 times, but their resolution is limited for very small objects like molecules.
• 😀 Electron microscopes, invented in the 1930s, use electrons instead of light, allowing for much higher magnification and clearer images of small specimens.
• 😀 Scanning probe microscopes, developed in the 1980s, use sharp probes to scan specimens and create incredibly detailed images, up to 100 million times the original size.
• 😀 Despite their power, microscopes have limitations, such as the inability to view live specimens with electron microscopes due to sample preparation.
• 😀 New techniques like cryo-electron microscopy and fluorescence microscopy have enhanced our ability to capture detailed images of molecules and watch biological processes in real time.

Q & A

Who was the first person to observe bacteria, and how did they make this discovery?

Anthony Von Leeuwenhoek was the first person to observe bacteria. He made this discovery by using a single lens microscope to examine plaque from his teeth, revealing tiny living organisms swimming through his saliva.

What were the tiny organisms that Leeuwenhoek observed called?

Leeuwenhoek called the tiny organisms 'animalcules,' which means 'little animals.' The term didn't stick, but his discovery of bacteria did.

How did microscopes improve after Leeuwenhoek's time?

Microscopes have improved in magnification and resolution, allowing us to see finer details. New techniques also enhance contrast, making it easier to distinguish between tiny structures, and microscopes have become more accessible.

What is the basic principle behind how a light microscope works?

A light microscope works by shining light through or onto a specimen. The light is then bent by lenses, making the specimen appear larger than its actual size, similar to how glasses magnify images for nearsighted people.

What is the difference between light microscopes and electron microscopes?

Light microscopes use visible light to magnify objects, while electron microscopes use beams of electrons, which are much smaller and can reveal more detailed images of specimens, especially those smaller than cells.

What is the advantage of using electron microscopes over light microscopes?

Electron microscopes provide much higher magnification and resolution, allowing scientists to observe extremely small details, like the structure of viruses or molecules. They can magnify specimens up to 100,000 times.

What is scanning probe microscopy, and how does it work?

Scanning probe microscopy uses sharp probes that pass over the surface of a specimen to gather information. This method can create highly detailed images, magnifying specimens up to 100 million times their original size.

What is cryo-electron microscopy, and how does it help scientists?

Cryo-electron microscopy involves freezing samples to extremely low temperatures and taking thousands of pictures, which are then combined into 3D images. This method is especially useful for studying molecules like proteins in great detail.

What are some limitations of electron microscopes?

Electron microscopes require samples to be prepared in a way that usually kills the cells, making it impossible to observe living organisms. Additionally, the energy from the electrons can sometimes damage delicate specimens.

What is the basic process of using a light microscope effectively?

To use a light microscope effectively, you should start by setting the stage to its lowest position, choose the lowest power objective lens, center and focus the specimen, then gradually adjust the magnification while using fine adjustments for clarity.