Microscopy is your gateway to exploring the invisible world of...
Biology68 views·Updated 12 Aug 2026·4 pagesUnderstanding Microscopy and Cell Fractionation
Waffle 🏴🇵🇸@amuslimah
1 / 4
1
of 4
Light Microscope Basics
Light microscopes are brilliant tools that use two convex glass lenses to magnify tiny objects, but they've got limits. They can only resolve images that are 0.2 micrometers apart - that's because light waves themselves restrict how much detail you can see.
You'll need to master the magnification formula: Magnification = size of image ÷ size of real object. This equation pops up in exams regularly, so get comfortable with it! Resolution is equally important - it's the minimum distance apart that two objects can be seen as separate things.
When you peer through a light microscope, you'll spot different structures in plant and animal cells. Plant cells show off their cell walls, chloroplasts, and large vacuoles, whilst animal cells reveal centrioles and other organelles. Some structures like ribosomes (25nm) are too small to interfere with light waves, so they're tricky to see clearly.
Quick tip: Remember that anything smaller than the wavelength of light (400nm) becomes difficult to distinguish clearly under a light microscope.
2
of 4
Electron Microscopes
Electron microscopes smash through the limitations of light microscopes by using electron beams instead of light. They can resolve objects just 0.1 nanometers apart - that's 2000 times better than light microscopes!
There are two main types you need to know. Transmission electron microscopes (TEM) fire electrons through ultra-thin specimens, creating detailed internal images where electron-absorbing areas appear darker. Scanning electron microscopes (SEM) bounce electrons off surfaces to build stunning 3D images based on how the electrons scatter.
Both types need a vacuum environment to work properly - air particles would knock the electrons off course. This creates some serious limitations: you can't observe living specimens, samples need complex staining (which might create artificial structures), and TEM specimens must be incredibly thin.
Remember: SEM gives you 3D surface detail, whilst TEM shows internal structures - but TEM has better resolution than SEM.
3
of 4
Cell Fractionation and Ultracentrifugation
Cell fractionation is like sorting your laundry, but with cell organelles! Scientists use differential centrifugation to separate different cell parts so they can study each component individually.
The process starts with homogenisation - cells get blended up in a special solution to create a mixture called homogenate. Then comes the clever bit: the homogenate gets spun in a centrifuge at increasing speeds. Heavy organelles like nuclei settle out first at low speeds, forming a pellet at the bottom.
The remaining liquid (supernatant) gets transferred to a new tube and spun faster. This time, mitochondria form the pellet. Keep increasing the speed and you'll separate out progressively lighter organelles. The initial homogenate must be kept cold, buffered, and at the same water potential as the original cells.
Key point: The process works because different organelles have different densities - heavier ones settle out at lower centrifuge speeds.
4
of 4
Measuring with Eyepiece Graticules
An eyepiece graticule acts like a tiny ruler built into your microscope, but here's the catch - it shows different measurements depending on which objective lens you're using. You'll need to calibrate it every single time you change magnification.
Calibration involves lining up your eyepiece graticule with a stage micrometer (a precise microscopic ruler). Count how many eyepiece graticule divisions fit into one stage micrometer division. If 35 graticule divisions equal 10 micrometers on the stage micrometer, then one graticule division equals 10 ÷ 35 = 0.29 micrometers.
Once calibrated, measuring becomes straightforward. Count the graticule divisions that span your specimen, then multiply by your calibration factor to get the actual size in micrometers. This technique is essential for measuring cellular structures accurately in coursework and exams.
Pro tip: Always recalibrate when switching between objective lenses - the calibration factor changes with magnification!
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Biology68 views·Updated 12 Aug 2026·4 pagesUnderstanding Microscopy and Cell Fractionation
Waffle 🏴🇵🇸@amuslimah
Microscopy is your gateway to exploring the invisible world of cells and their tiny components. From basic light microscopes to powerful electron microscopes, these tools let scientists see structures thousands of times smaller than what your naked eye can detect.
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Light Microscope Basics
Light microscopes are brilliant tools that use two convex glass lenses to magnify tiny objects, but they've got limits. They can only resolve images that are 0.2 micrometers apart - that's because light waves themselves restrict how much detail you can see.
You'll need to master the magnification formula: Magnification = size of image ÷ size of real object. This equation pops up in exams regularly, so get comfortable with it! Resolution is equally important - it's the minimum distance apart that two objects can be seen as separate things.
When you peer through a light microscope, you'll spot different structures in plant and animal cells. Plant cells show off their cell walls, chloroplasts, and large vacuoles, whilst animal cells reveal centrioles and other organelles. Some structures like ribosomes (25nm) are too small to interfere with light waves, so they're tricky to see clearly.
Quick tip: Remember that anything smaller than the wavelength of light (400nm) becomes difficult to distinguish clearly under a light microscope.
2
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Electron Microscopes
Electron microscopes smash through the limitations of light microscopes by using electron beams instead of light. They can resolve objects just 0.1 nanometers apart - that's 2000 times better than light microscopes!
There are two main types you need to know. Transmission electron microscopes (TEM) fire electrons through ultra-thin specimens, creating detailed internal images where electron-absorbing areas appear darker. Scanning electron microscopes (SEM) bounce electrons off surfaces to build stunning 3D images based on how the electrons scatter.
Both types need a vacuum environment to work properly - air particles would knock the electrons off course. This creates some serious limitations: you can't observe living specimens, samples need complex staining (which might create artificial structures), and TEM specimens must be incredibly thin.
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Cell Fractionation and Ultracentrifugation
Cell fractionation is like sorting your laundry, but with cell organelles! Scientists use differential centrifugation to separate different cell parts so they can study each component individually.
The process starts with homogenisation - cells get blended up in a special solution to create a mixture called homogenate. Then comes the clever bit: the homogenate gets spun in a centrifuge at increasing speeds. Heavy organelles like nuclei settle out first at low speeds, forming a pellet at the bottom.
The remaining liquid (supernatant) gets transferred to a new tube and spun faster. This time, mitochondria form the pellet. Keep increasing the speed and you'll separate out progressively lighter organelles. The initial homogenate must be kept cold, buffered, and at the same water potential as the original cells.
Key point: The process works because different organelles have different densities - heavier ones settle out at lower centrifuge speeds.
4
of 4Sign up to see the content. It's free!
- Access to all documents
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- Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Measuring with Eyepiece Graticules
An eyepiece graticule acts like a tiny ruler built into your microscope, but here's the catch - it shows different measurements depending on which objective lens you're using. You'll need to calibrate it every single time you change magnification.
Calibration involves lining up your eyepiece graticule with a stage micrometer (a precise microscopic ruler). Count how many eyepiece graticule divisions fit into one stage micrometer division. If 35 graticule divisions equal 10 micrometers on the stage micrometer, then one graticule division equals 10 ÷ 35 = 0.29 micrometers.
Once calibrated, measuring becomes straightforward. Count the graticule divisions that span your specimen, then multiply by your calibration factor to get the actual size in micrometers. This technique is essential for measuring cellular structures accurately in coursework and exams.
Pro tip: Always recalibrate when switching between objective lenses - the calibration factor changes with magnification!
We thought you’d never ask...
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
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