This site is not maintained. Click here for the new website of Richard Dawkins.

Cell Size and Scale

http://learn.genetics.utah.edu/content/begin/cells/scale/

Some cells are visible to the unaided eye

The smallest objects that the unaided human eye can see are about 0.1 mm long. That means that under the right conditions, you might be able to see an ameoba proteus, a human egg, and a paramecium without using magnification. A magnifying glass can help you to see them more clearly, but they will still look tiny.

Smaller cells are easily visible under a light microscope. It’s even possible to make out structures within the cell, such as the nucleus, mitochondria and chloroplasts. Light microscopes use a system of lenses to magnify an image. The power of a light microscope is limited by the wavelength of visible light, which is about 500 nm. The most powerful light microscopes can resolve bacteria but not viruses.

To see anything smaller than 500 nm, you will need an electron microscope. Electron microscopes shoot a high-voltage beam of electrons onto or through an object, which deflects and absorbs some of the electrons. Resolution is still limited by the wavelength of the electron beam, but this wavelength is much smaller than that of visible light. The most powerful electron microscopes can resolve molecules and even individual atoms.
...
Continue reading
http://learn.genetics.utah.edu/content/begin/cells/scale/


---

TAGGED: BIOLOGY, GENETICS


RELATED CONTENT

Blogging the Human Genome

Sam Kean - Slate Comments

Blogging the Human Genome

Scientists place 500-million-year-old...

- - PhysOrg.com Comments

Using a process called paleo-experimental evolution, Georgia Tech researchers have resurrected a 500-million-year-old gene from bacteria and inserted it into modern-day Escherichia coli (E. coli) bacteria. This bacterium has now been growing for more than 1,000 generations, giving the scientists a front row seat to observe evolution in action. Credit: Georgia Institute of Technology

Q&A: Plant scientists answer your...

- - Sense About Science 6 Comments

Welcome to this questions and answer session on cross fertilisation, which has also been called contamination, with Wendy harwood and Huw Jones.

Open letter and video re threat to GM...

Rothamsted Research - YouTube/Sense... 79 Comments

Add your support to the appeal from scientists at the publicly funded Rothamsted Research: Don't Destroy Our Research.

Finding Phenotypes

Edyta Zielinska - TheScientist 7 Comments

Genes shared across species that produce different phenotypes—deafness in humans and directional growth in plants—may reveal new models of disease.

Synthetic Genetic Evolution

Ruth Williams - TheScientist 9 Comments


Synthetic Genetic Evolution

MORE

MORE BY LEARN.GENETICS UNIVERSITY OF UTAH

MORE

Comments

Comment RSS Feed

Please sign in or register to comment