Microscopy

Question 1

How have microscopy techniques developed?

Answer 1

First microscopes in mid 17th century
Light microscopes magnify up to 2,000 times - cheap, good for live specimens
Electron microscopes in mid 1930s up to 2,000,000 times with 2D image
Scanning electron microscopes give 3D image but lower magnification
Large, expensive and only at special temperature, pressure and humidity

Question 2

Explain how electron microscopy has increased understanding of subcellular structures?

Answer 2

Use beam of electrons to form and magnify image with 2D image up to 2,000,000 times
Scanning electron microscopes give 3D image eg chromosomes in cell division

Question 3

What does an electron microscope have?

Answer 3

Much higher magnification and resolving power

It can be used to study cells in much finer detail

Question 4

How do you calculate magnification?

Answer 4

Magnification = size of image/actual size
Answers in standard form (x10 to the number of decimal places)
Actual size = size of image /magnification
Size of image = actual size x magnification

Question 5

What can we see with a light microscope

Answer 5

Individual cells and large subcellular structures eg nucleus

Question 6

What can we see with electron microscope

Answer 6

Much smaller objects eg structures of mitochondria, chloroplasts, ribosomes, plasmids