Unit 3: Microscopy

Question 1

When were the first microscopes invented?

Answer 1

16th century
(~1500s and early 1600s)

Question 2

Anton van Leeuwenhoek

Also sometimes referred to as Antoni

Answer 2

Studied living tissues under microscope and extensively documented their structures
Called them “animalcules” meaning “little animals”

Question 3

Robert Hooke

Answer 3

Early naturalist
First credited with using the term “cell”

Question 4

Three parameters to consider with light microscopy

Answer 4

Magnification
Resolution
Contrast

Question 5

Magnification

Answer 5

Ratio of object’s image size to its actual size
In light microscopes, it is the product of the magnifications of the ocular and objective lenses
Ex: Ocular lens = 10x; Objective lens = 4x; then the total magnification is 10 * 4 = 40X

Question 6

Resolution

Answer 6

An image’s clarity
Higher resolution means being able to distinguish smaller details
Is inversely proportional to magnification

Question 7

Contrast

Answer 7

Difference in brightness between areas
Can be enhanced using dyes and by changing the illumination settings on a microscope

Question 8

How electron microscopes work

Answer 8

A beam of electrons are shot through (TEM) or at (SEM) a specimen
A computer then determines where the electrons struck after the specimen, and uses those data to construct an image

Question 9

Two types of electron microscopes

Answer 9

SEM = scanning EM
TEM = transmission EM

Question 10

Benefits of light microscopy

Answer 10

1. Inexpensive
2. Can use live specimens
3. Faster / easier to prepare specimens

Question 11

What types of micrographs can be made by each type of microscope?

Answer 11

Light: mostly flat image (can only focus at one distance) that shows whole cells within a tissue; may be able to distinguish large organelles

TEM: flat images, produced by making thin slices of specimen; often shows details of particular organelles

SEM: 3D images, produced by bouncing electron beam off of surface of specimen