L1: Life is Cellular

Question 1

Robert Hooke

Answer 1

1665 English philosopher/architect
Used an early compound light microscope to observe a dead cork-plant specimen
Discovers thousands of tiny “chambers” and calls them Cells
= Cells contain an array of structures and organelles each with unique functions

Question 2

Anton van Leeuwenhoek

Answer 2

1665 Dutch tradesman/scientist
Used a single lens microscope to observe a pond water specimen
Discovers a multitude of organisms in water & bacteria cells in the mouth
= Cells are the basic unit of life

Question 3

Matthias Schleiden

Answer 3

1838 German botanist
Discovers that ALL plants are made up of cells

Question 4

Theodor Schwann

Answer 4

1839 German biologist
Discovers that ALL animals are made up of cells

Question 5

Rudolf Virchow

Answer 5

1855 German physician
Discovers that new cells can ONLY be produced from the division (mitosis & meiosis) of pre-existing cells

Question 6

Cell Theory

Answer 6

1. All living things are made up of cells
2. Cells are the basic units of structure and function in living things
3. New cells can only be produced from pre-existing cells

Question 7

Compound Light Microscope

Answer 7

A typical compound light microscope uses light focused through 2 glass lenses to penetrate the specimen and form a magnified image
More light absorption = Darker appearance
1st lens: objective lens (just above specimen)
scanning (4x) Red
low (10x) Yellow
high (40x) Blue
oil immersion (100x) White
2nd lens: ocular lens (placed in the eyepiece)

Question 8

Electron Microscope

Answer 8

Electron microscopes use beams of electrons that are focused by magnetic fields in vacuum
Offer much higher magnification and resolution than CLM

Question 9

Scanning Electron Microscope (SEM)

Answer 9

Electron gun shoots a beam of electrons
Anode focuses the beam of electrons
Several focusing electromagnets(lens)
Scanning coils
Electron detectors which generate image based on amount of electrons reflected from the sample
Stage holds sample and reflects the electrons back from the sample

Question 10

Transmission Electron Microscope (TEM)

Answer 10

Electron gun shoots a beam of electrons
Anode focuses the beam of electrons
Several focusing electromagnets(lens)

Question 11

Compound Light Microscope Magnification

Answer 11

2000x Max

Question 12

Electron Microscope Magnification

Answer 12

SEM : 200,000x Max
TEM : 500,000x Max

Question 13

CLM Advantages & Disadvantages

Answer 13

Advantages:
Easy to operate
CHEAP
Can use live specimen
True color images
Disadvantages:
Low resolution (0.2 µm)
Low magnification
Samples must be super thin = does not reveal enough about the specimen

Question 14

EM Advantages & Disadvantages

Answer 14

Advantages:
Higher magnification
Higher resolution (0.2 nm)
Detailed images of surface (SEM) and interior (TEM) structures
Disadvantages:
False coloring is used (b/c images are black and white)
Lots of training required to operate
Produces toxic heavy metals
EXPENSIVE
Specimen must be dead and preserved (to pass through the vacuum)

Question 15

Early Microscopy

Answer 15

1500’s eye glass makers discover that by stacking several glass lenses you can magnify the image of objects
Hence the discovery of the
microscope
Most microscopes use lenses to magnify the image of an object by focusing light or electrons

Question 16

CLM Coloring

Answer 16

Most living cells are transparent(ish)
So chemical stains or dyes which reveal specific compounds and structures within the cell are used.
Fluorescent dyes that give off light of a particular color under specific wavelengths are used to identify and locate certain molecules within a cell.
Fluorescent microscopes detect and image molecules that are attached to these fluorescent dyes.

Question 17

EM Coloring