Cell Theory

Question 1

Robert Hooke’s Discovery of Cells with the use of a microscope

Answer 1

1665
- Examined cork slices (dead plant tissue) and saw box like structure + called them cells
- Cells weren’t seen as dead
- Microscope was limited to 30x magnification

Question 2

What did Antoine van Leeuwenhork do?

Answer 2

• Made lense that 300x + was 1st to observe living cell + single cells pond organisms

Question 3

Factors that restricted further understanding of cells in the 19th century

Answer 3

• Limited resolution
• Descriptive nature of 17th century biology
  => only observation with little attempt to explain discoveries

Question 4

Improvements made in microscopes in the 1830s

Answer 4

• Improvements were made in lens quality
• Compound microscopes ( 1st lens is an eyepiece + 2nd lens is an objective lens that magnify images)=> resulted in higher magnification and better resolution (however, only 1 micrometer could be seen clearly)

Question 5

What did Robert Brown discover?

Answer 5

Found a round structure in plant cell + called it the nucleus

Question 6

What did Matthias Schleiden do in 1838?

Answer 6

• Concluded all plant tissues are made of cells and that embryonic plants arises from a single cell

Question 7

What did Theodor Schwann do in 1839?

Answer 7

• Reported similar conclusions to Schleiden but with animal tissue
  => discredited idea that plants and animals don’t resemble each other due to lack of cell walls
  => convinced there are common similarities between the two, forming cell theory

Question 8

What is Cell Theory? (intial 2 principles)

Answer 8

(1) All organisms consist of 1 or more cells

(2) The cell is the basic unit of structure for all organisms

Question 9

Principles added to Cell Theory later

Answer 9

Added 20 years later - includes Brown’s nucleus description + Nageli’s observation of cell division

Virchow concluded cells arose by division of a preexisting cell

(3) All cells arise only from preexisting cells

Question 10

What formed Modern Cell Biology?

Answer 10

Results in weaving together cytology, biochemistry, and genetics into a single discipline

(also benefitted from advancement in chemistry, physics, computer science, and engineering)

Question 11

1st Discipline to emerge - Cytology

Answer 11

‘cyto-‘ = hollow vessel
Concerned with cellular structure
Had origins from over 300 years ago, relying on light microscopes

Question 12

2nd Discipline to emerge - Biochemistry

Answer 12

Important to developing lab techniques e.g. chromatography, electrophoresis

Question 13

3rd Discipline to emerge - Genetics

Answer 13

Stretches back over 150 years but most understanding in 75 years

Question 14

How is Microscopy invaluable in cell biology?

Answer 14

Cellular structure is better understood as most cells + organelles are too small to be seen by the naked eye

Question 15

About Light Microscopes

Answer 15

• Lead to the development of the microtome (instrument developed for rapid prep of thin tissue slices)
• Dyes are used for staining subcellular structures
• Limit of resolution is 400nm (objects must be that distance to be told apart)

Question 16

Brightfield Microscope

Answer 16

• Passes light through a specimen unless cell is naturally pigmented (little contrast)
• Dyes enhance contrast and require cells to be fixed

Question 17

Phase Contrast Microscope

Answer 17

Enhances contrast in unstained cells by increasing variation in specimen
=> useful for living unpigmented cells

Question 18

Fluorescence Microscope

Answer 18

Shows location of certain molecules in cells
- Absorb UV + emit visible light
- Fluorescence may be naturally occuring but often made by tagging molecule with dyes or antibodies

Question 19

Confocal Microscope

Answer 19

Uses lasers to focus illuminating beam on a single plane
=> only these regions within narrow depth of focus is imaged

Question 20

Differential interference contrast microscope

Answer 20

Uses optical mods to exaggerate diffs in refractive index