Microscopes and Cell Models

Question 1

Smallest functional unit of life.

Answer 1

Cell

Question 2

• 1665
• 1st to see dead cells
• had microscope around 30X magnification

Answer 2

Robert Hooke

Question 3

• 1670s
• made his own glass lens
• microscope (which wasn’t a compound microscope) could maybe get up to 200X (SEE NOTES FOR DIAGRAM)
• 1st to see living cells

Answer 3

Antoni van Leeuwenhoek

Question 4

Cell Theory: Schleiden and Schwann 1839

-Has three main parts that are:

Answer 4

1. All organisms consist of 1 or many cells.
2. The cell is the basic unit of structure for all organisms.
3. All cells come from pre-existing cells.

Question 5

Eduard Strasburger and his “time-lapse” observations in 1880

Answer 5

He could track mitosis in plant cells

Question 6

Goal is to decipher underlying principles that govern the structure and activity of the cell.

Answer 6

Microscopy

Question 7

Two powers of microscopy:

Answer 7

1. Magnification
   - lens (4x,10x,40x) and eye piece (4x, 10x)
2. Resolution

Question 8

Ability to make an object appear larger.

Answer 8

Magnification

Question 9

Ability to distinguish two objects from each other (as being separate).

Answer 9

Resolution

Question 10

Resolution

d=(0.5*wavelength)/n sin(theta)

Answer 10

d=distance

nsin(theta)=numerical aperture

Question 11

Resolution Cont…
-The # found on the lens on the microscope.
-n sin(theta)
n=refractive index of the medium you’re using (ex. air, n=1; oil, n=1.5; H2O, n=1.3)
(theta)=1/2 angle of cone light (SEE NOTES FOR DIAGRAM)

Answer 11

Numerical aperture

Question 12

To increase resolution, what parameters would you change when d=(0.5*wavelength)/n sin(theta)?
-Remember, smaller distance = greater resolution!

Answer 12

1. Shorten wavelength (smaller numerator = smaller distance)
2. Change n (larger denominator = smaller distance)
3. Change cone of light by bringing objective closer to specimen (larger denominator = smaller distance)

Question 13

• Can see dead or alive cells
• light path is at the bottom
• Ocular lens (eye piece) usually 10x
• Objective: 10x, 40x, 100x
• Condenser (no magnification)

Answer 13

Light microscopy

Question 14

Focuses light to a single area.

Answer 14

Condenser on microscope

Question 15

Stained light micrographs

Answer 15

• Staining kills specimen (fixing and staining procedures)

- There are controls in case staining makes something funny happen.

Question 16

Variations of light microscopy to view living cells

Answer 16

1. Bright-field
2. Phase contrast
3. Differential interference contrast (DIC)

Question 17

Basic light microscopy

Answer 17

Bright-field

Question 18

Can make shadows, give more topography of cell, and takes advantage of refractive indexes to cast shadows.

Answer 18

Phase contrast

Question 19

Shines light both below and on the side of specimen.

Answer 19

Differential interference contrast (DIC)

Question 20

Excitation and Emission

Answer 20

Fluorescence Microscopy

Question 21

Microscopy that requires one wavelength to excite sample and another wavelength to emit light.

• Need fluorescence molecules (most common is GFP)
• Good magnification, but poor resolution

Answer 21

Fluorescence Microscopy (SEE NOTES FOR DIAGRAM)

Question 22

Microscopy that uses a laser at a particular wavelength that will excite a sample (is a modification of florescence microscopy)
-Sample will emit light through the eye piece

Answer 22

Confocal microscopy

Question 23

Can focus on a particular plane of view, because it blocks out some of the light.

Answer 23

Pin Hole Aperture

Question 24

Moves to be able to look from layer to layer of specimen.

Answer 24

Motorized stage

Question 25

Microscopy that transmits electrons instead of light | -advantageous because as wavelength gets smaller, distance gets smaller and thus resolution is increased.

Answer 25

Transmission Electron Microscopy (TEM)

Question 26

TEM (and SEM) sample is dead because ___________.

Answer 26

1. You're using heavy metals with it | 2. It's in a vacuum

Question 27

Microscopy that looks at a sample's topography (3D image) by scanning electrons at it.

Answer 27

Scanning Electron Microscopy (SEM)

Question 28

TEM:SEM as Bright-field:?

Answer 28

DIC (dissecting microscope)

Question 29

What types of cells are there?

Answer 29

Prokaryotes and Eukaryotes

Question 30

Advantageous characteristics of model organisms:

Answer 30

- lots of offspring - fast lifecycle - small - easy to maintain - can genetically manipulate (can also manipulate behavior, & environment) - have a well-studied history - can live in culture, outside organism - ethically allowed to use - has genetic variation (can be severe or not)

Question 31

Is prokaryotic, single-celled, easy to maintain and manipulate, and can reproduce in 20min. - has circular DNA enclosed in a nucleoid region. - about 90% of what we know of DNA replication comes from this model organism

Answer 31

E. coli

Question 32

Model organism that is a fungus, eukaryotic, has quick replication (~30min), have a cell wall

Answer 32

Saccharomyces cerevisiae ("brewer's yeast")

Question 33

Model organism that is eukaryotic and can make 1000s of offspring in 8-10 weeks. -Is a plant

Answer 33

Arabidopsis thaliana

Question 34

Model organism that is easily genetically manipulated, can grow fast (takes a few weeks), has lots of phenotypes to observe, and is eukaryotic. -Studied this organism to find out about genes on chromosomes and linkage.

Answer 34

Drosophila melanogaster

Question 35

Model organism that is eukaryotic, develops like clock-work, and found everywhere. - has 959 body cells (we know exactly what every cell will do) - quintessential to apoptosis studies

Answer 35

Caenorhabditis elegans

Question 36

Model organism that is a vertebrate eukaryote, easy to maintain, takes only 3-4 months to develop, and can lay between 200-300 eggs a week -The embryos are transparent

Answer 36

Danio rerio (zebra fish)

Question 37

Model organism that is a mammal. - Reproduces quickly (~4 months) and has larger litter sizes - easy to maintain - small - genetics are similar to humans' genetics - are bred for a large variety of characteristics (domesticated animals) and are often inbred w/o much genetic variation to balance all the other varieties

Answer 37

Mus musculus (mouse)

Question 38

Model organism that scientists use to study fibroblasts, myoblasts, and epithelial cells among other things

Answer 38

Homo sapiens (humans)