Module 2 - chapter 2 Flashcards
List the parts of a laser scanning confocal microscope.
Eyepiece, objective lens, specimen, condenser lens, lamp
List the parts of a light microscope
Eyepiece, body tube, coarse adjustment screw, fine adjustment screw, arm, high power objective lens, low power objective lens, stage, condenser, mirror, base
What was the first development to cell theory?
The cell was first observed:
Robert Hooke observed the structure of thinly sliced cork using an early light microscope. He described the compartments he saw as ‘cells’. As this was dead plant tissue he was observing only cell walls.
When was the first development to cell theory?
1665
What was the second development to cell theory?
The first living cells were observed:
Anton van Leeuwenhoek developed a technique for creating powerful glass lenses and used his handcrafted microscope to examine samples of pond water. He was the first person to observe bacteria and protoctista and described them as “little animals” or “animalcules” - today we call them microorganisms. He went on to observe red blood cells, sperm cells, and muscle fibres for the first time.
When was the second development to cell theory?
1674-1683
Who made the first development to cell theory?
Robert Hooke
Who made the second development to cell theory?
Anton van Leeuwenhoek
What was the third development to cell theory?
Evidence for the origin of new plant cells:
Barthélemy Dumortier was the first to observe cell division in plants providing evidence against the theories of the time, that new cells arise from within old cells or that cells formed spontaneously from non-cellular material. However it was several more years until cell division as the origin of all new cells became the accepted theory.
When was the third development to cell theory?
1832
Who made the third development to cell theory?
Barthélemy Dumortier
What was the fourth development to cell theory?
Nucleus first observed:
Robert Brown was the first to describe the nucleus of a plant cell.
When was the fourth development to cell theory?
1833
Who made the fourth development to cell theory?
Robert Brown
What was the fifth development to cell theory?
The birth of a universal cell theory:
- Matthias Schneider proposed that all plant tissues are composed of cells.
- Jan Purkyne was the first to use a microtome to make ultra-thin sliced of tissue for microscopic examination.
- Based on his observations, he proposed that not only are animals composed of cells but also that the “basic cellular tissue is clearly analogous to that of plants”.
- Not long after this, and independently, Theodor Schwann made a similar observation and declared that “all living things are composed of cells and cell products”.
- He is the scientist credited with the “birth” of cell theory.
When was the fifth development to cell theory?
1837-1838
Who made the fifth development to cell theory?
Matthias Schleiden, Jan Purkyne, Theodor Schwann
Which scientist is credited with the “birth” of cell theory?
Theodor Schwann
What was the sixth development to cell theory?
Evidence for the origin of new animal cells:
Robert Remak was the first to observe cell division in animal cells, disproving the existing that new cells originate from within old cells. He was not believed at the time however, and Rudolf Virchow published these findings as his own a decade later in 1855.
When was the sixth development in cell theory?
1844
Who was responsible for the sixth development in cell theory?
Robert Remak
Who published the findings for the sixth development to cell theory? When?
Rudolf Virchow in 1855
What was the seventh development to cell theory?
Spontaneous generation disproved:
Louis Pasteur disproved the theory of spontaneous generation of cells by demonstrating that bacteria would only grow in a sterile nutrient broth after it had been exposed to the air.
When was the seventh development to cell theory?
1860
Who made the seventh development to cell theory?
Louis Pasteur
What does a dry mount entail?
Solid specimens are viewed whole or sectioned. Mounting a specimen onto a microscope slide without any stain or liquid. This is used for hair, pollen and dust.
What does a wet mount entail?
A wet mount is when a specimen is prepared for being viewed using a stain or liquid. A wet mount is aquatic. The specimen is suspended in a liquid such as water or immersion oil.
What is a squash mount?
A squash mount is when a soft sample is squashed using a cover slip in preparation for viewing with the microscope. A wet mount is prepared first then the sample is squashed using lens tissue. This is used for onion cells.
What is a smear mount?
When a specimen is smeared across the microscope slide before being covered with a cover slip and studied. This is used for blood and other bodily fluids. The edge of a slide is used to smear the sample - creating a thin, even coating on another slide.
How do you prepare a slide for a light microscope?
1) Take a thin slice of the specimen and place it onto a clean microscope slide.
2) Add a drop of water or a drop of stain onto the specimen.
3) Take a clean cover slip and lower it slowly onto the specimen, taking care to avoid air bubbles.
For a specimen that is in solution add a drop of specimen onto the slide and then add a drop of stain. You can then cover the specimen with a cover slip.
What are some uses of staining?
- To highlight a particular organelle.
- To distinguish between different cell types.
- To distinguish different tissue types.
What are photographs of specimens taken down the microscope called?
Micrographs
What is the definition for resolution?
The degree to which it is possible to distinguish between two objects that are very close. In order to see greater detail.
What is the maximum resolution for a light microscope?
200nm
What are the charges of crystal violet and methylene blue?
Positively charged dyes
How do positively charged dyes work to stain cell components?
The positively charged dyes are attracted tot the negatively charged materials in the cytoplasm. This stains the cell components.
What are the charges of nigrosin, Congo red and cytosol dye?
Negatively charged
What is a negative stain technique?
when negatively charged dyes are repelled from each other and so stay outside the cells, leaving the cells unstained. This makes the cells stand out against a stained background
What is differential staining?
When staining is used to distinguish between two types of organisms which would otherwise be hard to identify. It can also differentiate between different organelles of a single organism within a tissue sample.
What is gram staining technique?
When staining is used to separate bacteria into two groups: Gram-positive and Gram-negative bacteria.
How is gram staining carried out?
- Crystal violet is applied to a bacterial specimen on a slide, then iodine which fixes the dye.
- The slide is then washed with alcohol and the gram-positive bacteria retain the crystal violet stain and will appear blue or purple under a microscope.
- Gram negative bacteria have thinner cell walls and so lose the stain.
- The bacteria are then stained with safranin dye which is a counterstain. The bacteria appear red.
What colour does safranin dye stain?
Red
What is sectioning?
When solid specimens are cut into very thin slices with a sharp blade. Specimens are dehydrated with alcohols and then placed in a mound with sac or resin to form a hard block which is then sliced using a microtome.
