Cell structure. paper 1

Question 1

what are the features of a light microscope?

Answer 1

• they have a lower resolution (max. 0.2 µm) and magnification(Max of about x 1,500) compared to other microscopes.

Question 2

what was the first type of microscope to be developed and how do they work?

Answer 2

thee light (optical) microscope.
- they worked by creating an image that is much larger than the real object.

Question 3

What are the 4 steps to preparing a wet mount?

Answer 3

1. Use a pipette to place a small drop of water onto the centre of the glass slide.
2. Use a pair of forceps to place a thin section of the specimen onto the drop of water. The specimen should be thin enough to allow light to pass through.
3. Add a few drops of stain (e.g. iodine in potassium iodide) to the specimen. This increases contrast and allows cell components to become visible.
4. Slowly add a cover slip (a clear glass square) onto the specimen.

Question 4

what are other sample preparation methods?

Answer 4

• Dry mounts The specimen is placed directly onto the slide and covered with a cover slip.
  -Squash slides A wet mount is prepared and the cover slip is pressed to squash the cells.
  -Smear slides The edge of a slide is used to smear the sample to create a thin, even coating on a separate slide.

Question 5

What are the 6 steps to using a light microscope?

Answer 5

1. Clip the prepared microscope slide onto the stage.
2. Select the objective lens with the lowest power.
3. Use the coarse focus to bring the stage just below the objective lens.
4. Look down the eyepiece and use the coarse focus to move the stage downwards until the image is roughly in focus.
5. Use the fine focus to make the image clearer.
6. If a higher magnification is needed, swap to a more powerful objective lens and refocus.

Question 6

what is the use of a biological drawing?

Answer 6

-They are used to record observations when looking at specimens.

Question 7

What should biological drawings include?

Answer 7

• Include a title
• State the magnification or scale
• Be drawn with a sharp pencil
• Include smooth, continuous lines
• Include labels
• Include accurate sizes of observable structures

Question 8

electron microscope qualities.

Answer 8

• Shorter wavelength compared to light microscopes meaning they have a better resolution than light microscopes.
• however, electron microscopes are more expensive and only produce images in black and white. (computers can add colour to the images.

Question 9

what are the two types of microscopes?

Answer 9

Scanning electron microscopes (SEM)
- Transmission electron microscopes (TEM)

Question 10

what are artefacts?

Answer 10

-They are visible details that aren’t part of the specimen being observed, such as air bubbles or fingerprints.