AS Chapter 1 The Microscope in Cell Studies

• 1 and 2

• 1 and 3

• 2 and 3

• 1, 2 and 3

Answer explanation

• A

• B

• C

• D

Answer explanation

Both the magnification and resolution that can be achieved by an electron microscope are higher than those achieved by a light microscope.

At approximately which magnification would the resolution of a light microscope become too low to produce a clear image?

• × 100

• × 200

• x 400

• × 1500

Answer explanation

The correct answer is D because:

The maximum magnification that can be achieved with the resolving power of alight microscope can be somewhere around x2000, but useful magnifications are closer to a maximum of x1000

The other options in the table all would be low enough magnification for a light microscope to have a clear resolution.

Which of the following is not a step involved in the preparation of an onion cell specimen for viewing under a light microscope?

• Place one edge of a coverslip on the slide and carefully lower the rest of the coverslip onto the specimen.

• Add a drop of iodine stain.

• Remove a layer of onion tissue that is one cell thick from a piece of onion.

• Add a drop of methylene blue stain.

Answer explanation

Methylene blue stain is used to stain the nuclei of animal cells. Iodine solution is used to stain plant tissue, such as onion epidermis.

Specimens can be measured using eyepiece graticules and stage micrometers.

Which of the following correctly describes the role of a stage micrometer?

• Directly measuring the size of a specimen.

• Determining the size of the eyepiece graticule units.

• Determining the magnification at which at object is being viewed.

• A type of slide upon which a specimen can be prepared.

Answer explanation

The size of the eyepiece graticule units varies depending on the magnification being used and minor differences between microscopes; the stage micrometer allows calibration of the eyepiece units, which can then be used to measure the length of a specimen.

A microscope has a resolution of 200 nm.

Which of the following organelles would not be resolved by this microscope?

• Mitochondria

• Lysosomes

• Ribosomes

• Chloroplasts

Answer explanation

Ribosomes are 20-30 nm in diameter; they would therefore not be resolved at a resolution of 200 nm.

Which of the following is not a convention that should be used when producing biological drawings of cells?

• Single, clear pencil lines should be used.

• Shading should be used to indicate light and dark regions of cells.

• Label lines should not have arrow heads.

• At least half of the available space on the page should be taken up by the drawing.

Answer explanation

No shading should be used in biological drawings, which should be line drawings only.

Which of the options gives the resolution, in nanometres, of an electron microscope and a light microscope?

• A

• B

• C

• D

Answer explanation

200 nm is the maximum resolution of a light microscope

0.5 nm is the maximum resolution of a electron microscope

A lysosome has a diameter of 0.4 μm.

Which of the following gives the lysosome diameter in nm?

• 4

• 40

• 400

• 4000

Answer explanation

There are 1000 nm in a μm, so to convert from one to the other you need to multiply by 1000

0.4 x 1 000 = 400

Which of the following correctly defines the term

resolution in light microscopy?

• The size of the smallest object that can be seen.

• Twice the wavelength of the light used to illuminate the specimen.

• The shortest distance at which two objects can be seen as separate points.

• The product of the magnifications of the eyepiece and the objective lens.

Answer explanation