B1

Question 1

What is a light microscope?

What do lenses do?

Answer 1

A light microscope passes light through an object placed on a slide on a stage. Lenses magnify the object so you can see it in more detail.

Question 2

How can you view cells under a light microscope?

Answer 2

1. Move the stage to its lowest position
2. Select the objective lens with the lowest magnification
3. Place the slide, with cells on it, on the stage
4. Turn the coarse focus knob slowly until you see the object (it’ll normally be blurred)
5. Turn the fine focus knob until your object comes into clear focus

Question 3

Why stain cells?

Answer 3

As many cells are colourless, stains can be used to make them easier to observe

Question 4

How do you apply a stain?

Answer 4

1. Place the cells on a glass slide
2. Add one drop of stain
3. Place a coverslip on top
4. Tap the coverslip gently to remove air bubbles

Question 5

What stains highlight what structures?

Answer 5

methylene blue makes it easier to see the nucleus of an animal cell
iodine makes it easier to see plant cell nuclei
crystal violet stains bacterial cell walls

Question 6

What are eukaryotic cells?

Answer 6

Eukaryotic cells are cells that contain genetic material inside a nucleus
They are complex and relatively large, with sizes between 10um and 100um

Question 7

What are prokaryotic cells?

Answer 7

Prokaryotic cells don’t have a nucleus. Their genetic material floats around in the cytoplasm. Most have a size from 1um to 10um

Question 8

What sub-cellular structures do eukaryotic cells contain?

Answer 8

cell membrane, cytoplasm, mitochondria, nucleus

Question 9

Nucleus function

Answer 9

Controls activities of the cell. It contains the organisms genetic material, arranged as chromosomes, which determines the cells function and appearance.

Question 10

Cell membrane function

Answer 10

A selective barrier that controls which substances pass into and out of the cell. It also contains receptor molecules

Question 11

Mitochondria function

Answer 11

Where respiration happens, in which enzymes enable glucose and oxygen to react together. The reactions transfer vital energy to the organism

Question 12

Cytoplasm function

Answer 12

A ‘jellylike’ substance, where the chemical reactions that keep the cell alive happen

Question 13

What other sub-cellular structures do plant cells contain?

Answer 13

cell wall, chloroplasts, vacuole

Question 14

Chloroplasts function

Where are chloroplasts found?

Answer 14

Contains green chlorophyll, which transfers energy from the Sun to the plant as light, which is used in photosynthesis. Chloroplasts are only in the green parts of the plant

Question 15

What sub-cellular structures do prokaryotic cells contain?

Answer 15

cell wall, genetic material, cell membrane, cytoplasm

Question 16

Genetic material in prokaryotes

Answer 16

Floats freely in the cytoplasm. It is one long strand of DNA, called the bacterial chromosome

Question 17

Plasmid function

Answer 17

A circular piece of DNA that stores extra genes. They are normally not needed for the cells day to day survival, but may be used in times of stress

Question 18

What is an electron microscope?

Answer 18

An electron microscope is one that uses electrons instead of light to produce an image. By doing this, it can produce a much higher resolution than a light microscope.

Question 19

What are transmission electron microscopes and how do they work?

Answer 19

TEMs are microscopes that produce the most magnified images, and have increased resolution. A beam of electrons passes through a very thin slice of a sample. The beam is focused to produce an image.

Question 20

How has electron microscope increased our understanding of sub cellular structures?

Answer 20

It has allowed scientists to see more detail within sub cellular structures such as chloroplasts