Cell structure

Question 1

Define magnification.

Answer 1

How many times bigger the image is when compared to the object.

Question 2

What is the resolution?

Answer 2

The minimum distance apart that two objects need to be in order for them to be distinguished as separate.

Question 3

Why is the solution before fractionation cold?

Answer 3

To reduce enzyme activity which might break down organelles.

Question 4

Why is the solution before fractionation isotonic?

Answer 4

To prevent cells bursting from movement of water due to different water potentials.

Question 5

Why is the solution before fractionation buffered?

Answer 5

So that pH does not fluctuate, changing enzyme activity or damaging organelles.

Question 6

What are the two processes in fractionation?

Answer 6

• Homogenisation,

- Ultracentrifugation.

Question 7

Name 4 limitations of the transmission electron microscope.

Answer 7

• May contain artefacts,
• The sample must be extremely thin,
• A complex colour staining process is required,
• The whole system much be in a vaccum so cannot be operated on living organisms.

Question 8

What piece of equipment is used when measuring the size of objects though a light microscope?

Answer 8

Eye-piece graticule.

Question 9

What piece of equipment is used to calibrate an eye-piece graticule?

Answer 9

Stage micrometer.

Question 10

What are the folds in the inner membrane of the mitochondrion called?

Answer 10

Cristae.

Question 11

Which form of ribosome is found in Eukaryotic cells and are they larger or smaller?

Answer 11

80S, larger than in prokaryotic cells.

Question 12

Where do you find epithelial tissues?

Answer 12

Lining the walls of organelles.

Question 13

Name 3 organ systems.

Answer 13

• Digestive,
• Circulatory,
• Respiratory.

Question 14

What is the cell wall of bacteria made up of?

Answer 14

Murein.

Question 15

What happens in prophase?

Answer 15

• Chromosomes become visible, shorten and thicken,

- Spindle fibres develop at the poles of the cell,

Question 16

What happens in metaphase?

Answer 16

• Spindle fibres attach to the centromere of the two sister chromatids,
• Sister chromatids line up along the equator of the cell.

Question 17

What happens in anaphase?

Answer 17

• Centromeres divide in two as spindle fibres contract,

- Sister chromatids are pulled to the poles of the cell.

Question 18

What happens in telophase?

Answer 18

• Chromatids reach poles of cell,

- Elongate and become thinner back into chromosome form as chromatin.

Question 19

What is cytokinesis?

Answer 19

When the cytoplasm of the cell divides.

Question 20

What is cell division in prokaryotic cells called?

Answer 20

Binary Fission

Question 21

What are the three stages that make up the cell cycle?

Answer 21

• Interphase,
• Nuclear division,
• Cytokinesis.

Question 22

How does chemotherapy interupt the cell cycle? Two ways.

Answer 22

• Preventing the DNA from replicating,

- Inhibiting the metaphase stage by interfering with spindle formation.

Question 23

Name 2 structures in a eukaryotic cell that cannot be identified using an optical microscope.

Answer 23

• Ribosomes,

- Endoplasmic Reticulum.

Question 24

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains through an optical microscope.

Answer 24

Place a few drops of water on the slide,
Obtain a thin slide of plant tissue and place on slide,
Stain with iodine,
Lower cover slip using mounted needle.