The table below shows the diameters of four yeast cells measured by a student during a brewery investigation. Fig. 1 is a diagram showing a yeast cell with ...
Question 1 Report
The table below shows the diameters of four yeast cells measured by a student during a brewery investigation. Fig. 1 is a diagram showing a yeast cell with a small bud growing from its surface. The brewer wants yeast cells to divide rapidly when sugar solution is added.
| yeast cell | diameter / micrometres |
|---|---|
| 1 | 3.8 |
| 2 | 4.1 |
| 3 | 3.9 |
| 4 | 4.0 |
(a) Calculate the mean diameter of the four yeast cells. Give your answer to two decimal places. [2]
(b) Explain how the diagram shows that yeast can reproduce asexually. [3]
(c) Describe four differences between a yeast cell and a cell from a green plant leaf. [4]
(d) Design a method the student could use to compare the number of living yeast cells in two sugar solutions after 30 minutes. [3]
Answer Details
(a)
\[\text{mean diameter}=\frac{3.8+4.1+3.9+4.0}{4}=\frac{15.8}{4}=3.95\ \mu\text{m}\]
The mean diameter is 3.95 µm. [2]
(b) A small bud grows from the parent yeast cell. The bud receives a nucleus, or genetic material, by mitosis. It separates to form a genetically identical new yeast cell, so only one parent is involved and reproduction is asexual. [3]
(c) Four differences are:
- Yeast has no chloroplasts, whereas a green leaf cell has chloroplasts.
- Yeast has no large permanent vacuole, or has smaller vacuoles.
- Yeast cells are usually oval or round, whereas leaf cells are more regular or box-shaped.
- A green leaf cell contains chlorophyll, whereas yeast does not.
- Leaf cells are arranged in tissues, whereas yeast cells may occur singly.
Any four correct differences gain credit. [4]
(d) Place equal volumes and concentrations of the two sugar solutions into separate containers with equal starting amounts of yeast. Keep temperature, time and other relevant variables the same for 30 minutes. Add a dye such as methylene blue, then use a microscope or haemocytometer to count unstained living cells and compare the counts. [3]
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