AS & A Level Biology - 9700 Paper 3 2009 Winter Zone 2

(a) (i) Using only the materials provided test the four samples S1, S2, S3 and S4. You will need to consider carefully how you will carry out the tests so that you can determine the relative concentrations of starch and glucose.
(ii) Prepare the space below and record:
• the tests you used
• the quantities of the samples and reagents
• and your results.

(iii) Using the information provided and your results, complete Table 1.1 below to identify the samples.

Table 1.1

| sample from | sample identified |
|----------------------|--------------------|
| starch about to be eaten | ................. |
| mouth | ................. |
| stomach | ................. |
| small intestine | ................. |

(iv) Explain your answer to (a)(iii).

(b) A student wanted to obtain a \textbf{quantitative} measurement of the glucose concentrations.
Suggest how the student could modify this investigation to obtain quantitative measurements of the glucose concentrations.

(c) (i) Plot a graph of these data shown in Table 1.2.

Table 1.2

| concentration of starch /g dm$^{−3}$ | mean time taken for 1 cm$^3$ of starch to be hydrolysed /seconds |
|----------------------------------------|-------------------------------------------------------------|
| 5 | 12 |
| 15 | 39 |
| 20 | 53 |
| 30 | 79 |

(ii) Use your graph to find the rate of hydrolysis by finding the gradient of the line.
Show on your graph where you took the readings to calculate the gradient.
Show your working.
rate of hydrolysis ............................. g dm$^{-3}$s$^{-1}$

(a) Fig. 2.1 is a photomicrograph of a transverse section through a tubular organ of a mammal.
[Image]
Fig. 2.1
Draw a large plan diagram of the section shown in Fig 2.1.
No labels are required.

(b) Fig. 2.2 is a photomicrograph showing a high-power view of the surface of a leaf.
[Image]
Fig. 2.2
(i) Make a large, labelled drawing to show two guard cells and the complete cells that surround them. Do not draw more than six cells in total.
Show on Fig. 2.2 the cells that you have drawn.

(ii) Calculate the actual length in micrometres ($\mu$m) of one of the guard cells.
Show all the steps in your calculation.
.......................$\mu$m

You are provided with two samples of plant material.
A suspension of leaf cells in a dish, labelled L.
A piece of peeled potato tuber in a dish, labelled P.
1. Label four slides, two with L and two with P.
2. Using a pipette, place one drop of L on each of the two slides labelled L.
3. Add one drop of iodine solution to one of the slides labelled L.
4. Using a sharp blade or scalpel, cut the potato piece to show a fresh surface.
5. Carefully scrape off some potato cells from the fresh surface and smear them onto the middle of each of the two slides labelled P.
6. Add one drop of iodine solution to one of the slides labelled P.
7. Add a coverslip to each slide and use a paper towel to absorb the excess liquid.
8. Use your microscope to search each slide carefully and record the observations of the cells you can find.

(a) Prepare the space below and record all your observations. [3]

(b) Explain your observations. [2]