Pupil sheet · Absorption
Villi under the microscope — questions
Name ______________________ Date ____________
Try every question before you use a nudge. Write in full sentences where you are asked to explain.
1. identify
Supplement. Which row describes a villus?
| Row | Made of | Can be seen |
|---|---|---|
| A | many cells | with a light microscope at ×100 |
| B | many cells | only with an electron microscope |
| C | part of one cell | with a light microscope at ×100 |
| D | part of one cell | only with an electron microscope |
Circle one answer.
- A
- B
- C
- D
Nudge (only if you are stuck): Decide one column at a time. Then check that your row does not describe the much smaller structure that is easy to mix up with a villus.
2. calculate
Supplement. A pupil lays a string along a stretch of the folded edge of a section of ileum: the string is 5.2 mm long. The straight distance between its two ends is 1.3 mm. Calculate how many times longer the folded edge is than the straight length.
Times longer: ______________ unit ________
Nudge (only if you are stuck): Times longer = string length ÷ straight length.
3. state
Supplement. Complete the sentences about villi and microvilli.
Villi and microvilli increase the internal … of the small intestine,
so … nutrient molecules can be absorbed
in the same … .
Nudge (only if you are stuck): What do the folds increase, and what does that allow?
4. state / explain
Supplement. (a) State one difference between villi and microvilli. (b) Explain why microvilli speed up absorption.
(a) A difference
(b) Why microvilli speed up absorption
Nudge (only if you are stuck): For (a): think of size, and of how many cells each is made of.
5. calculate
Supplement. A pupil measures two stretches of the folded edge of a section of ileum. Calculate the times longer for each stretch and the mean of the two.
| Stretch | String along the edge / mm | Straight length / mm |
|---|---|---|
| A | 3.6 | 1.2 |
| B | 10.0 | 2.0 |
Stretch A: times longer: ______________ unit ________
Stretch B: times longer: ______________ unit ________
Mean: ______________ unit ________
Nudge (only if you are stuck): Times longer = string ÷ straight; the mean is the two results added and divided by 2.
6. identify / calculate
Supplement. A pupil measures the outline ratio (string length ÷ straight length) for four stretches of the folded edge of one section of ileum. In one stretch the edge was torn, and the string had to be lifted across the torn part. (a) Identify the stretch with the anomalous result, and explain why it is anomalous. (b) Calculate the mean of the other three results.
| Stretch | Times longer |
|---|---|
| 1 | 4.6 |
| 2 | 4.2 |
| 3 | 1.9 |
| 4 | 4.8 |
(a) Number of the anomalous stretch: ______________ unit ________
(b) Mean of the other three: ______________ unit ________
(a) Why the result is anomalous
Nudge (only if you are stuck): An anomalous result does not fit the pattern of the others. What happens to the string length where it is lifted off the edge?
7. suggest / explain
Supplement. After part of the small intestine is removed, the villi of the part that is left slowly grow taller over the next few months. Suggest how this helps the patient.
(a) What taller villi change
(b) How this helps
Nudge (only if you are stuck): Compare one centimetre of intestine lined with short villi and with tall villi.
8. explain
Supplement. A pupil measures the outline ratio of the folded edge on one slide of rat ileum and one slide of rabbit ileum. The rat section was cut straight across the wall of the ileum. The rabbit section was cut at an angle to the wall, so many of its villi show as separate ovals that do not touch the edge. The ratio is 4.9 for the rat and 2.5 for the rabbit. The pupil concludes: "Rabbit villi increase the internal surface area of the small intestine much less than rat villi do." Explain why this conclusion may be incorrect. Give two reasons.
(a) First reason
(b) Second reason
Nudge (only if you are stuck): Look for differences between the two measurements other than the animal.