Mass transport
A student used a potometer to measure the movement of water through the shoot of a plant. As water is lost from the shoot, it is replaced by water from the capillary tube.
In one experiment, the air bubble moved 10.5 mm10.5\text{ mm}10.5 mm in 15 minutes15\text{ minutes}15 minutes. The diameter of the capillary tube was 1.2 mm1.2\text{ mm}1.2 mm.
Calculate the rate of water uptake by the shoot in this experiment.
Give your answer in mm3 hour−1\text{mm}^3\text{ hour}^{-1}mm3 hour−1. Show your working. (The area of a circle is found using the formula, area=πr2\text{area} = \pi r^2area=πr2)
A student dissected a mammalian heart to study its internal anatomy. They performed a coronal (longitudinal) cut to expose the chambers and produced a scientific drawing of the exposed section.
Suggest two ways the student could improve the quality of their scientific drawing of this longitudinal section of the heart.
Identify which ventricle is represented by X X\,X and which is represented by YYY. Describe one visible feature in the drawing that allowed you to make this identification.
Describe two safety or hygiene precautions the student should take specifically during the dissection process when handling sharp instruments and fresh tissue.
In an investigation into the transport mechanisms of soybean plants (Glycine max), scientists applied a localized metabolic respiratory inhibitor (sodium azide, which blocks ATP production) to a section of the stem using a treated collar. Control plants received a collar containing only distilled water. They then applied a solution of radioactively-labelled sucrose, containing 14C^{14}\text{C}14C, to a leaf situated above the treated collar.
After 6 hours, they:
- Identified the distribution of the 14C^{14}\text{C} 14C radiolabel in each plant.
- Recorded the relative water content (RWC) of the leaves above the treated section.
The results showed:
- In control plants, the 14C^{14}\text{C}14C radiolabel was distributed throughout the plant, including the roots and lower stem.
- In inhibitor-treated plants, the 14C^{14}\text{C}14C radiolabel was only detected in the leaf that was supplied with 14C^{14}\text{C}14C-sucrose and did not pass below the treated collar.
The relative water content data are presented in the table below:
| Plant group | Leaf relative water content / % of maximum (±2 \pm 2\,±2 standard deviations) |
|---|---|
| Inhibitor-treated | 78.4 (±6.8)78.4\ (\pm 6.8)78.4 (±6.8) |
| Control | 82.1 (±5.9)82.1\ (\pm 5.9)82.1 (±5.9) |
Explain how the distribution of the radioactively-labelled sucrose supports the conclusion that translocation in the phloem requires metabolic energy.
Explain how the leaf relative water content results support the conclusion that water transport via the xylem is a passive process.
A student dissected a mammalian heart to observe its internal structure. They made a transverse slice through the ventricles and produced a scientific drawing of the cross-section.
Suggest two ways the student could improve the quality of their scientific drawing of this heart cross-section.
Identify which ventricle is represented by A A\,A and which is represented by BBB. Describe one visible feature in the drawing that allowed you to make this identification.
Describe two safety or hygiene precautions the student should take specifically when clearing away after completing the dissection.
The following graphs show pressure and blood flow changes during the cardiac cycle of a thoroughbred horse at rest:
At point X\mathbf{X}X (at 1.65 s), the pressure in the left ventricle is rapidly increasing. At this time, the rate of blood flow in the aorta has not yet started to increase. Explain why this is the case, referencing pressure differences and the state of the relevant heart valve.
At point Y\mathbf{Y}Y (at 2.20 s), there is a temporary small increase in pressure and in the rate of blood flow in the aorta. Explain how this occurs and why it is physiologically important.
If a researcher correctly plotted the right ventricle pressure on the same grid as the left ventricle: Describe one similarity and one difference you would expect to see between the curves.
Calculate the heart rate of this horse in beats min−1\text{beats min}^{-1}beats min−1. Show your working.
A student dissected a mammalian heart to observe its internal anatomy. They made a coronal slice along the longitudinal plane to expose all four chambers and produced a scientific drawing of the section.
Suggest two ways the student could improve the quality of their scientific drawing of this longitudinal heart section.
Identify which ventricle is represented by PPP and which is represented by QQQ. Describe one visible feature in the drawing that allowed you to make this identification.
Describe two safety or hygiene precautions the student should take specifically when clearing away after completing the dissection.
In an investigation into mass transport in sunflower plants (Helianthus annuus), scientists applied a localized metabolic inhibitor (sodium azide, which blocks ATP production via cellular respiration) to a 2 cm2\text{ cm}2 cm band of the stem. Control plants received water instead of the inhibitor. They then supplied carbon dioxide containing radioactively-labelled carbon, 14CO2^{14}\text{CO}_214CO2, to a source leaf situated above the treated stem section as shown in the diagram below.
After 6 hours, they:
- Tracked the distribution of the radioactively-labelled carbon in each plant.
- Recorded the relative water content of the leaves above the treated stem section.
The results showed:
- In control plants, the radioactively-labelled carbon was found throughout the plant (including the roots and lower leaves).
- In inhibitor-treated plants, the radioactively-labelled carbon was only detected in the source leaf supplied with 14CO2^{14}\text{CO}_214CO2 and did not pass past the treated stem section.
The relative leaf water content data are presented in the table below:
| Plant group | Relative leaf water content / % of maximum (±2\pm 2±2 standard deviations) |
|---|---|
| Inhibitor-treated | 78.4 (±6.8)78.4\ (\pm 6.8)78.4 (±6.8) |
| Control | 82.1 (±5.5)82.1\ (\pm 5.5)82.1 (±5.5) |
Explain how the distribution of the radioactively-labelled carbon supports the conclusion that translocation in the phloem requires metabolic energy (ATP).
Explain how the relative leaf water content results support the conclusion that transport in the xylem is a passive process that does not require metabolic energy.
A student set up a potometer to investigate the rate of transpiration in a leafy shoot of cherry laurel (Prunus laurocerasus). As water is transpired by the leaves, it is replaced by water drawn from the capillary tube.
In one experimental run, the air bubble in the capillary tube moved a distance of 14.2 mm14.2\text{ mm}14.2 mm over a period of 25 minutes25\text{ minutes}25 minutes. The internal diameter of the capillary tube was measured as 1.4 mm1.4\text{ mm}1.4 mm.
Calculate the rate of water uptake by the leafy shoot under these conditions.
Give your answer in mm3 hour−1\text{mm}^3\text{ hour}^{-1}mm3 hour−1. Show your working. (The area of a circle is calculated using the formula, area=πr2\text{area} = \pi r^2area=πr2)
The following graphs show pressure and blood flow changes during the cardiac cycle of a sheep:
At point X\mathbf{X}X (at 0.80 s), the pressure in the left ventricle is rapidly increasing. At this time, the rate of blood flow in the aorta has not yet started to increase. Explain why this is the case, referencing pressure differences and the state of the relevant heart valve.
At point Y\mathbf{Y}Y (at 1.15 s), there is a temporary small increase in pressure and in the rate of blood flow in the aorta. Explain how this occurs and why it is physiologically important.
If a researcher correctly plotted the right ventricle pressure on the same grid as the left ventricle: Describe one similarity and one difference you would expect to see between the curves.
Calculate the heart rate of this sheep in beats min−1\text{beats min}^{-1}beats min−1. Show your working.
A marine biologist investigated cardiac adaptations in Weddell seals (Leptonychotes weddellii) during different physiological states.
For each state, the biologist determined:
- the mean maximum ventricular volume (MVV) in a ventricle just before contraction.
- the mean ejection fraction (EF), which is the proportion of blood pumped out of a full ventricle in one contraction.
The EF is calculated using the formula: EF=Stroke VolumeMVV\text{EF} = \frac{\text{Stroke Volume}}{\text{MVV}}EF=MVVStroke Volume where Stroke Volume is the volume of blood pumped out of the ventricle during a single contraction.
The table below shows the biologist's results:
| State | Resting on ice | Deep foraging dive |
|---|---|---|
| Mean MVV / cm3\text{cm}^3cm3 | 400 | 320 |
| Mean EF | 0.70 | 0.55 |
Using this table, a student calculated that the percentage change in the stroke volume of the seal during a deep foraging dive compared with its stroke volume when resting on ice is −59.1%-59.1\%−59.1%.
The student's answer is incorrect because they performed the final step of the calculation incorrectly.
Using the formula and the table, calculate the correct percentage change in the stroke volume of the seal during a deep foraging dive compared with its stroke volume when resting on ice. Give your answer to 1 decimal place.
Identify the mathematical error in the final step of the student's calculation.
Mass transport Questions
Practise AQA A Level Biology Mass transport with exam-style questions for A Level Biology. 15 questions covering Mass transport in animals and Mass transport in plants, matched to the AQA A Level Biology (7402) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.