12.2. Respiration
A subsection of Biology, 9700, through 12. Energy and respiration
Listing 10 of 158 questions
A respirometer is a piece of apparatus that can be used to measure the rate of respiration of living tissue such as germinating peas. A simple respirometer is shown in . cm U-shaped tube ruler coloured liquid syringe wire gauze germinating peas test-tube potassium hydroxide solution A student carried out an investigation to determine the effect of temperature on the rate of respiration of germinating peas. • The student set up the respirometer as shown in and placed the respirometer in a water-bath at 10 °C. • After five minutes, the student used the syringe to adjust the position of the coloured liquid in the right-hand side of the U-shaped tube so that it lined up with 0 cm on the ruler. The student immediately started a timer. • The germinating peas used up oxygen, causing the coloured liquid in the U-shaped tube to move. • The student measured the distance moved by the coloured liquid after 20 minutes. • The student repeated the experiment at temperatures of 20 °C, 30 °C, 40 °C and 50 °C. State the function of the potassium hydroxide solution used in the investigation. Suggest how the validity of the results could be assessed. Explain why the respirometer was left in the water-bath for five minutes before starting the experiment. The rate of movement of the coloured liquid in the U-shaped tube, calculated from the results, is shown in Table 6.1. Table 6.1 temperature / °C rate of movement / mm min–1 0.40 0.70 1.30 1.15 0.60 Plot a graph of the results shown in Table 6.1 on the grid in . Draw a curved line of best fit. 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 rate of movement / mm min–1 temperature / °C The rate of movement of the coloured liquid is related to the rate of respiration. Explain the effect of temperature on the rate of respiration shown in Table 6.1 and .
9700_m24_qp_42
THEORY
2024
Paper 4, Variant 2
View
When gold is associated with mineral ores such as iron sulfide, the sulfides must be oxidised to release the gold particles. Since the mid 1990s, gold has been extracted from such ores by bioleaching. Suitable bacteria oxidise iron sulfide to soluble iron sulfate, releasing Fe3+ and SO4 2– ions. The reaction releases heat energy and temperatures within a heap of ore that is being bioleached (a bioheap) can reach 70 °C or higher. Examples of bacteria used in this bioleaching are shown in Table 2.1. Table 2.1 example of bacterium temperature range for growth / °C activity natural habitat Acidithiobacillus ferrooxidans 35 – 45 oxidise iron and sulfur compounds acid springs Sulfobacillus thermosulfidooxidans 45 – 65 Sulfolobus metallicus 65 – 95 With reference to Table 2.1, suggest a natural habitat for organisms such as S. thermosulfidooxidans and S. metallicus why all three species of bacteria, rather than just one species, are mixed with ore in a bioheap. The rate of oxidation of the iron in iron sulfide ore was compared in the presence and absence of A. ferrooxidans at pH 2.0. The results are shown in . in presence of A. ferrooxidans in absence of A. ferrooxidans 2.0 concentration of Fe3+ ions / arbitrary units 1.0 1.5 0.5 time / days With reference to , describe the effect of A. ferrooxidans on the oxidation of the ore. Explain why bioleaching is now used on a large scale throughout the world. Gold-bearing sulfide ores often contain arsenic, which is potentially toxic to the bacteria used in bioleaching. However, arsenic-resistant strains of A. ferrooxidans have been found in some mines. The activity of two strains of the bacterium, in the presence and absence of arsenic ions, is shown in Table 2.2. Table 2.2 oxidation rate of iron in the ore / mg dm–3 h–1 strain of A. ferrooxidans arsenic ions absent arsenic ions present Describe the results shown in Table 2.2 and explain the role of natural selection in the evolution of arsenic-resistant bacteria.
9700_s11_qp_41
THEORY
2011
Paper 4, Variant 1
View
When a dormant seed absorbs water it will start to germinate and its rate of respiration will increase. Name the plant growth regulator involved in the initiation of germination of seeds. A respirometer can be used to measure the rate of respiration of germinating seeds. shows a respirometer. coloured liquid graduated tube mesh potassium hydroxide solution pea seed State the role of potassium hydroxide solution in the use of a respirometer. As respiration takes place, oxygen is used by the seeds and the coloured liquid moves down the tube. Describe the role of oxygen in aerobic respiration. Respirometers, as shown in , were used to investigate the effect of temperature on the rate of respiration of germinating pea seeds. Four respirometers, A, B, C and D were set up: • A and B in a water-bath maintained at 10 °C. • C and D in a water-bath maintained at 25 °C. • A and C each contained 30 germinating pea seeds. • B and D each contained glass beads with a total volume equivalent to 30 pea seeds. • The respirometers were left in the water-baths for 10 minutes. • In each respirometer the position of the coloured liquid in the graduated tube was then marked (time 0 minutes). • After 5 minutes the distance moved by the coloured liquid was measured. • The volume of oxygen taken up was calculated for each respirometer. • This was repeated after 10, 15 and 20 minutes. shows the results of the experiment. 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 C A B and D time / minutes volume of oxygen taken up / cm3 Suggest why the respirometers were left for 10 minutes before measurements were made. Suggest why respirometers B and D were used in this investigation. Calculate the rate of oxygen uptake in cm3 per minute for respirometer C between 5 and 20 minutes. Give your answer to two significant figures. Show your working. answer cm3 min–1 Explain why there is an increased rate of respiration of germinating pea seeds between 10 °C and 25 °C. Suggest why carrying out the experiment with germinating seeds at 50 °C could result in a lower rate of respiration than at 25 °C.
9700_w16_qp_41
THEORY
2016
Paper 4, Variant 1
View
When a dormant seed absorbs water it will start to germinate and its rate of respiration will increase. Name the plant growth regulator involved in the initiation of germination of seeds. A respirometer can be used to measure the rate of respiration of germinating seeds. shows a respirometer. coloured liquid graduated tube mesh potassium hydroxide solution pea seed State the role of potassium hydroxide solution in the use of a respirometer. As respiration takes place, oxygen is used by the seeds and the coloured liquid moves down the tube. Describe the role of oxygen in aerobic respiration. Respirometers, as shown in , were used to investigate the effect of temperature on the rate of respiration of germinating pea seeds. Four respirometers, A, B, C and D were set up: • A and B in a water-bath maintained at 10 °C. • C and D in a water-bath maintained at 25 °C. • A and C each contained 30 germinating pea seeds. • B and D each contained glass beads with a total volume equivalent to 30 pea seeds. • The respirometers were left in the water-baths for 10 minutes. • In each respirometer the position of the coloured liquid in the graduated tube was then marked (time 0 minutes). • After 5 minutes the distance moved by the coloured liquid was measured. • The volume of oxygen taken up was calculated for each respirometer. • This was repeated after 10, 15 and 20 minutes. shows the results of the experiment. 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 C A B and D time / minutes volume of oxygen taken up / cm3 Suggest why the respirometers were left for 10 minutes before measurements were made. Suggest why respirometers B and D were used in this investigation. Calculate the rate of oxygen uptake in cm3 per minute for respirometer C between 5 and 20 minutes. Give your answer to two significant figures. Show your working. answer cm3 min–1 Explain why there is an increased rate of respiration of germinating pea seeds between 10 °C and 25 °C. Suggest why carrying out the experiment with germinating seeds at 50 °C could result in a lower rate of respiration than at 25 °C.
9700_w16_qp_42
THEORY
2016
Paper 4, Variant 2
View
DCPIP is an indicator and can be used to determine the rate of respiration of organisms such as yeast. State the category of indicators to which DCPIP belongs. Describe the colour change that occurs in DCPIP during experiments to determine the rate of respiration. An investigation was carried out to determine the effect of temperature on the rate of respiration of yeast. • A suspension of yeast cells was added to a test‑tube containing glucose solution. • A further four test‑tubes were set up in the same way. • One test‑tube was placed in a water‑bath at 10 °C for 5 minutes. • DCPIP was added to the test‑tube and the time taken for the DCPIP to change colour was measured. • The experiment was repeated using the other test‑tubes at 20 °C, 30 °C, 40 °C and 50 °C. The results are shown in . temperature / °C time taken for DCPIP to change colour / minutes State two variables that need to be kept constant in this experiment. Explain the results shown in .
9700_w24_qp_42
THEORY
2024
Paper 4, Variant 2
View
Thermoregulation is the control of the core temperature of the body. Thermoreceptors send information about a change in core temperature to the hypothalamus. The hypothalamus controls the core temperature by sending impulses to activate several physiological responses. Table 6.1 lists physiological responses to a decrease in core temperature. Complete Table 6.1 to explain how each response contributes to maintaining a core temperature within narrow limits. Table 6.1 response explanation blood vessels near the surface of the skin constrict shivering occurs hairs rise reduction in the production of sweat Animals can also use behaviour to adapt to temperature changes. Suggest why some animals curl up their bodies in cold weather. The Sitatunga deer, Tragelaphus spekii, and the Nile monitor lizard, Varanus niloticus, live in Africa. shows a Sitatunga and shows a Nile monitor. An investigation was carried out to measure the core temperature of the Sitatunga and the Nile monitor as the environmental temperature was increased. The results are shown in . core temperature / °C environmental temperature / °C Nile monitor Sitatunga Describe the results shown in . When the environmental temperature is low, Nile monitors are relatively inactive. Suggest one disadvantage to the Nile monitor of being inactive. Thermoregulation relies on negative feedback. Explain what is meant by negative feedback.
9700_s21_qp_41
THEORY
2021
Paper 4, Variant 1
View
Questions Discovered
158