Bioenergetics - Worksheets, Questions and Revision

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GCSE · Biology

B4 Bioenergetics

AQA 8461 · Calculator allowed · about 110 minutes
Total Marks
Name: _______________________________    Date: ____ / ____ / ______
Answer ALL questions. Show all your working.
1
Photosynthesis is the process by which green plants and algae make glucose using energy transferred from light.
(a)Complete the word equation for photosynthesis: carbon dioxide + ______ --[light energy]--> ______ + oxygen(2)
(b)State whether photosynthesis is an exothermic or endothermic reaction, and explain your answer in terms of energy transfer.(2)
(Total for Question 1 is 4 marks)
2
Photosynthesis can also be represented using a balanced chemical symbol equation.
(a)Write the balanced symbol equation for photosynthesis.(2)
(b)Name the organelle in a plant cell where photosynthesis takes place.(1)
(Total for Question 2 is 3 marks)
3
Several environmental factors can affect the rate of photosynthesis in a plant.
(a)Define the term 'limiting factor'.(1)
(b)State three environmental factors that can limit the rate of photosynthesis.(3)
(c)Which of these three factors is most likely to be limiting the rate of photosynthesis at night?(1)
(Total for Question 3 is 5 marks)
4
A student measured the rate of photosynthesis of a plant at increasing light intensities, keeping temperature and carbon dioxide concentration constant. The results are shown below.

Light intensity (arbitrary units): 0, 10, 20, 30, 40, 50, 60
Rate of photosynthesis (mm3 of O2 per minute): 0, 4, 8, 11, 12, 12, 12
(a)Describe the relationship between light intensity and rate of photosynthesis shown between 0 and 30 arbitrary units.(2)
(b)Explain why the rate of photosynthesis does not increase further between 40 and 60 arbitrary units.(2)
(c)Suggest one change the student could make to their investigation to determine which other factor is limiting the rate above 40 units.(2)
(Total for Question 4 is 6 marks)
5
Required practical: A student investigated the effect of light intensity on the rate of photosynthesis of pondweed (Elodea). A single strand of pondweed was placed in a boiling tube of dilute sodium hydrogencarbonate solution, with a lamp positioned at different distances from the tube. At each distance, the student counted the number of bubbles of gas released from the cut end of the pondweed in one minute, repeating the count three times. The results are shown below.

Distance from lamp (cm): 10, 20, 30
Bubbles per minute (Repeat 1): 45, 12, 5
Bubbles per minute (Repeat 2): 47, 11, 6
Bubbles per minute (Repeat 3): 46, 13, 4
(a)Identify the independent variable and the dependent variable in this investigation.(2)
(b)State two variables, other than distance, that should be controlled to make this a fair test.(2)
(c)Calculate the mean number of bubbles produced per minute at a distance of 30 cm. Show your working.(2)
(d)Give one reason why counting bubbles is not a very accurate way to measure the volume of gas produced, and suggest a more accurate method.(2)
(e)The relative light intensity reaching the pondweed can be estimated using the equation: relative light intensity = 1 / distance2. Calculate the relative light intensity when the lamp is placed 20 cm from the pondweed.(2)
(f)The student wants to double the relative light intensity calculated in part (e). Calculate the new distance, in cm, that the lamp should be placed from the pondweed. Give your answer to 1 decimal place.(3)
(g)Identify one hazard associated with using a lamp close to water in this investigation, and state a precaution that should be taken.(2)
(h)Suggest two ways this investigation could be made more reliable.(2)
(Total for Question 5 is 17 marks)
6
Glucose produced during photosynthesis can be used by the plant in several ways.
(a)Complete the sentences below.

(i) Some glucose molecules are joined together and stored as an insoluble carbohydrate called _____.
(ii) Some glucose is converted into _____, used to strengthen plant cell walls.
(iii) Glucose combines with nitrate ions, absorbed from the soil, to produce _____, which are used to build proteins.
(iv) Glucose combines with other substances to form _____, used for storage in seeds and in cell membranes.(4)
(b)Explain why plants need to absorb nitrate ions from the soil in order to make amino acids from glucose.(2)
(Total for Question 6 is 6 marks)
7
Aerobic respiration is the main process used by cells to release energy from glucose.
(a)Complete the word equation for aerobic respiration: glucose + oxygen -> ______ + ______(2)
(b)Write the balanced symbol equation for aerobic respiration.(2)
(c)Name the cell organelle where most of the reactions of aerobic respiration take place.(1)
(Total for Question 7 is 5 marks)
8
During vigorous exercise, muscle cells may not receive enough oxygen and so respire anaerobically.
(a)Complete the word equation for anaerobic respiration in muscle cells: glucose -> ______(1)
(b)State one difference between the reactants needed for aerobic and anaerobic respiration.(1)
(c)Explain why anaerobic respiration releases much less energy per glucose molecule than aerobic respiration.(2)
(d)Define the term 'oxygen debt'.(2)
(Total for Question 8 is 6 marks)
9
Yeast is a single-celled fungus that can respire anaerobically in a process called fermentation.
(a)Complete the word equation for anaerobic respiration in yeast: glucose -> ______ + ______(2)
(b)State two industries that make use of anaerobic respiration in yeast.(2)
(c)State one difference between the products of anaerobic respiration in yeast and in human muscle cells.(1)
(Total for Question 9 is 5 marks)
10
Complete the table below to compare aerobic and anaerobic respiration in human muscle cells. Each lettered blank is worth one mark.
FeatureAerobic respirationAnaerobic respiration (muscle cells)
Oxygen required?(a) _____No
Waste product(s)carbon dioxide and water(b) _____
Relative amount of energy released per glucose molecule(c) _____relatively small amount
Is glucose completely broken down?(d) _____No
Rate at which energy can be released(e) _____faster, but cannot be sustained for long
(Total for Question 10 is 5 marks)
11
During vigorous exercise, several changes occur in the human body to supply the muscles with more energy. Explain how heart rate, breathing rate and breathing depth change during exercise, and describe how the body repays an oxygen debt after exercise has finished.
(Total for Question 11 is 6 marks)
12
After a 400 m race, an athlete's oxygen consumption took 12 minutes to return to the resting rate. During this recovery period, the athlete repaid a total oxygen debt of 21.6 dm3. Calculate the mean rate of repayment of the oxygen debt, in dm3 per minute.
(Total for Question 12 is 3 marks)
13
Metabolism describes all the chemical reactions that take place in the cells of the body.
(a)Define the term 'metabolism'.(1)
(b)State the name of the large molecule formed when: (i) many glucose molecules join together for storage in the liver and muscles (ii) many amino acid molecules join together (iii) glycerol and fatty acid molecules join together(3)
(c)Excess amino acids cannot be stored in the body. Describe what happens to them.(2)
(Total for Question 13 is 6 marks)
14
A student measured the volume of carbon dioxide gas released by a flask of respiring yeast over time. Between 5 and 15 minutes, the volume of carbon dioxide collected increased from 12 cm3 to 42 cm3. Calculate the mean rate of respiration during this time interval, in cm3 per minute.
(Total for Question 14 is 3 marks)
15
A student used a respirometer to investigate the effect of temperature on the rate of respiration of germinating pea seeds. The respirometer contained a tube of soda lime, and coloured liquid in a capillary tube that moved as the volume of gas in the apparatus changed. An identical respirometer, but containing glass beads instead of seeds, was set up alongside as a control.
(a)Explain why the respirometer contains soda lime.(2)
(b)Explain why a control respirometer, containing glass beads instead of seeds, was set up alongside.(2)
(c)At 25 degC, the coloured liquid moved 24 mm along the capillary tube in 8 minutes. Calculate the rate of movement of the liquid, in mm per minute.(2)
(d)Predict and explain what would happen to the rate of movement of the liquid if the temperature were increased to 45 degC.(1)
(Total for Question 15 is 7 marks)
16
Answer each multiple-choice question by selecting the correct letter.
(a)Which organelle is the main site of aerobic respiration in a cell?(1)
  • A) Nucleus
  • B) Mitochondria
  • C) Chloroplast
  • D) Ribosome
(b)Which gas is released by plant cells as a product of photosynthesis?(1)
  • A) Carbon dioxide
  • B) Nitrogen
  • C) Oxygen
  • D) Hydrogen
(c)Photosynthesis is best described as:(1)
  • A) An exothermic reaction
  • B) An endothermic reaction
  • C) A type of anaerobic respiration
  • D) A type of aerobic respiration
(d)Which two products are formed during anaerobic respiration in yeast?(1)
  • A) Lactic acid only
  • B) Oxygen and water
  • C) Ethanol and carbon dioxide
  • D) Glucose and oxygen
(Total for Question 16 is 4 marks)
17
In a greenhouse at high light intensity and constant temperature, the rate of photosynthesis of tomato plants can be increased by raising the carbon dioxide concentration of the air.
(a)Explain, in terms of collisions between carbon dioxide molecules and enzyme molecules, why increasing the carbon dioxide concentration increases the rate of photosynthesis.(3)
(b)Explain why, above a certain carbon dioxide concentration, further increases have no additional effect on the rate of photosynthesis.(2)
(Total for Question 17 is 5 marks)
18
A student investigated the rate of photosynthesis of pondweed by counting bubbles of gas released at different light intensities, using the method described in Question 5. Evaluate this method, and suggest how the investigation could be improved to produce more valid and reliable data.
(Total for Question 18 is 6 marks)
19
A green plant's cells carry out both photosynthesis and respiration throughout each 24-hour period.
(a)Explain why, in bright sunlight, a green plant releases oxygen into the environment overall, even though its cells are also respiring.(2)
(b)At a certain light intensity, a leaf's rate of photosynthesis is exactly equal to its rate of respiration. (i) Name this point. (ii) Describe the net exchange of oxygen and carbon dioxide between the leaf and the environment at this point.(3)
(c)Explain why, at night, there is a net release of carbon dioxide from a green plant.(2)
(Total for Question 19 is 7 marks)
20
Using the equation relative light intensity = 1 / distance2, calculate the percentage increase in relative light intensity when a lamp is moved from 40 cm to 25 cm away from a plant. Give your answer to 3 significant figures.
(Total for Question 20 is 4 marks)
Mark scheme · B4 Bioenergetics

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20