Topic 8: Cell respiration and photosynthesis

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1 Topic 8: Cell respiration and photosynthesis

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3 8.1 Cell respiration Topic 8: Cell respiration and photosynthesis Assessment Statement IBO Notes Student Notes State that oxidation involves the loss of electrons from an element, whereas reduction involves a gain of electrons; and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation. In the cytoplasm, one hexose sugar is converted into two three carbon atom compounds (pyruvate) with a net gain of two ATP and two NADH + H Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H +, the electron transport chain and the role of oxygen. In aerobic respiration (in mitochondria in eukaryotes), each pyruvate is decarboxylated (CO removed). The remaining two carbon molecule (acetyl group) reacts with reduced coenzyme A, and, at the same time, one NADH + H + is formed. This is known as the link reaction. In the Krebs cycle, each acetyl group (3CO) formed in the link reaction yields two CO. The names of the intermediate compounds in the cycle are not required. Thus it would be acceptable to note:, and so on Explain oxidative phosphorylation in terms of chemiosmosis Explain the relationship between the structure of the mitochondrion and its function. Limit this to cristae forming a large surface area for the electron transport chain, the small space between inner and outer membranes for accumulation of protons, and the fluid matrix containing enzymes of the Krebs cycle.

4 1. The diagram below shows possible pathways for the breakdown of glucose in various cells. Glucose A Process Q (no oxygen present) Process R (oxygen present) (a) State the names of processes Q and R. B C + D D + E Q:... R:... (b) Deduce the names of substances A and D. A:... D:... (c) State the organelle in which process R takes place. (Total 5 marks). Explain the process of aerobic respiration including oxidative phosphorylation. (Total 8 marks)

5 3. Of the following products, which is produced by both anaerobic respiration and aerobic respiration in humans? I. Pyruvate II. III. ATP Lactate A. I only B. I and II only C. I, II and III D. II and III only 4. Which is not a product of the Krebs cycle? A. CO B. NADH + H + C. Pyruvate D. ATP 5. How many ATP molecules (net yield) are produced per molecule of glucose as a direct result of glycolysis? A. B. 4 C. 10 D. 38

6 6. What happens during muscle contraction? A. Both actin and myosin filaments shorten. B. Na + ions are taken up by the sarcoplasmic reticulum. C. The actin and myosin filaments slide over each other. D. Cross bridges remain attached to the filaments. 7. Explain the similarities and differences in anaerobic and aerobic cellular respiration. (Total 8 marks) 8. Anaerobic respiration occurs in the absence of oxygen while aerobic respiration requires oxygen. (a) State one final product of anaerobic respiration. (b) Complete the table showing the differences between oxidation and reduction. Electrons gained or lost Oxygen or hydrogen gained or lost Oxidation Reduction

7 (c) The structure of a mitochondrion is shown in the electron micrograph below. Name the parts labelled A, B and C and state the function of each. Part A: Name:... Function:... Part B: Name:... Function:... Part C: Name:... Function:... (3) (Total 6 marks)

8 9. The rate of carbon dioxide uptake by the green succulent shrub Aeonium goochiae can indicate the amount of photosynthesis taking place in the plant. This rate was measured at 15 C and 30 C over a 4-hour period. The units of carbon dioxide absorption are mg CO h 1. The results are shown below. The centre of the graph corresponds to mg CO h 1 and the outer ring is +.5mg CO h (late evening) (evening) (midnight) Key: 30ºC 15ºC 0300 (early morning) (morning) (early afternoon) 0900 (late morning) (mid-day) 1000 [Source: adapted from (a) Identify a time that carbon dioxide uptake was the same at both temperatures. (b) State the maximum rate of carbon dioxide uptake at 15 C.

9 (c) Compare the rate of carbon dioxide uptake at each temperature in daylight and darkness. (3) (d) Suggest why the carbon dioxide uptake may at times be negative. (Total 6 marks) 10. (a) (i) Identify the cell organelle shown in the micrograph below....

10 (ii) Identify the structure labelled I above and explain how it is adapted for the organelle to function efficiently (3) (b) Describe the role of acetyl CoA in the metabolism of lipids. (Total 6 marks) 11. Which way do the protons flow when ATP is synthesized in mitochondria? A. From the inner matrix to the intermembrane space B. From the intermembrane space to the inner matrix C. From the intermembrane space to the cytoplasm D. From the cytoplasm to the intermembrane space 1. What accumulates in the inter-membrane space of the mitochondrion during electron transport? A. ATP B. Electrons C. Protons (hydrogen ions) D. Oxygen

11 13. Biosphere, an enormous greenhouse built in the Arizona desert in the USA, has been used to study five different ecosystems. It is a closed system so measurements can be made under controlled conditions. The effects of different factors, including changes in carbon dioxide concentration in the greenhouse, were studied. The data shown below were collected over the course of one day in January CO / 800 ppm light / 1000 μmol m s Key: CO Light Time / hours [Source: (a) (i) Identify the time of day when the sun rose.... (ii) Identify the time of minimal CO concentration.... (b) Determine the maximum difference in the concentration of CO over the 4-hour period.

12 (c) Suggest reasons for changes in CO concentration during the 4-hour period. (Total 5 marks) 14. (a) State two functions of proteins with a named example of each. (b) Explain chemiosmosis as it occurs during cell respiration. (Total 4 marks) 15. What is the sequence of stages during the conversion of glucose into pyruvate in glycolysis? A. lysis phosphorylation of sugar oxidation B. lysis oxidation phosphorylation of sugar C. phosphorylation of sugar lysis oxidation D. phosphorylation of sugar oxidation lysis

13 16. (a) State two products of the process of glycolysis. (b) Explain the significance of polar and non-polar amino acids within the cell. (3) (Total 4 marks) 17. The respiratory quotient (RQ) is a measure of the metabolic activity of an animal. It is the ratio of CO produced to O consumed. In general, the lower the RQ value the higher the energy yield. The RQ is dependent on the diet consumed by the animal. The following table lists the typical RQ values for specified diets. Diet RQ Lipid 0.71 Carbohydrate 1.00 Protein 0.74 [Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages Reproduced by permission of The Company of Biologists Ltd] In an experiment to assess RQ values for house sparrows, the birds were fed a diet of pure mealworms (beetle larvae) or millet (a type of grain).

14 The graph below shows the RQ values of a house sparrow fed on a high carbohydrate diet (millet) and a high lipid diet (mealworms). 1.0 Respiratory quotient Key: Millet Mealworms Time after feeding / h [Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages Reproduced by permission of The Company of Biologists Ltd] (a) Compare the RQ values for millet and mealworms between 1 hour and 6 hours after feeding. The expected RQ value for house sparrows metabolizing millet is The expected value when metabolizing mealworms is (b) Explain why the expected RQ values for millet and mealworms are different.

15 (c) Suggest reasons for (i) the high initial RQ values for house sparrows fed on millet (ii) the rapid fall in RQ values for house sparrows fed on millet (Total 6 marks) 18. Which of the following produce ATP in mitochondria? A. The movement of protons from the matrix to the intermembrane space B. The movement of protons from the intermembrane space to the cytoplasm C. The splitting of water molecules and the movement of electrons to oxygen D. The movement of protons from the intermembrane space to the matrix

16 19. How many molecules of acetyl CoA (ethanoyl CoA) does the oxidation of the fatty acid stearic acid produce? A. B. 6 C. 9 3 COOH Stearic acid D Explain the process of aerobic cellular respiration. (Total 8 marks)

17 8. Photosynthesis Assessment Statement IBO Notes Student Notes 8..1 Draw and label a diagram showing the structure of a chloroplast as seen in electron micrographs. 8.. State that photosynthesis consists of light dependent and light independent reactions. These should not be called light and dark reactions Explain the light dependent reactions. Include the photoactivation of photosystem II, photolysis of water, electron transport, cyclic and noncyclic photophosphorylation, photoactivation of photosystem I, and reduction of NADP Explain photophosphorylation in terms of chemiosmosis Explain the light independent reactions. Include the roles of ribulose bisphosphate (RuBP) carboxylase, reduction of glycerate 3 phosphate (GP) to triose phosphate (TP), NADPH + H +, ATP, regeneration of RuBP, and subsequent synthesis of more complex carbohydrates. TOK: The lollipop apparatus used to work out the biochemical details of the Calvin cycle shows considerable creativity. To what extent is the creation of an elegant protocol similar to the creation of a work of art? 8..6 Explain the relationship between the structure of the chloroplast and its function Explain the relationship between the action spectrum and the absorption spectrum of photosynthetic pigments in green plants Explain the concept of limiting factors in photosynthesis, with reference to light intensity, temperature and concentration of carbon dioxide. Limit this to the large surface area of thylakoids for light absorption, the small space inside thylakoids for accumulation of protons, and the fluid stroma for the enzymes of the Calvin cycle. A separate spectrum for each pigment (chlorophyll a, chlorophyll b, and so on) is not required. TOK: This is an opportunity to discuss the need for very carefully controlled experiments. If we want to investigate the effect of one factor, all other factors that could have an influence must be controlled. In photosynthesis, the situation is relatively simple, and we can ensure that factors other than the one we are investigating are maintained at a constant and optimal level. In other areas, there are much greater problems. In the many investigations of human health, there are almost always complicating factors. For example, vegetarians have a longer life expectancy than meat eaters. We would be wrong to conclude that eating meat lowers life expectancy unless we could show that the only difference between the vegetarians and the meat eaters in our trial was the meat eating.

18 1. There are many abiotic factors that affect the rate of photosynthesis in terrestrial plants. Wheat is an important cereal crop in many parts of the world. Wheat seedlings were grown at three different concentrations of carbon dioxide (in parts per million) and the rate of photosynthesis was measured at various light intensities. Rate of photosynthesis / μ l CO min Light intensity / 10 lumen m key: 1300 ppm CO 500 ppm CO 80 ppm CO [Source: Adapted from J P Kimmins, Forest Ecology, (nd edition) page 161] (a) Describe the relationship between the rate of photosynthesis and light intensity for wheat seedlings grown at a CO concentration of 500 ppm. (b) Outline the effect of CO concentration on the rate of photosynthesis of the wheat seedlings. (3)

19 (c) The normal atmospheric concentration of CO is 370 ppm. Deduce the effect of doubling the CO concentration to 740 ppm on the growth of wheat plants. Leaf area and chlorophyll levels were measured in sun leaves and shade leaves of Hedera helix (English Ivy) and Prunus laurocerasus (Cherry Laurel). Sun leaves developed under maximal sunlight conditions while shade leaves developed at reduced sunlight levels in the shadow of other leaves. Species Leaf Type Chlorophyll/ μg ml -1 Leaf Area/ cm Ivy Shade Sun Laurel Shade Sun [Source: D Curtis, Plant Ecology independent project, 1990] (d) Calculate the percentage increase in the amount of chlorophyll in shade leaves of ivy compared to sun leaves of ivy (e) Suggest a reason for the differences in chlorophyll concentration and leaf area in sun and shade leaves in these two species. (Total 10 marks)

20 . Explain the reasons for (a) a large area of thylakoid membrane in the chloroplast. (b) low rates of photosynthesis in plants growing beneath trees, where the light has already passed through the trees leaves. (c) large amounts of RuBP carboxylase in the chloroplast. (Total 6 marks)

21 3. The unicellular green alga Phaeodactylum tricornutum is photosynthetic. Cell biologists genetically modified this organism by adding a glucose transporter gene. The modified and unmodified algae were grown in a nutrient medium under a series of different conditions and the growth rate of the cells was measured Cell density / cells cm Unmodified algae Modified algae Time / days Key: = light and no glucose in the medium = light and glucose in the medium = dark and glucose in the medium [Source: L A Zaslavskaia, et al., Adapted (001) Science, 9, pages ] (a) State the role of glucose in the metabolism of cells. (b) Deduce where you would expect to find the glucose transporter protein in the modified algae cells. (c) Compare the effect of light on the modified and the unmodified cells.

22 Commercially, unmodified algae are grown in shallow sunlit ponds or illuminated containers. The cells only grow in the top few centimetres. However, the modified algae can grow at any depth. (d) Explain why the modified algae can grow at any depth whereas the unmodified algae can only grow at the surface. (3) (Total 8 marks) 4. State two products of the light dependent reaction of photosynthesis. (Total marks) 5. Which two colours of light does chlorophyll absorb most? A. Red and yellow B. Green and blue C. Red and green D. Red and blue 6. During photosynthesis in plants, light energy is absorbed by chlorophyll. This energy is then used to carry out photolysis, which supply substances that are needed to convert carbon dioxide into organic molecules such as glucose. (a) State the names of two products of photolysis in photosynthesis

23 (b) Explain briefly one method for measuring the rate of photosynthesis in a plant. (c) The rate of photosynthesis is affected by light intensity. Draw a line on the graph below to show the relationship between light intensity and the rate of photosynthesis. rate of photosynthesis light intensity (d) State two factors in the environment of a plant, apart from light intensity, that can affect the rate of photosynthesis in the plant (Total 8 marks) 7. (a) State the main photosynthetic pigment in plants. (b) State the two materials used to convert carbon dioxide to organic molecules in plants.

24 (c) Explain two ways in which the rate of photosynthesis can be measured. (4) (Total 7 marks) 8. (a) State the site of the light-independent reactions in photosynthesis. The absorption spectrum of chlorophyll a and chlorophyll b are shown in the graph below. chlorophyll b chlorophyll a Absorbance Wavelength / nm (b) On the graph above, draw the action spectrum of photosynthesis for a green plant.

25 (c) Explain photophosphorylation in terms of chemiosmosis. (3) (Total 5 marks) 9. Explain the reactions involving the use of light energy that occur in the thylakoids of the chloroplast. (Total 8 marks) 10. Explain how the light-independent reactions of photosynthesis rely on light-dependent reactions. (Total 8 marks) 11. Outline the effect of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis. (Total 6 marks) 1. What is needed in photosynthesis to convert carbon dioxide into organic molecules? A. Light and hydrogen from the splitting of water B. Light and oxygen from the splitting of water C. ATP and hydrogen from the splitting of water D. ATP and oxygen from the splitting of water

26 13. How is the proton gradient generated in chloroplasts during photosynthesis? A. Flow of electrons from carrier to carrier in the thylakoid membrane causes pumping of protons across the thylakoid membrane. B. Light causes protons to flow through protein channels in the thylakoid membrane. C. Light splits water molecules in the stroma, causing the release of protons. D. Protons are pumped across the thylakoid membrane using energy from ATP. 14. Why is the action spectrum for photosynthesis similar to the absorption spectra of photosynthetic pigments? A. Photosynthetic pigments have the same optimum temperature as the enzymes used in photosynthesis. B. Plants absorb the same photosynthetic pigments for use in photosynthesis. C. Only wavelengths of light absorbed by pigments can be used in photosynthesis. D. The amount of energy absorbed by photosynthetic pigments is equal to the activation energy for photosynthesis. 15. (a) Draw and label the structure of the chloroplast as seen in the electron microscope. (3)

27 (b) Explain the relationship between the structure of the chloroplast and its function. (c) Outline the process of chemiosmosis. (Total 7 marks) 16. (a) State where, in the chloroplast, the enzymes of the Calvin cycle are located. (b) Explain how the proton gradient in the chloroplast is generated by chemiosmosis. (3)

28 (c) Explain the relationship between the position of a leaf on a tree and the photosynthetic rate of the leaf. (Total 6 marks) 17. Pigments are extracted from the leaves of a green plant. White light is then passed through the solution of pigments. What effect do the leaf pigments have on the white light? A. Green wavelengths are absorbed and red and blue wavelengths are transmitted. B. Red and blue wavelengths are absorbed and green wavelengths are transmitted. C Blue wavelengths are absorbed and green and red wavelengths are transmitted. D. Green and red wavelengths are absorbed and blue wavelengths are transmitted.