Some species of bacteria that live on the ocean floor do not have access to light for photosynthesis. Instead, they use the process of chemosynthesis to make glucose using energy stored in substances such as methane, hydrogen sulfide (H2S) and carbon dioxide. A simplified equation of one such reaction is shown below.
The rate of photosynthesis can be expressed as either gross or net rates. Gross photosynthesis is the total rate of carbon fixation (reduction of CO2) without considering that some of the CO2 is lost in respiration. Net photosynthesis is the carbon fixation rate minus the rate of CO2 loss in respiration.
The graph below shows the effect of temperature on the net rate of photosynthesis at three different light intensities and the effect of temperature on the rate of respiration.
Note to illustrators: Please remove the letters X, Y and Z from the graph above.
Use the graph to calculate the gross rate of photosynthesis at 15oC and low light intensity.
The average global temperature is 14oC. Scientists predict that over the course of the next 100 years, the average temperature could increase by up to 4oC. It is also predicted to become cloudier in many regions.
Use the graph to describe and explain how these changes are likely to affect the growth of plants.
The enzyme rubisco catalyses the reaction between RuBP and carbon dioxide to form two molecules of glycerate-3-phosphate (GP). Rubisco can also catalyse a reaction between RuBP and oxygen to form one molecule of GP and one molecule of phosphoglycolate.
The reactions are shown in the diagram below.
Use the diagram to deduce to number of carbon atoms in one molecule of phosphoglycolate.
The scientists investigated the effect oxygen concentration had on the absorption of carbon dioxide in leaves from tomato plants. The graph below shows their results.
Graphic designer: Please change the y axis numbers to increase in 5s not 10s and go up to 30 instead of 60.
Explain the results in the graph above using the diagram and information from part b) of the question.
Use all the information provided and your knowledge of the light-independent reaction to explain why the yield from tomato plants decreases at higher concentrations of oxygen. Note: Phosphoglycolate is not used in the light-independent reaction.
Some scientists were investigating photosynthesis in seaweed. During their investigation, they applied lights of different wavelengths to study the amount of light absorbed by the seaweed species.
Their results can be seen in the graph below.
State, with a reason, the types of pigments found in these species of seaweed.
Compare and contrast the processes that occur in the electron transport chain (ETC) of the light dependent reaction with the electron transport chain in respiration.
One mark is available for clarity of communication throughout this question.
a)
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours.
Use your knowledge of photosynthesis to describe and explain these changes. You can assume there is no air movement through wind throughout the 24 hour period.
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glucose + sulfur + sulfur compounds
State, with a reason, the types of pigments found in these species of seaweed.
