Podcast
Questions and Answers
Which of the following accurately describes the mechanism of Crassulacean acid metabolism (CAM) plants?
Which of the following accurately describes the mechanism of Crassulacean acid metabolism (CAM) plants?
During photorespiration, where does the initial interaction between RuBP and oxygen take place?
During photorespiration, where does the initial interaction between RuBP and oxygen take place?
In what cellular compartment does the conversion of phosphoglycolate to glycine occur?
In what cellular compartment does the conversion of phosphoglycolate to glycine occur?
What is a significant implication of understanding photorespiration in the context of agriculture?
What is a significant implication of understanding photorespiration in the context of agriculture?
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Which of the following statements accurately describes the flow of metabolites during photorespiration?
Which of the following statements accurately describes the flow of metabolites during photorespiration?
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What is the main consequence of photorespiration in plants?
What is the main consequence of photorespiration in plants?
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What is the primary reason for higher photorespiration rates under intense light conditions?
What is the primary reason for higher photorespiration rates under intense light conditions?
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Which enzyme is responsible for the initial step of photorespiration?
Which enzyme is responsible for the initial step of photorespiration?
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What is the primary reason that increasing CO2 concentration can reduce photorespiration?
What is the primary reason that increasing CO2 concentration can reduce photorespiration?
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Which of the following describes a strategy used by C4 plants to mitigate photorespiration?
Which of the following describes a strategy used by C4 plants to mitigate photorespiration?
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Which of these are NOT factors influencing photorespiration rates?
Which of these are NOT factors influencing photorespiration rates?
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What is the 2-carbon compound produced during the initial step of photorespiration?
What is the 2-carbon compound produced during the initial step of photorespiration?
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Why is photorespiration considered a wasteful process?
Why is photorespiration considered a wasteful process?
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Flashcards
Crassulacean acid metabolism (CAM)
Crassulacean acid metabolism (CAM)
A process used by certain plants like cacti to fix CO2 at night.
Role of chloroplast in photosynthesis
Role of chloroplast in photosynthesis
Chloroplasts are where the initial interactions of RuBP and oxygen occur in photosynthesis.
Function of peroxisomes
Function of peroxisomes
Peroxisomes convert phosphoglycolate into glycine in plants.
Mitochondria's role in glycine metabolism
Mitochondria's role in glycine metabolism
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Significance of studying photorespiration
Significance of studying photorespiration
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Photorespiration
Photorespiration
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Rubisco
Rubisco
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Phosphoglycolate
Phosphoglycolate
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Factors influencing photorespiration
Factors influencing photorespiration
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Consequences of photorespiration
Consequences of photorespiration
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C4 plants
C4 plants
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CAM plants
CAM plants
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Improving Rubisco efficiency
Improving Rubisco efficiency
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Study Notes
Introduction to Photorespiration
- Photorespiration is a metabolic pathway that occurs in plants when there is a high concentration of oxygen in relation to carbon dioxide within the leaves.
- This process is a wasteful process where a plant consumes energy to release carbon dioxide.
Process of Photorespiration
- It is initiated when the enzyme Rubisco combines RuBP (ribulose 1,5-bisphosphate) with oxygen instead of carbon dioxide.
- This reaction, unlike the normal carboxylation reaction using Rubisco, results in a 2-carbon compound (phosphoglycolate) instead of a 3-carbon compound.
- Phosphoglycolate is subsequently metabolized through a series of reactions involving peroxisomes, mitochondria, and chloroplasts.
- These reactions release carbon dioxide, consume ATP and NADPH.
- The net effect is a loss of fixed carbon and the expenditure of energy.
Factors Influencing Photorespiration
- Light intensity: Photorespiration is more enhanced under intense light conditions.
- Temperature: Elevated temperatures favor photorespiration rates.
- Oxygen levels: A higher oxygen to carbon dioxide ratio in the leaf environment stimulates photorespiration.
- CO2 concentration: Low CO2 levels will enhance photorespiration.
Consequences of Photorespiration in Plants
- Reduced photosynthetic efficiency: It decreases the overall rate of carbon assimilation, which reduces plant growth.
- Energy loss: Photorespiration consumes ATP energy needed for other plant metabolic processes.
- Negative impact on crop yield: Increased photorespiration in crops translates to reduced crop yields.
Mechanisms to Reduce Photorespiration
- Improving Rubisco efficiency: This aims to reduce the oxygenase activity and increase the carboxylase activity.
- Increasing CO2 levels: Increasing carbon dioxide around the leaf to favor carboxylation of RuBP.
- Changes in photosynthetic pathways: Some plants use alternative photosynthetic pathways to minimize photorespiration's impact. C4 plants and CAM plants have strategies to efficiently concentrate CO2 to Rubisco.
- Genetic engineering approaches to improve Rubisco activity: New research in genetic engineering attempts to limit the effects of photorespiration in crops.
C4 and CAM Photosynthesis as Strategies to Mitigate Photorespiration
- C4 plants such as sugarcane, maize, and sorghum have evolved a specialized pathway to concentrate CO2 around Rubisco, limiting the opportunity for oxygen to bind and start the photorespiration process. They utilize two distinct cells, which separate the light-dependent and CO2-fixing steps.
- Crassulacean acid metabolism (CAM) plants such as cacti and succulents open their stomata at night to take in CO2, converting it into organic acids. These acids are stored until the day, when stomata close to retain water, and the stored CO2 is released to be used in photosynthesis. This process reduces water loss associated with daytime photosynthesis while limiting photorespiration.
Significance and Importance of Studying Photorespiration
- Understanding photorespiration is crucial for developing strategies to improve crop yields. Scientists are investigating ways to modify photosynthesis mechanisms to boost crop productivity in diverse environments. The study also provides important understanding of carbon-oxygen relationships in complex systems like photosynthesis and its environmental repercussions.
Different Roles of Cellular Compartments
- Chloroplast: The initial interaction between RuBP and oxygen occurs in the chloroplast. Later reactions involving phosphoglycolate are sent to adjacent peroxisomes and mitochondria.
- Peroxisome: A significant portion of phosphoglycolate metabolism takes place here, converting it to glycine.
- Mitochondria: Glycine, produced from the peroxisomes, continues to be metabolized, producing serine and carbon dioxide.
- Chloroplast: Ultimately, the process returns to the chloroplast to regenerate RuBP.
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Description
Explore the complex process of photorespiration, a metabolic pathway in plants that occurs when oxygen levels are high relative to carbon dioxide. Learn how the enzyme Rubisco's preference for oxygen over carbon dioxide leads to energy consumption and carbon loss. Understand the implications of light intensity and other factors on this wasteful process.
