Podcast
Questions and Answers
What structure in carboxysomes helps resist CO2 efflux?
What structure in carboxysomes helps resist CO2 efflux?
- A double helix
- A porous membrane
- A lipid bilayer
- An icosahedral protein shell (correct)
Which transporter is present in thylakoids that facilitates the uptake of inorganic carbon?
Which transporter is present in thylakoids that facilitates the uptake of inorganic carbon?
- Transporters for glucose
- Transporters for O2
- Transporters for HCO3- (correct)
- Transporters for phosphate
What is the role of Rubisco in carboxysomes?
What is the role of Rubisco in carboxysomes?
- To transport CO2
- To synthesize glucose
- To release oxygen
- To catalyze the fixation of carbon dioxide (correct)
What type of molecular structure does the carboxysome have?
What type of molecular structure does the carboxysome have?
What primary function do transporters for CO2 serve in cyanobacteria?
What primary function do transporters for CO2 serve in cyanobacteria?
In the C4 cycle proposed by Hatch and Slack, which compound accumulates first after the incorporation of 14CO2?
In the C4 cycle proposed by Hatch and Slack, which compound accumulates first after the incorporation of 14CO2?
What is the main role of the compounds that accumulate during the C4 cycle?
What is the main role of the compounds that accumulate during the C4 cycle?
Which of the following is directly associated with the Rubisco-catalyzed reaction in the context of the C4 cycle?
Which of the following is directly associated with the Rubisco-catalyzed reaction in the context of the C4 cycle?
What cellular process is primarily affected by the accumulation of 3-PGA in the outlined cycle?
What cellular process is primarily affected by the accumulation of 3-PGA in the outlined cycle?
Which component is essential for the initial carboxylation reaction in the C4 cycle?
Which component is essential for the initial carboxylation reaction in the C4 cycle?
What role does carbonic anhydrase (CA) play in the chloroplast?
What role does carbonic anhydrase (CA) play in the chloroplast?
What is the first product accumulated during the carboxylation reaction described by Hatch and Slack in 1966?
What is the first product accumulated during the carboxylation reaction described by Hatch and Slack in 1966?
Why is back-diffusion of CO2 slowed in the pyrenoid?
Why is back-diffusion of CO2 slowed in the pyrenoid?
In the study by Engel et al. (2015), what technique was used to reveal the native architecture of the Chlamydomonas chloroplast?
In the study by Engel et al. (2015), what technique was used to reveal the native architecture of the Chlamydomonas chloroplast?
Which statement about HCO3- transport is correct?
Which statement about HCO3- transport is correct?
Which compound is labeled first during a pulse-chase study with 14CO2 according to the findings by Hatch and Slack?
Which compound is labeled first during a pulse-chase study with 14CO2 according to the findings by Hatch and Slack?
What is the permeability of the CO2 molecule across the membrane?
What is the permeability of the CO2 molecule across the membrane?
Which of the following statements is NOT true regarding the carbon fixation machinery as discussed in the referenced studies?
Which of the following statements is NOT true regarding the carbon fixation machinery as discussed in the referenced studies?
What does the starch layer in the pyrenoid do?
What does the starch layer in the pyrenoid do?
What did the study by Liu (2016) focus on in cyanobacteria?
What did the study by Liu (2016) focus on in cyanobacteria?
How does CO2 concentration occur in the pyrenoids?
How does CO2 concentration occur in the pyrenoids?
Which of the following acids does the 14CO2 label accumulate in first during Hatch and Slack's carboxylation reaction?
Which of the following acids does the 14CO2 label accumulate in first during Hatch and Slack's carboxylation reaction?
What impact does HCO3- have on CO2 availability in chloroplasts?
What impact does HCO3- have on CO2 availability in chloroplasts?
What type of study did Hatch and Slack conduct to explore the carboxylation reaction?
What type of study did Hatch and Slack conduct to explore the carboxylation reaction?
Which of the following was NOT mentioned as a product or intermediate in the carbon fixation studies referenced?
Which of the following was NOT mentioned as a product or intermediate in the carbon fixation studies referenced?
What is the relationship between Rubisco and pyrenoids?
What is the relationship between Rubisco and pyrenoids?
What type of membrane is permeable to CO2?
What type of membrane is permeable to CO2?
What is the main function of transporters in the pyrenoid?
What is the main function of transporters in the pyrenoid?
At what temperatures do C3 plants have an advantage over C4 plants?
At what temperatures do C3 plants have an advantage over C4 plants?
What is a significant energy requirement for C4 photosynthesis?
What is a significant energy requirement for C4 photosynthesis?
What happens to photorespiration as temperature increases?
What happens to photorespiration as temperature increases?
Why hasn’t C4 photosynthesis evolved in all environments?
Why hasn’t C4 photosynthesis evolved in all environments?
Which statement accurately describes the relationship between C4 plants and temperature?
Which statement accurately describes the relationship between C4 plants and temperature?
Study Notes
Cyanobacteria Carbon Fixation
- Cyanobacteria use carboxysomes to concentrate carbon dioxide
- Carboxysomes are icosahedral protein shells with Rubisco packed inside
- Carboxysomes resist carbon dioxide efflux
- Cyanobacteria use bicarbonate transporters to bring inorganic carbon into the cell
Pyrenoids
- Pyrenoids are organelles used by cyanobacteria and algae for CO2 fixation
- Pyrenoids concentrate CO2 via transporters and carbonic anhydrase
- Pyrenoids are surrounded by a starch layer which is impermeable to CO2 and HCO3-
- CO2 is permeable across the plasma membrane
- Pyrenoids have specific transporters to move HCO3- through the chloroplast envelope and thylakoids
C4 Photosynthesis
- C4 photosynthesis was discovered by Hatch and Slack in 1966. They used pulse-chase experiments with 14C labeled CO2
- C4 photosynthesis involves a new carboxylation reaction
- The first product of C4 photosynthesis to be labeled was malate and other C4 acids, then 3-PGA
- The core of the C4 cycle was proposed by Hatch and Slack in 1966
C4 vs. C3 Photosynthesis
- C3 photosynthesis is favored at cooler temperatures
- C4 photosynthesis requires more energy
- C4 photosynthesis is favored at high temperatures
- The main advantage of C3 photosynthesis is that it is less costly in terms of energy use
- Photorespiration increases as temperature increases for C3 plants
- C4 plants are favored at high temperatures due to lower levels of photorespiration
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Description
Explore the fascinating mechanisms of carbon fixation in cyanobacteria and C4 plants. This quiz covers topics such as carboxysomes, pyrenoids, and the discoveries made by Hatch and Slack in 1966. Test your knowledge on how these organisms concentrate carbon dioxide for photosynthesis.
