C3 vs C4 Photosynthesis Mechanisms
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Questions and Answers

What is the primary function of transporters for HCO3- in the inner membrane of cyanobacteria?

  • To facilitate the efflux of harmful substances
  • To help regulate oxygen levels in the cell
  • To assist in the synthesis of chlorophyll
  • To bring inorganic carbon into the cell (correct)
  • What structural feature do carboxysomes possess?

  • An icosahedral protein shell that resists CO2 efflux (correct)
  • A bilayer membrane for selective permeability
  • A cylindrical protein shell for gas exchange
  • A vesicular structure for lipid storage
  • Which enzyme is packed into carboxysomes for carbon fixation?

  • Phosphofructokinase
  • PEP carboxylase
  • Rubisco (correct)
  • Fructose-1,6-bisphosphatase
  • What type of transporters do thylakoids have to assist in carbon processing?

    <p>CO2 transporters</p> Signup and view all the answers

    Why are bicarbonate transporters considered for improving leaf photosynthesis in C3 crops?

    <p>They improve the uptake of inorganic carbon</p> Signup and view all the answers

    What is the primary function of pyrenoids in cyanobacteria?

    <p>Site of Rubisco organization</p> Signup and view all the answers

    Which of the following structures is found interspersed within pyrenoids?

    <p>Thylakoid membranes</p> Signup and view all the answers

    What was revealed by the in situ cryo-electron tomography study of Chlamydomonas chloroplasts?

    <p>The native architecture of chloroplasts</p> Signup and view all the answers

    Which process is influenced by light modulating the electron flow in cyanobacteria?

    <p>Carbon fixation machinery organization</p> Signup and view all the answers

    What specific enzyme is crucial for the carbon fixation process in the chloroplasts of cyanobacteria?

    <p>Rubisco</p> Signup and view all the answers

    What temperature range primarily favors C3 plants over C4 plants?

    <p>Between 10°C and 35°C</p> Signup and view all the answers

    Why has C4 photosynthesis not evolved universally in all plants?

    <p>The conditions favoring C4 plants are not present everywhere.</p> Signup and view all the answers

    What is a key disadvantage of C4 photosynthesis compared to C3 photosynthesis?

    <p>C4 photosynthesis requires more energy.</p> Signup and view all the answers

    At which temperature does photorespiration significantly increase for plants?

    <p>Above 35°C</p> Signup and view all the answers

    Which of the following scenarios would most benefit C4 plants?

    <p>Development in high temperature areas with abundant light.</p> Signup and view all the answers

    What structures do C4 plants use to concentrate CO2?

    <p>Carboxysomes</p> Signup and view all the answers

    Which compound is primarily involved in the carboxylation reaction in C4 plants?

    <p>Phosphoenolpyruvate</p> Signup and view all the answers

    In algae, where is CO2 concentrated?

    <p>Pyrenoids</p> Signup and view all the answers

    What is the role of carbonic anhydrase in CO2 concentration mechanisms?

    <p>Converts HCO3- to CO2</p> Signup and view all the answers

    What protein is primarily involved in the Calvin-Benson cycle?

    <p>Rubisco</p> Signup and view all the answers

    Which of the following best describes pyrenoids in algae?

    <p>Protein structures that concentrate CO2</p> Signup and view all the answers

    What type of organisms use carboxysomes for CO2 concentration?

    <p>Cyanobacteria</p> Signup and view all the answers

    What is the significance of using phosphoenolpyruvate in C4 plants?

    <p>It initiates the fixation of CO2</p> Signup and view all the answers

    Which of the following is NOT a function of carboxysomes?

    <p>Storing C4 acids</p> Signup and view all the answers

    What is the primary purpose of concentrating CO2 in C4 plants?

    <p>To increase the efficiency of photosynthesis</p> Signup and view all the answers

    What is a primary characteristic of C4 plants in relation to CO2 assimilation?

    <p>They are more efficient at CO2 assimilation in dry, hot, sunny regions.</p> Signup and view all the answers

    What is the role of glycine decarboxylase (GDC) in the photorespiratory pathway?

    <p>It decarboxylates glycine in the mitochondria of bundle sheath cells.</p> Signup and view all the answers

    What is a potential strategy for engineering more efficient C3 plants?

    <p>Raise CO2 levels at Rubisco through HCO3- transporters.</p> Signup and view all the answers

    What is the significance of centripetal microanatomy in C4 plants?

    <p>It facilitates the reassimilation of CO2 in bundle sheath cells.</p> Signup and view all the answers

    Which of the following is a common challenge that C3 plants face compared to C4 plants?

    <p>They are less efficient in warm temperatures.</p> Signup and view all the answers

    What adaptation do C4 plants have that helps them perform better in warm climates?

    <p>They utilize PEP carboxylase for initial CO2 fixation.</p> Signup and view all the answers

    What is a potential consequence of introducing carboxysomes into C3 crops?

    <p>Enhanced carbon fixation at lower light intensities.</p> Signup and view all the answers

    What is the primary function of HCO3- transporters in the context of improving C3 plants?

    <p>They facilitate the transport of bicarbonate, improving CO2 availability.</p> Signup and view all the answers

    Study Notes

    ### Carbon Concentration Mechanisms

    • Cyanobacteria use carboxysomes to concentrate CO2, these are icosahedral structures with a protein shell containing Rubisco
    • C4 plants use PEP carboxylase for the primary carboxylation reaction, to concentrate CO2 upstream of Rubisco
    • Many algae concentrate CO2 in pyrenoids within their chloroplasts
    • Pyrenoids are highly packaged Rubisco, interspersed with thylakoid membranes

    C3 vs C4 Photosynthesis

    • C3 plants have an advantage at cool temperatures
    • C4 plants have an advantage at high temperatures
    • C4 plants require more energy than C3 plants
    • More CO2 is available for C4 plants at high temperatures
    • C4 plants have an advantage in full sunlight

    ### C3-C4 Intermediates

    • C2 photosynthesis is a C3-C4 intermediate
    • Photorespiratory glycine is transferred from mesophyll to bundle sheath cells, functioning as a two-celled photorespiratory CO2 pump
    • Glycine decarboxylase only occurs in the mitochondria of bundle sheath cells
    • Centripetal microanatomy facilitates reassimilation of CO2

    ### Engineering C3 Plants

    • Potential strategies to engineer C3 plants
    • Introduce HCO3- transporters, pyrenoids and carboxysomes to raise CO2 concentration at Rubisco
    • Increase Rubisco selectivity
    • Introduce synthetic or alternative carbon-fixation pathways
    • Engineer more efficient photorespiration pathways

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    Lecture 10 C4 Metabolism PDF

    Description

    Explore the distinct carbon concentration mechanisms in C3 and C4 plants through this quiz. Learn about the role of structures like carboxysomes and pyrenoids, as well as the advantages and energy demands of each photosynthetic pathway. Test your knowledge on how these mechanisms adapt to different environments.

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