Chapter 7 7
Sponsored Links
This presentation is the property of its rightful owner.
1 / 12

Chapter 7.7 PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

Chapter 7.7. C4 and CAM Carbon-Fixing Pathways. AP Biology Fall 2010. Gas Entry. Stomata : small pores on underside of leaves Entry and exit of gasses CO2, gas required for Calvin cycle, is not very abundant in nature. Gas Entry.

Download Presentation

Chapter 7.7

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Chapter 7 7

Chapter 7.7

C4 and CAM Carbon-Fixing Pathways

AP Biology

Fall 2010

Gas entry

Gas Entry

  • Stomata: small pores on underside of leaves

    • Entry and exit of gasses

  • CO2, gas required for Calvin cycle, is not very abundant in nature

Gas entry1

Gas Entry

  • Under hot and dry environmental conditions stomata close to reduce loss of water vapor, also results in diminished supply of CO2

  • Plants that normally live in these environments adapted different ways of initially fixing CO2 prior to it entering the Calvin cycle

  • Known as C4 and CAM pathways, takes place in cytoplasm of cell

C4 pathway

C4 Pathway

  • Designed to efficiently fix C2 at low concentrations

  • Plants that use this are known as C4 plants

  • First fix CO2 into a 4-C compound (C4) called oxalacetate

  • Occurs in cells called mesophyll cells

C4 pathway1

C4 Pathway

C4 pathway2

C4 Pathway

  • CO2 fixed to 3-C compound phosphoenolpyruvate to produce 4-C compound oxaloacetate

    • Enzyme catalyzing this reaction, PEP carboxylase, fixes CO2 very efficiently so C4 plants don’t need to have their stomata open as much

C4 pathway3

C4 Pathway

  • Oxaloacetate converted to 4-C compound malate

    • Requires reducing power of NADPH

    • Malate then exits mesophyll cells and enters chloroplasts of specialized cells called bundle sheath cells

    • Malate is decarboxylated to produce CO2, a 3-C pyruvate, and NADPH

C4 pathway4

C4 Pathway

  • Oxaloacetate converted to 4-C compound malate

    • CO2 combines with RuBP and goes through Calvin cycle

    • Pyruvate re-enters mesophyll cells, reacts with ATP, & converted back to phosphoenolpyruvate

      • Starting compound of C4 cycle

Cam pathway

CAM Pathway

  • CAM plants live in very dry conditions

  • Open stomata to fix CO2 only at night

  • Use PEP carboxylase to fix CO2, forming oxaloacetate

  • Oxaloacetate is converted to malate which is stored in cell vacuoles

  • During the day when stomata are closed, CO2 is removed from the stored malate and enters Calvin cycle

Cam pathway1

CAM Pathway



  • C3

    • Basswood, beans, peas

  • C4

    • Corn

  • CAM

    • Cactus



  • Adapted from Gary E. Kaiser


  • Login