1. A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.
  2. In __ this increases __ and greatly lowers the efficiency of __.
    • C3 plants
    • photorespiration
    • photosynthesis
  3. __ and __ are adaptations that capture carbon dioxide and then transport it to the chloroplasts or store it for later use – eliminating __.
    • C4 photosynthesis
    • CAM photosynthesis
    • photorespiration
  4. A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle.
    C4 plants
  5. A plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. Carbon dioxide entering open stomata during the night is converted into organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed.
    CAM plant
  6. __ plants are found throughout the world and are very well adapted to temperate conditions. Most of the trees and flowers that are familiar to you are these.
  7. __ is found primarily in tropical and sub–tropical grasses but is also found in some shrubs and eudicot herbaceous plants. There are a few important __ agricultural plants such as corn, sugarcane, sorghum, and millet.
    • C4 photosynthesis
    • C4
  8. __ photosynthesis is found primarily in succulents, but not all succulents use __. It is found in such diverse plant groups as cacti, orchids, and ferns. The important agricultural __ plants are pineapple and Agave.
    Crassulacean Acid Metabolism (CAM) x3
  9. The primary difference between C3 photosynthesis and the C4 and CAM photosynthetic pathways is in __.
    the process of carbon dioxide fixation
  10. In ___, carbon dioxide is captured by the Rubisco enzyme and added to RuBP inside the chloroplast. This produces 3–PGA, a three–carbon compound that gives the __ process its name.
    • C3 photosynthesis
    • C3
  11. In __ + __, carbon dioxide is fixed in the cytoplasm of the mesophyll cells, not inside the chloroplasts.
    Carbon dioxide enters these cells by diffusion from the stoma.
    C4 and CAM photosynthesis
  12. C4 plants have a special carbon acceptor molecule, __. ___, a highly efficient enzyme, reacts with carbon dioxide and PEP to produce __, a four–carbon compound that gives C4 photosynthesis its name.
    The __ quickly is converted into __ or __ acid (both of which are also 4–carbon molecules).
    • phosphoenolpyruvate (PEP). PEP carboxylase
    • oxaloacetate x2
    • aspartic
    • malic
  13. You will notice that __ uses an ATP molecule to fix the carbon dioxide. This energy expense is compensated by the reduction of __ in conditions limiting the availability of carbon dioxide.
    This use of ATP in the C4 process makes the C4 pathway more efficient in conditions with little photorespiration.
    • C4 photosynthesis
    • photorespiration
  14. The four–carbon molecules enter chloroplasts where the carbon dioxide will be released to be used in the __.
    Calvin cycle.
  15. Both the __ and the __ are the same in all types of photosynthesis. The enzyme __ fixes carbon dioxide within the chloroplast.
    • light reactions
    • Calvin cycle
    • Rubisco
  16. Ribulose carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP, or ribulose bisphosphate).
  17. An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated.
    concentration gradient
  18. As opposed to C3photosynthesis, __ and __ first fix carbon dioxide into four–carbon compounds in the cytoplasm of the mesophyll cells.
    C4 photosynthesis and CAM photosynthesis
  19. Lowering the concentration of carbon dioxide inside the leaf by fixing it into four–carbon molecules creates a steeper __, which increases the diffusion of carbon dioxide into the plant from the atmosphere. This permits C4 plants to have smaller openings at their __, thus reducing water loss.
    • concentration gradient
    • guard cells
  20. While both C4 and CAM plants fix carbon dioxide into four–carbon compounds,__ plants have important anatomical adaptations not found in the __plants.
    • C4
    • CAM
  21. In C3 plants and CAM plants, chloroplasts are scattered throughout the
    __ with large numbers found in the long uppermost cells called palisade cells.
  22. In __ plants, the chloroplasts are concentrated in the vascular bundle sheath cells. The four–carbon molecules produced in the mesophyll cells are transported to the chloroplasts in these cells, where they are broken down to release carbon dioxide.
  23. Actively transporting carbon dioxide into these chloroplasts raises the concentration of carbon dioxide inside the chloroplasts and eliminates losses to __.
    This process also speeds the entrance of carbon dioxide into the leaf, allowing the ___ to open less and reducing water loss.
    • photorespiration
    • stomata
  24. __plants do not have the anatomical adaptations of _ plants. In fact, their anatomy is comparable to __plants.
    • CAM
    • C4
    • C3
  25. The __ is to fix carbon dioxide at different times rather than in different locations. In __ plants the stomata are closed during the day.
    • CAM adaptation
    • CAM
  26. How do CAM plants obtain carbon dioxide if they keep their stomata closed?
    They open their stomata at night to allow carbon dioxide to enter the plant.
  27. By only opening the stomata at night, when evaporation is the lowest and relative humidity is the highest, __ is the most water-efficient of the types of photosynthesis.
    CAM metabolism
  28. Once inside the plant, the carbon dioxide must be stored for later use. __ plants fix carbon dioxide into four–carbon molecules, just like __ plants. These four–carbon molecules, such as __, are stored in the vacuoles of the cell while the guard cells are open at night.
    • CAM
    • C4
    • malic acid
  29. In __, nnce the sun rises, the guard cells close the stomata, and no more carbon dioxide will enter or leave the plant.
    During the day, the stored four–carbon molecules will be broken down to release carbon dioxide to be used in photosynthesis.
  30. The primary difference between C3 , C4 , and CAM photosynthesis is in the __.
    carbon fixation (initial fixation of carbon dioxide.)
  31. The __ pathway is the most energy efficient form of photosynthesis. But losses to __in warm, dry conditions reduce its efficiency. __ plants have the advantage in these conditions even though they spend more ATP per molecule of carbon dioxide.
    • C3
    • photorespiration
    • C4
  32. __ plants have anatomical adaptations that concentrate chloroplasts in cells into which 4–carbon carbon dioxide carriers are actively transported. This increases the flow of carbon dioxide into the leaf, allowing __ plants to have smaller stomata openings. This, in turn, decreases water loss.
    C4 x2
  33. __ plants adapt to harsh conditions by storing carbon dioxide in organic acids during the night and releasing it during the day.
    The __ pathway is the slowest and most inefficient in converting the sun's energy into glucose. However, it is the most water-efficient of the three types of photosynthesis. Thus it is most often found in desert plants.
    CAM x2
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