Question. (a) Give the basis of categorizing the green plants according to the first stable organic compound produced during photosynthesis. How will you place gram, maize and sugarcane under these categories? (b) Where do aerobic and anaerobic respirations occur in eukaryotic and prokaryotic cells respectively? (6)
Answers
Answer:
Ans 1. Based on the first stable organic compound produced during photosynthesis, the green plants may be catagorized into two groups:
C3 plants : C3 plants are those which fix and reduce inorganic CO2 into organic compounds using only the C3 pathway(also called Calvin Cycle or Reductive Pentose Phosphate Cycle) in photosynthesis. The C3 pathway is named so because the first stable product is 3PGA (a three -carbon compound). eg: most small seeded cereal crops such as rice (Oryza sativa), gram or chickpea (Cicer arietinum) wheat (Triticum spp.), barley (Hordeum vulgare), rye (Secale cereale), and oat (Avena sativa); soybean (Gycine max), peanut (Arachis hypogaea), cotton (Gossypium spp.), sugar beets (Beta vulgaris), tobacco (Nicotiana tabacum), spinach (Spinacea oleracea), potato (Solanum tuberosum); etc.
C4 plants : A C4 plant is a plant that cycles carbon dioxide into four-carbon sugar compounds (eg- malate, aspartate,etc) to enter into the Calvin cycle. eg- corn or maize (Zea mays), sugarcane (Saccharum officinarum), sorghum (Sorghum bicolor), and millets, as well as the switchgrass (Panicum virganum), etc.
So, in short, gram is a C3 plant while maize and sugarcane are C4 plants.
Ans 2. Aerobic respiration and anaerobic respiration in eukaryotes occurs in mitochondria and in prokaryotes occur in cytoplasm.