PP-01 Fill-in-the-Blank Exercises

Section A — Light Reactions

1. The reaction centre of PS I is _______ (absorbs at _______ nm), and PS II is _______ (absorbs at _______ nm). [P700, 700, P680, 680]

2. The Hill reaction equation: $2H_{2}O$ → _______ + _______ + _______ [4$H^{+}$, 4$e^{-}$, $O_{2}$]

3. In the Z-scheme, the order of electron carriers from PS II to PS I is: PQ → _______ → _______ [Cyt b6f, Plastocyanin (PC)]

4. Cyclic photophosphorylation involves only _______ and produces only _______. It occurs in _______. [PS I, ATP, stroma lamellae]

5. ATP synthesis in chloroplasts is driven by the flow of _______ from the _______ to the _______ through _______. [protons/$H^{+}$, thylakoid lumen, stroma, $CF_{0}$-$CF_{1}$ ATP synthase]

Section B — Calvin Cycle

6. The three stages of the Calvin cycle are: _______, _______, _______. Mnemonic: _______. [Carboxylation, Reduction, Regeneration, CRR/Cars Race Rapidly]

7. RuBisCO fixes C$O_{2}$ to _______ (5C) producing _______ (3C) as the first stable product. [RuBP, 3-PGA]

8. One glucose requires _______ turns of the Calvin cycle, _______ ATP, and _______ NADPH. [6, 18, 12]

9. In the regeneration stage, _______ G3P molecules are used to regenerate _______ RuBP, consuming _______ ATP. [10, 6, 6 (total per cycle)]

Section C — C3/C4/CAM

10. In C4 plants, initial C$O_{2}$ fixation occurs in _______ cells by _______ enzyme, forming _______ (4C). [mesophyll, PEP carboxylase, OAA/oxaloacetate]

11. The anatomical feature unique to C4 plants is _______ anatomy, characterised by large _______ cells. [Kranz, bundle sheath]

12. CAM plants fix C$O_{2}$ _______ via PEP carboxylase and run the Calvin cycle _______. Stomata are open _______ and closed _______. [at night, during the day, at night, during the day]

13. Photorespiration is caused by _______ activity of RuBisCO, producing _______ instead of 3-PGA. [oxygenase, phosphoglycolate]

14. Blackman's law: the rate of photosynthesis is limited by the factor present in _______. [minimum/least amount]