CBSE Class 11 Biology Worksheet Set 02 Solved

1. Which part of the mitochondria is the Electron Transport system of aerobic organisms located?

2. Why is respiratory pathway termed as Amphibolic pathway? 

3. During Photosynthesis which substrate is the hydrogen donor, and gets oxidized to O₂? 

4. In which two regions of light spectrum, maximum absorption of Chlorophyll a take place? 

5. What is Glycolysis? Where does it take place and what are the two monosaccharides that enter this pathway?

6. Give the equation of oxidative decarboxylation of Pyruvate after the glycolysis? 

7. State following two differences , between C ₃ and C ₄ plants:
(i) First stable compound and
(ii) CO₂ acceptor.

8. What is Photorespiration? Why it does not occur in C₄ plants? 

9. How does PS II get a supply of electrons continuously? Explain and write the equation. 

10. Explain the C ₄ pathway. 

11. Explain the Citric Acid cycle.

VALUE POINTS 

1. It is in the inner mitochondrial membrane space. 

2. Though Respiratory pathway is mainly a catabolic pathway, but it also involves anabolic pathway where respiratory intermediates are synthesized from fatty acids, glycerol or amino acids.

3. Water 

4. Blue and Red 

5. Glycolysis is the stepped process in which 6 C Glucose breaks into two molecules of 3C Pyruvic acid. It takes place in the cytoplasm and the two monosaccharides are Glucose and Fructose.

6. Pyruvic Acid +CoA+NAD⁺  Mg⁺² Pyruvate dehydrogenase   Acetyl Co A + CO₂ + NADH + H⁺

                                                  → 

Acetyl Co A
CO₂ 
NADH₂
Pyruvate
Dehydrogenase

7. In C3 plants the first stable compound is Phoshoglyceric acid(PGA) but in C4 plants it is Oxalo acetic acid(OAA) .
In C3 plants the Co₂ acceptor is RuBP in mesophyll cells In C4 plants it is Phosphoenol pyruvate(PEP) in mesophyll cells and RuBP in bundle sheath cells.

8. RuBisCo is the most abundant enzyme and is characterized by the fact that its active site can bind to both CO₂ &O _2. It has greater affinity for CO₂ . In C3 plants RubisCo binds to O₂ and reduces CO ₂ fixation. In C4 plants it does not occur as they have a mechanism to increase the concentration of CO ₂ at the enzyme site.

9. Splitting of water is associated with the PSII ,water splits into H+ , O and electrons .This creates oxygen and electrons that were removed from PSI get replaced.
2H₂O  →  4 H ⁺ + O₂ + 4 e^-

10. The primary CO₂ acceptor is Phosphoenol Pyruvate that is present in mesophyll cells of C4 plants. Phosphoenol Pyruvate carboxylase is helps to convert it into a 4C molecule Oxalo acetic acid.It then forms malic or aspartic acid in mesophyll cells and it is then transported to bundle sheath cells.In these bundle sheath cells these acids are broken to a 3C molecule and and CO₂ is released. The CO₂ released enters the C3 cycle as bundle sheath cells have RuBisCO.This 3 C molecule is transported back to mesophyll cells and converted to PEP again.

11. TCA cycle or Citric acid cycle begins with condensation of Acetyl CoA and Oxalo Acetic acid catalysed by citrate synthase forming Citric Acid. Citrate is the isomerised to Isocitrate.
Then decarboxylation leads to formation of α ketoglutaric acid releasing one NADH ₂ and CO₂ and then Succinyl Co A. is formed again releasing NADH ₂ and CO₂ This is then converts to Succinic acid and a molecule of GTP is formed. The succinic acid is then converted to Malic acid releasing FADH ₂ and finally back to Oxaloacetic acid .

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