Biology Questions and Answers – Higher Plants Photosynthesis – C4 Pathways

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This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Higher Plants Photosynthesis – C4 Pathways”.

1. Which of these is not a characteristic of C4 plants?
a) Toleration of higher temperatures
b) Response to high light intensities
c) Greater productivity of biomass
d) Photorespiration
View Answer

Answer: d
Explanation: C4 plants show some special adaptations to survive extreme climate, such as tolerance of higher temperatures, response to high intensity lights, lack of photorespiration and greater productivity of biomass.
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2. What is the special leaf anatomy in C4 plants known as?
a) Mesophyll anatomy
b) Vascular anatomy
c) Kranz anatomy
d) Calvin anatomy
View Answer

Answer: c
Explanation: C4 plants have a special type of anatomy of the leaves. This is known as Kranz anatomy. It is characterized by the presence of large cells around the vascular bundles known as bundle sheath cells.

3. What is the arrangement of cells in plants showing Kranz anatomy?
a) Tapered
b) Irregular
c) Wreath
d) Triangular
View Answer

Answer: c
Explanation: C4 plants have a special type of anatomy of the leaves. This is known as Kranz anatomy. It is characterized by the presence of large cells around the vascular bundles in the form of a wreath.
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4. Which of the following is false regarding the bundle sheaths of plants showing Kranz anatomy?
a) They lack chloroplasts
b) They are layered around the vascular bundles
c) They have thick walls
d) They lack intercellular spaces
View Answer

Answer: a
Explanation: In plants showing Kranz anatomy, the bundle sheaths surrounding the vascular bundles have characteristics such as thick walls, a large number of chloroplasts and no intercellular spaces. They are layered around the vascular bundles.

5. Which of these is a C4 plant?
a) Wheat
b) Maize
c) Rice
d) Cotton
View Answer

Answer: b
Explanation: C4 plants have a special type of anatomy of the leaves. This is known as Kranz anatomy, characterized by the presence of large cells around the vascular bundles. Wheat, rice and cotton are C3 plants.
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6. Which of these features cannot help us differentiate between C3 and C4 plants?
a) Presence of Kranz anatomy
b) Presence of photorespiration
c) Presence of chloroplasts
d) Presence of bundle sheath
View Answer

Answer: c
Explanation: C4 plants show Kranz anatomy in which bundle sheath cells surrounds the vascular bundles. They lack photorespiration and show presence of bundle sheaths. However, chloroplasts are present in both types of plants.

7. Which of these is the primary carbon dioxide acceptor in the Hatch and Slack pathway?
a) PEP
b) PGA
c) OAA
d) PEPcase
View Answer

Answer: a
Explanation: The primary carbon dioxide acceptor in the Hatch and Slack pathway is PEP or phosphoenol pyruvate. PEP is present in the mesophyll cells. Phosphoenol pyruvate is a 3-carbon molecule.
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8. Which of these are not present in mesophyll cells?
a) OAA
b) PEP carboxylase
c) PEPcase
d) RuBisCO
View Answer

Answer: d
Explanation: The mesophyll cells contain PEP or phosphoenol pyruvate, which is the primary carbon dioxide acceptor. It also contains the enzyme PEPcase or PEP carboxylase. However, it lacks RuBisCO.

9. Which of these is the C4 acid?
a) PEP
b) PGA
c) OAA
d) RuBisCO
View Answer

Answer: c
Explanation: The C4 acid has 4 carbon atoms. It is oxaloacetic acid or OAA. It is the first stable product of carbon dioxide fixation in C4 plants. PGA is a 3-carbon organic acid while PEP also has 3 carbon atoms.
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10. Plants adapted to dry tropical regions use the C4 pathway. True or false?
a) True
b) False
View Answer

Answer: a
Explanation: Plants using the C4 pathway have special adaptations which help them survive extreme climatic conditions. Some such adaptations are toleration of high temperatures, response to high light intensities and lack of photorespiration.

11. Which of these is not a 4-carbon compound?
a) Aspartic acid
b) OAA
c) Malic acid
d) PGA
View Answer

Answer: d
Explanation: Oxaloacetic acid or OAA is the first stable product of carbon dioxide fixation in C4 plants. OAA, along with malic acid and aspartic acid are 4-carbon compounds. However, PGA is a 3-carbon compound.

12. Which enzyme is a major component of the bundle sheath cells?
a) PEPcase
b) PEP
c) RuBisCO
d) PEP carboxylase
View Answer

Answer: c
Explanation: PEP or phosphoenol pyruvate is not an enzyme. PEPcase, also known as PEP carboxylase is not present in bundle sheath cells. However, bundle sheath cells are rich in the enzyme RuBisCO.

13. Which of these is common to C3 and C4 plants?
a) OAA
b) PGA
c) Calvin cycle
d) Photorespiration
View Answer

Answer: c
Explanation: In C3 plants, the first stable product of carbon dioxide fixation is 3-PGA or 3-phosphoglyceric acid. For C4 plants, it is OAA or oxaloacetic acid. C4 plants lack photorespiration. The Calvin cycle is common to both.

14. In which of these cells does the Calvin pathway occur in C3 plants?
a) Mesophyll cells
b) Bundle sheath cells
c) Epidermal cells
d) Sieve cells
View Answer

Answer: a
Explanation: The Calvin pathway occurs in C3 plants in the mesophyll cells. In such plants, the first stable product of carbon dioxide fixation is 3-PGA or 3-phosphoglyceric acid. In C4 plants, the Calvin cycle occurs in bundle sheath cells.

15. In which of these cells does the Calvin pathway occur in C4 plants?
a) Mesophyll cells
b) Bundle sheath cells
c) Epidermal cells
d) Sieve cells
View Answer

Answer: b
Explanation: The Calvin pathway occurs in C4 plants in the bundle sheath cells. The bundle sheath cells are a characteristic of C4 plants. They surround the vascular bundles in layers. It is the site of Calvin cycle.

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