MCQ on Photosynthesis in Higher Plants    

MCQ on Photosynthesis MCQ on Photosynthesis MCQ on Photosynthesis

1. If a chemical process is affected by more than one factors then its rate will be determined by
a) Two closely related factor
b) Only one factor, which is close to its minimal value
c) Only one factor, which is close to its maximum value
d) Only one factor, which is close to its appropriate value

2. I. Temperature
II. CO_2 concentration
III. Chlorophyll arrangement
IV. Water
◼Among the given factors, identify the external factors that affects the rate of photosynthesis and correct option accordingly
a) I, II and IV      
b) I, II and III      
c) II, III and IV    
d) I, III and IV

3. Which activity is performed by PS-I in light reaction
a) Reduction of NADPH 
b) Reduction of NADP⁺
c) Oxidation of NADP⁺
d) Oxidation of NAD

4. C_4 pathway for CO₂-fixation was proposed by
a) Benson and associates             
b) Arnon and associates
c) Rouhani et al.,              
d) Hatch et al.,

5. A scientist disrupted the chloroplast and separated the stroma from lamella. For fixing CO₂ he supplied stroma with
I. ATP
II. NADPH
III. Glucose
◼Select the correct option
a) I and III           
b) III and II          
c) I and II      
d) I, II and III

6. CAM helps the plants in
a) Secondary growth     
b) Disease resistance     
c) Reproduction
d) Conserving water

7. PEP is present in
a) Mesophyll cell             
b) Bundle sheath cell     
c) Meristematic cell        
d) Both (a) and (b)

8. The absorption spectrum of chlorophyll
a) Show that some colours of light are absorbed more than the other
b) Approximates the action spectrum of photosynthesis
c) Explains why chlorophyll is a green pigmen
d) Has all the above properties

9. PGA as the first carbon dioxide fixation product was discovered in photosynthesis o
a) Bryophyte     
b) Gymnosperm              
c) Angiosperm  
d) Alga

10. In C_3-plants, the first stable compound formed after carbon dioxide fixation is
a) Phosphoglyceraldehyde
b) Malic acid
c) Oxaloacetic acid
d) 3-phosphoglycerate

11. Which chemical compound/molecule supplies electrons continuously to PS-II?
a) CO₂
b) O₂ 
c) H₂ O              
d) NADPH

12. Colour that we see in leaves is due to the presence of
I. Chlorophyll-a 
II. Chlorophyll-b
III. Xanthophyll   
IV. Carotenoid

a) I and II
b) I, III and IV     
c) II, III and IV    
d) I, II, III and IV

13. Quantasomes occur on the surface of
a) Cristae            
b) Plasmalemma             
c) Nuclear envelope      
d) Thylakoids

14. First carbon dioxide acceptor in C_4- plants is
a) PEP  
b) PGA 
c) RuBP
d) Pyruvic acid

15. In Calvin cycle, if one molecule of RuBP is carboxylated then how many PGA molecule will be formed?
a) 2        
b) 3       
c) 4        
d) 5

16. The type of carbon dioxide fixation seen in many succulent plant species is

a) C_4-pathway
b) C_2-pathway
c) CAM-pathway             
d) C_3-pathway

17. Water stress causes the stomata to …A… hence reducing the …B… availability.
Here A and B refer to
a) A-open; B-H₂ O        
b) A-close; B-H₂ O        
c) A-close; B-CO₂          
d) A-open; B-CO₂

18. Photosynthesis cannot continue for long if during light reaction, only cyclic photophosphorylation takes place. This is because
a) Only ATP is formed, NADPH⁺+H⁺ is not formed
b) Photosystem-I stops getting excited at a wavelength of light beyond 680 nm
c) There is unidirectional cyclic movement of the electrons          
d) There is no evolution of oxygen

19. Light reaction of photosynthesis occurs inside
a) Stroma           
b) Grana
c) Endoplasmic reticulum
d) Cytoplasm

20. Bundle sheath cells are rich in which enzyme
a) PEP carboxylase          
b) Malate dehydrogenase
c) Phosphofructokinase
d) RuBisC

Hints and Explanation

1. (b)

Only on factor, which is close to the minimal value. Law of limiting factor was proposed by F. F. Blackman. (1905). It stated that when a process is conditioned as to its rapidly by number of separate factors, the rate of the process is limited by the pace of the slowest factor (i.e., the factor present in minimum amount)

2. (a)

The external factors would include the availability of sunlight, temperature, CO₂ concentration and water. As a plant photosynthesizes, all these factors will simultaneously affect its rate. Hence, through several factors interact and simultaneously affect photosynthesis or CO₂ fixation, usually one factor is the major cause or is the one that limits the rate. Hence, at any point the rate will be determined by the factor available at sub-optimal levels

3. (b)

Reduce NADP⁺

Light reaction begins with the PS-II. In photosystem-II the reaction center chlorophyll-a absorb 680 nm. wavelength of red light causing electrons to become excited and jump into orbit further from the nucleus. These electrons are picked up  by an electron acceptor, which passes them to an electron system consisting of cytochromes. The movement of electrons in ETS of photosynthesis is down hill in terms of oxidation reduction or redox potential scale. The electrons are not used up as they pass through the electron transport chain, but they passed on the pigments of photosystem I. Simultaneously, electrons in the reaction center of PS-I are also excited, when they receive red light of wavelength 700 nm and are transferred to another acceptor molecule that has greater redox potential. These electrons than are moved down hill again this time to a molecule of energy rich NADP⁺. The addition of these electrons reduces the NADP⁺ to NADPH+H⁺

4. (d)
The detailed study of -cycle was introduced by M D Hatch and C R Slack (1966).

5. (c)
In stroma, the fixing of CO₂ takes place by expanding NADPH₂ and ATP formed by light reaction. So, scientist should have supplied NADPH₂ and ATP to intact stroma for CO₂ fixation

6. (d)
CAM plants are mostly succulent xerophytes. The stomata in these plants remain closed during the day. They help to check the transpiration. In this way, water is conserved

7. (a)
PEP (Phospho-enol pyruvate) present in mesophyll cell

8. (d)
Absorption spectrum of chlorophyll explain the green colour of chlorophyll. It is approximate to action spectrum of photosynthesis and the rate is different at different colour.

9. (d)
 The use of radioactive ¹⁴C by Melvin Calvin in algal (Chlorella) photosynthesis studies led to the discovery that the first carbon dioxide fixation product was a 3-carbon organic acid. The first product identified was 3-phosphoglyceric acid (PGA).

10. (d)
The first step or Calvin Cycle or C_3-pathway is Carboxylation in which a 5 C sugar RuBP acts as carbon dioxide acceptor in the presence of enzyme RUBISCO and produces 6C unstable compound. This unstable 6C compound splits into molecules of 3-phosphoglyceric acid (3C-compound), which is the first stable product of this pathway.

11. (c)

H₂O
Electron excited by PS-I used in the formation of NADPH+H⁺. These electrons come ultimately from H₂O through photosynthesis

12. (d)

A chromatographic separation of the leaf pigment shows that the colour that we see in leaves is not due to the single pigment but due to four pigments. They are Chlorophyll-a (bright or blue green in chromatogram)
Chlorophyll-b (yellow green)
Xanthophyll (yellow
Carotenoids (yellow to yellow orange)

13. (d)

Quantasomes are present on inner membrane of thylakoids. Each quantasome have 230 molecules of chlorophyll.

14 (a)

In C₄-plants, leaf shows Kranz anatomy. In these plants, the carbon dioxide first accepted in the mesophyll cells by PEP (phosphoenol pyruvate) and form a four carbon compound oxaloacetic acid.

15. (a)

16. (c)

CAM-pathway (Crassulacean Acid Metabolism) is a mechanism of photosynthesis involving double fixation of carbon dioxide, which occurs in succulents belonging to Crassulaceae, cacti, euphorbias and some other plants of dry habitats where the stomata remain closed during the daytime and open only at night.

17. (c)

A-Close, B-CO₂. Water stress causes the stomata to close hence, reducing the CO₂ availability

18. (a)

Assimilatory power, i.e., ATP and NADPH₂ should produced during light reaction of photosynthesis

19. (b)

Grana are the stacks of thylakoids which contain photosynthetic pigments. Therefore, grana are the sites of light reaction.

20. (d)

In bundle sheath cell C₃-cycle performed. So, these cells have high number of RuBisCo as compared to other cells