Photosynthesis in Higher Plants - 2 - Free MCQ Practice Test with solutions,

Chlorophyll a, shows higher rate of photosynthesis. Hence, it is conclude that chlorophyll a is the chief pigment associated with photosynthesis.

The key features of plant photosynthesis were known, namely, that plants could use light energy to make carbohydrates C₆H₁₂O₆ from CO₂ and water,  Where C₆H₁₂O₆ represents glucose.

Each photosystem has all the pigments (except one molecule of chlorophyll a) forming a light harvesting system also called antennae. These pigments help to make photosynthesis more efficient by absorbing different wavelengths of light.

Phytochrome is the pigment that absorbs red light at a wavelength of 660 nm (as Pr form) and far-red light at 730 nm (as Pfr form). These absorptions play crucial roles in plant photomorphogenesis, regulating processes such as:

• Seed germination
• Flowering

Phytochrome functions by converting between active and inactive states, which is essential for the growth and development of plants.

The C₄ plants respond to higher temperatures and show higher rate of photosynthesis while C₃ plants have a much lower temperature optimum.

Joseph Priestley (1733-1804) in 1770 performed a series of experiments that revealed the essential role of air in the growth of green plants. Priestley, you may recall, discovered oxygen in1774.

The central element present in chlorophyll is magnesium, which is essential for its structure and function in photosynthesis.

This option is correct. Cyt b₆-f complexes are evenly distributed in the stroma and granal thylakoids.

Photolysis of water is mainly carried out to compensate the electrons that are transferred to photosystem I by photosystem II during the non-cyclic photophosphorylation that reduce NADP⁺ into NADPH.

Hence for every CO2 molecule entering the Calvin cycle, 3 molecules of ATP and 2 of NADPH are required. It is probably to meet this difference in number of ATP and NADPH used in the dark reaction that the cyclic phosphorylation takes place. To make one molecule of glucose 6 turns of the cycle are required.
Therefore in synthesis of one molecule of GLucose: 6 Carbon dioxide , 18 ATP  and  12 NADPH Required

In chloroplast there is the membranous system consisting of grana, the stroma lamellae, and the fluid stroma. There is a clear division of labour within the chloroplast. The granum is responsible for trapping the light energy.

• In pure state, chlorophyll b is olive-green. In pure state, chlorophyll a is blue-green.
• Chlorophyll b is an accessory photosynthetic pigment.
• Chlorophyll a is a primary photosynthetic pigment.
• Chlorophyll b absorbs more violet-blue wavelength than red wavelength of light.
• Chlorophyll a absorbs more red wavelength than violet-blue wavelength of light.
• Chlorophyll b is soluble in 92% methyl alcohol.

Excitation of electrons, transfer to another accepter, and finally down-hill to NADP⁺ causing it to be reduced to NADPH⁺ H⁺ is called the Z scheme.

Fixing of one molecule of carbon dioxide in Calvin cycle require 3 ATP and 2 NADPH₂ as the source of energy. One NADPH₂ molecule produces 3 molecules of ATP.

RuBisCO that is the most abundant enzyme in the world and is characterised by the fact that its active site can bind to both CO₂ and O₂ hence the name.

Photosynthesis takes place only in the green parts of the plants, mainly the leaves.

Living organisms have the capability of extracting energy from oxidisable substances and store this in the form of bond energy. Special substances like ATP, carry this energy in their chemical bonds.

Photosystem II's reaction centre, P₆₈₀, primarily absorbs red light at a wavelength of approximately 680 nanometres.

ATP is formed in the first part of photosynthesis, (light reaction). In the second part of the cycle, known as dark reactions (or Calvin Cycle), which happens in the stroma of the plant, ATP (and NADPH) combine with CO2 and H2O to make glucose. The energy required in the dark reaction comes from ATP (and NADPH)

• C₄ plant species have a higher temperature optimum for photosynthesis than C₃ plants due to the operation of a CO₂ concentrating system that inhibits RuBisCO oxygenase activity.
• In C₃ plants, photosynthesis is decreased at higher temperature due to increased photorespiration.

There is maximum absorption by chlorophyll a, in the red region and so there is higher rate of photosynthesis.

Correct option: B

• Stroma is the aqueous matrix inside the chloroplast that surrounds the thylakoid system; it contains the enzymes required for the light-independent (dark) reactions which fix carbon and form sugars.
• The stroma also contains ribosomes, circular chloroplast DNA and starch grains, all of which are components of the chloroplast matrix.
• Chlorophyll and the protein complexes that carry out the light-dependent reactions are located in the thylakoid membranes (grana), not dissolved in the stroma; therefore chlorophyll is not a stroma component.

Therefore, option B is correct.

• In the photosystem II (PSII) reaction center, energy from sunlight is used to extract electrons from water.
• The electrons travel through the chloroplast electron transport chain to photosystem I (PSI), which reduces NADP⁺ to NADPH.
• The electron transport chain moves protons across the thylakoid membrane into the lumen.

Quantum yield is the number of Oxygen molecules released per photon or quantum of light. During light reaction of photosynthesis oxygen molecules are release during photolysis.

• 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.