Photosynthesis in Higher Plants Test - 3

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 absorbs red of wavelength 660nm and far red of wavelength 730nm.

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 of chlorophyll contain Magnesium element.

Carotene is present in chloroplast along with chlorophyll pigment. This pigment protect the plants from photo-oxidation during photosynthesis at higher intensity of light.

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.

Synthesis of glucose molecules during photosynthesis involves the utilization of ATP molecules. In C₄ plants, 30 ATP molecules are required to fix one molecule of glucose.

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.

Separation of leaf pigments of any green plant through paper chromatography. A chromatographic separation of the leaf pigment shows that the colour that we see in leaves is not due to a single pigment but due to four pigments: Chlorophyll a (bright or blue green in the chromatogram), chlorophyll b (yellow-green), xanthophylls (yellow) and carotenoids.

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.

While PS II has a P680 reaction centre that absorbs red light at 680 nm.

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)

A. The release of H₂​ occurs in light reaction during the photolysis of water.

B. Synthesis of PGA/PGAL - occurs in dark reaction, it is a three-carbon compound which is the first stable product of the Calvin cycle.

C. Formation of ATP- occurs in light reaction.

D. The release of O2​- occurs in light reaction during photolysis of water.

Hence, the correct answer is 'Synthesis of PGA/PGAL'.

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

The dark reactions of photosynthesis is purely enzymatic and slower than the primary photochemical reaction. It takes place in stroma portion of the chloroplast and is independent of light i.e., it can occur either in presence or in absence of light provided that assimilatory power is available.

• 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.

• Photoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals.
• Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods.