Photosynthesis in Plants

Photolysishappens in the thylakoids, producing H+ ions inside the thylakoid membrane., a gradient of hydrogen ions will form across the membrane, ATP synthase take the advantage of this gradient, by allowing hydrogen ions to leak out of the membrane capturing their energy and phosphorylating ADP into ATP, while another statement is correct for mitochondria.

NADH and FADH$ _{2}$ transfer their electrons to molecules near the beginning of the transport chain. As electrons are passed down the chain, they move from a higher to a lower energy level, releasing energy. Some of the energy is used to pump H$^{+}$ ions, moving them out of the matrix and into the intermembrane space. The energy released in these reactions is captured as a proton gradient, which is then used to make ATP in a process called chemiosmosis. Together, the electron transport chain and chemiosmosis make up oxidative phosphorylation. 

The Hill reaction is defined as the photoreduction of an electron acceptor by the hydrogens of water, with the evolution of oxygen. In vivo, or in the organism the final electron acceptor is NADP⁺. We can measure the rate of the Hill reaction in isolated chloroplasts. first demonstrated by Robert Hill in 1939, in which illuminated chloroplasts evolve oxygen when incubated in the presence of an artificial electron acceptor (e.g. Ferricyanide). The reaction is a property of photosystem II. 

During photosynthesis, carbon dioxide is fixed to form carbohydrate by the dark reaction. The water molecules are broken down during the light reaction and release oxygen. Thus, the two process helps to maintain the balance of oxygen and carbon dioxide in the atmosphere.

The rate of photosynthesis would be maximum at the equator because the the rate of photosynthesis depends on the light intensity. Maximum intensity of light occurs at the equator, and gradually decreases with increasing distance from the equator to the south and north poles. So the correct answer is 'Equator'.

Transpiration is the process of loss of water, in vapour form, through stomata. The process depends on the turgidity of guard cell. An increase in turgidity of guard cells opens stomatal pore, whereas a decrease in turgidity of guard cells closes stomatal pore. The change in turgidity of guard cells is brought about by reversible influx and efflux of potassium ions.

(A) Hexokinase is the enzyme catalysing the production of fructose from glucose.

Plants have photoreceptors, which are proteins that are specially designed to perceive light and signal certain biological effects in the plant. There are two types of photoreceptor proteins in plants - Phytochromes and Blue light receptors. Phytochromes absorb red light and far red light and help the plants to sense seasonal changes in night length, or photoperiod, thereby controlling the opening and closing of stomata.

Chlorophyll is the pigment responsible for photosynthesis. The light active in photosynthesis is a small part in the visible spectrum (400- 700 nm). The chlorophyll pigments mainly absorb blue and red light. Maximum absorption is in blue light but maximum photosynthesis occurs in red light.

Photosynthetically active radiation, often abbreviated PAR, designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. Sunlight comprises all effective lights PAR (photosynthetically active radiations) as required for photosynthesis. Thus, option A is correct.

• Around 50% of the total radiation from sunlight falls under photosynthetically active radiation and supports the process of photosynthesis. It constitutes the light of 400-700 nm wavelength which is absorbed by chlorophyll pigment. Out of which only 2 - 10% are captured by plants. Thus, the correct answer is option B.

Photosynthesis is the process by which light energy is converted to chemical energy. In plants, light is absorbed by pigments such as chlorophyll. Light hits these molecules and raises them to a higher energy. Light, however, occurs in a spectrum of wavelengths ranging from ultraviolet to visible light to infrared. The energy accompanying the absorption of light is dependent on the wavelength of the light. The amount of energy absorbed during the processes of photosynthesis depends on the wavelength of light absorbed. For processes requiring more energy, pigment molecules must be able to absorb the necessary wavelengths. 680 nm wavelength is absorbed maximum for photosynthesis because, 680 nm will be utilized by both the pigment systems.