Question

Is there any trick to learn Cycles in Photosynthesis and Respiration?

Answer 1

This is the process of making glucose—which cells use as an energy source—from sunlight energy, water and carbon dioxide. Only plant cells can do this, and the special organelle in the plant cells that can do through this process is called a chloroplast. Photosynthesis goes through two stages.

Stage 1: light-dependent reaction (this reaction depends on the presence of light; it can’t happen in the dark):

This starts when photons from sunlight strike the leaf, excite the chlorophyll (the light absorbing pigment that drives photosynthesis) and activate electrons. During this process, water is split into oxygen and hydrogen ions. This is where the oxygen generated during photosynthesis comes from. The activated electrons then go through a series of electron carriers, also referred to as the electron transport chain, and in the process lead to the accumulation of the hydrogen ions inside the thylakoid membrane (the disc-like structures in the chloroplast that contain chlorophyll), generating a proton gradient. As the protons go down their concentration gradient through the ATP synthase, ADP and P come together to form ATP—the energy molecule. The electrons going through the electron transport chain eventually end up combining with NADP+ to form NADPH, another energy-rich molecule that will be used later.

Thus, the result of the light reaction is the production of oxygen (released from the leaves), and ATP and NADPH, which will be needed for the later steps.

Stage 2: Light-independent or dark reaction (this reaction can proceed in the absence of light, but calling it a dark reaction might be misleading as it doesn’t happen only in the dark—it can just as well happen in the light).

Answer 2

The relationship between photosynthesis and cellular respiration is such that the products of one system are the reactants of the other. Photosynthesis involves the use of energy from sunlight, water and carbon dioxide to produce glucose and oxygen. Cellular respiration uses glucose and oxygen to produce carbon dioxide and water. To emphasize this point even more, the equation for photosynthesis is the opposite of cellular respiration.

There is no particular trick to learn cycles,you have to keep practicing and daily revising what you want to learn.