Respiration and Photosynthesis

“Respiration” and “Photosynthesis” All life depends on two chemical reactions “Respiration” and “Photosynthesis”. These two processes are quite crucial because they are a source to nearly all life on Earth. Both of these processes are quite similar yet differentiate vastly. In this essay I’ll be comparing and contrasting “Photosynthesis” and “Respiration”. I’ll start by discussing what actually happens in both these processes and how? Moving on to the energy transfers these processes go through and how these reactions relate to each other.

Plants feed using a process called ‘Photosynthesis’. Photosynthesis is the chemical change which happens in the leaves of green plants. It’s the first step towards making food; not just for plants but ultimately every animal on the planet. During this reaction carbondioxide and water are converted into glucose and oxygen. For this reaction to occur both carbon and nitrogen are absorbed from the roots as nitrate and so is carbon as carbondioxide from the air and it also needs energy as the reaction is endothermic, therefore the energy is ‘light’ from the sun.

This is absorbed by a green substance called chlorophyll in the leaf. Therefore, photosynthesis takes place in the chloroplasts which are present in the palisade cells (found near the top of the leaf. ) (fig: 1 ) As chloroplasts contain a green pigment called chlorophyll, which absorbs light energy needed to make photosynthesis happen. The equation for this reaction is: 6CO2 + 6H2O+ light energy ---> C6H12O6 + 6O2

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Sugars created in photosynthesis can be later converted by the plant to starch for storage, or it can be combined with other sugar molecules to form specialized carbohydrates such as cellulose, or it can be combined with other nutrients such as nitrogen, phosphorus, and sulfur, to build complex molecules such as proteins and nucleic acids. Moreover, ‘respiration’ is reversibly related to photosynthesis because it takes in light energy and respiration gives out energy, which is used by the body as the glucose is converted into starch or stored.

Oxygen is consumed unlike in photosynthesis, although in respiration energy is released in a more controlled and manageable way. During photosynthesis water and carbondioxide are chemically combined to make glucose and oxygen. The equation as follows: C6H12O6 + 6O2 ---> 6CO2 + 6H2O In addition, respiration and photosynthesis are both processes which depend on each other on a very wide scale. Fig: 2 explains this. (Fig: 2 ): Shows a cycle and how photosynthesis and respiration are dependent on each other.

As the leaf produces oxygen through photosynthesis and then that oxygen is inhaled by an animal. Later, the animal breathes out carbondioxide, and that is then absorbed by the plants through leaves by the air, in order for respiration to happen; making this ongoing cycle continue. Though photosynthesis only takes place in leaves of plants (inside palisade cells) during the presence of light, respiration takes place in every living organism inside the mitochondria of the cell, with or without light being present or not.

As all cells need energy through the sugar they made in their leaves; oxygen moves through diffusion through the plant from cell to cell. Any oxygen not used by the plant in respiration, leaves the plant through tiny holes under the leaf called stomata. That’s then part of the air we breathe, making the whole process start again. That’s how closely photosynthesis and respiration are linked to each other. Whilst, both respiration and photosynthesis are quite similar yet unlike at the same time. Respiration is a process by which energy is liberated.

On the other hand photosynthesis is a procedure where energy is stored in carbohydrate molecules as in, photosynthesis is an anabolic (constructive) process, resulting in the building up of carbohydrate molecules. While in respiration a catabolic (destructive) process occurs, resulting in the breakdown of carbohydrate molecules. So, respiration results in a loss in dry mass where photosynthesis is totally the opposite, it results in a gain in ordinary mass. Furthermore, there are enzymes involved in the process of respiration.

Enzymes are biological catalysts that speed up a reaction. The organic compounds that are broken down are substrates. Glucose is the most common substrate. The general equation for respiration is: C6H12O6 + 6O2 ---> 6CO2 + 6H2O + 38ATP During respiration, glucose undergoes glycolysis forming pyruvic acid. Glycolysis consists of nine separate chemical reactions, each catalysed by a specific enzyme. The key players in glycolysis are the enzymes ‘dehydrogenase’ and a coenzyme (a non-protein helper). So, in photosynthesis is catalysed by chlorophyll.

To summarize, photosynthesis takes the raw ingredients of water, carbondioxide and uses light to make glucose and oxygen. Despite, respiration uses glucose and oxygen to produce carbondioxide and water as waste products. Both these processes takes place in cells except respiration takes place in the mitochondria of a cell. Photosynthesis is catalysed by chlorophyll acting in concert with lipids or sugars, while in respiration ‘dehydrogenase’ is used. Nevertheless, photosynthesis and respiration both are a part of an ongoing cycle and work together in order for plants or animals to survive.

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