Stages of Cellular Respiration
Lumb (2016) asserted that cellular respiration is a process characterized by metabolic processes and reactions that convert food nutrients into a form of energy known as adenosine triphosphate (ATP). It is a process that occurs both in the eukaryotic and prokaryotic cells, and the reactions take place in the cytoplasm and mitochondria in the prokaryotes and eukaryotes respectively. Oxygen is an essential component in the production of ATP. In the aerobic respiration process, sugar which occurs in the form of glucose is oxidized to produce water, carbon dioxide, and ATP. The cellular respiration occurs in three distinct processes that include glycolysis, citric acid cycle, and the oxidative phosphorylation.
The process of glycolysis involves the splitting of sugars. Glucose is naturally a six carbon molecule, and during the process, it is split into two different molecules each containing three carbon sugar. The process of glycolysis occurs in the cytoplasm of the cell. Both the glucose molecules and oxygen are taken to the cell via the bloodstream. Glycolysis results in two molecules each of ATP and pyruvic acid. Also, in the process, two molecules of an electron carrying molecule known as NADH are produced. The process of glycolysis can occur in the presence or absence of oxygen. Aerobic respiration occurs in the presence of oxygen and is the first step of cellular respiration. Anaerobic respiration is also known as fermentation and occurs in the absence of oxygen leading to the production of lactic acid and small amounts of ATP. The lactic acid can accumulate in the muscles resulting in soreness. Secondly, the citric acid cycle also known as the Krebs cycle occurs when the molecules of the three carbon components of the glucose are converted to a compound known as acetyl CoA. The process occurs in the matrix of the mitochondria. Compounds reduced in this process include adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD) to produce energy that is required in the next stage. This process is oxygen dependent. The third and final stage of cellular respiration is oxidation phosphorylation and electron transport. In aerobic respiration, the electron transport requires oxygen. A series of reactions generates electrons which are passed to oxygen. The ATP is produced through a process called oxidative phosphorylation with the help of an enzyme called ATP synthase.
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Stages of Photosynthesis
Photosynthesis a process where plants capture energy from the sunlight and convert it into a chemical form which is henceforth changed chemical energy in the form of sugars and molecular compounds of different nature. Zelitch (2012) pointed out that plants do not need to depend on other organisms for food because they can make their food molecules through the use of sunlight. The process of photosynthesis occurs in several stages, and the raw materials are carbon dioxide, sunlight, substrates, and water. The products of photosynthesis include oxygen and glyceraldehyde-3-phosphate which can further be converted to sugar molecules such as glucose and sucrose. The process of photosynthesis can be divided into two broad stages include the light-dependent and the light-independent stages such as ATP, NADPH, and energy carrier molecules.
The light-dependent stage, as its name suggests, requires sunlight. The chlorophyll in the plants is responsible for absorbing energy from sunlight hence converting it into chemical energy which is in the form of nicotinamide adenine dinucleotide phosphate (NADPH) and ATP. This stage occurs in the region of the plant's cell known as the thylakoid membranes that are found in the chloroplasts. In the light-independent stage, energy used in this process emanates from the energized electrons from the light-dependent stage. The reaction in this step occurs in a cyclical nature giving its name ‘'Calvin cycle.'' The energy from the electrons is responsible for converting the carbon dioxide molecules to carbohydrates. Although the step does not require light, it is dependant on the products of the light-dependent stage.
Interaction and Interdependence
The processes of respiration and photosynthesis are interdependent and mutually beneficial. The rates of respiration increase due to substrate accumulation. The reactants and products of photosynthesis and cellular respiration are similar. The products of photosynthesis are oxygen and glucose while those of respiration are water and carbon dioxide. Photosynthesis utilizes water and carbon dioxide that is created in the process of cellular respiration to form oxygen and glucose. On the other hand, cellular respiration utilizes oxygen and glucose which result from photosynthesis to form water and carbon dioxide.
Importance and Significance of the Processes
Cellular respiration is an important process the cell uses to release energy that is used in fueling cellular activities. The energy that is stored in the form of ATP is used to steer processes that require energy such as locomotion, biosynthesis, and transport across cell membranes. Schwartz and Brown (2013) asserted that the process of photosynthesis, on the other hand, is vital in ensuring that the oxygen levels on earth remain at a stable level. The photosynthetic process also ensures that human beings are supplied with organic compounds used in building biological materials such as cotton, wool, and wood. Through this process, energy becomes available hence making life possible on earth. Photosynthesis is also a major source of energy in the fossil fuels. The cyclic interactions of both photosynthesis and respiration ensure that there is survival on earth due to the vital products and by-products released through the process. The resultant energy is vital in ensuring survival through consumption as nutrients while the gases produced are used in ensuring survivability on earth.
References
Lumb, A. B. (2016). Nunn's Applied Respiratory Physiology eBook . Elsevier Health Sciences.
Schwartz, R., & Brown, M. H. (2013). Understanding photosynthesis and cellular respiration: Encouraging a view of biological nested systems. In Multiple Representations in Biological Education (pp. 203-223). Springer Netherlands.
Zelitch, I. (Ed.). (2012). Photosynthesis, photorespiration, and plant productivity . Elsevier.
