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Photosynthesis and Respiration Essay


Photosynthesis is the process by which plants assemble carbon-based compounds which are the building blocks and energy stores of life. Plants first entrap sunlight energy and convert it to a chemical energy in ATP molecules which are in form of bonds. ATP brings energy to reactions where glucose is formed from water and carbon dioxide. To finish, glucose molecules are combined to form starch and other molecules. Oxygen is also produced during photosynthesis which is released in to the atmosphere (Koning, 1994, p. 1). The process of photosynthesis is summarized in the equation below;

12 H2O+6 CO→→6 O2+C6H12O6+6H2O

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Aerobic respiration is a procedure of cellular respiration that utilizes oxygen to split molecules to release electrons and form energy (Gregory, 2006, p. 2). In this process adenosine triphosphate (ATP) is produced which is liable for storing up and transporting most energy to other body cells. Aerobic respiration has two by-products which are water and carbon dioxide. It usually involves three main stages of reactions glycolysis which include the Kreb’s cycle and electron transport phosphorylation. The equation below is a summary of aerobic respiration;

C6H12O6+6O2 →→6CO2+6H2O

How the two processes are linked between plants and animals based on the reactants and products of both pathways

The two processes are the life blood of plants and animals. These processes link in the way that the by-products of one process are used as the raw materials of the other. Photosynthesis uses carbon dioxide and water from aerobic respiration to produce oxygen, food (glucose) and water. Whereas aerobic respiration in animals will require glucose and oxygen from photosynthesis to produce energy (ATP molecules) as well as carbon dioxide and water used again in photosynthesis.

A description of how energy is transferred from sunlight to ATP, from ATP to sugars, and from sugars to your cells

Sunlight is trapped by organelles called chloroplasts in the form of chlorophyll (a red and blue light) to start the process of photosynthesis. In this process molecules of carbon dioxide gas and water are combined in the presence of the solar energy and chemical energy is formed. Calvin cycle then takes place to convert ATP to sugars through carbon fixation where 6 molecules of carbon dioxide are combined with Ribulose Biphosphate to form Phosphoglycerate (PGA) (Bergman, 1999, p. 1). It is then converted into G3P (Glyceraldehyde-3-phosphate) which is a sugar. The sugars are then consumed by human beings in the form of starch.

The role of fermentation in allowing an organism to generate energy for its cell(s) in the absence of oxygen

In the deficiency of oxygen, pyruvic acid can be converted into compounds such as lactic acid through the combination of glycolysis and other additional pathways in the process of fermentation. This is important during exercise especially because breathing cannot provide the body with all the oxygen needed for aerobic respiration and the cells turn to lactic acid fermentation, therefore providing the muscles with the energy required in exercise.

How the energy from the sun ends up as chemical energy for the anaerobic organism or cell

Before fermentation occurs, one glucose molecule is split into two pyruvate molecules through glycolysis summarized as;

C6H12O6+2 ADPi+2 P+2NAD+ →2CH3COCOO + 2ATP +2NADH + 2H2O +2H+

Thereafter, fermentation can take place where sugars are converted into cellular energy producing carbon dioxide and ethanol because of the absence of oxygen as shown below (Paustian,2000, p.2);



How an enzyme catalyzes a reaction

During a reaction a substrate that requires processing is carried towards the enzymes. Enzymes accelerate reactions via lowering the free energy of activation barrier, which is the Ea barrier (Kornberg, 1989, p.198). The enzymes are substrate definite and therefore can just speed up the creation of one form of a substrate. Usually, weak hydrogen or ionic bonds join the substrate to the enzyme. Then the enzyme lessens the Ea Barrier of a reaction by appropriately adjusting the substrates, damaging substrate bonds, giving a good microenvironment for the reaction to occur in the optimum PH. temperature and I.E and participating thoroughly in the reaction.

There are three main steps of the cycle of enzyme-substrate interactions

  1. Enzyme + substrate
  2. Enzyme-substrate complex
  3. Enzyme + product

How enzyme activity regulated by the cell

Cells regulate enzyme activity through end-product inhibition. The enzyme catalyzing one of the stages in the metabolic pathway is inhibited by the end-product.

Subsequently, if the quantity of product swells, the pathway is hindered and less is formed. If the quantity reduces, the inhibition is condensed and more is manufactured.

Additionally, the gene that produces the enzyme is possibly switched on or off by courier molecules for instance hormones.

Reference list

Bergman, J. (1999). ATP: The perfect energy currency for the cell; creation research society quarterly. Web.

Gregory, M. (2006). Cellular respiration. The biology web. Web.

Kornberg, A. (1989). For the love of enzymes. Harvard University Press. Cambridge, MA.

Koning, R. E. (1994). Respiration. Plant Physiology Information Website. Web.

Paustian, T. (2000). University of Wisconsin-Madison. Web.