Case Study Question #1
Timothy M. Murphy
Dr. Bosak
I have decided to choose the case study subject on the three main energy processes/cycles
that the human body uses to make ATP. The body uses nutrients that are turned in energy and
burned. ATP (Adenosine triphosphate) is the main unit used to have energy in the body. The
three-energy process/cycles are Glycolysis, Krebs Cycle, and Oxidative Phosphorylation. These
processes have many different steps to be taken before turning into energy. The body is like a
well-oiled machine and needs the proper fuel to keep in up and running (Powers and Howley,
2018).
ATP was discovered back in the late 1920s and was found as a way to help muscle
contraction. To the scientist research, they found out that ATP revolved around consumption and
production of the cell membrane. The concept of ATP is very complex since there are many
reactions happening in the cells. ATP is classified as a nucleoside triphosphate with the following
substance are in the nitrogenous base, the sugar ribose, and the triphosphates.
The first process is Glycolysis, this is a six-carbon molecule that turns into two three-
carbon keto acids or also known as pyruvate molecule. This is an anaerobic pathway used to
transfer bond energy from glucose to ATP. When broken down to pyruvate molecules it takes two
different phases the first is the energy investment phase and the second one is the energy
generation phase. Anaerobic glycolysis is universal in all cell types but may cause different
outcomes in the body. When a person is working out, they are intaking oxygen helping pyruvic
acid and then is converted in lactic acid in the muscles. This show how the body is breaking
down the muscles and building them right back up.
The second process is the Krebs cycle or the citric acid cycle. This process happens when
the cells generate energy during aerobic respiration. sing up oxygen and producing carbon
dioxide and water as waste products, and ADP is converted to energy-rich ATP. This is one of the
most complexed cycles the body goes through. The process starts off with Acetyl-CoA and
Oxaloacetate to make Citrate then goes in Isocitrate by the process aconitase, from that we get
Alpha- ketoglutarate by the process Isocitrate dehydrogenase, this cause NAD+ to be reduced to
NADH and causing the carbon dioxide (CO2) to be generated. The next part of the cycle is
Succinyl CoA by the process of Alpha-ketoglutarate dehydrogenase, causes another NAD+ to be
reduced to NADH and releasing another carbon dioxide (CO2). The next process is Succinate by
the process Succinyl CoA synthetase, cause a GTP molecule. Next is Fumarate by the process of
Succinate dehydrogenase, the part of the cycle is Malate by the process of Fumarase. Malate is
converted into Oxaloacetate by the Malate dehydrogenase causing NAD+ to be reduced to
NADH (Pelley, 2007). This process is done twice since glucose has two molecule compounds
then goes through the Electron Transport Chain causing it to become into ATP.
The third is Oxidative Phosphorylation or Electron Transport Chain which ATP is formed
as a result of the transfer of electrons from NADH or FADH2 to O2 by a series of electron
carriers to generate energy. This process takes place in the mitochondrial. This is the main source
of energy in the aerobic pathway. ATP Synthase helps transport hydrogen ions into the matrix of
the mitochondria since hydrogen ions cannot cross in the electrochemical gradient. There are
four different complexes in the chain the first is the NADH Dehydrogenase Complex which
removes hydrogen from NADH. Its main purpose is to receive electrons from NADH and
transport it more into the electron transport chain. The second complex is called the Succinate
Dehydrogenase Complex. This process removes hydrogen from succinate and oxidizes into
fumarate. This second complex is also a part of the Krebs Cycle. The complex is the Cytochrome
Reductase or also known as Q-Cytochrome C Oxidoreductase. This complex contains three
Cytochrome which are C, C1, and B. The main job this complex has is to accept electrons from
the Electron Transport Chain to Cytochrome C than from there it’ll go to the fourth complex.
The final complex in this stage is called Cytochrome C Oxidase. This complex contains Heme
and Copper units to help oxidize Cytochrome C to help reduce oxygen to water (Kahwaji, 2018).
Fatty acids are molecules with chains of lipid-carboxylic, this is found fats and in oils in
the cell membrane as a fundamental part of phospholipids and glycolipids. Fatty acid comes
from multiple food sources that intake into our bodies. Free fatty acids are the by-product of the
metabolism of fats in the adipose tissue. This tissue is used to store the energy in the form of fat
and help insulate the body and give it a cushion. Fatty acids are the preferred fuel for the human
body since it gives more energy to metabolism. The main source of glucose that is body received
comes from the liver.
Carbohydrates are a large group of organic compounds that happen in foods and in the
tissue, we have in our body. Carbohydrates are one of the main resources that give the body
energy or calories to burn during your daily life. The three sources that are in our body is sugars,
starch, and cellulose. There are four chemical groups of carbohydrates, they are
monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Carbohydrates
producing sugar with taking longer to get into the bloodstream, and once there and depending on
how active you are as a person the sugar in the blood will turn into energy to help the body.
When the body tries to metabolize fats and carbohydrates it tends to acclimate to the
source the body most frequently receives. The pathways required to store or actually use
carbohydrates has a specific enzyme from the metabolism used to breakdown fats. The other
factor is insulin clearly stops the use of fats for energy by hindering the release of glucagon.
Glucagon is a hormone that increases blood sugar and will battle with insulin. Since this constant
battle is ongoing between fats and carbohydrates, fats will only be used with there is no insulin.
Work Cited:
Powers, S. K., & Howley, T. (2018). Exercise physiology: Theory and application to fitness and
performance (10th ed.). New York, NY: McGraw-Hill.
Glycolysis. (2015). Retrieved from https://www.khanacademy.org/science/biology/cellular-
respiration-and-fermentation/glycolysis/a/glycolysis
Pelley, J. W. (2007). Citric Acid Cycle, Electron Transport Chain, and Oxidative
Phosphorylation. Elseviers Integrated Biochemistry,55-63. doi:10.1016/b978-0-323-03410-
4.50013-4
Ahmad M, Kahwaji CI. Biochemistry, Electron Transport Chain. [Updated 2018 Oct 27]. In:
StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from:
https://www.ncbi.nlm.nih.gov/books/NBK526105/
Murphy
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