Similar to the way the world is powered by money, our bodies depend on energy.
In the same way, as money is represented by euros, yen or dollars, energy is represented by a “currency” molecule called ATP in our bodies. One can think of this chemical compound like a rechargeable battery. It is charged through processes by machines in the cell such as mitochondria and chloroplasts, or even by bacterial cells themselves. Similar to charged batteries, ATP can discharge the stored energy for certain cellular processes when needed. The production of ATP requires a molecule called Adenosine diphosphate (ADP), a chemical group called a phosphate group (Pi), a membrane embedded protein called ATP synthase, and a proton gradient across the membrane.
Membranes are a type of barrier which separates the inside of a cell from the external environment. The protons in a proton gradient across a membrane is similar to water accumulating behind a dam. If this dam had a floodgate that would open when the accumulated water level is too high, the water would flow from a higher level to a lower level. The energy from this natural movement of water can be harnessed and stored for later use. The floodgate equivalent for membranes is the FOF1-ATP synthase (ATP synthase).
This protein is composed of two domains- specific parts of the protein that each have their own function. One domain called the FO complex is considered hydrophobic or “water-hating” and is comparable to a door within the membrane. The other domain called the F1.complex is hydrophilic, or “water-loving” and exists inside the cell (or mitochondrial matrix). The FO complex consists of 3 different subunits named a, b, and c, which together, make a rotating motor. On the other hand, the F1 complex consists of 5 different subunits named after greek letters (Alpha, Beta, Gamma, Delta and Epsilon).
Like the energy stored in the built up water behind the dam, there is potential energy called an electrochemical gradient across membranes due to a high concentration of protons on one side compared to the other. The free potential energy from this gradient is harnessed by the enzyme ATP synthase to synthesize ATP as protons move across the membrane through the ‘floodgate’. Each proton powers the FO motor as it enters a partial channel open only to the area of higher proton concentration. The free energy is used to rotate this motor which rotates the ? subunit of F1 complex known as the shaft. The shaft is connected to the ? subunits which responds to the rotation of the shaft.
A full 360 degree rotation of the FO complex and shaft results in changes in the shape of the active sites – the site of ATP production – of the catalytic ? subunits. This change in shape allows for the binding of ADP and Pi to the subunit where they react to form ATP. Overall, the energy from the electrochemical gradient is harnessed and stored in the bond between ADP and Pi. The rotational mechanism was proven by a lab experiment where researchers physically connected the shafts of the F1 complexes to one of the three ? subunits through a special bond called the disulfide bond. The other two ? subunits were then tagged with a special chemical so that they can easily be detected and distinguished from the third subunit. The disulfide bond was temporarily broken while the complex was placed in presence of a proton gradient, ADP, and Pi which promotes ATP synthesis. After exposure to these conditions and the production of ATP, the disulfide bond was reformed. If there was a lack of rotation in the complex, the bond would re-form with the original ? subunit but the results of the experiment however, showed that many of the shafts formed a disulfide bond with the tagged subunits as well.
This is indicative of rotation occurring in the complex and helped us in a step towards understanding exactly how energy is stored in our bodies. 2. a) Medium-chain acyl-CoA dehydrogenase (MCAD) sounds very complicated, but simply put, it is a biological machine – called an enzyme – inside the baby’s body that breaks down certain fats into a molecule called acetyl-CoA. This breakdown of the molecule (also called oxidation) is vital to the baby because fatty acids must be broken down to be used as energy. The body needs energy for many reasons. For example, energy is required to keep the heart beating, to keeps the lungs breathing, and to circulate blood throughout the body.
If this enzyme does not work, the fats cannot be converted to energy, leading to devastating health consequences. The cause of this abnormality of the enzyme is genetic. There is an issue with the gene coding for the medium-chain acyl-CoA dehydrogenase enzyme in the DNA.
Genes are like a formula book which details how to make a certain protein. If there is a problem with the gene, it will likely lead to a problem with the protein. Proteins are responsible for most bodily processes and structures, like transporting oxygen in the blood, and repairing our bodies after damage. In our case, the protein that breaks down fats to use as energy is affected.b) An unaffected individual without MCADD is capableIn of storing unused energy as fat that can be used when needed. Since the baby has MCADD and cannot break down stored fats into energy, he needs to consume the energy he is going to use right before it gets converted into fats. Therefore, he needs to consume carbohydrates (wheats, grains) and other sources of energy like protein before he engages in energy consuming activities. If he doesn’t feed for a long time, the body will convert the sugars into fat, but cannot convert the fat into a source of energy.
The baby will experience something called hypoglycemia (low blood sugar). Symptoms of hypoglycemia are shakiness, dizziness, and cold skin. If untreated, MCADD can even lead to a coma, seizure or death. c) In genetics, they call a disorder like this autosomal-recessive. The fact that it is recessive is good news to the parents since it means that the disorder has to come from both the mother and the father to be expressed. Every person has two copies of any single gene.
For example, there are two copies of the gene that is responsible for making MCAD in each parent. Two recessive genes are required in a person for that recessive gene to be expressed. To use an analogy, a dominant gene is like the sun and recessive genes are like the stars.
If the sun is in the sky the stars cannot be seen even though they are there. Likewise, when a dominant gene is present the recessive genes are all hidden. However, if there is no sun but rather two stars, the stars would be seen. Similarly, the existence of two recessive MCADD genes would display the disorder. Since we already know that the mother and father don’t have the disorder, but have the gene abnormality that is not expressed (Ie. they are carriers), geneticists can calculate that the probability of their next baby having MCADD is 25%. A popular analogy involves the sun and the stars in the sky. The sun can be comparable to a dominant gene and the stars can be comparable to a recessive gene.
During the time the sun is out, none of the stars can be seen. This does not, however mean that the stars are not there. In a similar way, recessive genes that are still existent within the genome cannot be expressed in the presence of dominant genes.3. The process our group used to determine the answers for the given questions was to prepare individual ideas on our own and worked as a team to brainstorm ideas to come up with a final answer. Using this method, we were able to bring multiple ideas and viewpoints for each topic and were able come up with the answer as a group.
The process was different than what we expected as the first scientific article was a lot more complicated than our expectations and we had the most difficulty in being able to translate the scientific language into words that everyone can understand. By working as a team on this assignment, we learned that having multiple viewpoints when trying to solve a problem is far more efficient than trying to work on it individually. We have also learned that when trying to understand complex scientific topics, it is much easier if we form study groups and work together. Additionally, we have learned that for future group assignments, it is more time efficient to work together in person rather than online.