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Biology of Food

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Biology-of-Food

Ideally, we should consume just about our optimum calorific requirements, which ensures that we are able to eat efficiently. However, that is not always the case, and we cannot help going back for an extra snack, especially if it is something we particularly like. When we consume above our calorific requirements in a meal or in a day, our bodies convert the excess into a form, in which it can be stored for future use, as the body abhors waste.

Following a high fructose corn syrup meal, the normal digestive process ensues. This involves the breaking down of this fructose-rich diet starting from the mouth by the enzyme amylase, a process, which continues in the stomach. By the time that chyme (the slurry of partially digested food, saliva, and stomach juices) gets into the duodenum, the pancreatic juices, which contain pancreatic amylase, work on breaking down the polysaccharides, and maltase breaks down maltose into glucose for use in the body. This glucose is absorbed from the small intestine via capillaries into the bloodstream. Not long following this surge of glucose in the blood, the pancreas secretes insulin to remove this sugar from the blood (this explains post-prandial hyperglycemia, which disappears soon afterward in healthy people) and converts this sugar into glycogen (the form, in which it is stored in muscles). Moreover, this glucose can as well be converted into fats that are high-energy reserves of the body.

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What we see as a red mass of muscle in abattoirs and restaurants is actually a band of tightly bound fibers, whose synchronized movements produce what we interpret as muscle contraction and relaxation. Skeletal muscle is made up of several muscle fibers tightly bound to form a fasciculus. The fibers are made up of myofibrils that consist of myofilaments. An examination of a myofibril will reveal several bands of varying shades. The bands include the H, Z, A, and I bands, respectively. The myofibrils basically contain actin and myosin fibrils that are inter-digitated. Myosin fibrils possess a globular head and an elongated filamentous body. These fibrils wrap around each other to give a filament, which the head sticks out from. Actins, on the other hand, are globular molecules that are joined-end and look like a string of beads. The globular heads of the myosin make contact with them. Both of these actin and myosin are held in place by protein titin.

An action potential running along the length of the muscle fibers triggers a series of biochemical reactions along with the bi-lipid layer of the membranes, resulting in the opening of Ca gates. The flood of the Ca-ions triggers the attractive forces between the globular heads of the myosin fibrils and the actin globules, causing them to slide across each other length-wise; this is the way a contraction occurs. More specifically, the muscles make use of energy in the form of ATP to power their movements. The binding of an ATP molecule causes the release of the myosin head from the actin molecule; this causes the actin to move forward. Soon afterward, the hydrolysis of the ATP causes a change in the alignment of the globular myosin head, leading the muscle to the relaxed state. With the release of calcium from the sarcomeres, the shape of the myosin changes one more, and it immediately attaches to the actin molecules again with the release of a molecule of phosphate. After the binding, ADP is released, and this causes forward motion of the myosin head; this is the contraction phase or the power stroke of the muscle fibers. This cycle repeats itself until all of the ATP is utilized. Remember that it is the binding of ATP to the myosin head that results in the relaxation of the muscle. Thus, if ATP stores are exhausted, the muscle will stay in a permanently contracted state, as is the case when a person dies of a condition known as rigor mortis.

The above process happens in a single myosin/actin fiber. A large amount of ATP is utilized in a single contraction; imagine what will happen, if millions of these same actions would occur in all the muscles of a person running a marathon. Remembering that the ATP stores are finite, eventually, if nothing but the above happens, the person will be unable to move, because the muscles will be fused in place. In conclusion, he will not get very far, especially uphill, which requires more muscular effort.

Enzymes are protein catalysts that increase the speed of transactions, therefore, the frequency of biochemical reactions in a biological system. In order for them to work effectively, enzymes need to be specific. This means that an enzyme can catalyze only a particular kind of reaction and work on only one kind of substrate. Using chemical terms, enzymes lower the activation energy threshold required for the reactions to occur but, in the end, are unchanged by the reactions themselves. Imagine the two people trying to fit a frozen turkey into a microwave grill. Their efforts are unsuccessful, until a chef (the enzyme) puts on his coat, expertly defrosts the turkey, and slides it into an Aga (the active site), then he turns it on and bakes the turkey just in time for Thanksgiving.

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In order to keep the supply of ATP from running out, the muscles have to be able to utilize the raw materials available to them to synthesize ATP for their own use. They usually do this in the presence of oxygen in a process known as glycolysis, but when there is an insufficient amount of oxygen, as is the case with exertion, they can use an anaerobic pathway. This reaction involves utilizing the stores of glucose in the muscles to synthesize ATP. The glucose is broken down to a 3-carbon sugar in a series of catalyzed steps to pyruvate with the release of ATP. It is vital to state here that the vitamin niacin is very important for this process because it plays the role of the reducing agent accepting hydrogen ions released in the process of carbohydrate breakdown. So if Rupert’s body is involved only in the reactions described so far, he would stand a better chance of getting to the top, but that might not suffice, as soon enough his oxygen supply will begin to dwindle due to exertion.

As stated earlier, pyruvate is the result of the breakdown of glucose in cells; however, it is still quite energy-rich, so in the presence of oxygen, it is broken down to acetyl- CoA, which goes into the citric acid cycle as a substrate to yield NADH, FADH, Co2, and water, releasing more energy in the process. However, in the muscle cells with depleted oxygen supply, it takes another anaerobic pathway yielding lactic acid as a product but releasing less energy than the previous aerobic pathway. In this pathway, vitamins B1 and B2 are particularly important for the oxidative phosphorylation step. ATP synthase is an enzyme that catalyzes the addition of one phosphate molecule to ADP (adenosine diphosphate). The presence of the additional phosphate group converts ADP to the energy-rich ADP. All of the above-described processes ensure that there is a steady supply of ATP for the actions of the muscles of the two cows described.

As he takes every step, the muscles use up the ATP they have stored in them, and immediately begin to breakdown glucose to build more ATP for use. However, when the stores are exhausted, as is the case with Francine, there isn’t enough oxygen to push the biochemical reactions that power muscle contractions. When there isn’t sufficient oxygen or energy in the form of ATP, the muscles are unable to relax, and movement becomes particularly difficult (fatigue). The process described above is very similar to that, which occurs in the production of wine, yogurt, or sourdough bread, in the sense that they all need the reactions that breakdown sugar, yielding various products.

When cows are moved to feed, the first result is that their energy needs drop significantly and their bodies immediately convert the excess glucose to glycogen and fat in their muscles. This makes them put on weight very quickly, because they are fed relatively high-energy meals, but perform only the most rudimentary work. The farmers benefit from this because they are in a short time able to increase the pound for pound selling price for the cattle, as their animals move from being just lean muscle to fattened market quality beef in a short time.

The switch from grass to seeds causes a proliferation of the bacteria that break down starch while reducing the bacteria that produce cellulase enzymes in the gut. With grass, they had to breakdown cellulase, which has lower starch content and absorbs the product of the breakdown of cellulose. On the other hand, with corn seeds, the starch content is much higher than that, which is available in the grass, in addition to the fact that there is no cellulose. This new reaction causes the stomach of the animal to turn a huge fermenting vat filled with the hydrogen gas and methane from the breakdown of starch; hence, the feeling that the stomach is about to burst. However, these various bacteria “share” the glucose produced by the breakdown of sugar and not all of the digested food produced by the animal is absorbed by it. The way around this particular dilemma is to administer antibiotics to the animals. They ensure that the animals do not get infected with bacteria that can grow in their gut and that more glucose is absorbed by the animal since the parasitic bacteria are dead. This makes the feeding regimen more effective, as the animals get most of the food and are mostly healthy.

One of the biggest emerging health issues in the 21st century following the discovery of antibiotics is the emergence of drug-resistant bacteria; this is of a particular significance because most drugs have some side effects, so the prescriptions provided by the doctors are with this in mind. Consequently, when someone goes to a drug store and takes some antibiotics for a slight infection, or when a patient refuses to take his/her medication as prescribed, or stops taking them when feeling some relief, that reduction of peak concentration allows the bacteria to “recover” and to develop some form of resistance to the drug. In the case of cattle, the dose of antibiotics being administered to the cattle was not a therapeutic dose, but an indiscriminate unsupervised prophylactic measure, the bacteria in the gut of the cattle slowly build up resistance to the drugs. So, if the meat that has some of these bacteria in it is improperly prepared and consumed, the resultant infection will be very hard to take care of. Because the doctors will, most probably, be trying to treat the infection with the same drug that the bacteria are used to, or better put, resistant to.

The food chain of any ecosystem has at the bottom of it those organisms, that are able to harness and utilize the energy released by the sun. Without exceptions, this place is reserved for plants, because they are photo-synthesizers. However, carnivores are unable to break down cellulose, because their digestive systems are bereft of the enzyme cellulase. So herbivores form the link between the plants and the carnivores. The transfer of energy from one trophic level to another is very inefficient, as only 10% of the energy carried from one level is transferred to the next one. Rupert, the cow, in this example eats grass. If he consumes for instance 100 grass units of energy in his lifetime, from the available 1000000 units available to him, of the 100 units that he eats, he is only able to truly utilize 10 units for growth and metabolism. He passes on just 10% units of that quantity to the farmer that raises him for food. Now assuming that a normal human needed for example 15 grass units of energy, you would theoretically have to eat the equivalent of 8 cows to meet those energy requirements for one person. Based on this analogy, it is quite easy to see, why there is a very clear need for a larger population mass of herbivores to supply the nutritional needs of carnivores and omnivores.

As earlier alluded to, the energy transfer across trophic levels is very inefficient. Humans have evolved to be the most efficient eaters on the planet, as most animals require a significant percentage of the body weight in food at one sitting, but humans are able to produce more energy from much less quantity of food. One of the most substantial arguments for vegetarianism is that the amount of energy of feed that goes to putting a single cow, or chick or hog on the table is simply not efficient and consequently non-sustainable. Humans with their highly efficient digestive systems are better equipped to make use of the plants that grow in nature.

On the basis of that alone, vegetarianism is a far better alternative from an ecological point of view. Because humans will be better consumers of plant food than the animals that eat it and are butchered for meat. This means that massively larger amounts of land would be required to sustain table animals that would be required to sustain a vegetarian society.

The hobbling of government infrastructure with regard to supervision and control of the meat industry is particularly alarming. Due to the economies of scale that have forced the companies that produce meat to coalesce into huge monopolies, it is nearly impossible for any kind of regulation to be placed on the meatpacking industry, given that most of the lawmakers have essentially been installed by the same men they will be seeking to put the reins on. Ideally, the way out of this will be to break up the monopolies that control the meatpacking industries and to strengthen the farmers by giving them incentives to improve their lot in life and set up special facilities that they specifically could have access to. Another way to fight the potential powder keg that is drug-resistant bacteria is to bring pressure to bear on the pharmaceutical companies that supply these antibiotics by raising taxes on them or creating a meat quality system that rates meat produced from concentrated feeding operations very low and by using institutions of government to blacklist such meat and increase the value of pasture grown animals. Another way is to open avenues for conversations on this subject to be initiated following thorough education of the general public on the hazards of consuming such “tainted” meat.

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