Protein and amino acid metabolism
Section A
How protein and amino acid metabolism play an essential part in energy metabolism and maintain the ‘amino acid pool’
Protein as well as amino acid metabolism plays an important part in the process of metabolism and maintaining the amino acid pool. Much of the body is always made up of proteins; however, these proteins take on myriad of forms. The proteins represent cell signaling receptors, signaling molecules, structural membrane, ion channels, carbon (IV) oxide as well as oxygen transporters, among others. Nevertheless, there are also proteins in bones, for instance, it is referred to as collagen, and also, the proteins are present in muscles as well as tendons. More importantly, the hemoglobin that carries oxygen and enzymes that are used to catalyze all biochemical reactions possess proteins. Proteins are used for growth and repair. The body always requires for growth and maintenance of the tissues. The proteins in the body are in a constant state of turnover. Under normal circumstances, the body breaks down the same amount of protein that is utilized in building and repairing the body. Notably, this can happen during periods of illness, during pregnancy as well as during breastfeeding. Proteins always hold the potential to serve as a metabolic fuel source. More specifically, enzymes cause biochemical reactions in the body. The structure of the enzymes grants them room for combination with other molecules inside the cell referred to as substrates, which catalyze reactions that are crucial in the process of metabolism. Compared to other sources, proteins are never stored so as they can be used for later use, therefore, the excess proteins are converted into glucose or triglycerides hence used for supplying energy or rather build the energy reserves.
Albeit, the body synthesizes proteins from amino acids, an essential source of amino acids is food. More specifically, human beings can not synthesize all the 20 amino acids that are used in building proteins. Proteins in the body are constantly synthesized as well degraded, partially draining and refilling the cellular amino acid pools. For example, in adults that are well fed, approximately 300 to 600 grams of proteins are degraded and approximately 300 to 600 grams of new protein are synthesized every day. Furthermore, in muscles, when the body is undergoing fasting process or other related stresses, the synthesis equilibrium is always shifted towards degradation hence resulting in loss of muscle mass. Therefore, the resulting amino acids are released into the blood to be converted to glucose by the liver to supply metabolic energy for essential tissues, for instance, the brain and red blood cells or supplies amino acids to tissue organs that respond to particular stress.
During the process of protein synthesis, glutamine is released from the skeletal muscle and other tissues. Notably, in the kidney the nitrogen that is transported by glutamine is released and excreted into the urine, therefore, allowing removal as ammonium ions of protons formed during fuel oxidation. Moreover, glutamine provides a fuel for the kidney. For instance, in the cells that are rapidly dividing, glutamine is applied as a fuel, as a nitrogen donor for biosynthetic reactions and as substrate for the process of protein synthesis. proteins and amino acids acts as messengers that help communication between the cells, tissues as well as organs. The proteins are made and secreted by the endocrine tissues or glands and transported in the blood to their target tissue organs where they are bound to protein receptors on the cell surface.
Some proteins are fibrous therefore; they provide cells and tissues with stiffness as well as rigidity. For example, these proteins involve keratin, collagen and elastin that help form the connective framework of certain structures in the body. More importantly, keratin is a structural protein found in the skin, hair, and nails. Collagen is the most abundant protein in the body and it is the structural protein of the bones, tendons, skin, and ligaments. the cells in the body takes up the amino acids that enters the cellular amino acid pools. Notably, the body maintains a relatively large free amino acid pool in the blood, for instance, approximately 35-65 mg/deciliter, even during fasting. In this case tissues possess continuous access to individual amino acids for process of protein synthesis and essential amino acid derivatives, like neurotransmitters. Besides, amino acid pool provides the liver with the substrates for gluconeogenesis as well as ketogenesis.
Amino acids serve as precursors of several crucial metabolites. Examples of these metabolites are pyrimidine, heme, nucleotides, and glutathione, among others. In various microorganisms, amino acid metabolism is intimately connected with that of the carbon skeleton that it uses, particularly during photorespiration. The majority of the amino acid carbon skeletons are always degraded to intermediates of the Krebs cycle just after transamination; therefore, they can increase the blood glucose levels through the gluconeogenic pathways. Nonetheless, the mixed amino acids tend to be degraded to amino acids of Krebs cycle and to acetyl-CoA, with characteristics of both glycogenic as well as ketogenic amino acids.
There are enzyme mutations that are problematic for the breakdown of an essential amino acid. An example of the mutations is translation. Due to colinearity of genes, the genes may be translocated from one site to the other hence changing the original shape of the gene. As a result, it causes problems for the breakdown of essential amino acid.
Section B
Discuss what drives glycogenesis and glycogenolysis, comparing and contrasting the post-prandial and fasting periods. (10 marks) Further expand your answer by considering diabetes mellitus and demonstrate your understanding of the effects of this disease on the control of blood glucose levels. (15 marks)
Glycogenesis takes place when the blood glucose levels are sufficiently high to allow excess glucose to be stored in the liver as well as muscle cells. More importantly, glycogenesis is stimulated by the hormone insulin. Insulin has various functions in the body, for instance, it facilitates the uptake of glucose into glucose the liver cells. Albeit, insulin possesses profound impacts on glucose metabolism in the liver cells, stimulating glycogenesis and inhibiting glycogenolysis, which is the breakdown of glycogen into glucose. During postprandial, the rate at which the glucose enters the circulation after ingestion of meal always depends on glucose release as well as the appearance into the circulation of ingested glucose. After an overnight fast, the contribution of the liver approximates close to 80 % as a result of a combination of glycogenolysis and gluconeogenesis and the 20 % that is remaining is as a result of gluconeogenesis.
Glycogenolysis is simply the breakdown of the molecule glycogen into glucose, a simple sugar that the body uses to produce energy. Presumably, glycogen is essentially energy that is stored in the form of long chain of glucose, and glycogenolysis takes place in muscle as well as the liver cells when more energy requires to be released. More specifically, glycogenolysis is maintained by hormones. The levels of blood of the hormones glucagon and insulin raise and lower glucose respectively that affects whether glycogenolysis takes place or does not take place. During fasting, healthy human beings appears to have only minimal glycogen activities. Glycogen cycling during hyperglycemic-hyperinsulinemic clamps mimicking post prandial conditions in healthy humans. Many studies reveal that healthy individual’s hyperinsulinemia as well as hypoglucagonemia can stimulate glycogen cycling. Contrary, Patients with type 2 diabetes exhibit glycogen cycling of approximately 25 % after overnight fasting. As a result, this could indicate lower glycogen stores and hence contributing to post prandial hyperglycemia.
Diabetes mellitus, commonly referred to as diabetes, is a metabolic disease that causes high blood sugar. Both glycogenesis and glycogenolysis have an impact on the body regarding the development of diabetes mellitus. Glycolysis is a simple pathway of glucose metabolism that regulates insulin secretion and metabolic functions of several cells. Diabetes mellitus affect the two processes, for instance, glycogenesis and glycogenolysis regarding this, diabetes is a chronic condition that is associated with abnormally high levels of sugar in the blood. Insulin that is released by the pancreases lowers blood glucose. The absence or insufficient production of insulin as well as inability of the body to adequately utilize insulin causes diabetes, in this case, the glycogenesis and glycogenolysis process are tampered with hence the body cells becoming weak.
Diabetes mellitus has adverse effects on the control of blood sugar levels. Nevertheless, the disease can be effectively managed if it diagnosed early. Albeit, when left untreated, it can lead to complications that may involve heart disease, stroke, kidney damage as well as damage of the nerves. High levels of blood glucose can cause gastroparesis. When it is hard for the stomach to completely empty. As a result, the delay may cause the levels of blood glucose to rise. Diabetes mellitus causes kidney damage. In this case, it affects the ability of the kidneys to filter waste product from the blood stream. When the kidneys are damaged the body will encounter problems in controlling the blood sugar levels since there is no constant exchange of products in the body.
Diabetes mellitus can also affect the skin which is the largest organ of the body that plays a bigger role in control of blood sugar levels. Along with dehydration, the lack of moisture in the body as a result of high blood sugar can cause the skin to dry and crack. Nevertheless, diabetes mellitus causes damage to the nerves in the body. This can also be referred to as diabetic neuropathy. Regarding this, it affects the perception of heat, cold and pain. Moreover, it can make one to be more susceptible to injuries since the perception to pain is reduced. Perception to cold makes the body not to sense the changes in the temperature hence there will be less control of blood sugar levels in the body. Diabetes mellitus affects the circulatory system. Concerning this, it raises the risk of developing high blood pressure which puts strain on the heart. When an individual has high blood glucose levels, it can contribute to the formation of fatty deposits in blood vessels walls. After sometime, it can result in restricted blood flow as well as increase the risk of arteriosclerosis.