(City, State)
Introduction
A balanced diet refers to the food intake, which incorporates all the dietary needs of an organism in the right proportions. This is unlike the adequate diet, which includes the energy that is sufficient energy for the need of an individual. A balanced diet, therefore, includes both sufficient energy as well as all the dietary requirements that are needed by an individual at the right proportion. The main components that make up a balanced diet include carbohydrate, proteins, vitamins, fats, dietary fiber, water and minerals. Carbohydrates as a source of nutrients in the body are usually broken down through the digestive system to produce glucose that is then absorbed in the blood. The glucose is then metabolized to form energy that is used in the processes such as active transport, cell division, biochemical macromolecule synthesis and in the contraction of muscles. There are different types of carbohydrate disaccharides, monosaccharide, oligosaccharides, and some polysaccharides. Proteins are usually referred to as the building blocks and are very important in the growth as well as in the repair and maintenance of body tissues. The fats are either saturated or unsaturated fats and are very essential in the maintenance of a healthy body. The products of fat, fatty acid and glycerol are used in the body in the synthesis of cell membranes and steroid hormones (Ivy, 2013)
Sugar
Sugar is the general term that refers to a class of the compounds that are chemically-related and are sweet-flavored and are in most cases used as food. The basic structure of the sugar molecule is composed of hydrogen, carbon, and oxygen. Sugars are divided into either simple or complex sugars. Simple sugars are referred to as monosaccharide such as glucose, galactose and fructose. The complex sugars include the disaccharides such as sucrose, maltose, lactose and the polysaccharides such as starch (Kimball, 2011).
Processing of Sugar in Cellular Level
The intake of sugar in the body results in the digestion of sugar into simple sugars such as glucose, fructose and galactose. The major fuel source for the body is mainly the glucose. Glucose is absorbed in the small intestine into the blood. The glucose is then transported throughout the parts of the body in blood. In case the reserves for the cellular energy are low, the glucose molecule is degraded through a pathway to form energy (McKee & McKee, 2008). A pathway through which, a small amount of energy is produced through the conversion of glucose into two pyruvate molecules is called glycolysis. The process is an ancient pathway and is found almost in all organisms. In the process of converting glucose into pyruvate, NADPH, which is an essential cellular reducing agent, is also released.
The glycolysis process takes place in two main parts resulting in the splitting of each glucose molecule converting it into two three-carbon molecules, pyruvate. During the glycolysis process, there is oxidation of several carbon atoms with a small amount of energy being captured and stored temporarily in ATP and NADH molecules. The total reactions in the two main parts that are involved in a glycolysis pathway are ten. The first part involves the double phosphorylation of the glucose molecule followed by a cleavage process in order to form two glyceraldehyde-3-phosphate (G-3-P) molecules. The two phosphorylation processes use up two molecules of ATP acting as an investment as this stage is the one that creates the actual substrate necessary for the oxidation process in a form that is held in the cells.
The second part of glycolysis involves the conversion of glyceraldehyde-3-phosphate to make the pyruvate molecules. In this part, there are four ATP and two molecules of NADH that are produced. Since there were two ATP molecules that were utilized in the first stage, the net ATP produced per one molecule of glucose is two. The whole glycolysis process can be summarized in the equation below
D-Glucose+2 ADP+2 Pi→2 NAD++2 pyruvate+2 ATP
The first step in glycolysis is the synthesis of glucose-6-phosphate. The entry of glucose, as well as the other sugar molecules in the cell, is immediately followed by the phosphorylation process. The phosphorylation ensures that the glucose molecule is not transported from the cell and at the same time increases the reactivity of oxygen in the phosphate ester that results. There are several enzymes known as hexokinases, and are involved in catalyzing the hexose phosphorylation in all cells, in the body.
The second step of glycolysis is the conversion of the molecule of glucose-6-phosphate produced in the first step into fructose-6-phosphate. The process involves the conversion of the aldose glucose-6-phosphate into an open chain of fructose-6-phosphate which is a ketone. The process is catalyzed by phosphoglucose isomerase (PGI) in a reaction that is readily reversible. The third step is the phosphorylation process of fructose-6-phosphate using an enzyme called phosphofructokinase-1 (PFK-1). The reaction is irreversible and leads to the formation of fructose-1, 6-bisphosphate.
The fourth step is the cleavage of the molecule of fructose-1, 6-bisphosphate which marks the end of the first part of glycolysis. The molecule is cleaved to form two three-carbon molecules which are glyceraldehyde-3-phosphate (G-3-P) as well as dihydroxyacetone phosphate (DHAP). The reaction is an aldol cleavage, which makes the enzyme that catalyzes the process to be referred as aldolase.
The fifth step of glycolysis and the first step for the second part of glycolysis is the interconversion of both molecules produced in the first part, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. However, it is only the G-3-P that is used as a substrate in the following reaction of glycolysis. The triose phosphate isomerase is useful in the conversion of DHAP to G-3-P, and this helps prevent the other three-carbon unit from being lost.
The sixth reaction is the glyceraldehyde-3-phosphate oxidation as well as phosphorylation to produce glycerate-1, 3-bisphosphate. The glycerate-1, 3-biphosphate is a product that has a high-energy phosphoanhydride bond that may be useful in the generation of ATP. The seventh step of glycolysis involves the transfer of phosphoryl group and the synthesis of ATP as the phosphoglycerate kinase enzyme is catalyzing the transfer of the high-energy phosphoryl group to ADP from glycerate-1, 3-bisphosphate forming glycerate-3-phosphate.
The process of interconverting the 3-phosphoglycerate and 2-phosphoglycerate is the eighth step in glycolysis. The glycerate-3-phosphate molecule has a potential in the transfer of phosphoryl group. The cells are able to convert the glycerate-3-phosphate forming phosphoenolpyruvate (PEP). PEP possesses a phosphoryl group that has high transfer potential. Phosphoglycerate mutase is the enzyme that plays a part in catalyzing the interconversion reaction. The ninth reaction is the dehydration of the 2-phosphoglycerate produced using the enzyme enolase. The process produces phosphoenolpyruvate which is acted upon by the pyruvate kinase in the tenth reaction producing pyruvate. The pyruvate kinase enables the transfer of a phosphoryl group from the reactant PEP and adds it to the ADP forming pyruvate and ATP.
Figure 1: Glycolysis process
At the end of glycolysis, one molecule of glucose ends up with a production of two molecules of ATP and two molecules of NADH. The final product, pyruvate is still a molecule that is rich in energy and can provide a substantial amount of energy in the form of ATP if taken for further metabolism. The ability to metabolize pyruvate further is dependent on the type of cell and the oxygen availability. When the oxygen is available, pyruvate is converted into acetyl-CoA, which is the molecule that enters the next stage of metabolism, the citric acid cycle.
The citric acid cycle is an amphibolic pathway capable of oxidizing the two acetyl carbons completely leading to the formation of carbon dioxide molecule and the reduced molecules FADH2 and NADH. The amphibolic nature of the citric acid cycle enables it to do both anabolic as well as catabolic processes.
Figure 2: The citric acid cycle
The reduced molecules FADH2 and NADH are then taken to the electron transport system, which is a series of reactions of reduction and oxidation and are involved in the transfer of the electrons contained in the reduced molecules to the molecule of oxygen forming water. The released during the process of electron transfer is usually coupled to a mechanism that produces ATP molecules. From the total oxidation process of one molecule of a glucose molecule forming carbon dioxide and the oxidation of all the coenzymes, there is the production of 31 molecules of ATP.
Figure 3: Electron transport chain
Effects of High Sugar in the Diet
When a meal that is excess in sugars the sugar is digested, and after absorption it is taken to the liver where glucose is converted to the storage form called glycogen. The storage of the glycogen takes place both in the skeletal muscles and liver cells. In the muscles, glycogen acts as the ready energy store to be used in muscle contraction. In the liver, the stored glycogen can be reconverted to form glucose that can then be used in the case of fasting to provide as well as sustain the required energy. When the excess glucose that is in the body is more than the amount needed to produce the maximum amount of glycogen, the extra glucose is usually converted to form fat. The production of fat uses fatty acids and glycerol molecules both of which can be produced using the breakdown of glucose. The fatty acids are made from a compound known as acetyl CoA, which is converted to malonly coA using the enzyme acetyl coA carboxylase. This is the starting step in the production of fatty acid.
Excess glucose may also be used in the production of nucleic acids and nucleotides as well as other monosaccharide molecules. This is through the conversion of glucose-6-phosphate, which is the product for the first step of glycolysis to form ribose-5-phosphate, the substrate for the formation of the monosaccharide and other molecules.
Effects of Low Sugar in the Diet
When the sugar consumed is less than the body needs, there is a breakdown of glycogen that had been stored in the liver to produce glucose that is then taken to the cells in the body through the blood. In case the stored glycogen is not enough, additional glucose is then synthesis from non-carbohydrate precursors through a process that is referred to as gluconeogenesis. Additional source of energy may come from fat deposits in the adipose tissues. This is the main source of energy during starvation. The use of fat as a source of energy results in the increased amount of ketone bodies both in the blood and urine. Under such conditions, there is a decreased level of malonyl CoA. The fatty acid molecules get into the mitochondria where they are degraded to form acetyl-coA.
Good and Bad Sugars
Sugar may be classified as either good sugars or bad sugars. The good sugars are mainly found in whole foods such as vegetables and fruits. This is because the sugar is bundled with other components such as fluid, vitamins, fiber, minerals as well as antioxidants. For instance, a single cup of cherries of chopped carrot contains only 6 grams and a cup of cherries has about 17 grams of sugar. At the same time, they contain a lot of good components. On the other hand, the bad sugars are the refined sugars that are contained in products such as sodas, baked products, and candy among others. The table sugar is also classified as a bad sugar (Sass, 2013).
How Genetic Makeup affects the way Body Reacts to Sugar
The way the body responds to sugar is dependent of the availability of insulin in the blood. Diabetes, which is the disease condition whose cause is related to sugar, is mainly classified into Type 1 and Type 2 diabetes. The type 1 diabetes is usually caused by the lack of insulin that results from the damage of insulin releasing cells in the pancreas. There is a factor of hereditary in the development of Type 1 diabetes. The genes that are involved in carrying the instructions for the production of the human leukocyte antigens HLAs are the ones that are linked to an increased risk of the development of type 1 diabetes. It is the proteins that are produced by HLA genes that help in the determination of whether the immune system will be able to recognize a cell as self are as a foreign material. There are some HLA gene variants combinations that predict whether a person will have a higher risk of developing type 1 diabetes than others (NIH, 2011).
For the type 2 diabetes, there are different factors that result into the condition such as resistance to insulin. This prevents the normal utilization of insulin by muscle, fat and liver cells. The disease develops when the body is no longer capable of making the needed insulin compensate for the ineffective ability to use insulin by the body cells. There is a big role that is played by genetic makeup of an individual in determining the susceptibility of developing type 2 diabetes. The presence of certain genes or even a combination of genes may enhance or reduce the risk of an individual developing. Studies have indicated the variation of TCF7L2 gene to have a way of increasing the susceptibility to suffer from type 2 diabetes (Grant, et al., 2009).
An Experiment That Shows the Amount of Sugar that is Needed Per Day
An experiment that shows the amount of sugar that is needed per day according to gender and age can be done by calculating 10% of the daily calories that are needed in a day. This value gives the amount of sugar that is needed for each individual. The amount of calories that is needed per day is calculated by multiplying the basal metabolic rate (BMR) of an individual by the appropriate activity factor. This factor varies depending with the activeness of an individual. Those who are sedentary active, the activity factor is 1.200, for those who are lightly active the activity factor is 1.375, for those who are moderately active the factor is 1.550 and those who are very active and extra active have an activity factor of 1.725 and 1.900 respectively. To determine the BMR, the following formulas are used for the male and female.
The male BMR is calculated as follows
BMR = 10×weight + 6.25×height - 5×age + 5
The female BMR is calculated as follows
BMR = 10×weight + 6.25×height - 5×age – 161
Where the measurements of weight are in kilograms, age measurements are in years, and those of height are in centimeters (Zamora, 2013). Different people at different age are selected males and females and their weight, height as well as age are recorded. The measurements are then used to calculate the BMR for each individual. Assuming all of them are moderately active, the active factor of 1.550 is then used to determine the calories needed per day. The 10% of this value is then used to determine the amount of sugar that is needed by the different people per day. If people who are of the equal weight and height at different ages were used, the following can be the data from the experiment.
Drawing a chart of sugar needs for the two genders at different ages is as shown below
Figure 4: A graph of Sugar needs against age
The sugar needs increase as age increases while the female need less sugar per day than male.
Reference List
Grant, R. W., Moore, A. F. & Florez, J. C., 2009. Genetic architecture of type 2 diabetes: recent progress and clinical implications. Diabetes Care, 32(6), p. 1107–1114.
Ivy, R., 2013. What is a Balanced Diet ?. [Online] Available at: http://www.ivy-rose.co.uk/HumanBiology/Nutrition/What-is-a-Balanced-Diet.php[Accessed 10 May 2013].
Kimball, J. W., 2011. Carbohydrates. [Online] Available at: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Carbohydrates.html[Accessed 10 May 2013].
McKee, T. & McKee, J. R., 2008. Biochemistry: the Molecular Basis of Life. Oxford: Oxford University Press.
NIH, 2011. Causes of Diabetes. [Online] Available at: http://diabetes.niddk.nih.gov/dm/pubs/causes/[Accessed 10 May 2013].
Sass, C., 2013. Good Sugar Vs. Bad Sugar: Become More Sugar Savvy. [Online] Available at: http://www.shape.com/latest-news-trends/good-sugar-vs-bad-sugar-become-more-sugar-savvy[Accessed 10 May 2013].
Zamora, A., 2013. Calorie Restriction Calculator. [Online] Available at: http://www.scientificpsychic.com/health/cron1.html[Accessed 10 May 2013].
