How the Structures of Starch, Glycogen, and Cellulose Enable Them to Perform Their Function - Essay Example

- Describe how the structures of starch, glycogen and cellulose enable them to perform their biological function . Different organisms use monosaccharides, such as glucose, to build several different polymers or polysaccharides: starch, glycogen, and cellulose. Each of them molecules is synthesized by dehydration synthesis, but there are subtle differences in the covalent bonds that lead to different overall structures and functions. Starch is used for long term energy storage only in plants. Starch molecules are helical and may be either branched or unbranched. Animals hydrolyze this polymer to obtain glucose. Glycogen has the same kind of bond between monomers as starch , but it is highly branched. Glycogen also is used for long term energy energy storage, but only animals. Animals can hydrolyze this polymer to obtain glucose. Starch and glycogen have many hydrogen and oxygen rich functional groups which make them reactive with water, during the hydration and condensation processes which created and store energy within the body. Cellulose has a different king of bond between monomers, forming linear polymers that are cross-linked by hydrogen bonds with other linear chains. Cellulose is the principal structural molecule in the cell walls of plants and algae. Animals cannot hydrolyze this polymer to obtain glucose without the help of intestinal bacteria, it is referred to as fiber. Lugol's Test for Starch: Lugol's reagent (I2KI) changes from a yellowish-brown to blue-black in the presence of starch. Monosaccharides and disaccharides do not react with Lugol's reagent. - Relate the behaviour of reducing sugars to their structural characteristics. Another characteristic of monosaccharides is that they can act as mild reducing agents. This is because the aldehydo group that is present can be oxidized to form a carboxylic acid group, or in the presence of a base, a carboxylate ion group. Fructose can also act as a reducing sugar, even though it has a ketone group instead of an aldehyde group. Under basic conditions, the fructose molecules can, essentially, have the location of the carbonyl bond switched to convert them into a glucose molecule. This occurs in a number of steps involving removing hydrogens from the #1-C and its oxygen and moving them to the #2-C and its oxygen. Glucose is heated with Benedict's reagent (CuSO4, NaOH, and tartaric acid) to form a brick red precipitate. Sucrose does not react under these conditions. Fructose does form a red precipitate with Benedict's reagent. Carbohydrates that contain aldehydes or a-hydroxymethyl ketones can be oxidized by Cu(II) ion and are classified as reducing sugars. They reduce the Cu(II) ion to Cu(I). - Relate the behaviour of the amino acids / proteins under test to their structural characteristics. Biuret Test for Proteins: Biuret reagent is a light blue solution which turns purple when mixed with a solution containing protein. The purple color is formed when copper ions in the biuret reagent react with the peptide bonds of the polypeptide chains to form a complex. Because amino acids contain a free amino group, they are readily detected with ninhydrin reagent which reacts with free amino groups to form a purple or violet colored substance. Ninhydrin reagent can also be used to detect proteins, but the proteins must be heated or digested to hydrolyze the protein into free amino acids. - Relate the behaviour of the lipids under test to their structural characteristics. In lipids carbon and hydrogen predominate because there is very little oxygen which makes them more of less hydrophobic. Diverse types of lipids have different roles including energy storage and structural and metabolic functions. Fats are polymers of fatty acids (usually three) and one glycerol molecule, formed by dehydration reactions, and are called triglycerides or triacylglycerided. Fats are tremendous sources of energy and can store approximately 2 times better than polysaccharides. Saturated fatty acids have no double bonds between carbons, and are therefore saturated with hydrogen. The molecular backbones are flexible and tends to ball up into tight globules. Saturated fats, such as butter and lard, are solid at room temperature. Unsaturated fats may include several double bonds between carbons. This causes the molecules to be less flexible, and they do not pack into solid globules. Unsaturated fats, such as olive oil and corn oil, are liquid at room temperature. Sudan red is a lipid soluble dye. When Sudan red is added to a mixture of lipids and water, the dye will move into the lipid layer coloring it red - Describe the 3D structure of enzymes and explain how their structure enables them to carry out their catalytic function. Enzymes are large proteins molecules that function as biological catalysts. A catalyst is a chemical that speeds up the reaction without itself being consumed. Enzymes are made from several to more than a thousand amino acids long and the specific sequence determines the function. An enzyme has many levels of organization and have primary, secondary, tertiary, and quaternary structure. Each enzyme has an active site which awaits for a substrate to bind. One binding has occurred the enzyme is able to induce a fit, locking in the substrate. At the end of the reaction, the substrate changed into the product and is released and the enzyme is unchanged. - Identify and explain the factors that affect the rates of enzymatic reactions. There are several factors which affect the rates of enzymatic reactions. These factors include temperature, pH, salt concentration, and cofactors (which often compete with the substrate for the active site binding). As well as the availability of substrate and product. If these factors are to high or to low, enzyme activities decrease. Therefore these factors must be at an optimal level for enzymes to function most efficiently. - Explain how the rates of enzymatic reactions are affected by changes in temperature and how you would use information you have gathered in this experiment to help you decide on the best temperature for washing white cotton clothes. Enzyme activity can be increased or decreased by the increase or decrease of temperature. Enzymes within the body work best at normal body temperatures which is the reason that a fever can be so harmful to the human body. The best temperature for washing white clothes is the temperature at which enzyme activity was highest and this temperature is --------------. - Discuss the factors that need to be considered in order to retain an enzyme's optical activity. - Discuss the role of immobilization in industrial, commercial and medical processes, giving named examples of such uses. Read More