Question

COLOR 2 mlogg albumen 2 mL. honey 2 ml. amino acid solution 2 mL. distilled water 2 mL. peosein solution bWhich contains more protein (C-N bonds), egg albu- men or honey? How can you tell? Amino acid Amino ackd e. Do free amino acids have peptide bonds? d. What are the functions of proteins in living organisms? но HOH O Polypeptide chain Figure 6.7 A peptide bond joins two amino acids, and pepside bonds link mmany amino acids to form polypeptides, or proteins. The formation of a asit's carboxyl group and the nisogen of another amino acid's amino Lipids include a variety of molecules that dissol group) iberates a water molecule. The R in these amino acids represents a variable side chain that characterizes each type of amino acid peptide bond (i.e, between the carbon of one amino e in non- polar solvents such as ether, but not as well in polar solvents such as watenr and three acetone, methanol, or ethanol, Triglycer- ides (fats) are abundant lipids made of glyceipid's Do not spi the NOH is extremely caustic. Rinse your skin if it comes in contact with NaOH fatty acids (fig. 6.8), Tests for lipids are ability to selectively absorb pigments in tat on a lipid's such as Sudan IV. Question 6 Examine figure 6.8. What are the reactive groups o 4 Add three drops of Biuret reagent to each tube and mix. acids? Question S Which of the solutions is a positive control? Which is a negative

Answer 1

5. a. Positive control in an experiment can be defined as a solution or a substance that is known to show definite results on the reaction in support of the hypothesis. A negative control can be defined as a solution or substance that will not produce any result in the experiment. In the table given above, Water is the negative control since we know that water won't react with the Biuret reagent in the experiment. Protein solution is the positive control since we know the Biuret test is used for the detection of protein in a solution.

b. Biuret test is used primarily to detect peptide bonds or proteins. Biuret reagent reacts with the peptide bonds in a protein and the color changes to violet or purple. However, if no peptide bonds are present, there won't be any change in color. When egg albumin is added to biuret reagent, the color changes to violet/purple, indicating the presence of protein in albumin. When honey is added to Biuret reagent, no color change is observed, indicating the absence of peptide bonds. Therefore, Egg albumin has more protein than honey.

c. Peptide bonds are formed when 2 amino acids undergo condensation reaction between the carboxyl group of one molecule and the amino group of another molecule of amino acid. A free amino acid can never have a peptide bond.

d. Proteins are essential for humans. They are the building blocks of many body organs and the main constituent of hair, nails, muscles etc. Hormones are important for metabolic activities and most hormones are composed of proteins. Most enzymes are globular proteins and are responsible for accelerating various catalytic activities in the body, including digestion. Hemoglobin is responsible for oxygen transport throughout the body, it is also a protein. Antibodies provide immunity by acting against the pathogens, they are proteins too. Fibrinogen is the blood clotting substance, composed of a glycoprotein. Hence, protein is a major constituent of almost all parts of our body