Ncert Questions
Question 1. What are Macromolecules? Give examples.
Answer: Macromolecules are complex, large molecules assembled by the polymerisation of simple monomers. They have molecular weights in the weights in the range of ten thousand daltons and above. Examples include carbohydrates, proteins and nucleic acids.
Question 2. What is meant by tertiary structure of proteins?
Answer: Tertiary Structure of Proteins:When secondary proteins undergo a third degree of twisting or torsion formed by additional bonds of both functional groups; the proteins is then called tertiary structure of proteins. The polypeptide chain is twisted and folded to from a stable structure. It is maintained by three types of bonds i.e. ionic bonds, hydrogen bonds and disulphide bond e.g. Myoglobin protein shows a tertiary structure.
Question 3. Proteins have primary structure. If you are given method to know which amino acid is at either of two terminal ends of a protein, can you connect this information to purity or homogeneity of a protein?
Answer: The terminal ends are always with – COOH (carboxylic) and – NH2 (amino group). The two terminal are called C- Terminal and N- terminal. This will not help in finding the homogeneity of a protein.
Question 4. Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (e.g. Cosmetics etc).
Answer: Antibodies used as vaccines to carry out immunisation of animals. Humulin artificially synthesised protein to act as a substitute for insulin.
Question 5. Can you describe what happens when milk is converted into curds or yoghurt from your understanding of proteins?
Answer: When milk is converted into curd or yoghurt, the milk protein (casein) undergoes denaturation i.e. there is a disruption in the native state of the protein. Since this conversion process is carried out by bacteria (Lactobacillus). It is called biological denaturation.
Question 6. Attempt titrating an amino acid against a weak base and discover the number of dissociating (ionizable) functional groups in the amino acid.
Answer: Only one functional group –COOH (carboxylic) can be discovered.
Question 7. What are gums made of ? Is fevicol different?
Answer: Gums are made of hexoses and pentoses. Yes, Fevicol is a syntheitc gum.
Question 8. Find out a qualitative test for proteins, fats and oils, amino acids and test any fruit juice, saliva, sweat and wine for them.
Answer: Test for Proteins. Burette test – Take 3 ml of egg albumin in a test tune and add an equal volume of 10% NaOH. Mix thoroughly and add 0.5% CuSO4 drop wise. Mix well. A purple – violet or pinkish violet colour develops. Text for Fats. Solubility test – In five test tubes, take 3ml of water, alcohol, ether, benzene and chloroform. To each test tube add 3 drops of lipid. Shake well and note the solubility. The lipid floats on water but it is miscible with ether, benzene and chloroform, while it sinks to the bottom in alcohol.
Question 9. Find out how much cellulose is made by all the plants in the biosphere and compare it with how much of paper is manufactured by man and hence what is the consumption of plant material by man annually. What a loss of vegetation!
Answer: The amount of paper manufactured by man exceeds the quantity of cellulose made by the plants in biosphere upto a great extent. The demand for paper is increasing day by day leading to intense deforestation by mankind. This leads to loss of vegetation, the net result of which is a disturbance in ecological equilibrium and loss of plant and animal species.
Question 10. Describe the important properties of enzymes.
Answer: The important properties of enzymes are listed below :– Chemical Nature:The enzymes are proteinic in nature. Some enzymes have additional non-protein (inorganic or organic) substances associated with them for their action. Molecular Weight:The enzymes have very high molecular weights. These vary from 6000 for bacterial ferredoxin to 4,600,000 for pyruvate dehydrogenase complex. Chemical Activity:The enzymes accelerate a chemical reaction by lowering activation energy. Changeless Form:The enzymes combine temporarily with the substrate molecules but are not consumed or changed permanently in the reaction they catalyse. They are produced in same form at the end of reaction. Reversibility of Reaction:The enzyme – controlled reactions are reversible. High Efficiency:Most enzymes have high turnover number. A molecule of the enzyme catalse from cattle liver decomposes 5,000,000 molecules of hydrogen peroxide to water and hydrogen in one minute at 0oC. The turnover number of carbonic anhydrase present in the RBCs is 36 million. The higher the turnover number, the more efficient is enzyme. Action Specificity:The enzymes are specific in action. Temperature Sensitivity:The enzymes function best at an optimum temperature. The optimum temperature for human enzymes is 35 to 40oC- close to human body temperature. The enzyme activity decreases as well as increase in temperature, and stops at 0oC and above 800C. the enzymes of bacteria inhabiting hot springs have an optimum temperature of 700C or more. pH Sensitivity:The enzymes show maximum activity at an optimum pH (6-8) but enzymes have specific pH for their action.