What are macromolecules? Give examples.
Macromolecules are large complex molecules that occur in colloidal state in intercellular fluid. They are formed by the polymerization of low molecular weight micromolecules. Polysaccharides, proteins, and nucleic acids are common examples of macromolecules.
Illustrate a glycosidic, peptide and a phospho-diester bond. Answer
(a)Glycosidic bond is formed normally between carbon atoms, 1 and 4, of neighbouring monosaccharide units.
(b)Peptide bond is a covalent bond that joins the two amino acids by – NH – CO linkage.
(c)Phosphodiester bond is a strong covalent bond between phosphate and two sugar groups. Such bonds form the sugar phosphate backbone of nucleic acids.
What is meant by tertiary structure of proteins?
The helical polypeptide chain undergoes coiling and folding to form a complex three-dimensional shape referred to as tertiary structure of proteins. These coils and folds are arranged to hide the non-polar amino acid chains and to expose the polar side chains. The tertiary structure is held together by the weak bonds formed between various parts of the polypeptide chain. Question 5:
Proteins have primary structure. If you are given a method to know which amino acid is at either of the two termini (ends) of a protein, can you connect this information to purity or homogeneity of a protein? Answer
Yes, if we are given a method to know the sequence of proteins, we can connect this information to the purity of a protein. It is known that an accurate sequence of a certain amino acid is very important for the functioning of a protein. If there is any change in the sequence, it would alter its structure, thereby altering the function. If we are provided with a method to know the sequence of an unknown protein, then using this information, we can determine its structure and compare it with any of the known correct protein sequence. Any change in the sequence can be linked to the purity or homogeneity of a protein. For example, any one change in the sequence of haemoglobin can alter the normal haemoglobin structure to an abnormal structure that can cause sickle cell anaemia.
Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (e.g., cosmetics, etc.) Answer
Proteins used as therapeutic agents are as follows:
1. Thrombin and fibrinogen – They help in blood clotting.
2. Antigen (antibody) – It helps in blood transfusion.
3. Insulin – It helps in maintaining blood glucose level in the body. 4. Renin – It helps in osmoregulation.
Proteins are also commonly used in the manufacture of cosmetics, toxins, and as biological buffers.
Explain the composition of triglyceride.
Triglyceride is a glyceride, which is formed from a single molecule of glycerol, esterified with three fatty acids. It is mainly present in vegetable oils and animal fat.
Structure of triglyceride
The general chemical formula of triglyceride is , where R1, R2, and R3 are fatty acids. These three fatty acids can be same or different.
Can you describe what happens when milk is converted into curd or yoghurt from your understanding of proteins. Answer
Proteins are macromolecules formed by the polymerization of amino acids. Structurally, proteins are divided into four levels. (a) Primary structure – It is the linear sequence of amino acids in a polypeptide chain. (b) Secondary structure – The polypeptide chain is coiled to form a three-dimensional structure. (c) Tertiary structure – The helical polypeptide chain is further coiled and folded to form a complex structure. (d) Quaternary structure – More than one polypeptide chains assemble to form the quaternary structure. Milk has many globular proteins. When milk is converted into curd or yoghurt, these complex proteins get denatured, thus converting globular...