Biomolecules Exercises
Exercises
1. What are macromolecules? Give examples.
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Answer
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.
2. What is meant by tertiary structure of proteins?
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Answer
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.
3. Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.
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Answer
(a)
| Molecule | Structure |
|---|
(b)
| Compound | Manufacturer | Buyer | |
|---|---|---|---|
| 1. | Starch products | Kosha Impex (P) Ltd. | |
| 2. | Liquid glucose | Marudhar apparels | Research laboratories, educational institutes, and other industries, which use biomolecules as a precursor for making other products. |
| 3. | Various enzymes such as amylase, protease, cellulase | Map (India) Ltd |
4. Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (e.g., Cosmetics etc.)
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Answer
Proteins used as therapeutic agents are as follows:
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Thrombin and fibrinogen - They help in blood clotting.
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Antigen (antibody) - It helps in blood transfusion.
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Insulin - It helps in maintaining blood glucose level in the body.
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Renin - It helps in osmoregulation. Proteins are also commonly used in the manufacture of cosmetics, toxins, and as biological buffers.
5. Explain the composition of triglyceride.
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Answer
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 $R_2 COO-CH_2 CH(-OOCR_1) CH_2-OOCR_3$, where $R_1, R_2$, and $R_3$ are fatty acids. These three fatty acids can be same or different.
6. Can you attempt building models of biomolecules using commercially available atomic models (Ball and Stick models).
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Answer
Ball and stick models are 3-D molecular models that can be used to describe the structure of biomolecules.
In ball and stick model, the atoms are represented as balls whereas the bonds that hold the atoms are represented by the sticks. Double and triple bonds are represented by springs that form curved connections between the balls. The size and colour of various atoms are different and are depicted by the relative size of the balls.
It is the most fundamental and common model of representing biomolecular structures.
In the above ball and stick model of D-glucose, the oxygen atoms are represented by red balls, hydrogen atoms by blue balls, while carbon atoms are represented by grey balls.
7. Draw the structure of the amino acid, alanine.
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Answer
Structureof alanine
8. What are gums made of? Is Fevicol different?
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Answer
Gums are hetero-polysaccharides. They are made from two or more different types of monosaccharides. On the other hand, fevicol is polyvinyl alcohol (PVA) glue. It is not a polysaccharide.
9. Find out a qualitative test for proteins, fats and oils, amino acids and test any fruit juice, saliva, sweat and urine for them.
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Answer
(a)Test for protein
Biuret’s test â€" If Biuret’s reagent is added to protein, then the colour of the reagent changes from light blue to purple.
(b)Test for fats and oils
Greaseor solubility test
(c)Test for amino acid
Ninhydrin test â€" If Ninhydrin reagent is added to the solution, then the colourless solution changes to pink, blue, or purple, depending on the amino acid.
| Item | Name of the test Biuret’s test | Procedure | Result | Inference | ||
|---|---|---|---|---|---|---|
| 1. | Fruit juice | Biuret’s test | Fruit juice + Biuret’s reagent | Colour changes from light blue to purple | Protein is present. | |
| Greasetest | To a brown paper, add a few drops of fruit juice. | No translucent spot | Fats and oils are absent or are in negligible amounts. | |||
| Ninhydrin test | Fruit juice + Ninhydrin reagent + boil for 5 minutes | Colourless solution changes to pink, blue, or purple colour | Amino acids are present. | |||
| 2. | Saliva | Biuret’s test | Saliva + Biuret’s reagent | Colour changes from light blue to purple | Proteins are present. | |
| Greasetest | On a brown paper, add a drop of saliva. | No translucent spot | Fats/oils are absent. | |||
| Ninhydrin test | Saliva + Ninhydrin reagent + boil for 5 minutes | Colourless solution changes to pink, blue, or purple colour | Amino acids are present. | |||
| 3. | Sweat | Biuret’s test | Sweat + Biuret’s reagent | No colour change | Proteins are absent. | |
| Solubility test | Sweat + Water | Oily appearance | Fats/oil may be present. | |||
| Ninhydrin test | Sweat + Ninhydrin reagent + boil for 5 minutes | No colour change, solution remains colourless | Amino acids are absent. | |||
| 4. | Urine | Biuret’s test test | Few drops of urine + Biuret’s reagent | Colour changes from light blue to purple | Proteins are present. | |
| Solubility test | Few drops of urine + Water | Little bit of oily appearance | Fats may or may not be present. | |||
| Ninhydrin test | Few drops of urine + Ninhydrin reagent + boil for 5 minutes | Colourless solution changes to pink, blue, or purple colour depending on the type of amino acid | Amino acids are present |
10. 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!
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Answer
Approximately, 100 billion tonnes of cellulose are made per year by all the plants in the biosphere and it takes 17 full grown trees to make one ton of paper. Trees are also used to fulfil the other requirements of man such as for timber, food, medicines, etc. Hence, it is difficult to calculate the annual consumption of plant material by man.
11. Describe the important properties of enzymes.
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Answer
Properties of enzymes
(1) Enzymes are complex macromolecules with high molecular weight.
(2) They catalyze biochemical reactions in a cell. They help in the breakdown of large molecules into smaller molecules or bring together two smaller molecules to form a larger molecule.
(3) Enzymes do not start a reaction. However, they help in accelerating it.
(4) Enzymes affect the rate of biochemical reaction and not the direction.
(5) Most of the enzymes have high turnover number. Turnover number of an enzyme is the number of molecules of a substance that is acted upon by an enzyme per minute. High turnover number of enzymes increases the efficiency of reaction.
(6) Enzymes are specific in action.
(7) Enzymatic activity decreases with increase in temperature.
(8) They show maximum activity at an optimum $pH$ of 6 - 8.
(9) The velocity of enzyme increases with increase in substrate concentration and then, ultimately reaches maximum velocity.
