This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Biomolecules – Chemical Analysis – 1”.
1. What chemical is used to grind tissues for chemical analysis?
c) Hydrofluoric acid
d) Trichloroacetic acid
Explanation: To analyze tissues for chemical analysis, the tissue material needs to be grinded and homogenized using pestle and mortar. This grinding is done using trichloroacetic acid. The rest are generally toxic.
2. What is the nature of the filtrate after grinding tissue?
Explanation: The tissue is grinded using mortar and pestle in order to homogenize it, using trichloroacetic acid. It is then strained through cheesecloth and the filtrate obtained is acid-soluble in nature.
3. What is the acid-insoluble fraction of grinded tissue known as?
Explanation: The homogenized and grinded tissue material, when passed through layers of cheesecloth, divides into an acid-soluble fraction and an acid-insoluble fraction. The acid-insoluble fraction is the retentate.
4. How can we get a theoretical idea about the molecular formula of a compound?
a) Analytical techniques
b) Chemical treatment
c) Biological treatment
Explanation: Techniques defined under analytical chemistry and stoichiometric calculations allow us to approximately determine the molecular formula of a compound. It is the easiest and most accurate method out of all the options.
5. Which of these cannot be determined by analytical techniques?
a) Probable structure
b) Chemical properties
d) Molecular formula
Explanation: Analytical techniques are used to determine the probable structure and approximate molecular formula of compounds. Various conformations of a structure can also be determined but chemical properties cannot be determined.
6. What percentage of the Earth’s crust is Sulphur?
Explanation: Sulphur occupies 0.03% of the Earth’s crust by weight. Hydrogen occupies 0.14% of the Earth’ crust by weight, oxygen occupies 46.6% by weight and sodium occupies 2.8% of the Earth’s crust by weight.
7. Which of these elements is negligible in the human body?
Explanation: Sodium is an important electrolyte in our body. Magnesium is a cofactor for many enzymes. Sulphur is a component of some amino acids. The amount of silicon in our body is negligible.
8. Which of these components have the least percentage by weight in the Earth’s crust?
Explanation: Oxygen has the highest percentage by weight in the Earth’s crust, that is, 46.6%. Sodium and magnesium are also present in some amounts. However, the percentage by weight of nitrogen is very little.
9. What is done to obtain the inorganic substances from tissue?
c) Complete combustion
Explanation: In order to obtain inorganic substances from tissue, the tissue is first allowed to sit so that the water evaporates. The carbon compounds are eliminated. The remaining ash contains inorganic compounds.
10. All biomolecules are carbon compounds. True or false?
Explanation: A biomolecule is a compound produced by a living organism. It is divided into four broad groups, namely carbohydrates, proteins, nucleic acids and lipids. All of these substances contain carbon.
11. Which of these are not present in every amino acid?
a) Amino group
b) Acidic group
Explanation: Amino acids are the building blocks of proteins. The have a chiral carbon or α-carbon. It contains one amino group and one acidic group. Only a few amino acids such as cysteine and methionine contain Sulphur.
12. An amino acid is a substituted ______
a) carboxylic acid
Explanation: An amino acid has an α-carbon, surrounded by one amino group, one acidic group and two other groups. Methane is similar in structure, with four hydrogens surrounding the central carbon.
13. How many amino acids are present in the body?
Explanation: The body contains 21 amino acids and various combinations of sequences of these amino acids form peptides, polypeptides and proteins. They are classified into essential and non-essential amino acids.
14. Which of these amino acids do not possess a chiral carbon?
Explanation: Glycine is the only amino acid that does not possess a chiral carbon. This is because, along with one amino group and one acidic group attached to the α-carbon, it possesses two hydrogen atoms.
15. What is the simplest amino acid?
Explanation: Glycine is the simplest amino acid. This is because its R group, which is attached to the α-carbon is a hydrogen atom. Hence, the α-carbon is symmetrical and does not possess a chiral carbon.
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