Question

 Which one of the following is the most abundant protein in the animals? [NEET (Sep.) 2020]

(a) Collagen

(b) Lectin

(c) Insulin

(d) Haemoglobin

Answer/Explanation

Ans. (a)

Collagen is the most abundant protein in animal world and RuBisCO is the most abundant protein in the whole of the biosphere because it is present in every plant that undergoes photosynthesis and molecular synthesis through the Calvin cycle.

Question

Identify the substances having glycosidic bond and peptide bond, respectively in their structure. [NEET (Sep.) 2020)

(a) Glycerol, trypsin

(b) Cellulose, lecithin

(c) Inulin, insulin

(d) Chitin, cholesterol

Answer/Explanation

Ans. (c)

Inulin is a fructan(polysaccharide of fructose). Adjacent fructose units are linked through glycosidic bond. Insulin is a protein composed of 51 amino acids. Adjacent amino acids are attached through peptide bond.

Question

 Identify the basic amino acid from the following. [NEET (Sep.) 2020]

(a) Glutamic acid

(b) Lysine

(c) Valine

(d) Tyrosine

Answer/Explanation

Ans. (b)
Option (b) is correct as lysine is a basic amino acid because it’s side chain contain nitrogen and resemble ammonia, which is a base. Valine is a neutral amino acid, glutamic acid is an acidic amino acid, while tyrosine is an aromatic amino acid.

Question

“Ramachandran plot” is used to confirm the structure of [NEET (Odisha) 2019]

(a) RNA

(b) proteins

(c) triacylglycerides

(d) DNA

Answer/Explanation

Ans. (b)

‘Ramachandran plot’ is used to confirm the structure of proteins.
Ramachandran plot is a plot of the angles-phi $(\varphi)$ and psi $(\psi)$ of amino acids found in a peptide chain. This plot was developed by GN Ramachandran, an Indian Scientist in 1963.

Question

 Which of the following is an amino acid derived hormone? [NEET 2018]

(a) Estradiol

(b) Ecdysone

(c) Epinephrine

(d) Estriol

Answer/Explanation

Ans. (c)

Among the following, epinephrine is an amino acid derived hormone. It is a catecholamine which is produced in the chromaffin cells of adrenal medulla from amino acids tyrosine. On the other hand, estradiol and estriol are steroid hormone that are involved in the regulation of estrous and menstrual cycles.
Ecdysone is also a steroid hormone that controls moulting in insects.

Question

Which of the following is the least likely to be involved in stabilising the three-dimensional folding of most proteins? [NEET 2016, Phase II]

(a) Hydrogen bonds

(b) Electrostatic interaction

(c) Hydrophobic interaction

(d) Ester bonds

Answer/Explanation

Ans. (d)
Ester bonds are the least likely to be involved in stabilising the 3D folding of most proteins. A long protein chain gets folded upon itself like a hollow woolen ball, giving rise to a tertiary structure (3D) structure.
This structure is stabilised by several type of bonds, i.e. hydrogen bonds, ionic bonds, Vander waal’s interactions, covalent bonds and hydrophobic bonds.
Ester bond is formed between sugar and phosphate in a nucleotide and is not involved in stability of a polypeptide chain. Thus, option (d) is correct.

Question

 Which one is the most abundant protein in the animal world? [CBSE AIPMT 2012]

(a) Trypsin

(b) Haemoglobin

(c) Collagen

(d) Insulin

Answer/Explanation

Ans. (c)

Collagen is the most abundant protein (structural protein) in the animal world while Ribulose Bisphosphate Carboxylase Oxygenase (RuBisCO) is the most abundant protein in the whole of the plant world.

Question

 Which one out of $A-D$ given below correctly represents the structural formula of the basic amino acid?

(a) C

(b) D

(c) A

(d) B

Answer/Explanation

Ans. (c)
Structure $D$ represents basic amino acid lysine whereas structure $A$ represents glutamic acid (acidic amino acid) and structure $B$ represents alcoholic amino acid serine.

Question

 Which of the following is the simplest amino acid? [CBSE AIPMT 2005]
(a) Alanine

(b) Asparagine

(c) Glycine

(d) Tyrosine

Answer/Explanation

Ans. (c)

Proteins are polymers of amino acids in which amino acids are joined by peptide bonds. Glycine is the simplest amino acid.

Question

 Collagen is [CBSE AIPMT 2002]

(a) fibrous protein

(b) globular protein

(c) lipid

(d) carbohydrate

Answer/Explanation

Ans. (a)

Collagen is a major fibrous protein of connective tissue, occurring as white fibres produced by fibroblast.

Question

 Which is an essential amino acid? [CBSE AIPMT 2000]

(a) Serine

(b) Aspartic acid

(c) Glycine

(d) Phenylalanine

Answer/Explanation

Ans. (d)

For human beings, eight amino acids are essential : Leucine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. So, these are known as essential amino acids.Cannot be synthesised in animal body.

Question

Conjugated proteins containing carbohydrates as prosthetic group are known as [CBSE AIPMT 2000]

(a) chromoproteins

(b) glycoproteins

(c) lipoproteins

(d) nucleoproteins

Answer/Explanation

Ans. (b)
Glycoproteins(mucoproteins) are conjugated protein having a simple or complex sugar (galactose) residue at their $\mathrm{N}$-terminal end. Glycoprotein is found in egg white, mucin, antibody lgG. cell membrane, saliva, synovial fluid, heparin. Lipoproteins contain lipids and nucleoproteins contain nucleic acid as the prosthetic group.

Question

 What is common among amylase, rennin and trypsin? [CBSE AIPMT 1997]

(a) These are all proteins

(b) These are proteolytic enzymes

(c) These are produced in stomach

(d) These act at a $\mathrm{pH}$ lower than 7

Answer/Explanation

Ans. (a)

All three are proteins enzymes amylase, rennin and trypsin acts respectively on the substrates starch, lactose and protein. Amylase acts at an optimum $\mathrm{pH}-6.8-7$, rennin at $\mathrm{pH}-2$ and trypsin at an optimum $\mathrm{pH}-8.5$.

Question

 Most diverse macromolecules, found in the cell both physically and chemically are [CBSE AIPMT 1996]

(a)proteins

(b)carbohydrates

(c) nucleic acids

(d) lipids

Answer/Explanation

Ans. (a)

Proteins are the most diverse among organic compounds. Among the biomolecules, proteins constitute $9-12 \%$, fat $1-3 \%$, carbohydrates $1-2 \%$, minerals $1-3 \%$, nucleic acids $2 \%$ and water $60-75 \%$.

Question

 The pyrenoids are made up of [CBSE AIPMT 1995]

(a) proteinaceous centre and starchy sheath

(b) core of protein surrounded by fatty sheath

(c) core of starch surrounded by sheath of protein

(d) core of nucleic acid surrounded by protein sheath

Answer/Explanation

Ans. (a)

Pyrenoids consist of dense proteinaceous area surrounded by starchy sheath. These are unique to chloroplast of algae and are associated in polymerising sugars into reserve polymers (starch).

Question

 Amino acids are produced from [CBSE AIPMT 1992]

(a) proteins

(b) fatty acids

(c)essential oils

(d) $\alpha$-keto acids

Answer/Explanation

Ans. (d)

Amino acids are smallest structural units of proteins. Plants and some microorganisms can synthesise these amino acids from inorganic nitrogen/ $\alpha$-keto acids by reductive amination and transamination. Amino acids besides bearing a carboxyl group, possess an amino group attached to $\alpha$-carbon, hence, called as $\alpha$-amino acids.

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