Test: Proteins & Structure of Proteins - NEET MCQ

• The spatial arrangement produced by the twisting and folding of peptide chains in proteins is called secondary structure.
• Secondary structure is comprised of regions stabilized by hydrogen bonds between atoms in the polypeptide backbone.
• Tertiary structure is the three-dimensional shape of the protein determined by regions stabilized by interactions between the side chains.

Topic in NCERT: Secondary structure

Line in NCERT: "only some portions of the protein thread are arranged in the form of a helix. in proteins, only right handed helices are observed. other regions of the protein thread are folded into other forms in what is called the secondary structure (fig. 9.3 b)."

Proteins are building blocks of the body. The proteins are made up of amino acids. The amino acids are linked together by peptide bonds to form a protein. The amino acids consist of amine group made up of nitrogen and hydrogen and the carboxyl group at the end and a side chain of R group which is specific to a particular amino acid. This specific group brings a variability to the proteins. If R group is H it is glycine while if it is CH₂ it is alanine. The sequence of amino acids determines the protein. 

Topic in NCERT: Structure of proteins

Line in NCERT: "the sequence of amino acids i.e., the positional information in a protein - which is the first amino acid, which is second, and so on – is called the primary structure."

Glycine is the simplest amino acid represented by the symbol Gly or G. It is an amino acid that has a single hydrogen atom in its side chain. The

chemical formula of glycine is NH₂CH₂COOH. Glycine generally exists as colorless crystalline solid. Out of all the amino acids glycine is the only

achiral proteinogenic amino acid and it can be fit into hydrophilic or hydrophobic environments due to its chain of only one hydrogen atom.

Now in the given question glycine at pH4 will be exist as, at pH4 glycine is in acidic form and the zwitterion of glycine is shown by:

NH₃⁺ - CH₂COO^- when it reacts with H⁺ ion then the reaction can be described in the following manner:
NH₃⁺ - CH₂COO^- → NH₃⁺ - CH₂COOH

Hormones are chemical substances which are released in the body for regulation and metabolism in cells.

Many hormones such as insulin and parathormone are proteinic in nature.

Topic in NCERT: Proteins

Line in NCERT: "many of them are enzymes, some are antibodies, some are receptors, some are hormones and some others are structural proteins."

• Amino acids can be divided into two groups- essential amino acids and non-essential amino acids.
• Non-essential amino acids are produced by the body while essential amino acids are obtained through our diet.

Topic in NCERT: Proteins

Line in NCERT: "hence, dietary proteins are the source of essential amino acids. therefore, amino acids can be essential or non-essential. the latter are those which our body can make, while we get essential amino acids through our diet/food."

A conjugated protein is a protein that functions in interaction with other (non-polypeptide) chemical groups attached by covalent bonding or weak interactions. Many proteins contain only amino acids and no other chemical groups, and they are called simple proteins.

Amino acids joined by peptide bonds form proteins. Twenty types of amino acids are present in natural proteins.

Topic in NCERT: Proteins

Line in NCERT: "each protein is a polymer of amino acids. as there are 20 types of amino acids (e.g., alanine, cysteine, proline, tryptophan, lysine, etc.), a protein is a heteropolymer and not a homopolymer."

Proteins are building blocks of the body. The proteins are made up of amino acids. The amino acids are linked together by peptide bonds to form a protein.The amino acids consists of amine group made up of nitrogen and hydrogen and the carboxyl group at the end and a side chain of R group which is specific to a particular amino acid. The amine group (NH₂) is made up of nitrogen and hydrogen.

So, the correct answer is option D.

Topic in NCERT: Proteins

Line in NCERT: "proteins serve a variety of cellular functions."

In proteins, only right-handed helices are observed. This means that the helical structures in proteins have a specific orientation and twist.

Topic in NCERT: Secondary structure

Line in NCERT: "in proteins, only right handed helices are observed."

Essential amino acids not synthesised in the body. As a result, they must come from food. The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Topic in NCERT: Amino acids and proteins

Line in NCERT: "hence, dietary proteins are the source of essential amino acids. therefore, amino acids can be essential or non-essential. the latter are those which our body can make, while we get essential amino acids through our diet/food."