Are proteins composed of repeating units?

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I am currently studying the chapter called macromolecule. I get that a nucleic acid consists of repeating units of nucleotides, and I personally think "the repeating units" does not mean the nucleotdes are all the same, as nitrogen bases have four types either in DNA or RNA. How about the protein molecule. A protein molecule is made up of amino acids. However, I am sure about whether a protein molecule are made up of same and repeating units of amino acids. Theoretically, the R group in each protein is differed from one another. Therefore, does that mean we cannot state that a protein molecule is made up of repeating units of amino acids?

asked Dec 26, 2016 at 9:01

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They are repeating units in the sense that all of the units are amino acids. The R group is different in different amino acids (it is not just different theoretically). The different R groups contribute to the different shape, structure, function of proteins, and if all were the same, then we would have a very limited range of proteins.You will still say it is composed of repeating units, since all units are amino acids, and there are no foreign groups between them.

Similarly, all repeating units of DNA/RNA are nucleotides, even if they aren't the same nucleotides.

answered Dec 26, 2016 at 9:36

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Proteins are composed of repeated units of aminoacids with different R groups.

CO-CH(R1)-NH - CO-CH(R2)-NH - CO-CH(R3)-NH -

See how the aminoacid backbone is repeated again and again even if the R groups attached to that backbone is different.

answered Dec 26, 2016 at 17:07

JayCkatJayCkat

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Proteins are heteropolymers of amino acids. Many Amino acids are joined together by peptide bond. During peptide bond formation C terminal of former amino acid & N terminal of successive amino acid join , that's why proteins always start with the N terminal and end with C terminal.

answered Dec 26, 2016 at 14:56

AScientistAScientist

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Answer

Verified

Hint: Proteins are large molecules having high molecular weight. These molecules are of high importance in many fields. Within the organisms, proteins perform a vast variety of functions. Some of these include performing DNA replication, acting as catalysts during biological reactions.

Complete answer:
Proteins are known as polymers, that is they are molecules of greater molecular weight composed of repeating units of smaller structural and functional units. These repeating units present in a protein molecule are known as amino acids. It is also known as the monomers in a protein polymer. These are organic compounds that contain an amino group, that is –NH2 and a carboxylic acid group –COOH, along with an R side chain group, which can be either an H atom or an alkane chain of any length. The nature of the amino acid depends on the composition of the R group. The major atoms that constitute amino acids are C, H, O, S and N. There exist about 500 naturally occurring amino acids.

Note:
A protein molecule has different structures. That is, primary, secondary, tertiary and quaternary. The primary structure includes the arrangement of amino acids one after the other connected by peptide bonds. The secondary structure involves the further folding of the primary structure; there are two types of secondary structures, known as the alpha helix and the beta pleated structures. The tertiary structure involves further forming a loop and forming a three dimensional structure. Quaternary structure involves looping of further more amino acid strands.

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What repeating subunit is protein made of?

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Do all proteins have multiple subunits?