Answer:
Proteins, large complex molecules, are major building blocks of all living organisms. Discuss the following in relation to proteins.
(a) The chemical composition and levels of structure of proteins.
Proteins are chemically macromolecules formed by manomeric units called amino acids. The structural organization of proteins is as follows: Primary, Secondary, Tertiary and Quaternary.
(b) The roles of DNA and RNA in protein synthesis
From DNA, ribosomal RNA is formed, a type of RNA present in ribosomes that is responsible for protein synthesis. Therefore, the role of DNA in protein synthesis is essential: without DNA, there are no proteins.
(c) The roles of proteins in membrane structure and transport of molecules across the membrane
Proteins can work by transporting ions in different ways.
Explanation:
(a) The chemical composition and levels of structure of proteins.
Proteins are chemically macromolecules formed by manomeric units called amino acids, these have in their structure a carboxyl group and amino group, attached to the same carbon. To be assimilated by the body, proteins must be degraded in the amino acids that make them up.
The amino acids are linked together by peptide bonds. In those bonds, the amino group of one amino acid reacts with the carboxyl group of the other.
The structural organization of proteins is as follows:
Primary: Sequence of the amino acids in the chain with peptide bonds.
Secondary: Spatial arrangement of the amino acids of a protein. They stabilize by means of hydrogen bonds. There are two types: the propeller a and the folded blade b.
Tertiary: Three-dimensional arrangement of the polypeptide chain, stabilized by forces of Waals.
Quaternary: Union of weak bonds of arias polypeptic chains that originate a protein complex.
(b) The roles of DNA and RNA in protein synthesis
RNA fulfills numerous functions, the most important being protein synthesis, in which it copies the genetic order contained in the DNA to use it as a standard in the manufacture of proteins and enzymes and various substances necessary for the cell and the organism. For this, it goes to the ribosomes, which operate as a kind of molecular protein factory, and it does so following the pattern that the DNA prints on it.
(c) The roles of proteins in membrane structure and transport of molecules across the membrane
The cells contain proteins that are embedded in the lipid bilayer of their plasma membranes. These proteins can work by transporting ions in different ways. Then, most of the water-soluble ions and molecules are unable to spontaneously cross the lipid bilayer of the membrane (which act as a barrier) and require the concurrence of special carrier proteins or protein channels. In this way the cell maintains concentrations of ions and small molecules different from those prevailing in the external environment.
