Describe how the Organelles in the Beta Cells Work Together to Produce and Secrete Insulin
The hormone insulin is produced by the beta cells in the pancreas. Beta cells are located in the pancreas in clusters known as the islets of Langerhans. Insulin is vital in the body to lower blood glucose levels. Although it does not directly decrease glucose levels in the blood, it stimulates the muscle and liver cells to store excess glucose.
The production and secretion of the protein insulin requires certain substances to be brought in to and taken out of the cell and also involves many organelles.
The process begins in the nucleus where the DNA (deoxyribonucleic acid) molecules can be found. DNA is folded and coiled into chromosomes in the nucleolus. This is surrounded by a double membrane which has pores in it. Genes are sections of DNA which contain instructions on how to make proteins; however, the DNA molecule is too large to get through the pores in the membrane so a section is copied into RNA (ribonucleic acid). This is called transcription.
The RNA then leaves the nucleus and joins with a ribosome in the cytoplasm where it can be used to synthesise a protein.
The messenger RNA is 'read' by the ribosome. Ribosomes are made of protein and RNA in 2 subunits and they have 2 tRNA binding sites. The mRNA passes between the subunits. It selects the complementary transfer RNA which carries the corresponding amino acid. Amino acids are joined in a chain to make the protein. The function of the protein is determined by the bonds formed from its primary structure (sequence of amino acids).
Ribosomes are either free in the cytoplasm or are on the rough endoplasmic reticulum. Once the amino acid chain is formed it travels through the membrane tubes of the R.E.R.. It folds into its secondary structure, using hydrogen bonding, to form an alpha-helix or a beta-pleated sheet. This then travels further through the R.E.R. And folds into a tertiary structure, using hydrogen bonds, ionic and disulphide bonds. This process turns the amino acid into a globular (3-D) protein. In the case of insulin; pro-insulin is formed first. It has non-functional sections so it is cut and the non-coding sections are taken out. This forms functional insulin.