University:
Yeshiva University
Course:
BIO1011 | Biology Principles Lectures
Academic year:

2021
Views:

102

Pages:

2
Author:

Stevan J.

Insuline Hormone Insulin hormone The pancreatic islands secrete at least four types of hormones, namely:  Isulin  Glucagon  Somastotatin  Pancreatic Polypeptide The human insulin gene is located on the short arm of chromosome 11. Insulin is secreted as preproinsulin. Preproinsulin is a long chain peptide with a BM of 11,500. The guide sequence or hydrophobic sequence functions as a signal to direct this molecule to the endoplasmic reticulum and then excreted. Here the process of cleavage of the preproinsulin molecule occurs by microsomal enzymes to produce proinsulin molecules (BM approximately 9000). Proinsulin is transported to the Golgi apparatus where the packaging process takes place into clathrin-coated secretory granules. These granules are mature, contain insulin which consists of 51 amino acids; contained in the A chain 21 amino acids and the B chain 30 amino acids and C- Peptides. Insulin is secreted from the pancreas at 40-50 units/day (15-20% of stores). Insulin secretion can take place by:  Basal insulin secretion: occurs in the absence of exogenous stimuli. This is the amount of insulin secreted under conditions fast.  Stimulated insulin secretion: insulin secretion due to a response to exogenous stimuli. A number of substances involved in the release of insulin here are:  Glucose most potently stimulates insulin release. Glucose can enter the pancreatic ÿ cells by passive diffusion mediated by a specific membrane protein called Glucose Transporter 2 ÿ stimulates insulin secretion.  Amino acids, fatty acids, ketone bodies  Hormonal factors ÿ adrenergic preparations stimulate insulin release possibly by increasing intracellular cAMP. Continuous exposure to excessive amounts of growth hormone, cortisol, placental lactogen, estrogen, progestin also increases secretion. insulin  Pharmacological preparations, namely sulfonylurea and tolbutamide compounds The function of insulin is to stimulate the synthesis of kinase enzymes in the liver, for example pyruvate kibase, glucokinase, and phosphofructokinase. In addition, insulin also functions as an inhibitor or suppressor of the formation of gluconeogonic enzymes, for example glucose-6 phosphatase, Fructose-1,6- diphosphatase and pyruvate carboxylase. Thus insulin can control the process of carbohydrate metabolism and therefore glucose levels in the blood of normal people are relatively constant. Insulin is a protein with a molecular weight of 5734 and has an isoelectric point of 5.3 to 5.36. This hormone can act with alkali and can produce ammonia. A lack of the hormone insulin in the body results in a decrease in enzyme activity in the glycolysis process and thus glucose levels become higher than normal. Apart from its role in the use of glucose for the body, insulin also has an influence on protein and nucleic acid metabolism, for example insulin facilitates the entry of amino acids into cells, increasing protein synthesis in ribosomes.

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