Blood Glucose Regulation: Insulin | A-level Biology | OCR, AQA, Edexcel

The key points covered of this video include:

1. Introduction to Insulin
2. Mechanism of Insulin Action
3. How Insulin Reduces Blood Glucose

Introduction to Insulin

Insulin is a hormone that is released from the B-cells in the pancreas when blood glucose concentration rises. It travels in the blood and attaches to receptors on the surfaces of almost all cells. This brings about changes inside the cell that lower the glucose concentration in the blood. This brings about changes inside the cell that lower the glucose concentration in the blood. After blood glucose concentration has been lowered, insulin stops being released. This is an example of negative feedback.

Mechanism of Insulin Action

Insulin is a peptide hormone, meaning it cannot enter cells. It binds to the insulin receptor on cell surfaces - this activates the enzyme tyrosine kinase. Tyrosine kinase phosphorylates other enzymes inside the cell. Phosphorylation means adding a phosphate group - this turns inactive enzymes into active enzymes. The active enzymes go on to reduce the blood glucose concentration.

How Insulin Reduces Blood Glucose

When insulin binds to an insulin receptor in a cell a number of changes take place inside the cell to reduce blood glucose. Vesicles of glucose transporter lie in the cytoplasm of cells - when insulin binds they fuse with the surface. Insulin also causes the glucose transporter to change shape so that it opens and lets more glucose into the cell. These processes mean that more glucose is absorbed into the cell from the blood. Insulin also causes more glucose to be used in respiration, instead of using fat or protein. Glucose is converted into fat and glycogen. Working in concert these processes reduce the concentration of glucose in the blood.

Summary

Insulin is secreted from B-cells in the pancreas in response to high blood glucose
It binds to receptors and activates the intracellular enzyme tyrosine kinase
Tyrosine kinase phosphorylates enzymes and activates them, resulting in the lowering of blood glucose
This is done via increasing glucose absorption into cells
Glucose is converted into glycogen and fats, as well as using up glucose in respiration