5.1.4 Regulation Of Bood Glucose l Flashcards
What is the concentration of glucose in the blood?
90 mg cm-3
How does blood glucose increase because of diet
When you eat carbohydrate rich foods such as pasta and rice, and sweet foods such as cakes and fruit, the carbohydrates that they contain are broken down in the digestive system to release glucose, which is absorbed back into the blood stream and blood glucose conc rises
How does glycogenolysis increase blood sugar?
Glycogen stored in the liver and muscle cells is broken down into glucose, which is released into bloodstream increasing blood glucose conc
How does gluconeogenesis increase blood sugar levels
Is The Production of glucose from non carbohydrate sources. E.g. the liver is able to make glucose from glycerol and amino acids. This glucose is released into the bloodstream and causes thr conc to increase
How does respiration REDUCE Blood sugar conc
some glucose used by cells to release energy. This is required for normal body functions. However during exercise more glucose is needed as the body needs to generate more energy in order for muscle cells to contract. The more exercise, the more demand for glucose and the greater decrease in blood sugar conc
How does glycogenesis REDUCE blood sugar conc
Through the production of glycogen. When blood glucose conc is too high, excess glucose taken in through thr diet is converted into glycogen and stored in the liver .
When does insulin get released
Insulin is released by the B cells of the islets of langerhans in the pancreas when the B cells detect that blood glucose concentration is too high.
Almost all cells in the body have insulin receptors on their cell surface membranes. When insulin binds to its glycoproetein receptors, it causes a change in the tertiary structure of the glucose transport protein channels. This causes channels to open, allowing more glucose to enter the cell. Insulin also activates the enzymes within some cells to convert glucose to glycogen and fat
How does insulin lower blood glucose conc
- Increasing absorption rate of glucose by cells, especially in skeletal muscle cells
- increasing respiratory rate of cells, increasing their need for glucose and cause a higher uptake of glucose from the blood
- increasing glycogenesis - insulin stimulates liver to remove glucose from blood by turning it into glycogen and storing it in the liver and muscle cells
- increasing conversion of glucose to fat
- inhibiting release of glucagon from alpha cells
How is insulin broken down?
By enzymes in cells of the liver. So in order to be in effect, insulin needs to be constant secreted. When blood glucose levels drop, beta cells reduce their production, acting as a negative feedback
What is the role of glucagon?
Produced by Alpha cells of the IOL when blood glucose levels are too low. Glucagon is secreted direct,y into bloodstream. Unlike insulin, glucagon has very few receptors, only on liver and fat cells . Only they can respond to glucagon.
How does glucagon raise blood sugar levels?
Glycogenolysis - liver breaks down its glycogen stores into glucose to be released into bloodstream.
Reducing the amount of glucose absorbed by liver cells
Increasing gluconeogenesis - increasing conversion of amino acids and glycerol into glucose in thr liver
What happens when blood glucose gets too high?
Negative feedback.
- production of glucagon stops…
What is the mechanism of insulin release
1) at a normal level, potassium channels in plasma membrane of beta cells are open and potassium ions diffuse out
2) when blood gluc rises, glucose enters via glucose transporter
3) glucose metabolised inside mitochondria, resulting in ATP production
4) ATP binds to potassium channels causing them to close
5) since potsssium ions can’t diffuse outside the cell, depolarisation occurs
6) depolarisation causes the voltage gated calcium channels to open
7) calcium ions enter cell and cause secretory vesicles to release the insulin they contain by exocytosos
