14.3 Regulation of Blood Glucose Concentration

Question 1

What are the characteristics of glucose?

Answer 1

-Small, soluble molecule that is carried in blood plasma
-Concentration is normally maintained at 90 mg cm-3

Question 2

What are the reasons that blood glucose can increase

Answer 2

Diet - When you eat carbohydrate-rich foods (eg. pasta, rice) and sweet foods, the carbohydrates are broken down to release glucose which is then absorbed into the bloodstream to increase blood glucose concentration
Glycogenesis - Glycogen stored in the liver and muscle cells is broken down into glucose which is released into the blood stream
Gluconeogenesis - The production of glucose from non-carbohydrate sources (glycerol and amino acids), and glucose is then released released into the bloodstream

Question 3

What are the reasons for blood glucose concentration decreasing?

Answer 3

Respiration - Glucose is used by cells to release energy through respiration. The higher the level of physical activity, the higher demand for glucose, the greater the decrease in blood glucose concentration
Glycogenesis - When blood glucose is too high, excess glucose is converted into glycogen which is stored in the liver

Question 4

What does lysis mean?

Answer 4

To split

Question 5

What does neo mean?

Answer 5

New

Question 6

What does genesis mean?

Answer 6

Birth

Question 7

Where is insulin produced?

Answer 7

By β cells of the Islets on Langerhans in the pancreas

Question 8

How do β cells respond to a high blood glucose concentration?

Answer 8

The β cells detect the rise in blood glucose and secrete insulin directly into the bloodstream.

Question 9

How does insulin lower blood glucose?

Answer 9

-Increasing the rate of absorption of glucose by cells
-Increasing the respiratory rate of cells, this will increase their need for glucose and causes a higher uptake of glucose from the blood
-Increasing the rate of glycogenesis, insulin stimulates the liver to remove glucose from the blood by turning the glucose into glycogen and storing it in the liver and muscle cells
-Increasing the rate of glucose to fat conversion
-Inhibiting the release of glucagon from the α cells of the Islets of Langerhans

Question 10

How is insulin broken down

Answer 10

Broken down by enzymes in the cells of the liver.

Question 11

What is a normal blood glucose concentration

Answer 11

90 mgcm-3

Question 12

How does insulin allow the blood glucose to decrease?

Answer 12

Cells have insulin receptors. The insulin will bind to its glycoprotein receptor and change the tertiary structure of the glucose transport protein channels. The channels will now open allowing glucose to enter the cell. Insulin also activates enzymes to convert glucose to glycogen and fat

Question 13

How is negative feedback used in the regulation of blood glucose concentration

Answer 13

-If blood glucose falls below a set level, β cells will detect this and decrease their secretion of insulin. Alpha cells will release glucagon for the conversion of glycogen to glucose and other compounds to glucose
-If blood glucose concentration is higher, β cells will release insulin

Question 14

What is glycogenolyisis?

Answer 14

Glycogen stored in the liver and muscle cells is broken down into glucose which is released into the blood stream increasing blood glucose concentration

Question 15

What is gluconeogenesis?

Answer 15

The production of glucose from non-carbohydrate sources (glycerol and amino acids) and released directly into the blood stream

Question 16

What is glycogenesis?

Answer 16

The production of glycogen when blood glucose is too high, excess glucose is taken in through the diet and converted into glycogen which is stored in the liver

Question 17

Where is glucagon produced?

Answer 17

In the alpha cells in the islets of Langerhans

Question 18

When is glucagon released into the bloodstream?

Answer 18

When blood glucose levels are too low, the alpha cells detect the fall in blood glucose and respond by secreting glucagon into the blood stream

Question 19

Where in the body are glucagon receptors?

Answer 19

liver and fat cells

Question 20

Where in the body are insulin receptors?

Answer 20

All body cells apart from RBC’s

Question 21

How does glucagon increased blood glucose concentration?

Answer 21

• Glycogenolysis - the liver breaks down its glycogen store into glucose and release it back into the bloodstream
• Reducing the amount of glucose absorbed by the liver cells
• Increasing gluconeogenesis - increasing the conversion of amino acids and glycerol into glucose in the liver

Question 22

What are the steps for the control of insulin secretion?

Answer 22

1. At a normal blood glucose concentration, potassium channels in the plasma membrane of β cells are open and potassium ions diffuse out of the cell. Resting potential is maintained at -70mv
2. When blood glucose concentration rises, glucose enters the cell by a glucose transporter
3. The glucose is metabolised by the mitochondria through aerobic respiration to make ATP
4. The ATP binds with the potassium channels and causes the to close as they are ATP sensitive postassium channels
5. As the potassium ions cannot diffuse out of the β cell, the potential difference reduces to around -30mv and depolarisation occurs
6. Depolarisation causes the voltage-gated calcium channels to open
7. Calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis