Hormones

Question 1

State the pathway of hormonal communication. (5)

Answer 1

Stimulus → receptors → hormone release → effector (on target cells) → response

Question 2

State the definition of an endocrine gland. (1)

Answer 2

Groups of cells that are specialised to release hormones directly into the blood

Question 3

State the definition of an exocrine gland. (1)

Answer 3

Groups of cells that are specialised to release hormones into a duct

Question 4

State the definition of a hormone. (1)

Answer 4

• A chemical messenger
• Can be proteins or peptides e.g. insulin
• Or steroids e.g. progesterone

Question 5

State the definition of target tissue. (2)

Answer 5

• A group of cells that contain receptors complementary to the hormone released
• When the hormone binds, it will trigger a response from the target cells

Question 6

Describe the structure of the adrenal glands. (3)

Answer 6

• The adrenal gland is located on top of the kidney
• The outer area is called the cortex
• The inner area is called the medulla

Question 7

Explain how what occurs when blood glucose concentration is too low. (7)

Answer 7

• Pancreas detects decrease in blood glucose concentration
• Pancreas secretes glucagon
• Glucagon binds to receptors on liver and muscle cells
• Glycogenolysis is activated (glycogen broken down in to glucose)
• Gluconeogenesis is activated (glycerol and amino acids used to make glucose)
• Cells respire less glucose
• Blood glucose concentration rises

Question 7

Describe the function of the adrenal medulla and the hormones that it secretes. (3)

Answer 7

• The medulla secretes catecholamine hormones (modified amino acids)
• e.g. adrenaline and noradrenaline when you’re stressed
• Effects include - increasing heart and breathing rate to make more energy available, causing cells to break down glycogen into glucose and constricting some blood vessels so blood is diverted to the brain and muscles

Question 8

Describe the function of the adrenal cortex and the hormones that it secretes. (4)

Answer 8

• The cortex secretes steroid hormones
• e.g. cortisol and aldosterone when you’re stressed
• Effects of cortisol include – stimulating the breakdown of proteins and fats in to glucose to be respired and suppressing the immune system
• Effects of aldosterone include – increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys

Question 9

Describe the structure of the pancreas. (4)

Answer 9

• The pancreas contains Islets of Langerhans which acts as endocrine tissue which are surrounded by capillaries
• They consist of alpha cells that secrete glucagon and beta cells that secrete insulin
• The pancreas also contains exocrine tissue
• Which secretes digestive enzymes into the pancreatic duct

Question 9

Describe the causes and treatments of type 2 diabetes. (3)

Answer 9

• Occurs when the beta cells don’t produce enough insulin or when the body cells don’t respond properly to insulin
• This is because insulin receptors on the membranes do not work so glucose is not taken up in to cells
• It is managed through lifestyle changes but medication can be prescribed
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Question 10

Describe how to examine stained sections of the pancreas. (3)

Answer 10

• The cells can be differentiated if a special stain has been used to make them different colours
• The islets of Langerhans appear as paler patches amongst all other cells
• Beta cells will be stained purple
• Alpha cells will be stained pink

Question 10

Describe the causes and treatments of type 1 diabetes. (3)

Answer 10

• It is an autoimmune disease in which the body attacks and destroys the beta cells in the islets of Langerhans
• It is treated by using insulin injections, regular monitoring of blood glucose concentration, regular exercise and a healthy diet
• Some people have been successfully treated by having islet cell transplantation

Question 11

Explain how what occurs when blood glucose concentration is too high. (7)

Answer 11

• Pancreas detects increase in blood glucose concentration
• Pancreas secretes insulin
• Insulin binds to receptors on liver and muscle cells
• Cells take up more glucose
• Glycogenesis is activated (converting glucose to glycogen)
• Cells respire more glucose
• Blood glucose concentration falls

Question 12

Explain the control of insulin secretion by beta cells. (8)

Answer 12

• When high blood glucose concentration is detected, more glucose enters beta cells by facilitated diffusion
• This increases rate of respiration, more ATP is produced
• Increase in ATP triggers potassium ion channels to close
• Potassium ions build up inside the cells depolarising the membrane (inside is less negative)
• Depolarisation triggers calcium ion channels to open
• Calcium ions diffuse into the beta cell
• This causes vesicles to fuse with the plasma membrane
• Insulin is released via exocytosis

Question 12

Describe the action of hormones in cell signalling. (4)

Answer 12

• A hormone is called the first messenger because it carries the chemical message from the endocrine gland to the receptor on the target cell
• When a hormone binds to its receptor, it activates an enzyme in the cell membrane
• The enzyme catalysis the production of a molecule inside the cell called a signalling molecule
• This is known as the second messenger, it can activate a chain or reactions inside the cell to trigger a response

Question 13

Explain how adrenaline acts as a first messenger. (4)

Answer 13

• Adrenaline binds to specific receptors of many cells e.g. liver cells
• It activates an enzyme called adenyl cyclase
• This catalyses the production of cAMP from ATP
• cAMP acts as a second messenger to activate a cascade of enzyme reactions to make glucose more available

Question 14

Give 4 advantages of using insulin produced by genetically modified bacteria. (4)

Answer 14

• Producing insulin from GM bacteria is cheaper than extracting it from animal pancreases
• Larger quantities of insulin can be produced
• GM bacteria makes human insulin which is more effective and less likely to be rejected than using pig or cattle insulin
• Less ethical or religious reasons e.g. some vegetarians may object to the use of animals and some religious people may object to using insulin from pigs

Question 15

Explain how stem cells can be used to cure diabetes. (2)

Answer 15

• Stem cells can be used to make beta cells that could be implanted into the pancreas of a person with type 1 diabetes
• This would allow the person to make insulin as normal