Hormonal Communication

Question 1

The endocrine system

Answer 1

A communication system using hormones as signalling molecules

Question 2

Protein hormones

Answer 2

• derivatives of amino acids
• not soluble in the phospholipid membrane and do not enter the cell
• bind to cell surface membrane and release a second messenger inside the cell

Question 3

Steroid hormones

Answer 3

enter the cell and have a direct effect on the DNA in the nucleus

Question 4

Endocrine glands

Answer 4

ductless glands that release hormones directly into the blood in capillaries running through the gland.

Question 5

Exocrine glands

Answer 5

consist of groups of cells surrounding a small duct. Secrete products (not hormones) into the duct.

Question 6

Target cells

Answer 6

The cells receiving an endocrine signal. For non steroid hormones, cells possess a specific receptor on their plasma membrane.

Question 7

First messengers

Answer 7

Non steroid hormones are first messengers. They bind to the cell surface membrane and initiate an effect inside the cell. They cause the release of a second messenger.

Question 8

Second messengers

Answer 8

Second messengers are released after a first messenger has initiated a response. the G protein is activated when the hormone binds to the receptor and it activates an effector molecule such as the enzyme adenyl cyclase which converts ATP to cAMP. The second messenger may act directly on another protein or may initiate a cascade of enzyme controlled reactions.

Question 9

Adrenal glands

Answer 9

a pair of glands above the kidneys which release adrenaline and some other hormones known as corticoids.

Question 10

The outer layer of the adrenal cortex

Answer 10

Is called the zona glomerulosa and secretes mineralocorticoids

Question 11

The middle layer of the adrenal cortex

Answer 11

Is called the zona fasciculata and secretes glucocorticoids

Question 12

The innermost layer of the adrenal cortex

Answer 12

Is called the zona reticularis and secretes precursor molecules used to make sex hormones

Question 13

The action of steroid hormones

Answer 13

1. Hormone passes through cell membrane of target cell
2. Hormone binds with specific receptor in the cytoplasm
3. The receptor-steroid complex enters the nucleus of the target cell and binds to a specific receptor on the chromosomal material
4. Binding stimulates the production of mRNA which codes for the production of proteins.

Question 14

Mineralocorticoids

Answer 14

• from the zona glomerulosa
• helps to control concentrations of potassium and sodium in the blood
• contribute to maintaining blood pressure

Question 15

Glucocorticoids

Answer 15

• from the zona fasciculata

- helps control metabolism of carbohydrates, fats and proteins in the liver.

Question 16

Adrenaline

Answer 16

• from the adrenal medulla
• polar molecule so can’t enter plasma membrane
• many cells and tissues have adrenaline receptors so it has a lot of effects on the body

Question 17

Effects of adrenaline on the body

Answer 17

• relaxing smooth muscle in bronchioles
• increasing stroke volume of the heart
• increasing heart rate
• causes vasoconstriction to raise blood pressure
• stimulates conversion of glycogen to glucose
• dilates pupils
• increases mental awareness
• inhibits the action of the gut

Question 18

The exocrine function of the pancreas

Answer 18

Pancreatic cells synthesise and release digestive enzymes. The groups of cells are called acini and are grouped into small lobules separated by connective tissue. The enzymes are secreted into a tubule at the centre of the group. The tubules of the acini join to form intralobular ducts that combine to form the pancreatic duct.

Question 19

Alpha cells secrete…

Answer 19

glucagon

Question 20

Beta cells secrete…

Answer 20

Insulin

Question 21

Releasing insulin

Answer 21

1. Cell membrane has potassium and calcium ion channels
2. The potassium ion channels are normally open so K+ ions diffuse out making the inside more negative
3. When blood glucose concentration is high, glucose moves into the cell
4. Glucose is metabolised using the enzyme glucokinase to produce ATP
5. The ATP closes the K+ ion channels
6. [K+] increases altering the potential difference so the inside becomes less negative.
7. This change opens calcium ion channels
8. Calcium ions entering cause vesicles of insulin to fuse with the membrane and then be released by exocytosis

Question 22

Low blood glucose concentration is called and can cause…

Answer 22

Hypoglycaemia

tiredness, confusion, seizures, unconsciousness

Question 23

High blood glucose concentration is called and can cause…

Answer 23

Hyperglycaemia

Organ failure, diabetes

Question 24

If blood glucose rises too high

Answer 24

1. detected by beta cells in the islets of Langerhans
2. beta cells secrete insulin into the blood
3. Insulin binds to insulin receptors on liver and muscle cells activating the enzyme tyrosine kinase
4. Tyrosine kinase causes phosphorylation of inactive enzymes inside the cells activating a cascade of enzyme controlled reactions
5. Liver and muscle cells convert glucose to glycogen

Question 25

Insulin effects on cells

Answer 25

- more transporter proteins specific to glucose placed on plasma membrane - more glucose enters the cell - glucose is converted to glycogen for storage (glycogenesis) - more glucose converted to fats - more glucose used in respiration

Question 26

If blood glucose is too low

Answer 26

1. detected by alpha cells in islets of Langerhans 2 alpha cells secrete glucagon into the blood 3. glucagon binds to receptors on hepatocytes stimulating a G protein which activates adenyl cyclase inside the cell 4. ATP is converted to cAMP which activates series of ec reactions 5. liver cells convert glycogen to glucose

Question 27

effects of glucagon

Answer 27

- glycogen is converted to glucose (glycogenolysis) by phosphorylase A - more fatty acids used in respiration - amino acids and fats converted to glucose by gluconeogenesis

Question 28

Gluconeogenesis

Answer 28

Amino acids and fats converted to glucose

Question 29

glycogenesis

Answer 29

conversion of glucose to glycogen for storage

Question 30

glycogenolysis

Answer 30

glycogen converted to glucose by phosphorylase A

Question 31

Type 1 diabetes is caused by

Answer 31

An autoimmune response where the immune system attacks and destroys beta cells. Or a viral attack.

Question 32

Factors increasing chance of type 2 diabetes

Answer 32

- obesity - lack of regular exercise - diet high in sugars - family history

Question 33

Treating type 1 diabetes

Answer 33

- insulin injections - insulin pump therapy - islet cell transplantation - pancreas transplantation - stem cells

Question 34

Treating type 2 diabetes

Answer 34

Usually treated by changes in lifestyle - losing weight, regular exercise, carefully monitoring diet. This may be supplemented by medications.

Question 35

Advantages of using genetically modified bacteria to make human insulin

Answer 35

- exact copy of human insulin so effective - Less chance of rejection due to an immune response - lower risk of infection - cheaper than extracting from animals - manufacturing process is adaptable to demand - Less moral issues using bacteria rather than animals