5.4 Hormonal Communication

Question 1

What are some examples of protein vs steroid hormones?

Answer 1

Protein: adrenaline, insulin and glucagon
Steroid: oestrogen, testosterone

Question 2

What are endocrine glands?

Answer 2

groups of cells that secrete the hormone directly into capillariesinto the bloodstream. they are ductless

Question 3

What are target cells? What is special about them for non steroid hormones?

Answer 3

• cells recieving the signal
• have specific membrane receptor that is complementary to the hormone
• only those specific cells that possess the correct receptor will respond

Question 4

What is the first messenger?

Answer 4

non steroid hormone

Question 5

What is a second messenger?

Answer 5

a molecule stimulated by a first messenger and stimulates a change in cells activity, many act via a G protein

Question 6

What is the main cell signalling process?

Answer 6

• hormone binds to receptor
• activates a G protein
• this activates adenyl cyclase to produce cAMP from ATP (second messenger)
• this activates channel proteins or causes a cascade of enzyme-controlled reactions

Question 7

What is the inner and outer part of an adrenal gland called?

Answer 7

outer = cortex
inner - medulla

Question 8

What 3 layers make up the cortex?

Answer 8

zona glomerulosa
zona fasciculata
zona reticularis

Question 9

What hormones are released from the zona glomerulosa?

Answer 9

• mineralocorticoids:

e.g. aldosterone

• act on cells of DCT and CD
• maintain blood pressure
• inc Na+ absorp, dec K+ absorp, inc water retention

Question 10

What hormones are released from the zona fasciculata?

Answer 10

• glucocorticoids:

e.g. cortisol in response to stress and low glucose conc

• help to control carb, fat and protein metabolism in liver
• stimulates production of glucose from stored compounds.

Question 11

What hormones are released from the zona reticularis?

Answer 11

precursor androgens

taken up by ovaries and testes and converted to sex hormones, regulate gamete production and help development of secondary sexual characteristics

Question 12

How do steroid hormones act?

Answer 12

• use cholesterol to be produced
• dissolve into plasma membrane
  binds with specific receptor in cytoplasm
• this complex enters nucleus and binds to another receptor on chromosomal material
• stimulates transcription

Question 13

What hormones are released from the medulla?

Answer 13

Adrenaline: POLAR, derived from tyrosine. Many cells and tissues have receptors for it.
Effects-> relaxing bronchiole smooth muscle, inc heart rate, inc stroke volume, vasoconstriction, dilating pupils, inhibiting gut action, body hairs stand erect, glycogen conversion to glucose.

Nonadrenaline: inc heart rate and blood pressure, widens pupils.

Question 14

What is the role of acini?

Answer 14

small lobules separated by connective tissue. surround tiny tubules. they secrete enzymes into tubule at centre -> join to form intralobular ducts that then combine to make the pancreatic duct

Question 15

What is the role of the pancreatic duct?

Answer 15

carries fluid with enzymes into duodenum
amylase: digests amylose and maltose
trypsinogen: converted to active trypsin
lipase

also sodium hydrogencarbonate to neutralise contents

Question 16

Describe the endocrine function of the pancreas

Answer 16

In Islets of langerhans

Beta cells secrete insulin, alpha cells secrete glucagon.

Question 17

Explain the process of insulin release

Answer 17

1. Potassium ions USUALLY flow out
2. When glucose conc is HiGH it diffuses (facilitated) into cell.
3. Glucose metabolised to produce ATP. Involves glucokinase
4. ATP closes K+ channels
5. Accumulation of K+ alters potential difference across membrane: inside its less neg
6. This change opens Ca2+ channels
7. These ions cause vesicles with insulin in to fuse with the cell membrane
8. Exocytosis

Question 18

What is it called when glucose levels are too high or too low?

Answer 18

High: HYPERglycaemia (organ damage) Low: HYPOglycaemia (inadequate glucose to brain)

Question 19

What is the response to insulin in the target cells e.g. liver, muscle and some others like the brain?

Answer 19

• insulin binds to receptor
• activates tyrosine kinase
• causes phosphorylation of inactive enzymes to active ones
• vesicles with glucose transport proteins fuse with membrane and extra glucose enters
• glycogenesis occurs to make glycogen, glucose is also converted to fats and used in respiration

Question 20

What is the response to glucagon in the target cells (liver cells)?

Answer 20

same process as before with the G protein.

then glycogenolysis catalysed by phosphorylase A
fatty acids used in respiration
gluconeogenesis

Question 21

The regulating blood glucose process is done via ‘n…. f…..’ and hormones are ‘a…..’

Answer 21

negative feedback

antagonistic

Question 22

Hormones can be classed as either steroid or non steroid. Steroids are lipid soluble. Suggest the location of the receptors for steroid hormones and state a reason for your suggestion (2)

Answer 22

inside cells/ cytoplasm/ nucleus

can cross the cell surface membrane

Question 23

Studies on effects of hCG in humans have revealed the following:

Many different tissues are affected by hCG
Susceptible cells have glycoprotein receptors on their cell surface
These receptors are complementary to the shape of hCG molecules

What can be concluded from this information? (3)

Answer 23

• peptide hormone
• binds to cell surface receptor
• cell signalling is involved in its action
• uses cAMP/secondary messenger to bring about response

Question 24

Another hormone produced during pregnancy is oestrogen. Oestrogen is lipid soluble. Which molecule does oestrogen interact with when it changes cell activity? (1)

Answer 24

DNA

Question 25

What is diabetes mellitus?

Answer 25

condition in which blood glucose concentrations cannot be controlled effectively

Question 26

What causes Type 1 diabetes?

Answer 26

thought to be an autoimmune response, usually starts in childhood

bodys immune system destroys beta cells -> no longer able to synthesise enough insulin.

Question 27

What causes Type 2 diabetes?

Answer 27

can produce insulin, where many cells are resistant to it (cell receptors not as responsive) or not enough is produced

obesity, lack of exercise, high sugar diet.

Question 28

How do you treat type 1 diabetes?

Answer 28

insulin injections, insulin pump therapy, islet cell transplantation, pancreas transplant

or, recent research has shown possibility of using STEM CELLS. if human precursor pancreas cells can be found, they could be used to produce new beta cells = freedom from injections

Question 29

How do you treat type 2 diabetes?

Answer 29

changes in lifestyle -> lose weight, lower carb intake, exercise regularly, supplemented by medication

Question 30

More recently, insulin has been produced by ——- that have undergo ——- ——— to manufacture human insulin. What are the advantages?

Answer 30

1. exact copy -> more effective
2. less chance of rejection
3. lower risk of infection
4. cheaper to manufacture than to extract from animals
5. more adaptable to demand
6. less likely to have moral objections