5.4.1 endocrine communication

Question 1

endocrine system

Answer 1

communication system using hormones as signalling molecules

Question 2

hormones

Answer 2

molecules (proteins/steroids) that are released by endocrine glands directly into blood - act as messengers which carry signal from glands to specific target organ/tissues

Question 3

target cells

Answer 3

for non-steroid hormones, cells which possess specific receptor on plasma membrane - shape of receptor complementary to hormone molecule

–> many similar cells together form target tissue

Question 4

types of hormones

Answer 4

1. protein & peptide hormones, and derivatives of amino acids - eg. adrenaline, insulin, glucagon
2. steroid hormones eg. oestrogen, testosterone

Question 5

how do protein & peptide hormones work

Answer 5

• proteins not soluble in phospholipid membrane & don’t enter cell
• need to bind to cell surface membrane & release second messenger inside cell

Question 6

how do steroid hormones work

Answer 6

• pass through membrane & enter cell/nucleus
• have direct effect on dna in nucleus (if enter it)

Question 7

describe endocrine glands

Answer 7

ductless = consist of groups of cells that manufacture/release hormone directly into bloodstream via capillaries running through gland

Question 8

types of glands

Answer 8

• endocrine gland = secrete hormones
• exocrine glands = don’t secrete hormones & consist of group of cells surrounding small duct where the products are secreted from cells eg. salivary gland

Question 9

target cells

Answer 9

cells receiving endocrine signal

Question 10

target cells for non-steroid hormones

Answer 10

• must possess specific receptor on plasma membrane with complementary shape to signalling molecule (hormone)
• hormone binds to receptor & initiates changes in cell

Question 11

what are non-steroid hormones known as

Answer 11

first messengers

Question 12

what are first messengers

Answer 12

• signalling molecules outside cell
• bind to cell surface membrane
• initiate effect in cell
• usually cause release of another signalling molecule in cell = second messenger

Question 13

what are second messengers

Answer 13

• stimulates change in activity of cell
  eg. cAMP

Question 14

explain what occurs due to non-steroid hormones in the cell

Answer 14

1. non-steroid hormones act via G protein in membrane
2. G protein activated when hormone binds to receptor
3. G protein then activates effector molecule
   - usually enzyme which converts inactive molecule into active second messenger
4. many cells, effector is enzyme adenyl cyclase, which converts ATP to cyclic AMP (cAMP)
   - cAMP is second messenger
5. second messenger may act directly on another protein (eg. ion channel) or initiate cascade of enzyme-controlled reactions which alter cell activity