module 5.1.4

Question 1

what is the endocrine system

Answer 1

a system used for communication around the body. It uses hormones as signals and the circulatory system to transport them

Question 2

what do endocrine glands secrete

Answer 2

hormones directly into the blood—they consist of a group of specialised cells that manufacture and secrete the hormones into the capillaries running through the gland, with no visible ducts. examples include, the pituitary gland, thyroid gland, thymus, adrenal glands, pancreas, and ovaries/testes

Question 3

are steroid hormones lipid soluble or insoluble

Answer 3

lipid soluble

Question 4

as steroid hormones are lipid soluble, what does it mean it can do

Answer 4

therefore can diffuses across the plasma membrane and enter the cell and nucleus, to have a direct effect on the DNA in the nucleus

Question 5

steroid hormones action is specific, so what do they only act on

Answer 5

• target cells with complementary nuclear or cytosolic steroid hormone receptors. the steroid-receptor hormone complex enters the nucleus of the target cell and binds to another specific receptor on the chromosomal material. binding stimulates the production of mRNA molecules, which code for the production of proteins, often enzymes

Question 6

what are some examples of steroid hormones

Answer 6

oestrogen
testosterone

Question 7

what are some examples of protein and peptide hormones

Answer 7

adrenaline
insulin
glucagon

Question 8

are protein and peptide hormones lipid soluble or insoluble

Answer 8

not soluble in the lipid membrane and do not enter the cell

Question 9

what do protein hormones bind to

Answer 9

• a specific complementary receptor site in the plasma membrane of a target cell, triggering the release of a secondary messenger which effects a change in the cell
• this allows specific cells to be targeted, such as the action of adrenaline on cells in the central nervous system and tissues innervated by the peripheral nervous system, such as the heart, smooth muscle and skeletal muscle

Question 10

what do non-steroid hormones act as

Answer 10

primary, or first, messengers that bind to the cell surface membrane and effect a change inside the cell, through the action of a secondary messenger

Question 11

what is an example of a non steroid hormone

Answer 11

cyclic Adenosine Mono-Phosphate (cAMP)

Question 12

what does cAMP activate

Answer 12

proteins

Question 13

explain the process in which cAMP works

Answer 13

when a signalling molecule, such as the protein hormone glucagon or insulin, binds to receptor sites in the plasma membrane of a target cell, it activates a transmembrane protein, which activates a G protein
- this activates the membrane protein adenylyl cyclase, catalysing the formation of cAMP from ATP. cAMP phosphorylates protein kinase A, which phosphorylates a number of other proteins, facilitated by the hydrolysis of ATP. this activates enzymes in the cytoplasm which perform glycogenolysis - PKA also phosphorylates CREB, which acts as a transcription factor, altering gene expression at a transcriptional - level. at each stage, the number of product molecules increase, producing a cascade effect, augmenting the action of the enzyme