module 5.1.4 Flashcards
what is the endocrine system
a system used for communication around the body. It uses hormones as signals and the circulatory system to transport them
what do endocrine glands secrete
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
are steroid hormones lipid soluble or insoluble
lipid soluble
as steroid hormones are lipid soluble, what does it mean it can do
therefore can diffuses across the plasma membrane and enter the cell and nucleus, to have a direct effect on the DNA in the nucleus
steroid hormones action is specific, so what do they only act on
- 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
what are some examples of steroid hormones
oestrogen
testosterone
what are some examples of protein and peptide hormones
adrenaline
insulin
glucagon
are protein and peptide hormones lipid soluble or insoluble
not soluble in the lipid membrane and do not enter the cell
what do protein hormones bind to
- 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
what do non-steroid hormones act as
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
what is an example of a non steroid hormone
cyclic Adenosine Mono-Phosphate (cAMP)
what does cAMP activate
proteins
explain the process in which cAMP works
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