Hormones structure and function Flashcards
What are most hormones soluble in?
Water - therefore do not cross cell membranes, they interact with cells via receptors
What hormones CAN cross the cell membrane?
Lipid soluble hormones, e.g. testosterone
What are hormones?
Signalling molecules - messengers. They are secreted from a gland-like cell and circulate in the blood and have impacts upon target cells
What are target cells?
Cells that respond to a hormone (highly selective). They only respond to those hormones for which they have the cognate receptors
What are the 3 types of responses to hormones?
1) Endocrine
2) Paracrine
3) Autocrine
What is an endocrine response?
Delivered when target cell is some distance away from secretary cell
What is a paracrine response?
Where the target cell is closer to the secretary cell - sometimes right next to it (in the pancreas)
What is an autocrine response?
Where a hormone is released from secretary cell and loops back to have an effect on ITSELF (e.g. beta cell secretes insulin and has a negative feedback cell)
What has an effect on hormone response?
Distance travelled by the hormone
What are small chemical hormones?
Modified amino acids e.g. adrenaline, dopamine
What are peptide hormones?
Sequences of amino acids, generally in the range 3-20 e.g. endorphin (any more than 20 AAs and it becomes a protein hormone)
What are protein hormones?
Proteins may be larger single polypeptide chains e.g. growth hormone has 191 AAs and is a large protein)
What sort of hormone is insulin?
Protein hormone with 2 different subunits (A and B chains of insulin)
What are complex chemical hormones?
e.g. lipid-derived steroids, testosterone, cortisol etc
What may molecules with similar shapes do?
Bind to similar receptors and this may lead to side effects or cross reactivity
What are Oxytocin and Antidiuretic Hormone (ADH) produced by?
The posterior pituitary gland.
They’re very similar structures - only differ by 2 amino acids
They are PEPTIDE HORMONES
What effects can Oxytocin have?
Can have a slight anti-diuretic (as well as primary endocrine function) function and will bind to receptors
What effects can ADH have?
Can cause uterine contractions because it binds to oxytocin receptor
What are Growth Hormone and prolactin and what are they produced by?
PROTEIN HORMONES produced by the anterior pituitary.
What does Growth Hormone do?
Stimulates growth, cell division and regeneration. It is a mitogen (stimulates mitosis) specific only to specific to certain kinds of cells
What does prolactin do?
Protein closely related to GH and Placental Lactogen (PL) with properties and functions resembling both a hormone and a cytokine (stimulating growth)
What are FSH and TSH produced by?
Protein hormones produced in the anterior pituitary.
They have hetero-dimeric structures, both parts bind to receptor (e.g. insulin)
What does TSH stand for and what does it bind to?
Thyroid Stimulating Hormone, binds to TSH receptor in thyroid cells)
What does FSH stand for and what does it bind to?
Follicle Stimulating Hormone, binds to FSH receptor in ovarian cells
What is insulin?
Hetero-dimer produced by the pancreas hetero-dimer. It’s composed of 2 amino acid chains with disulphide bridges (these form specific 3D structures so that the structure can lock on to cognate receptors) holding them together (monomeric structure)
What can insulin form?
Can form dimers, trimers and crystalline structures (if stored in secretary granules) – breaks down as they are secreted with high concentration of hormone
Why can’t the oral route be used for delivering peptide and protein pharmaceuticals?
Because proteins get digested and broken down in the stomach
What are 3 options for peptide and protein drug delivery?
- Injection IV or SC
- Aerosols for inhalation
- Depot formulations, modified release systems (e.g. microspheres) etc used for delivery of growth hormone
To reduce need for multiple injections – better compliance etc
What does Tyrosine give rise to?
Adrenaline, noradrenaline and dopamine
What is PNMT?
Expression of this enzyme is induced by cortisol (STRESS) and associated with the production of adrenaline
Why is more adrenaline produced compared to noradrenaline?
4 times as many adrenaline producing cells in the medulla, therefore more adrenaline is produced compared to noradrenaline
What hormone is derived from tryptophan?
Melatonin
What are lipid-derived hormones?
Steroid hormones: progesterone, testosterone, cortisol, oestradiol
What is steroidogenesis?
A synthetic process that begins with cholesterol as a substrate and, through a series of enzymatic reactions, produces a wide array of bioactive interrelated signaling molecules
