Hormones Flashcards
What is a hormone?
A substance/chemical messenger that controls and regulates biological functions.
Acts by binding to a specific receptor on the cell surface/ within the target cell.
Interaction with receptor triggers and coordinates biological effect.
Autocrine ?
Local cell-cell diffusion
Act on neighbouring cells of same type
E.g. prostaglandins
Paracrine?
Local cell-tissue diffusion
Acts on different cell in the same tissue
E.g histamine
Endocrine?
Distributed by blood
Acts on distant target cells
E.g. insulin and growth hormone
What are peptide hormones?
Encoded by genes and synthesis as pre-propeptides by ribosomes.
Pre-propeptides transformers int biologically active peptide hormone b y proteolytic processing.
E.g. antidiuretic hormone
Synthesised as pro-insulin, which is converted to active insulin via 2 proteolytic enzymes.
What are amino-acid derived hormones?
Not directly encoded by genes.
Indirectly produced by genes of enzymes which enzymatically produce these hormones using certain amino acids.
E.g. adrenaline, serotonin, dopamine
Thyroxine - derives from amino acid tyrosine
Serotonin - derived from amino acid tryptophan
What are steroid and sterol hormones?
Not directly encoded by genes.
Indirectly produced by genes of enzymes which produce these hormones fro cholesterol.
E.g. cortisol, progesterone, testosterone
Testosterone and calciferol - synthesised from cholesterol
What are lipid hormones?
Synthesised from fatty acids by specific enzymes.
E.g leukotrienes, prostaglandins
What are gaseous hormones?
Produced from amino acids arginine and oxygen.
E.g. nitric oxide
How do ion channels work?
- Binding of hormone
- Receptor change conformation
- Open its ion channel
- Ions move from extracellular side into cell
- Membrane depolar - biological effect triggered by hormone
E.g. serotonin, GABA
How do G-protein coupled receptors work?
- Hormone binds to receptor
- Receptor changes shape
- Leads to exchange of GDP>GTP in the alpha subunit of the G protein
- Exchange leads to disassociation of alpha subunit
- Alpha subunit Indus to antohereffe chords protein (e.g Ca channel)
- Ca channel opens upon binding of subunit and Ca influx occurs
- Leads to increase of intracellular mediators
- Eventually the alpha subunit hydrolysed attached GTP to GDP
- Disassociation of subunit from Ca channel
- Ca channel closes, stopping Ca influx
- Alpha subunit re-associates with beta and gamma subunit so activation cycle can restart
E.g. adrenaline
How does G protein kinase pathway work?
- Hormone binds to receptor
- GTP to GDP, alpha subunit disassociated from beta and gamma subunits
- Alpha subunit binds to ardently cyclase
4.cAMP - second messenger which activates protein kinases - Protein kinases phosphorylates prolines, activating them
E.g glucagon
How does the G protein phospholipase C pathway work?
- Phospholipase C - enzyme which cleaves PIP2 to IP3 and DAG (which regulate activity of enzymes)
- IP3 releases Ca ions from endoplasmic reticulum and opens Ca channels in plasma membrane.
- DAG activates protein kinase C which phosphorylates other proteins activating them
E.g adrenaline
How does the guanyly cyclase pathway work? M
- Hormone binds to receptor.
- Conformational changes in receptor activates associated guanylyl cyclase
- GC converts GTP to cGMP
- CGMP activates protein kinases which them phosphorylates other proteins, activating them
E.g atrial natriuretic
How does the kinase pathway work?
- Hormone binds to receptor
- Conformational change triggers intrinsic kinase activity of receptor
- Receptor phosphorylates specific proteins using ATP
- Phosphorylation can lead to activation or inhibition of protein
E.g insulin
