multicellular organismi survive, grow and reproduce…
- multicellular organismi survive, grow and reproduce because they are able to detect and respond to signals from their internal and external environments.
a chemical or physical change that activates a receptor molecule in a cell and generates a response, such as the production of a hormone.
eg. changes in pressure, light, temperature and chemical molecules.
In cellular communication, the response is the action or change in functionality of a cell that occurs as a result of a specific stimulus.
eg. the release of a neurotransmitter into a synapse in response to an action potential.
a molecule, such as a neurotransmitter or hormone, that is involved in chemical communication between cells.
A cell that responds to signaling molecules.
Eg. a cell in which a signal transduction pathway activates an enzyme and causes metabolic change in the cell.
A molecule in a cell membrane (sometimes on the inside of a cell) that binds and responds to specific molecules such as hormones and neurotransmitters, triggering a response.
MODE OF TRANSMISSION
Autocrine signalling - signalling molecules act on the cell or same type of cell that secreted them.
Ex: T-cells produce cytokines for which they have a receptor --> promotes cell division.
Paracrine signalling - signalling molecules act on cells that are close to the secreting cells.
Eg. neurotransmitters act on post-synaptic cells.
Endocrine signalling - signalling molecules act on cells that are far from the cells that secretes them.
Eg. animal hormones released from gland into bloodstream.
ANIMAL HORMONES:source: glands and organs
mode of transmission: autocrine, paracrine (through intertextual fluid between cells), endocrine (via the blood circulation)
- produced in tiny amounts --> long lasting effects on target cells.
- regulate growth and activity of cells.
- part of the endocrine system
- hormones are transported to target cells via bloodstream
- a single hormone can trigger different responses in multiple target cells at the same time.
Lipid Hormones - hydrophobic
- derived from fatty acids (eicosanoids) and cholesterol (steroids).
- Eicosanids include prostaglandins, which are involved in cell growth, fever and inflammation.
- Steroid hormones help to regulate metabolism, salt and water balance, inflammation and sexual function.
Ex: testosterone , oestrogen and cortisol.
Peptide and protein hormones - hydrophilic
- Ex: peptide = insulin, protein = growth hormone.
Amino-acid-derived hormones - hydrophobic/hydrophilic
- derived from tyrosine and tryptophan.
- whether the hormone is hydrophobic or hydrophilic depends on the amino acid they are derived from, this changes because of the change in R group.
- Ex: thyroxine, adrenaline
PLANT HORMONES:source: most plant cells
mode of transmission: diffusion (various)
- produced in tiny amounts --> long-lasting effect on target cells.
- regulate growth and activity of cells
- each plant cell is able to produce many different types of plant hormones (different to animal!!)
mode of transmission: diffusion through air
- excreted into the external environment of an organism.
- influences behaviour or physiology of another individual.
- ex: triggering alarm, marking territory, marking food trails, attracting mates.
mode of transmission: paracrine
- hydrophobic signalling molecules
- neurotransmitters are released into synapses - they diffuse across the gap and bind to receptors on the surface of postsynaptic neuron.
- involved in cellular responses including; movement, relating hormone production and organ function.
- ex: serotonin, dopamine
source: cells of the immune system
mode of transmission:autocrine and paracrine (most common), endocrine.
- hydrophilic signalling molecules
- involved in communication between immune cells.
- released by cells in response to damage or pathogens (macrophages, T-lymphocytes, B-lymphocytes)
- bind to receptors on surface of target cells.
- ex: interferons, interluikins.