SAC - signalling molecules Flashcards
What is a signalling molecule?
is a molecule which enables communication between cells. When a signalling molecule binds to the receptor of a target cell it causes the target cell to carry out a response.
What are types of signalling molecules?
Hormones, neurotransmitters, neurohormones, cytokines, pheromones.
What is the stimulus response model?
Stimulus –> receptor–> control centre–> effector–> response
What is a hormone?
Signalling molecule produced by glands in multicellular organisms transported by the circulatory system to target organs to regulate physiology and behaviour.
What are neurotransmitters?
the body chemical messengers, they are the molecueles used by the nervous system to transmit messages between neurons.
What are neurohormones
group of substances which are secreted by cells which pass along nerve cell extensions and release into the blood stream.
What are cytokines
group of internal signalling molecules which act as cell messengers in a number of ways including stimulating cells to reproduce, initiate transduction pathways, inhibit cells from reproducing.
What are pheromones
external signalling molecules which are released into the environment with the hope of finding a target cell in another organism. They have a effect on a large number of organisms in a variety of ways?
What are the steps involved in the stimulus response model?
Reception - the binding of the signal molecule to its specific receptor.
Transduction - requires a series of changes in a sequence of different molecules.
Response - when the target cell responds to the signal received.
How do hydrophilic (lipophobic) hormones work?
Example - amines/ proteins.
Larger peptide hormones cannot pass through the membrane to a receptor site, so the receptor its therefore on the cell surface. The signal/ receptor complex begins stimulation of secondary messengers, which results in a response.
How do hydrophobic (lipophilic) hormones work?
Example - steroids.
small hydrophobic hormones can pass through the membrane, usually activating protein synthesis. Steroids enter the cell directly and interacts with protein receptor in the cytoplasm.
What is apoptosis?
The genetically controlled and highly regulated process of cell self destruction
What is intrinsic activation of apoptosis?
Or the mitochondrial pathway, is initiated from within the cell. The mitochondria is important in telling the cells when it is time to die.
What is extrinsic activation of apoptosis?
Is activated from outside the cell, when molecules from outside the cells bind to death receptors on the plasma membrane and it is signalled ‘its time to die’
