Summary
Summary Cell Signalling Module Complete Notes
Complete summary of the cell signalling module for the BIO1000F course at UCT but could be used for a variety of cellular biology courses at first year level :)
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Module 6 Cell CommunicationChapter 9
CELLULAR MESSAGING
Cells can..
• Send signals to other cells
• Interpret signals from
• Other cells
• The environment (eg. Light and touch)
• Signals = often chemicals
• eg. Epinephrine/adrenaline signalling molecules (secreted from adrenal glands
CONCEPT 9.1 EXTERNAL SIGNALS ARE CONVERTED TO RESPONSES WITHIN THE CELL
Evolution of Cell Signalling
• Sex = type of cell conversation
• eg. Saccharomyces cerevisiae (yeast for bread, wine + beer)
• Identify mates via chemical signalling
• Two sexes/mating types ( a and ⍺ )
• Each mating type secretes a speci c factor that binds ONLY receptors on the
other cell
• When exposed to each other’s mating factors…(=chemical messengers)
• Pair of cells of opposite type change shape, grow toward each other + fuse/mate
• a/⍺ cell contains the genes of
both original cells — combination
of genetic resources
∴ advantageous to cell’s
descendants (via subsequent cell divisions)
• Once mating signal is received by a
surface receptor
• Changed/transduced into a form
that brings about mating cellular
response
• SIGNAL TRANSDUCTION
PATHWAY = a series of steps by
which a signal on a cell’s surface
is converted to a speci c cellular
response
• Molecular details of signal transduction in
yeasts and mammals = similar
∴ ancestral signalling molecules evolved in
prokaryotes and single celled eukaryotes
• Were adopted for new uses in multicellular
descendants
fi fi
, MICROBIAL SIGNALLING
• Bacterial cells secrete molecules to be detected by other bacterial cells
• Quorum sensing = the concentration of signalling molecules allows bacteria to sense
population density
• Therefore bacteria can coordinate behaviours in activities that require a number of cells
acting synchronously
• Bio lm formation!! = aggregation of bacterial cells adhered to a surface
• Occurs when food is in short supply
• Forms a FRUITING BODY
• Fruiting body produces thick walled spores that can survive until conditions
improve
• Nutrition is derived from the surface
LOCAL AND LONG DISTANCE SIGNALLING IN MULTICELLULAR ORGANISMS
• Signalling distinguishes itself based on signalling speed
• Speed is based on distance across which communication occurs
• Local signalling = over a short distance
1. DIRECT CONTACT
• Molecules pass between cells without crossing the cell membrane
• Via cell junctions = connect the cytoplasms of adjacent cells
• Signalling substances dissolved in cytosol pass freely between adjacent cells
• In animal cells = gap junctions
• In plant cells = plasmodesmata
• Animal cells can use CELL TO CELL RECOGNITION
• Use of glycoproteins as identi cation tags
• Protrude from cell surfaces
• Embryonic development and immune response
2. LOCAL REGULATORS
• Molecules are secreted by a signalling cell
• Travel short distances
• Local regulators in uence cells in the vicinity
2.1 PARACRINE SIGNALLING
• Numerous cells simultaneously receive and respond to molecules produced by a
single cell in the vicinity
• Signals travel a short distance through tissue uid to the next cell which must have a
receptor for the signal to be susceptible
• Not very stable — rapid signal deterioration
• EG. Growth factors — compounds that stimulate nearby target cells to grow and divide
2.2 SYNAPTIC SIGNALLING
• Specialised type fo local signalling occurring in animal nervous systems
• Electrical signal along a nerve cell triggers the secretion of neurotransmitter molecules
• Molecules act as chemical signals — di use across the synapse (=narrow space
between nerve cell and target cell) to trigger response in the target cell
• eg. Neural signal to a muscle cell
• Target cells must have a receptor for the neurotransmitter
• Long distance signalling
• Hormones = chemical messenger molecules
• In plants = hormones — plant growth regulators — move through cells/di use through the air
• In animals = hormones travel via the circulatory system — ENDOCRINE SIGNALLING =
hormonal signalling in animals in which specialised cells release hormone molecules which
travel via the circulatory system to other parts of the body where they reach targets cells that
can recognise and respond to the hormones
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