BILD 1 Chapter Notes - Chapter 11: Mating Of Yeast, Paracrine Signalling, Signal Transduction
18 Dec 2018
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11.1 External signals are converted to responses within the cell
Evolution of Cell Signaling
● Two sexes called a or alpha → factor binds only to receptors on other type of cell
○ When exposed to each other’s mating factors → pair of cells of opposite type
change shape, grow toward each other and fuse
○ Contain genes of both original cells
○ Yeast cells that has mating factors altered proteins would bind to each other
but not to original parent of cells → mate with one another
■ Changes in genes encoding receptor and mating factor proteins can lead to
establishment of new species
○ Signal transduction pathway
○ Signaling mechanisms first evolved in ancient prokaryotes and single celled
eukaryotes → used by multicellular descendants
● Biofilm: aggregation of bacterial cells adhered to surface → cells in biofilm derive
nutrition from surface they are on
● Treatment of antibiotics doesn’t work because antibiotic resistance have evolved
Local and Long Distance Signaling
● Local signaling → cells communicate by direct contact
○ Plants and animal cells have cell junctions that directly connect cytoplasm of
adjacent cells
○ Signaling substances dissolved in cytosol pass freely between neighboring cells
○ Animal cells communicate via direct contact between membrane bound cell
surface molecules → cell cell recognition
● Signaling molecules secreted by signaling cell → travel short distance → paracrine
signaling → ex: growth hormones
○ Cells simultaneously receive and respond to growth factors
● Synaptic signaling:
○ Animal
○ Electrical signal trigger secretion of neurotransmitter molecules → chemical
signals diffusing across synapse → response in target cell
● Hormones:
○ Endocrine signaling
○ Specialized cells release hormones which travel vis circulatory system where they
reach target cells that respond to them
○ Plant hormones
■ Plant growth regulators
■ Travel in plant vessels or move through air and gas
● Ability for cell to respond is determined by whether it has specific receptor molecule that
can bind to signaling molecule
The Three Stages of Cell Signaling: A Preview
● Experiment wonders how epinephrine triggers the fight or flight response in animals by
breakdown of storage polysaccharide glycogen within liver cells
○ Glycogen breakdown releases sugar glucose 1-phosphate which cell converts
to glucose 6-phosphate → muscle cell use this compound
○ Or compound have phosphate removed → released from cell into blood as
glucose → fuel cells throughout the body
○ Epinephrine stimulates glycogen breakdown by activating cytosolic enzyme
→ when epinephrine was added to cell free mixture → no breakdown occurred
○ Glycogen phosphorylase could be activated by epinephrine when hormone was
added to intact cells
● Reception
○ Target cell detect signaling molecule
○ Signaling molecule binds to receptor protein located at the cell’s surface
● Transduction
○ Binding of signaling molecule changes receptor protein
○ Initiating transduction
○ Signal to a form that can bring specific cellular response
○ Signal transduction pathway: transduction occurs in single step but requires
sequence of changes in series of different molecules
● Response
○ Triggers specific cellular response
○ Response may be almost any imaginable cellular activity
11.2 Reception: A Signaling molecule binds to receptor protein, causing it to change shape
● Signals emitted by a mating type can only be received by prospective mates → alpha
cells
● Only certain target cells can detect and react because specific receptor protein
● Ligand: molecule that specifically binds to another (often larger molecule)
○ Ligand binding causes receptor protein to undergo change in shape
○ Shape change directly activates receptor, enabling it to interact with other cellular
molecules
Receptors in the Plasma Membrane
● G protein coupled receptors (GPCRs)
○ Water soluble signaling molecules bind to specific sites on transmembrane
receptor proteins that transmits information from extracellular environment to
inside of cell
Document Summary
11. 1 external signals are converted to responses within the cell. Two sexes called a or alpha factor binds only to receptors on other type of cell. When exposed to each other"s mating factors pair of cells of opposite type change shape, grow toward each other and fuse. Yeast cells that has mating factors altered proteins would bind to each other but not to original parent of cells mate with one another. Changes in genes encoding receptor and mating factor proteins can lead to establishment of new species. Signaling mechanisms first evolved in ancient prokaryotes and single celled eukaryotes used by multicellular descendants. Biofilm: aggregation of bacterial cells adhered to surface cells in biofilm derive nutrition from surface they are on. Treatment of antibiotics doesn"t work because antibiotic resistance have evolved. Local signaling cells communicate by direct contact. Plants and animal cells have cell junctions that directly connect cytoplasm of adjacent cells.
