CAS BI 105 Lecture Notes - Lecture 5: Signal Transduction, Autocrine Signalling, Melanin
30 Apr 2018
School
Department
Course
Professor
10/3: Cell Communication
•50 trillion cells in the human body
•Signals
•Inside v. Outside
•From Inside - hormone that controls cells reproduction, electrical wave down a neuron courses
muscle contraction
•From Outside - UV rays cause increase in melanin production, activation of vitamin D
•Behavioral/Physical changes coordinated by signals
•Why do we need these?
•Need signals to respond to changing environment
•ex: increased availability of glucose that cells want to take in —> need to increase their
expression of glucose transporters (insulin signaling controls the response)
•Need to communicate with each other for their own need and overall organism’s need
•cell-to-cell communication
•ex: muscle cells releases a vasodilator when it needs more glucose/oxygen
•Need for organisms who cannot communicate verbally (ex: bacteria, insects) to find mates or
communicate danger
•Types
•Very Local - two cells are connected by gap junctions (animal), surface proteins of two cells
interact
•Local - secreted molecules and/or contact
•Long Distance - secreted molecules that diffuse/are carried (by the bloodstream) throughout the
organism
•Must lead to changes inside of the cell
•Signal Transduction Pathway
Secreted Signals
•*-crine means “secrete”
•Types
•In each case, the cell(s) receiving the signal is/are called target(s) and a RECEPTOR IS
REQUIRED
•The secreted cell is called a ligand for the receptor
•Autocrine Signaling - a cell secretes a molecule that effects itself
•Paracrine Signaling - a cell secretes a molecule that effects neighboring cells
•Endocrine Signaling - a molecule is secreted into the bloodstream
Stages of Signaling
•1. Receptor Activation - signal binds to receptor molecule on target cell surface
•the binding of a signaling molecule causes a conformational change in a receptor that activates its
function
•2. Signal Transduction - the binding of the signaling molecule changes the receptor protein in some
way; converting the signal to bring about a cellular response
•the activated receptor stimulates a series of proteins that forms a signal transduction pathway
•3. Cellular Response - some cellular activity is triggered (can be anything)
•the signal transduction pathway affects the functions and/or amounts of cellular proteins, thereby
producing a cellular response
Question: how does the binding of a ligand change a receptor?
Answer: Reception
Reception Activation
•Polar signaling molecules cannot enter the cell so their receptors are found embedded in the membrane
•Make up 30% of all proteins in the human body
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Secreted signals: *-crine means secrete , types, in each case, the cell(s) receiving the signal is/are called target(s) and a receptor is. Receptor activation - signal binds to receptor molecule on target cell surface: the binding of a signaling molecule causes a conformational change in a receptor that activates its function, 2. Cellular response - some cellular activity is triggered (can be anything: the signal transduction pathway affects the functions and/or amounts of cellular proteins, thereby producing a cellular response. Exists as monomers, ligand binding triggers dimerization and phosphorylation: 2. Now conformation allows recognition by relay molecules: 3. Ligand binds to receptor, changing its shape and binding the g protein, activating it: 3. Now activated, the g protein releases from its receptor and diffuses along the membrane: 4. Nearby enzymes are activated: ligand-gated ion channel receptors, ex: neurotransmitters and their receptors, 1. Ions flow from one side of the membrane to the other: 5.
