Chapter 11: Cell Communication Flashcards
Cell-to-Cell Communication is essential for what organisms?
Multicellular Organisms
Cell Response
The combined effects of multiple signals
Each cell is programmed to respond to specific combos of extra cellular signal molecules
How do cells in multicellular organisms communicate?
Through chemical messengers
Cell junctions
Direct connection of the cytoplasm to the adjacent cells to exchange materials
No plasma membrane restrictions
What are the ways animal cells do local signaling?
Direct contact (cell junction) and cell-cell recognition
Paracrine Signaling
Type of local signaling
Local regulator diffuses through extracellular fluid.
The secreting cell secretes vesicles to target cell
Allows cells to communicate w/each other by releasing signaling molecules that binds to and activate surrounding cells
Messenger molecules released by cell travels short distances and carry a message to neighboring cells.
Growth factor is released in this manner
Synaptic Signaling
Type of local signaling, electrical signals along a nerve triggers the secretion of a chemical signal carried by neurotransmitter molecules to stimulate the target cell
Hormonal Signaling
Long distance signaling, hormones ,secretes by specialized endocrine cells ,travels in bloodstream to target cells
Nerve cells may use long distance signaling
Signal Transduction
The process by which a signal received on the cell surface is converted into a specific cellular response
Signal Transduction Pathways
A series of steps by which a signal on a cell’s surface is converted into a specific cellular response
Converts signals on the cell’s surface into cellular responses
How do Yeast mate?
There are 2 “sexes” of yeast (a &a)
(a )secretes a signaling molecules that binds to receptors on (a). The reverse is true of (a) cell
Signals cause cells to grow together.. produces one cell with combined genetics
What type of pheromones are people attracted to?
People whose pheromones are very different from our own. So baby can have the best immune system possible
Quorum Sensing
Control growth rate
Coordinate Activities
If nutrients are low, soil dwellers aggregate and produce biofilms
Cell to Cell Recognition
2 cells communicate by recognizing signal molecules of cell surfaces
What are the 3 stages of Signaling
Stage 1: Reception
Stage 2: Transduction
Stage 3: Response
Reception
The signal molecules binds to a receptor protein which causes it to change shape
Ligand
The signal molecule that binds to another molecule
What does the ligand do to receptor proteins?
change it shape( conformational change) —Activation
What happens during transduction?
Relay molecules in a signal transduction pathway
How many types of receptors are there?
2
What are the types of receptors?
Intracellular Receptors & Plasma Membrane Receptors
Intracellular Receptors
Found in the cytoplasm or nucleus of target cell ( inside the cell)
Signal pass through cell membrane to activate receptor
Signal must be small and non-polar
Ex: Steroid hormones ( cholesterol based) Thyroid hormones ( Tyrosine based)
Plasma Membrane Receptors
Found in the plasma membrane ( exterior of cell)
Signal doesn’t have to pass through the membrane; receptors proteins changes shape or join together to transmit info
Signals can be water-soluble
Ex: G-protein-linked receptors, receptor tyrosine kinase and ion channel receptors
What is the process of Intracellular receptors
The signal attaches to the receptor proteins
The protein then goes into the nucleus and makes a copy of the DNA needed. mRNA
The mRNA then gets out of the nucleus to make new protein
What are the signals used for Intracellular receptors?
Hormones
What are the receptors of the membrane
G-Protein Coupled Receptors
Enzyme Receptor (Tyrosine Kinases)
Ion Channel Receptors
What is a G Protien-coupled receptor?
Plasma membrane receptor that works with the help of a G- Protein
What does the G protein act as?
As an on/off switch, if the GDP is bound to the G-Protein, the G protein is inactive, if the GTP is bound to the G protein, it becomes active.
What are the G protein receptors used for l?
About 800 genes use these, over 400 are olfactory genes( nose)
What happens at the Receptor tyrosine kinase?
An enzymes( signal molecules) gets in the binding site. After the binding sites shift towards each other ( Dimer).
6 ATPs then proceeds to activate the receptors( 3 phosphate are given to each Tyrosine)
This then activates the relay proteins
What does RTK’s Trigger ?
This response triggers cell growth and cell differentiation
They always occur in pairs so that cross phosphorylation can occur in the dimer.
This binding activates enzyme activities
Ligand- Gated Ion Channel Receptor
Acts as a gate when the receptor changes shape the gate allows specific ions, such as Na+_ , through a channel in the receptor
Used a lot in the nervous system
Sometimes controlled by electrical signals rather than ligands
Transduction
A multiple step process which occurs when receptor receives signal
More steps -> greater responses
Many genetic disorders are seen where “steps” are missed
Retts Syndrome
MECP2 - gene that codes for MECP2 protein needed for brain development. The protein acts as a biochemical switch
If the MECP2 genes is mutated, the MECP2 protein will be mutated and genes will not be controlled properly
Phosphorylation
A process of the protein kinase transferring phosphates from ATP to protein
There may be several proteins kinases in b/tw to activate the protein
Protein kinase
An enzyme that transfers phosphate from ATP to protein
Cellular Response
Cell signaling leads to regulation of transcription or cytoplasmic activities
How may the cell response regulate protein synthesis?
By turning a gene on or off … can lead to the “extra” protein features w/ added exposure of hormone
How May the cell response regulate the activity of a protein?
Opening or closing protein channels used for transport
Affecting activity of enzyme with inhibitors
Progesterone
Triggers the female cells to prepare the inner lining of the uterus for Possible embryo & inhibit the contraction of the uterus
Not fertilized, progesterone levels drop and the endometrium level begin to breakdown… the cell within are programmed for apoptosis
Apoptosis
Cell signaling for cell suicide
What cells are given the orders for apoptosis
Damaged, old or infected to prevent enzyme leakages to other “healthy” cells
Cytochrome C
A protein in ETC can also function as a cell death factor
Mitochondria is induced to “leak” cytochrome c into the cytoplasm. The cell recognizes the leak and release Cassandra which order cell suicide
Who often send the cell death signals ?
It’s often the nucleus that send the signal, cell recognizing errors in the DNA beyond repair.
What does P53 do ?
It orders the cell to commit suicide if DNA is damaged beyond repair.
This is detected at G1 checkpoint
How is P53 used medically?
Cancer treatment, considered to be the tumor depressor gene
How is Apoptosis used developmentally ?
Used to eliminate “ extra” cell growth during embryo stage
