Cell Biology, Chap 16

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Signal Transduction Process of critical points where the relays occur where the message is converted from one form to another.
Cell Communication Individual cells & multicellular, need to sense and respond to their environment.
Cell Behavior Cells must interpret the multitude of signals they recieve from other cells to help coordinate their behaviors.
Where's the information coming from? Info is coming from a varitey of forms, and communication frequently involves converting info signals from one form to another.
Job's of a typical cell...? Must be able to track down nutrients, tell the difference between light and dark, and avoid poisons and predators.
Signal Tranduction? "Cell Signaling" Process whereby one type of signal is converted to another...cell commmunication. Signal transduction begins when the receptor protein on the target cell recieves an incoming extracellular signal and converts it to the intracellular signals that alter cell behavior.
Signaling Cell Produces a particular type of signal molecule receptop proteins that recognize and respond specifically to the signal molecule.
What types of extracellular molecules is used to send signals to one another? Cells use molecules such as... ...proteins, peptides, amino acids, nucleotides, steriods, fatty acid dx, and even dissolved gases.
Whats a "public" style of communication involving the broadcasting a signal throughout the whole body? The signal travels throughout the body by secreting the signal itself into the bloodstream...also know as the ENDOCRINE way of signaling.
wtF? are Endocrine Cells?? Signal molecules, involved in signal transduction, used are called HORMONES, the cells that produce these HORMONES are called ENDORINE cells.
Ya got an example of ENDOCRINE cells?? Part of the pancreas is an endocrine gland that produces the hormone insulin, which regulates glucose uptake in cells all over the body.
Whats a LESS "public" style of communication involving cell signaling? That process is known as "PARACRINE SIGNALING". Rather than the bloodstream, the signal molecules diffuse locally through the extracellular medium, but remaining close to the cell that secretes them.
Local Mediators on nearby cells? Recognized during PARACRINES SIGNALING, when having a less public form of communication, they as as local mediators on nearby cells.
Neura-Neura-Neuronal Signaling?? The 3rd form of cell comm. Like ENDOCRINE cells, neurons can deliver messages across long distances. ...however in this case, the message is delievered quickly and specifically to individual target cells through private lines.
Neuronal signaling, hmmmm... Chap 12, at specialized junctions (synapses), the axon of a neuron is killed. After neurons are activated, the cell sends a signal at 100m/sec through the axon. The signal is converted into a chemical signal ...which results in stimulants in the nerve terminal...which then signals the neurotransmitter to do their thing.
Neurotranmitters in Neura-neura-neuronal signaling?? The stimulated message from the nerve terminal sends out a pulse to release the neurotransmitters...which have to diffuse through the narrow
What other types cell signaling are there...specifically a short range? Contact-Dependant Signaling... ...the 4th style, it's cell-cell comm and its one of the most intimate and short range of all. It doesn't need secretion of the signal...instead it makes direct contact.
Explain Cell-Cell Signaling and how the fcuk does it's style work? It's also known as contact-dependent...during embryonic development, cell-cell comm means alot...b/c the tissues in adjacent cells are initally similar but they grow apart into their destined specializations.
yo...time to simplyfy these types of cell signaling!! Let's relate these bitches...aight, your chillin at a football game... ENDOCRINE signal flows through the PA system. Flyers everywhere posted with AD's on em are the PARACRINE signals. NEURONAL, long distance but personal - cell phone/email. CONTACT DEPENDENT would be just face to face.
...what's next eh? Hormones --> Adrenaline --> aka Epinephrine --> -->chills in the adrenal gland --> from TYR/Y/Tyrosine --> ^ the blood pressure, ^ the heart rate, and the metabolism.
...what's next eh? Local Mediators --> Transforming Growth Factor-B (TGF-B) --> -->cellular butterfly -->its p-p-protein -->n' it inhibits cell proliferation; stimulates extracellular matrix production.
...what's next eh? Neurotransmitters --> Acetylcholine --> -->very emotional, at nerve terminals --> it's a dx of choline -->it's excitatory neurotransmitter at many nerve-muscle synapses and in central nervous system.
...so what's a cell being exposed to anyway?? Cellular organisms are exposed to 100's of different signal molecules...they may be free in the extracellular fluid, embedded in the extracellular matrix in which cells rest, or bound to the surfaces of neighboring cells.
...if cells get exposed to a lot of shiiii, what do they do in response? The cells response is going to be selectively to this mixture of signals, disregarding some and reacting to others, according to the cells specialized function.
...you think cells every freaking cell signal?? Nah dude, it depends on if the cell has the correct receptor for the signal. ...if not, the cell is pretty much deaf to the signal and won't react.
...if cells can't randomnly hit up a signal, explain y not. Check it...w/out the appropiate receptor, a cell will be deaf, by producding only a limited set of receptors out of the thousands that are possible, the cell restricts the types of signals that can affect it... ...limited cell selectivity is limited range of signals can still be used to control the behavior of the cell in complex ways.
Each cell responds to a limited set of signals... ...the complexity is of the one of two sorts... ...1st, one signal, binding to one type of receptor protein, can cause a multitude of effects in the target cell; it can alter the cell's shape, movement, metabolism, and gene expression.
...so how's the signal from the cell-surface gonna make it past the bouncer to get inside the party in the cell? The signal from a cell-surface receptor is generally conveyed into the cell-interior via a set of interacting molecular mediators that are capable of producing widespread effects in the cell.
wtF? is an intracellular relay system & intracellular targets?? Off the bat, we notice the name says intra-, alright its going to the cell, somehow... ...its can basically be generalized into how the signal is gonna get into the cell...so, the relay system and targets, both will vary from one type of specialized cell to another...so that different types of cells respond to the same signal in different ways.
...when a heart muscle cell is exposed to the neurotransmitter acetylcholine... ...the rate and force of its contractions decrease, but when a salivary glad is exposed to the same signal, it secretes components of saliva. ...of course all this will happen rapidly, w/in seconds to mins only b/c the signals are interacting with the activity of the proteins and other molecules that are already present inside the cells.
Each cell responds to a limited set of signals... ...the complexity is of the one of two sorts... 2nd type of complexity arises...a typical cell posesses a collection of different receptors - tens to hundreds of thousands of receptors of a few dozen types... ...this would make a cell very sensitive to many extracellular signals...also would result in signals working together to have a great sum'd outcome.
...so cells are chilling together, but now a huge number of signals hit em up, so now the 2nd complexity is affected... ..but how is it related to intracellular relay system?? The intracellular relay systems for the different signals interact, so that the presence of one signal modifies the responses to others. ...so a combo of the signals would result in either the survival of the cell, other combo would be for the cell to differentiate or may even to divide.
What do you do if there is an absense of a signal?? ...the cell is screwed. note - b/c the execution of such a complex program often requires the synthesis of new proteins, it might take the cell hours to fully respond to the incoming signals.
Take home message about cells with limited set of signals... ...the integration of extracellular cues allows a relatively small number of signal molecules, used in different combo's, to exert subtle and complex control over cell behavior.
Whats the purpose of cell signaling? Cell signals to it's environment... ...aka Signal Transduction
Cell to Cell: Talk to me! ...4 basic types of cell signaling? -ENDOCRINE, inhibits growth hormone secretion among other functions, Somatostatin. -PARACRINE, local comm, signal molecules diffuse locally through extracellular medium, Testosterone. -NEURONAL, neurotransmitters that can be released w/autocrine feedback mechanism, Acetylcholine. -CONTACT-DEPENDENT, cell-cell, the most intimate and short range of all.
Whats a cell to do? Different signals to the cell, the cell must make a decision. The cell is always getting signals. Cells have to do semation, simply which signal is going to make it.
The usual animal cell just looks like a box. The animal cell is broken apart into 2 central things...control of DNA replication and gene expression or dealing with proteins around the cell.
...we want specificity. ...ligand (molecule) & receptor (on target)
Hormones or things that are made by peptides can't go across the membrane...so how do they get into the cell? ...they will bind to a cell-surface receptor. So things that can get across membrane will have intracellular receptors and things that can't go across would be called membrane receptors.
Breaking apart an animal cell. Cells have characteristic responses. Usually it's going to start with the "defined set of extracellular" -->Organization -->Structure and Catalysis -->Characteristic function or set of responses -->contribution to stucture and activity of animal.
When does signal reception begin? Signal Reception begins at the point where a signal originating outside the target cell encounters a target molecule belonging to the cell itself.
What's the target molecule during signal reception? The target molecule is a receptor protein (also called a receptor), and each receptor is usually activiated by only one type of signal.
...part of a long chain of intracellular signal transduction processes... the message, from a signal, is passed from one intracellular signaling molecule to another, each activating or generating the next signaling molecule in line, until...a metabolic enzyme is kicked into action, a gene is switched on...w/e happens, the final outcome is called the RESPONSE of the cell.
(A) Function of a Signaling Cascades? ...they transform or transduce the signal into a molecular form suitable for passing the signal along or stimulating a response.
(B) Function of a Signaling Cascade? ...they relay the signal from the point in the cell at which it is received to the point at which the response is produced.
Cellular signaling cascades can follow a complex path. A receptor protein located on the cell surface transduces an extracellular signal into an intracellular signal, initiating a signaling cascade that transfers the signal into the cell interior, amplifying and distributing it en route...many of the steps in the cascade can be modulated by other molecules or events in the cell.
...the same signal molecule can induce different responses in different target cells. ...different cell types are configured to respond to the neurotransmitter acetylcholine in different ways.
(C) Function of a signaling cascade? ...it also amplifies the signal received, making it stronger, so that a few extracellular signal molecules are enough to evoke a large intracellular response.
(D) Function of a signaling cascade? ...they distribute the signal so as to influence several processes in parallel; at any step, along the pathway, the signal can diverge and be relayed to a number of different intracellular targets, making branches...then to make a response.
(E) Function of a signaling cascade? ...during the cascade, it is open for modulation by other factors, including other external signals, so that the effects of the signal can be tailoredto to the conditions prevailing inside or outside the cell.
...extracellular signals alter the activity of a variety of cell proteins to change the behavior of the cell... ...the signal molecule binds to a cell surface receptor protein. the receptor protein activates an intracellular signaling pathway that is mediated by a series of intracellular signaling proteins. some of these signaling proteins interact with target proteins, altering them to change the behavior of the cell.
What's an effective strategy for direct activation if your a extracellular signal? ...use a gas, such as Nitric Oxide, this dissolved gas diffuses readily out of the cell that generates it and enters neighboring cells.
...Nitric Oxide (NO), what is it in relation to Cell Bio? NO is made from the amino acid arginine and operates as a local mediator in many tissues. NO acts only locally b/c it is quickly converted into nitrates and nitrites by reaction with the oxygen and water outside cells.
How does Nitric Oxide get inside a cell? Endothelial cells release NO in response to stimulation by nerve endings. This NO signal causes smooth muscle cells in the vessel wall to relax, allowing the vessel to dilate allowing blood to flow much better. The effect of NO on blood vessels accounts for the action of nitroglycerine.
What are Endothelial cells? The flattened cells that line every blood vessel.
Where does Nitric Oxide bind inside a target cell? NO binds to the enzyme GUANYLYL CYCLASE, stimulating the formation of cGMP from the nucleotide GTP.
...what the hell is a Cyclic GMP?? cGMP itself is a small intracellular signaling molecule that forms the next link in the signaling chain that leads to the cell's ultimate response. It's very similar in structure and mechanism to cAMP.
Some hormones cross the plasma membrane and bind to intracellular receptors... ...gases such as NO are not only signal molecules that can cross the plasma membrane.
What are Steriod Hormones? They are hydrophobic signal molecules, that include cortisol, estradiol, and testosterone, and the thyroid hormones such as thyroxine...all pass through the plasma membrane of the target cell. These are also proteins capable of regulating gene transcription, but they are typically present in an unactivated form of unstimulated cells.
When a hormone binds... The receptor protein undergoes a large conformational change that activates the protein, allowing it to promote or inhibit the transcription of a selected set of genes. ea hormone will bind to a diff receptor protein, & ea receptor acts at a different set of regulatory sites in DNA...these will envoke physiological responses.
Where do extracellular signal molecules bind to? Extracellular signal molecules bind either to cell-surface receptors or to intracellular enzymes or receptors.
What kind of binding occurs with cell-surface receptors? Most signal molecules are large and hydrophilic and are therefore unable to cross the plasma membrane directly; instead they bind to cell-surface receptors, which in turn generate one or more signals inside the target cell.
What kind of binding occurs at intracellular receptors? Some small hydrophobic signal molecules, by contrast, diffuse across the target cell's plasma membrane and activate enzymes or bind to intracellular receptors -- either in the cytosol or in the nucleus.
How does the steroid hormone cortisol acts by activating a gene regulatory protein? Cortisol diffuses directly across the plasma membrane and binds to its receptor protein, which is located in the cytosol...the hormone-receptor complex is then transported into the nucleus via nuclear pores. Cortisol binding activates the receptor protein, which is then able to bind to specific regulatory sequences in the DNA and activate gene transcription.
The two types of connective tissue. Resonance Cells and Immigrants Cells.
Immigrant Cells: Blood More focus on this besides, Resonance cells. The immigrant cells also deal with immune cells. There are two types of these cells, the residential cells (of course by name they don't move around) and there are moving cells, they keep moving.
What stem cell do indegenous connective tissue cells all originate from? A stem cell called a primitive mesenchymal cell.
Immigrant Cells: Blood (2) They move and they also have cargo. Through the lineage, a lot of things are possible.
Immigrant Cells: Blood (Lineage) The lineage shows that, throught it there are many outcomes. Platelets are formed from the Myloid lineage. Through the beginging the potential will drop, then the B-lymphocytes and T-lymphocytes.
What happens to a stationary monocyte? It will become a microphage, it will depend on cell-cell contact.
On the surface, whats the only contact being done? Cell - Cell adhesion, it's not soluble and its not secretion, and there is no gene trascription, they are just specific and only because of the amount of them available.
Principle of Adhesion... Cell to Cell adhesion is when there is communiation inside the body.
Principles of Adhesion...Homotypic and Heterotyptic? CAM, or cell adhesion molecules will deal with the ability of the adhesion molecule to either be attracted to itself or others or even a combo.
Principles of Adhesion...Surface density? Spacial Temporal Expression is dealing with the surface receptors. Low affinity with low expressors are related to low expressors.
Principles of Adhesion...cytoskeleton comm n' intracellular comm? ...all this is about cell communication.
What happens to immigrant cells when they aren't supposed to be floating around? They will ofcourse die b/c of the 8 rules of cell biology. Immigrant cells usually get recycled when they aren't attached to something.
Adhesion Kinase and Phosphorylation...? Adhesion kinase communicate with CAM and it deal with the CAM going in and out of the cell, all of it though deals with phosphorylation occuring.
Cytoskeleton...? An intricate network of protein filaments that extends throughout the cytoplasm.
Intermediate Filaments do what for the cytoskeleton? It offers structural intergrity, it holds the cell together and withstands tensil strengh and it also deals with mechanical stress. The point of origin is the Desminsome. The center of origin is also capable of interconnecting other cells.
The importance of the Lamina. Lamina, not to be confused with Laminin (extracellular, is the protein inside the nucleus that mesh's the wall and it provides strength. Mutation of this would give a person progeria, 10x the age.
What are the 3 classes of proteins in the cytoskeleton? Intermediate Filaments, Microtubles, and Actin Filaments.
Breakdown the 3 protein classes of the cytoskeleton. Intermediate Filaments are the structural proteins. Microtubles are made from centrosome, they also grow out of them in a polarized fashion and it allows for a good distrubution inside of the cell, transport, they also depend on polarity. Actin Filaments deal with the movement of the cell, it follows a chemotactic pattern of movement.
Microtubles, Anterograde transport? Getting outta cell transport, its useful because the cell always secretes with the help of the microtuble. The origin of the mictrotuble is the centrosome that also has a 7-tublin.
Microtubules, Retrograde Transport? Gettin into the cell, we need proteins back after the recycling of proteins, but there is a chance that you might even pick up a virus just because your allowing this to come into the cell.
Microtbules, what are the key points? Polarity is a huge key, gamma tubulin, the tubulin is responsible for forming the nucleation center of microtubules. There is polarity in the centrosomes. The alpha and betta tubilins will be responsible for growing, they will also interact non-convently, that will deal with the framework.
Microtubules want to leave and...? They will grow outward from the centrosome and they want to move to the plasma membrane, it is then stopped by the capping proteins.
Gamma tubilin will be stopped by the capping protiens in a... ...positive interaction and that will also stop the growth of the microtubules. only b/c 1st it doesn't want to waste the subunits and 2nd there is a docking dilemma that is related to the protein. This is all done in the origin...Centrosome.
MAP or Microtubule Associated Proteins...? MAP come in multiple flavors. The ability to anchor themselves to things in the network.
During Anterograde transport, you will use Kinesins, which will help generally while moving towards the plus end of a microtubule or away from the centrosome. This will have a cargo attached and that'll use up energy. During Retrograde, Dyneins are used and it will usually go the other way, to the negative end or otherwise know as towards the centrosome. This will have a cargo attached and that'll use up energy.
GTP is used in microtubles while they are growing. GDP is used while shrinking the microtubule.
G-Protein Linked Receptors, what are they? GPR's deal with extracellular signals, horomones, local mediators, and neurotransmitters. They are made out of a single polypeptide chain that goes through 7 layers and is also called, the seven-pass transmembrane receptor.
What happens when an extracellular signal binds to a G-protein receptor? There is conformational change.