Bio I - 7 Flashcards
 When a cell signals to another cell or receives a signal from the environment- what are the signals most often?
Chemicals
Why is communication important for the microorganism?
It provides insight into how cells send, receive and respond to signals.
What are the two meeting types of yeast?
A and alpha
What is another name for yeast?
Saccharomyces cerevisiae
How do cells of different mating types locate each other?
Via secreted factor specific to each type
What do signal transduction pathways contribute to cell signaling?
They convert signals received at a cell surface into cellular responses
True or false: the molecular details of a signal transduction in yeast and mammals are strikingly similar. 
True
What happens when there is a concentration of signaling molecules?
It allows bacteria to sense local population density
in a process called Quorum sensing
How do cells in a multicellular organism communicate?
Via signaling molecules
What happens in local signaling?
Animal cells may communicate by direct contact
What are cell junctions in what type of cells have them?
Animal and plant cells have cell junctions.
Cell junctions directly connect the cytoplasm of adjacent cells. 
What is cell junctions allow for?
Signaling substances in the cytosol can pass freely between adjacent cells
In other cases, animal cells communicate using secreted messenger molecules that travel only __________
Short distances
 What are one class of local regulators and animals?
Local regulators
What do growth factors do?
They stimulate nearby target cells to grow and divide
Local regulators in short distances is a type of local signaling in animals called _________. 
Paracrine signaling
What is synaptic signaling?
Synaptic signaling occurs in the animal nervous system when a neurotransmitter is released in response to an electric signal. 
Is local signaling in plants understood?
It is not well understood beyond communication between plasmodesmonta
What is used for long distance signaling and plants and animals?
Hormones
What is hormonal signaling called in animals? 
Endocrine signaling
What is endocrine/hormonal signaling?
It is when specialized cells release hormones, which travel to target cells and via the circulatory system.
When does a cell respond to a signal?
If it has the receptor that is specific to that signal
Who discovered how the hormone Epinephrine acts on cells?
Earl w. Sutherland
What are the three stages of cell signaling?
Reception
transduction
response
What is reception?
In reception, the target cell detects a signaling molecule that binds to a receptor protein on the cell surface
What is transduction?
In transduction, the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway; transduction often occurs in a series of steps.
What triggers a specific response in a target cell?
The transduced signal
What is another word for signal molecule?
Ligand
True or false: the binding between a signal molecule and receptor is not specific
False
What is often the initial transduction of the signal?
A shape change in a receptor
Most signal receptors are ________. 
Membrane proteins
What is the largest family of cells surface receptors?
G protein coupled receptors GPCRs
What type of signal molecule binds to specific sites on receptor proteins that spans a plasma membrane?
Most Water soluble signal molecules
What are the three main types of membrane receptors?
G protein coupled receptors
Receptor tyrosine kinases
Ion channel receptors
What are G protein coupled receptors/GPCRs?
They are cell surface transmembrane receptors that work with the help of a G-protein
What does a G protein do?
G proteins bind the energy rich GTP. G proteins are all very similar in structure. 
What are receptor tyrosine kinases/RTKs?
They are membrane receptors that attach phosphates to tyrosine
What does a receptor tyrosine kinase do?
It can trigger multiple signal transduction pathways at once
What is abnormal functioning of RTKs associated with?
Many types of cancer
What is a ligand gated ion channel receptor?
Ligand gated ion channel receptor acts as a gate when the receptor changes shape
What happens when a signal molecule binds as a ligand to the receptor?
Get a lot of specific I am such as Na and Ca2 through a channel in the receptor 
What are intracellular receptors?
They are proteins that are found in the cytoplasm or nucleus of target cells
True or false: small or hydrophobic chemical messengers can readily cross the membrane and activate receptors
True
What are examples of hydrophobic messengers?
The steroid and thyroid hormones of animals
What can an activated hormone receptor complex act as?
A Transcription factor, turning on specific genes
True or false: signal transduction usually involves one step
False. It usually involves multiple steps
Do multi step pathways amplify or reduce a signal?
Amplify
What do multi step pathways provide?
They provide more opportunities for coordination and regulation of the cellular response
What triggers the first step in a chain of molecular interactions?
The binding of a signaling molecule to a receptor
How is signal transduction pathways compared to falling dominoes?
Like following dominoes, the receptor activates another protein, which activates another and so on, until the protein producing the response is activated
What happens at each step of the signal transduction pathways?
The signal is transduced into a different form, usually a shape change in a protein
What is phosphorylation and dephosphorylation of proteins?
It is a widespread cellular mechanism for regulating protein activity
What does protein kinases?
Protein kinesis transfer phosphates from ATP to proteins, a process called phosphorylation. 
What is a phosphorylation cascade?
When many relay molecules in signal transduction pathways are proteins kinases this creates a phosphorylation cascade
What do protein phosphatases do? 
Protein phosphatases rapidly remove the phosphates from proteins, a process called the phosphorylation
What does this phosphorylation and dephosphorylation system act as?
It acts as a molecular switch, turning activities on and off or up or down, as required
True or false: many signaling pathways involve second messengers
True
What are second messengers?
Second messengers are small, non-protein, water soluble molecules or ions that spread throughout a cell by diffusion
Second messengers participate in pathways initiated by _______ and _____. 
GPCRs
RTK
What is cyclic AMP?
cAMP is one of the most widely used second messengers
What is Adenylyl cylase?
It is an enzyme in the plasma membrane, that converts ATP to cAMP in response to an extra cellular signal
True or false: many secretory molecules trigger formation of cAMP. 
False
Many signal molecules…
What are other components of cAMP Pathways?
G proteins, G protein coupled receptors, and protein kinases
What does CAMP usually activate?
Protein kinase A
Which phosphorylates to various other proteins
What is provided by G proteins systems that inhibit adenylyl Cyclase?
Further regulation of Cell metabolism
What is Vibrio cholerae? What does it do?
It’s a cholera bacterium. 
It produces a toxin that modifies a G protein so that it is stuck in its active form. This modified G-protein continually makes cAMP, causing intestinal cells to secrete large amounts of salt into the intestines.  water follows by osmosis and an untreated person can soon die from loss of water and salt. 
What do calcium ions act as?
A second messenger in many pathways
Why could calcium ion function as a second messenger?
Because its concentration in the cytosol is normally much lower than the concentration outside the cell
What happens when there’s a small change in number of calcium ions?
It thus represents a relatively large percentage change in calcium concentration
What may trigger an increase in calcium in the cytosol?
A signal relayed by a signal transduction pathway
Pathways leading to the release of calcium involve the following:
Inositol triphosphate (IP3)
Diacylglycerol (DAG)
As additional second messengers
What is the output response?
The cells response to an extra cellular signal
What does a signal transduction pathway lead to?
Regulation of one or more cellular activities
Where do signal transduction pathway responses occur?
In the cytoplasm or in the nucleus
How do many signaling pathways regulate the synthesis of enzymes or other proteins?
Usually by turning genes on or off in the nucleus
What may the final activated molecule in the signaling pathway function as?
A transcription factor
What do other pathways do? Give an example.
They regulate the activity of enzymes rather than their synthesis. 
A signal could cause opening or closing of an ion channel in the plasma membrane, or a change in cell metabolism. 
What else can a signaling pathway effect?
The overall behavior of a cell, for example a signal could lead to cell division
There are four aspects of signal regulation what are they?
Amplification of the signal
specificity of the response
overall efficiency of response, enhance by scaffolding proteins
termination of the signal
What do enzyme Cascades do?
The amplify the cells response to the signal. At each step, the number of activated products is much greater than the preceding step. 
True or false: different kinds of cells have different collections of proteins
True
What do different proteins allows cells to do?
Detect and respond to different signals
True or false: pathway branching and Crosstalk do not help the cell coordinate incoming signals
False
They do
What are scaffolding proteins?
They are large relay proteins to which other relay proteins are attached
What does scaffolding proteins increase?
They can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway.
In some cases, scaffolding proteins may also help activate some of the relay proteins. 
What happens if ligand concentration falls?
Fewer receptors will be bound. 
What happens to unbound receptors?
They revert to an inactive state
What does apoptosis?
Cells that are infected or damaged or have reached the end of their functional lives often undergo a program cell death
What happens during apoptosis?
 it is the cells programmed death and the components of the cell are chopped up and packaged into vesicles that are digested by scavenger cells
What does apoptosis prevent?
Prevents enzymes from leaking out of a dying cell and damaging neighboring cells
True or false: in humans and other mammals, several different pathways, including about 15 caspases, can carry out apoptosis. 
True
Do you or false: apoptosis can be triggered by signals from only inside of the cell
False.
Inside and outside
What’s does the internal signals for apoptosis result from?
It results from era irreparable DNA damage or excessive protein misfolding
Apoptosis is a normal part of development of _____ and ______. 
Hands and feet
Apoptosis may be involved in some diseases such as:
Parkinson’s and Alzheimer’s and cancers
