BIo Unit 3: Cell Signaling, Disease and Immunity, Mitosis/Cell Cycle/Cancer

3 basic methods of cell communication

contact dependent, local chemical (paracrine), and long distance signaling

Contact Dependent

allows direct cytoplastic transfer between cells, allowing small molecules to pass directly from cell to cell, and good for fast, unregulated communication

Local Chemical (Paracrine(

involves the diffusion of chemical signals by using receptors

Long Distance Signaling

the endocrine and nervous system
the endocrine system is CHEMICAL and hormones travel through blood
the nervous system is ELECTRICAL + CHEMICAL, and uses action potentials and neurotransmitters

Signaling involves…

signal generation, signal reception, and changes in cell signaling component, response

Signal Generation

another cell, self, or environmental stimulus (like a signaling molecule)

Signal Reception

cytoplasmic or membrane receptor (receptor accepts that signaling molecule)

Changes in Cell Signaling Component

the direct effect or signal transduction (relaying those molecules in a signal transduction pathway - turning an external signal into an internal cellular response)

Response

changes to protein activity or abundance (the activation of the internal cellular response)

Signaling molecules are usually recognized by receptors which are…

Proteins

Hydrophobic Signals are…

membrane permeable, recognized by cytoplasmic or nuclear receptors, often directly regulating DNA

Hydrophillic Molecules are…

membrane impermeable, recognized by membrane receptors

Agonist

mimics the signaling molecule and activates the receptor/pathway

Antagonist

blocks the receptor and inhibits the receptor/pathway

Signal Transduction (two ways that is mediated?)

internal amplification (either enzyme mediated or small molecule mediated)

Enzyme Mediated

phosphorylation cascade as one enzyme activates the rest

Kinase

an enzyme that adds a phosphate group to a molecule

Phosphate

an enzyme that removes a group in a molecule

Small-Molecule Mediated (diff between first and second messenger)

a second messenger that is a signaling molecule that is created and has effects inside of the cell

First Messenger

a signaling molecule

Second Messenger

is activated by intracellular molecules, and often produced by enzymes activated by the receptor

Response and Signal Termination (what does a response depend on?)

response depends on signals, receptors, and response molecules, and can alter protein by altering the protein activity or the protein synthesis

Destroying Signal

enzymes break down the signal

Removing the Signal (how AND what happens when this is blocked)

reuptake transporters bring signals back inside the cell, but when blocked, the signal is able to stay outside longer, increasing the signaling between the cells and binding

Removing the Receptor

the endocytosis of receptor prevents the cell from responding to further signals

How do some psychoactive drugs work by preventing or reversing uptake?

it causes the signals to activate receptors for longer, increasing the effects of the signal

Neuronal Signaling (the cell for information, what does it include?)

includes dendrites, cell body, and the axon

Dendrites

collects the electrical signals from other cells (extends from the cell body)

Cell body

integrates incoming signals and generates outgoing signal to the axon

Axon

passes the electrical signals to the dendrites of another cell

Action Potential (the nerve impulse or the neuron “firing”)

an electrical signal that is sent along the neuron’s axon

What is the difference between axons and wires?

wires are charged particles that move along a wire over time, but axons are charged particles that enter and leave the axon

Active Transport (that happens within the lipid bilayer, what does it include?)

includes an electrogenic pump and an electrochemical gradient

Electrogenic Pump

generates a difference in charge across the membrane (the membrane potential)

Electrochemical Gradient

the chemical and electrical gradient that influences ion movement

Sodium/Potassium Pump (how many NA and K ions pumped out per ATP? what charges does it include?)

3 NA+ ions pumped out per ATP, 2 K+ ions pumped out per ATP

charges: at rest membrane potential = -70mV, hyperpolarized = more negative (inhibitory/more below threshold), depolarized = more positive (excitatory/more above threshold)

Voltage-Gated Channels (what is the point of it?)

self perpetuating wave generators that include a positive and negative charge, to cause an action potential to travel down the axon

Positive Charge (what happens if positive charge inside cell?)

channels open to cause depolarization

Negative Charge (what happens if negative charge inside cell?)

channels close to keep it at membrane potential/below threshold

Repolarization (what can be done to reduce it from reaching threshold)

inactivation gate closes the sodium channels and leaky K+ channels keep ions moving in and out equally

Action Potential Steps (what are the steps for the action potential to be fired?)

1) at rest
2) stimulation
3) rising phase
4 + 5) falling phase
6) recovery/rest

At rest

voltage gated channels are closed and membrane potential stays at -70mV maintained by leaky K+ channels

Stimulation

the voltage-gated channels remain closed until it receives a signal strong enough to reach threshold

Rising Phase

NA+ channels open after threshold is reached, allowing NA+ to flow in, making the cell more positive (rapid depolarization)

Falling Phase (Peak, combined 4 + 5 step)

NA+ channels close, and K+ channels open to allow K+ to flow out, making the cell more negative to go back to membrane potential

Recovery/Rest

voltage-gated channels close, going back to -50mV

Chemical Signaling (what is used for a chemical signal?)

using neurotransmitters = chemical signals to communicate at synapses

What causes the release of neurotransmitters that send nerve signals to the next cell?

the arrival of an action potential to the end of the cell

Axon Hillock (where the axon potential STARTS, what does it contain and how is it stimulated?)

the cone-shaped part that connects to the cell body, contains the voltage gated channels and is stimulated by enough excitatory signals that the dendrites recieve

Disease And Immunity (NEW SECTION)

Pathogens (what does it cause?)

agents that cause disease, such as viruses, bacterial pathogens, and eukaryotic pathogens)

Virus Life Cycle (how do viruses come to be?)

a virus uses a host cell’s enzymes and monomers to replicate their genome (DNA replication) and make the proteins they need

The Immune System (what are the two main branches of immunity?)

innate immunity and adaptive immunity

Innate Immunity (all animals) (what defenses does it include?)

recognizes traits shared by a broad range of pathogens, and uses a small set of receptors, causing a rapid response

has barrier defenses (such as the skin) and internal defense (such as natural killer cells and inflammatory responses)

Adaptive Immunity (vertebrates only) (what responses does it include?)

recognizes traits specific to a particular pathogen, using a vast array of receptors, causing a slow response

has a humoral response (antibodies to defend infection in body fluids) and a cell-mediated response (cytotoxic cells that defend against infection in body cells)

Antigens (adaptive immunity, what are they and how does it recognize?)

usually proteins or sugars that recognizes specific pathogens by recognizing the organic molecules speciifc to that pathogen

Antibodies (adaptive immunity, how does it play a role in adaptive immunity? what are the two ways it protects from infections?)

are proteins produced by B-Cells that recognize antigens

two ways: antibodies can surround the pathogens to make it difficult for them to attach to surfaces or invade cells, or antibodies can help endocytic cells recognize and consume pathogens

Where do B-Cells emerge from?

b-cells emerge from the bone marrow with different and random antibodies that recognize different potential antigens

How does the adaptive immune response build a large, targeted response to a pathogen? (what is the point of this and what does it do?)

Antigens bind to the B-cell, and the B-Cell that recognizes the antigen divides many times and makes clones of itself. it produces large amounts of the antibody against the identified antigen to protect against the infection

MGH Proteins (what is the point of these proteins?)

used to display the internal antigens to the surface

T-Cells and T-Cell Receptor (how does this connect to MGH proteins and how is it activated after?)

the t-cells use the t-cell receptor to inspect the antigen displayed by the MGH proteins, and then the t-cell is activated when the TCR matches to the antigens presented by the MGH

Cytotoxic T-Cells (what do they do when the TCR is matched to the antigen?)

kills infected cells when they present antigens that bind to the TCR and perforin makes holes in the infected cell’s membrane, making the infected cell lyse (shrink)

What are the similarities of B-cells and T-cells?

much like B-Cells, T-Cells expand when they find a foreign antigen to mount a full immune response

T-Helper Cells (how does this connect to the similarity between B-Cells and T-Cells?)

signaling these allow the immune responses. the contact dependent antigen presentation activates the t-helper cells, and releases signaling molecules that further activate the B-cell and other T-cells

Immunological Memory (what is formed through these cell expansions)

some cells that are formed through colonial expansion to survive as a “memory” cell for decades

How do the memory cells formed by immunological memory play a role when the pathogen returns? (so what immune response strengthens?)

the memory cells that stick around after an initial infection causes a faster, bigger response when the pathogen responds (so that the second immune response is faster)

Vaccines (what is the point of this and how does it work?)

to create the immunological memory without the LIVE pathogen (stimulating the immune system to develop memory cells)

Mitosis (what is this and why does it happen?)

it is the seperation of sister chromatids and distribution to daughter cells, and it happens to replace dying/injured cells for reproduction/growth

Genetic Material (what is this in DNA?)

substance that contains the information for how to build an organism and for what each cell should do