Unit 4- Cell Communication

Population

all of the individual of a given species that live and reproduce in a particular geographical area

Communication steps

stimulus, release of a signal, signal reception, response

Signaling molecules

chemicals released by cells that alter the activities of other cells

Receptor proteins

proteins on the cell surface or cells interior that bind specific signaling molecules

Target cells

the cell that is supposed to receive the signal

Ligands

bind to receptor protein on or in a target cell

Quorum sensing

communication among bacteria that lead to a response only when there are a high number of bacteria present in a given area

Hormone

a type of signaling molecule that travels in the circulatory system and affects distant cells

Endocrine signaling

hormones traveling through circulatory system

Paracrine signaling

signaling that happens through diffusion, growth factor, motor neurons

Autocrine signaling

passing of signals in one cell, the signal and target cells are same, specialization

Contact-dependent signaling

allows the molecules to pass through their transmembrane proteins, molecules and ions pass directly between membranes

Gap-junctions

transmembrane protein channels between 2 neighboring cells, closely coordinate activities without having to release any signals into the extracellular space

Plasmodesmata

openings through a plant cell wall to let a signal travel between cells, continuous and larger than gap junctions

Whole cell cellular homeostasis

a set of mechanisms that allow the whole organism to regulate and stabilize its internal environment, ex. body temperature, heart rate, bp

Homeostasis communication

departure from normal conditions, response is the set of actions that restore normal conditions

Sensor

component of the system that detects when conditions have moved from partical levels

Set point

a particular optimal temperature

Effector

the thing that carries out the action

Negative feedback

a stimulus acts on a sensor that signals an effector, which produces a response that opposes the initial stimulus, turning off the signal, how it works: stimulus-departure from steady conditions, signal to effector, receptor triggers transduction pathway that causes a response

Positive feedback

describes a pattern in which the output or response of a system increases the activity of a system

Thermoregulation

ability to maintain a constant body temperature

Signal transduction

process by which a signal from outside the cell leads to response inside the cell

Ligand receptor complex

signaling molecule and its receptor protein bonded together by noncovalent molecular interactions can be uncoupled to stop signals and prevent irreversible changes

Signaling molecule type

hydrophilic and hydrophobic

Hydrophilic signaling molecules

readily dissolve in the body, easily transported, can’t travel through lipid bilayer so their receptor proteins are outside it, receptor proteins on target cells plasma membrane as embedded protein, responses usually rapid but short-lived

Ligand binding domain

piece of a receptor protein that is outside the cell

Intracellular domain

portion of receptor protein inside the cell

3 types if hydrophilic signaling molecules

6 protein-coupled receptors, receptor-protein kinases, and ligand-gated ion channels

Amplification

increase in volume of an original message generating a response

G protein coupled receptor

type of receptor protein that, when activated, use a molecule called a G protein as part of the signal transduction pathways, external cell is the first message to target cell changing its activity

Second messenger

an intermediate signaling molecule, amplifies the response inside the cell-things that pass on a message

Cyclic adenosine monophase (cAMP)

second messenger, binds and activates proteins called kinase

Kinase

enzyme that, when activated, catalyzes the transfer of phosphate groups from ATP to proteins

Signaling cascade

a small amount of signal is amplified to produce a large cellular response

Adrenaline termination

adrenaline detaches, GTP from G protein is dephosphorylated to become GDP (inactivates G Protein), G protein dissociates from adenylyl cyclase, stops producing cAMP into AMP, kinase isn’t activated, activated kinase shut down by phosphatase

Receptor-protein kinase

cell-surface receptor protein has a signal-binding extracellular domain and an intracellular kinase domain rapidly activates the kinase domain and triggers the signal transduction pathway, adding phosphate groups to activate other enzymes, transferring phosphate from ATP to protein

Ligand gated channels

receptor protein that includes a membrane-spanning channels that opens or closes in response to binding a signaling molecule, specific ion movement dictates the response

Hydrophobic signaling molecules

nonpolar lipids are lipid-soluble molecules that can diffuse into and out of cells through the cell membrane, signaling molecules are in the cell, free-floating in cytosol and nucleus, and can take time to start but are sustained, division of organelles and cytoplasm

Gene expression

turning some genes off and others on

Mutations

heritable changes in genetic material, can be caused by food, drugs, and environment

Endogenous ligand

ligands produced by the body

Exogenous ligand

ligands from outside the body can produce similar responses or stronger responses or no response, some can stay connected for longer periods of time, can be hydrophobic and hydrophilic

Agonist

any ligand that binds to a receptor and causes a response, can mimic endogenous ligands

Antagonist

any ligand that binds to a receptor and inhibits a response, bind to and block receptors

Adenosine

an antagonist that blocks G protein-coupled, receptor protein kinase, ligand-gated ion channels, and intracellular receptors with hydrophobic signals

Counter regulatory hormones

have opposite effects, insulin and glucagon, operate until setpoint is reacted

Positive feedback loop

signals become amplified after a signaling system has been initiated, works toward a peak or climax (self reinforcing), works till it “breaks”

Cell division

the process by which cells make more cells, used in growth and constant rebuilding, specific time, place, and environment

BInary fission

one prokaryote cell divides to produce two daughter cells, steps: grows, replicates DNA, circular DNA is attached by proteins to the cell membrane on two different places, as cells grows attachments move apart, construction forms in midpoint, divides

Asexual reproduction

reproduction of organisms in which an offspring inherits its DNA from signaling pathways

Chromosomes

a single DNA molecule with associated proteins, prokaryotes have 1 and eukaryotes have multiple

Cell cycle

a period from production of mew cells to the time it divides

M-phase

the parent cell divides into two daughter cells, mitosis and cytokinesis

Interphase

the time between successive M phases, copying DNA and growing, period of normal activity

S-phase

part of interphase, DNA molecules are copied, synthesis of DNA

Sister chromatids

identical copies of DNA, don’t separate

Centromere

a constriction holding sister chromatids together

G1 phase

part of interphase, between the end of M phase and the start of S phase, prepare to copy DNA, recover from cell division, grow

G2 phase

stage of interphase, between the end of S-phase and the start of the M phase, the shortest phase, synthesizes proteins to make spindles and microfilaments

G0 phase

part of interphase, a pause in the cell cycle between M and S phases, where some cells can get stuck

Chromosomes

appear a long thin thread but actually individual highly organized DNA, RNA, and chromatin

Prophase

first step of mitosis, visible chromosomes, longest stage, centrioles separate, nuclear envelope breaks down, spindle forms,

Mitotic spindle

a group of fibers made up of microtubules, pulls chromosomes to opposite ends of dividing cells

Centrosome

where the mitotic spindle radiates out from, duplicates during S phase and migrates around the nucleus, halt on opposite pole and make cell end

Prometaphase

nuclear envelope breaks down and the mitotic spindle attaches to chromosomes

Kinetochores

associated with the centromere, forms a site for mitotic spindle attachment, essential for moving chromosomes to daughter cells

Metaphase

stage of mitosis when chromosomes align in the middle of dividing cells, copies go to either side of cell, pole fibers stretch

Anaphase

sister chromatids separate, centromere splits, spindles shorten pulling poles apart, chromatids become chromosome and are taken to each pole, pole fibers are pushed apart

Telophase

begins when all new chromosomes enter the cytosol of daughter, the spindle breaks down and disappears, the nuclear envelope reforms around each set of chromosomes (distinct nuclei), ends mitosis, chromosome unwind, a new nuclear envelope forms, spindle breaks down

Cytokinesis

the division of cytoplasm to daughter cells

Contractile ring

in animal cells tightens the cell into 2 daughter cells

Telophase in plants

has vesicles carrying cell wall components, fuse in center in anaphase and telophase, then fuses with original cell wall to make daughter cells

Cyclins

protein family that appears and disappears in the cell cycle, present n interphase and peaks at mitosis, binds to kinase and activate the kinase

Cyclin dependent kinases (CDKs)

bind with cyclins to activate, binds a target protein and transfers a phosphate group from ATP to target proteins to activate the target protein, cyclin will then degrade and the signal ending

Checkpoint

a point in the cell cycle that makes sure the cycle is ready to go on, DNA must be copied, cell organelles must be produced in numbers sufficient to supply both of the daughter cells that will be produced, membrane synthesis must occur, if a checkpoint isn’t met cyclins ill stop producing and will break down which doesn’t let the next step of the cell cycle go on

DNA damage checkpoint

from G1 to S phase, check the DNA for damage

DNA replication checkpoint

makes sure the parent DNA has been fully copied

Spindle assembly check point

metaphase of mitosis, makes sure chromosomes are connected to the mitotic spindle

Necrosis

damage or lack of blood supply, cell contents leak out leak out, could damage neighbor cells

Apoptosis

cells die in an orderly way tieh a distinct set of cellular changes, how spaces in body form, enzymes dissemble it

Carcinogens

cancer causing radiation of chemicals

p35

when damaged, is phosphorylated and when activated binds to DNA blocking cyclin and CDK complex formation, many times the cause of cancer

M-phase

mitosis and cytokinesis