unit 4- Cell Communication and Cell Cy

CELL COMMUNICATION:

Direct Contact:

  • type of cell communication where cells interact through physical connections, allowing the transfer of signals and molecules directly b/w adjacent

Chemical Signaling:

  • short distances- local regulators in the extracellular fluid

  • long distances- hormones in the blood stream

Autocrine- a cell targets itself

Signaling across gap junctions- a cell targets a cell connected by gap junctions

Paracrine- a cell targets a nearby cell

Endocrine- a cell targets a distant cell through the bloodstream


SIGNAL TRANSDUCTION:

Reception:

  • ligand(signaling molecule) binds to receptor

  • causes confirmational shape change

  • ex: G protein coupled receptor

    Ligand:

  • Steroid Hormones:

  • Release: Simple Diffusion

  • Receptor: Intracellular

  • Ex: Testosterone, Estrogen

  • Protein Hormone:

  • Release: exocytosis

  • Receptor: extracellular

  • Ex: insulin

Transduction:

signaling cascades relay signals from receptors to cell targets often amplifying the incoming signals

    Phosphorylation Cascade:

  • Protein kinase

  • Phosphorylate relay molecules

    Secondary Hormones

  • Ca2+

  • cAMP

Response:

  • cell growth

  • secretion of molecules

  • gene expression

  • alter cell funciton/phenotype

  • apoptosis


FEEDBACK

Negative Feedback:

  • maintain homeostasis by reducing the intial stimulus

  • if system is disrupted, neg feedback returns it back to its target set spot

  • occurs at molecular, cellular, and organismal level

Positive Feedback:

  • mechanisms amplify responses and processes

  • variable initiating the response is moved further away from the initial set point


CELL CYCLE

G1(gap phase 1)-

  • metabolically active

  • duplicating organelles and cytosolic components

  • basically js doing its job as a cell

S(synthesis)-

  • DNA(chromatin) replicates to form sister chromatids

G2(gap phase 2)-

  • protein synthesis

  • ATP produced in large quanitites

  • centrosomes replicate

M(mitosis)-

  • nuclear division

G0-

  • no longer dividing, but can reenter the cell cycle in response to clue

Mitosis(expanded)

Prophase-

  • sister chromatides condense

  • mitotic spindle forms

  • centrosomes move to opposite poles

Metaphase-

  • spindle fibers align chromosomes along equator of the cell

Anaphase-

  • paired sister chromatids separate and pulled toward poles

Telophase-

  • mitotic spindle breaks down

  • new nuclear envelope devlops

  • cytoplasm divides

Cytokinesis-

  • cleavage furrow(animal cells)

  • cell plate(plate cells)

  • divide cytoplasm


REGULATION OF CELL CYCLE

internal controls or checkpoints regulate progressive through the cell cycle

G1- determines whether to complete the cell cycle

  • growth factor

  • adequate reserves

  • check for DNA damage

  • if do not pass, enter G0

G2- check all DNA replicated and not damaged

  • if detect problems w/ DNA, cell cycle halted to complete DNA rep or repair damaged DNA

M- check sister chromatids attached to spindle microtubules