AP BIO UNIT 4 (SEM 1 FINAL)

gap junctions

direct contact

local regulators

growth factors & neurotransmitters

hormones

long distance

3 stages of cell signaling

reception

reception

detection of a signal molecule (ligand) coming from outside the cell

plasma membrane receptors

water soluble ligands

intracellular receptors

inside the cell

cytoplasm

nucleus

G-protein coupled receptors

G-protein + GTP activates enzyme = cell response

Tyrosine Kinase receptor

insulin receptor
- dimer forms upon ligand binding
- activates multiple cellular responses at once

ligand-gated ion channel

signal receptor changes the shape (opens & closes)
- regulates flower of specific ions

transduction

convert signal to form that can bring about a cellular response
- cascades of molecular interactions relay signals
- protein kinase (enzyme that phosphorylates & activates proteins)

second messengers

small

response

response to the signal molecule
- regulate protein synthesis by turning on/off genes in nucleus
- regulate activity of proteins in cytoplasm

Apoptosis

programmed cell death
- signals activate cascade of "suicide" proteins
- protect neighboring cells from damage

Short-distance communication

Cell sends out local regulators (signals)
Target cell is within a short distance of the signal
Often used to communicate with cells of the same type

Long-distance communication

Traget cell is not in the same area as the cell emitting the signal
Signal travels a long distance to reach the target cell
Often used to signal cells of another type

mutation in transduction pathways

One disruption in a pathway can affect the downstream reactions
- change in function

the cell cycle

interphase (growth & reproduction)
m-phase (mitosis - division of nucleus

Interphase

G1 (cell growth)
S (copies of DNA are made)
G2 (the cytoplasmic components are doubled in preparation for dvision)

Mitosis

- growth

Mitosis process (PMAT. . .C)

Prophase
- Nuclear envelope begins to disappear
- DNA coils into visible chromosomes
- Fibers begin to move double chromosomes toward the center of the cell

Metaphase
- Fibers align double chromosomes across the center of the cell

Anaphase
- Fibers separate double chromosomes into single chromosomes (chromatids)
- Chromosomes separate at the centromere
- Single chromosomes (chromatids) migrate to opposite sides of the cell

Telophase
- Nuclear envelope reappears and establishes two separate nuclei
- Each nucleus contains a complete genome
- Chromosomes will begin to uncoil

Cytokinesis
- seperates into two daughter cells
- ensures each equal distribution of cytoplasm

regulation checkpoints

G1 Checkpoint
- At the end of the G1 phase
- Cell size check
- Nutrient check
- Growth factor check
- DNA damage check

G2 Checkpoint
- At the end of G2
- DNA replication check
- DNA damage check

M-spindle Checkpoint
- Fiber attachment to chromosome check

cyclins

proteins that regulate the cell cycle
- Used to activate cyclin-dependent kinases

cyclin-dependent kinases

Group of enzymes involved in cell cycle regulation
Requires cyclin binding for activation
Phosphorylate substrates

disruptions in cell cycle

may result in cancer and/or apoptosis
- Cancer is the result of an unregulated cell cycle with uncontrolled cell divison

feedback

homeostasis (stable internal enviorment)
- target set point

negative feedback

maintain homeostasis for a particular condition by regulating physiological processes
RETURNS SYSTEM BACK TO ITS TARGET SET POINT

positive feedback

The variable initiating the response is MOVED FARTHER AWAY FROM THE INITIAL SET POINT

cell signaling pathways are activated by. . .

cell-to-cell communication

an example of long-distance communication are . . .

hormones

cAMP activates. . .

protein kinase A (phosphorylates various other proteins) ~ type of ernzyme

what occurs first once a chemical messenger reaches a target cell?

a ligand binds to a receptor

cell signaling starts with. . .

the reception of the signal
- only cells with correct receptor can respond

Increased cell division will lead to. . .

the formation of a tumor

DNA replication occurs during. . .

the S phase (requires free nucleotides) - if unavailable