cell communication cheat sheet

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AP Biology - Core Concept Cheat Sheet
06: Cell Communication and Cycle
Key Concepts
• Calcium ion: A second messenger, involved in muscle
contraction, exocytosis, hormone secretion, T and B cell
activation, cell adhesion, apoptosis and signal transduction.
• CDKs: Cyclin-dependent kinase that binds to cyclin. This
binding activates its kinase activity, mostly for cell cycle
control.
• Cell cycle checkpoint: the Cell cycle progression is
monitored by surveillance mechanisms, or cell cycle
checkpoints, that ensure initiation of a later event is
coupled to the completion of an early cell cycle event.
There are 4 major checkpoints: G1 checkpoint, Intra-S
phase checkpoint, G2 checkpoit and sindle checkpoint.
• Cell cycle: A cell proliferation cycle from one cell to two
cells. Cycling cells are proliferating cells which undergo
G1,S, G2 and M phases.
• Chemical signal: Cell signals are often chemicals.
• Cyclin: Aclass of proteins that fluctuate in concentration at
specific points during the cell cycle and regulate the cycle
by binding to a kinase, therein regulate the kinase activity.
• DAG: Diacylglyceral, generated by phospholipase from
PIP2 and serves as a second messenger
• Endocrine Signal: Specialized cells release molecules
(often hormones) into blood vessels of circulatory system,
which move to distant target cells
• G Protein: A huge class of proteins that bind to guanine
nucleotide GDP and GTP, usually hetertrimers and
associated with GPCR or cytosol side
of cell membrane. Upon signal
binding by a GPCR, it undergoes a
conformational change and hydrolizes
GTP to activate the downstream
targets.
• G0 phase: Refers to cells in a
quiescent state. Cells enter the G0
phase from a G1 phase checkpoint and
out of cycling.
• GPCR: G-protein coupled receptors, usually has 7
transmembrane domains and has an intracellular domain to
bind signal molecule and a cytosol domain to bind G
protein.
• IP3: Inositol-1,4,5-trisphosphate, a second messenger
that can amplify the original signal
• Paracrine signal: Local signals that can only influence the
neighboring cells, such as neuron transmitters.
• PIP2: Phosphatidylinositol (4,5)-bisphosphate, localized in
cell membrane, precursors for second messengers IP3 and
DAG
• RTK: Receptor tyrosine kinase, numerous types but often
includes receptors for growth factors. It has intrinsic
tyrosine kinase activity and is capable of self activation by
phosphorylation and dimerization.
• Second messeger: A molecule that relays messages in a
cell from a receptor on a cell membrane to the final
destination where an action within the cell is to take place.
• Signal receptors: Often membrane proteins that can bind
signal molecules from cell surface except for intracellular
receptors which is localized in cytosol.
• Tumor suppressor:A gene or gene product that reduces
the probability that a cell in a multicellular organism will
turn into a tumor cell. A mutation or deletion of such a
gene will increase the probability of the formation of a
tumor.
Signal Reception and Transduction
For both GPCR and RTKs:
Signal reception --> Transduction --> Response
• GPCR:
Signal binds to serpent receptor
Binding triggers a conformation change on G protein which
then replace GDP with GTP (activation)
GTP-G protein activates a downstream signal molecule by
phosphorylation
• RTK:
• Intracellular receptors
Hormones pass through cell membrane
Hormones bind receptors in cytosol
Homone-receptor translocate into nucleus for gene activation
Cell Cycle
o contains G1, S, G2 and M phases
o Controlled by cyclins and CDKs
o Controlled by checkpoints
o When cell cycle goes wrong, cancer may arise
o Tumor suppressors are often related to cell cycle
regulation and checkpoint activation.
Phosphate group
Ligand
Ligand
binding
Signal
Receptor
Reception
Transduction
Transducer
Response
Cell
membrane
Effector
G1 checkpoint
Intra-S checkpoint
G2 checkpoint
Spindle checkpoint