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Cell Communication and Cycle

Topic Review on "Title":

Cell communicationCell-cell contact
Local signal transduction channels are through cell-cell contact. There are 4 types of cell-cell contacts in mammalian cells: tight junctions, adheren’s junctions, gap junctions and desmosomes.

Cell communication - Paracrine signal vs. Endocrine signal
Cell signals can be local signal (paracrine signal) which is communicated through cell-cell contacts, or endocrine signal which is mostly hormones secreted by glands and transported via blood.

Signal Reception
Cell signals are chemicals.  Signal reception is a process of ligand binding to the receptors; mimic a lock and key model.  There are three major types of signal receptors: receptor tyrosine kinases (RTKs), G protein-coupled receptors (GCPRs) and intracellular receptors.  Ligand binding activates RTKs via dimerization and phosphorylation; Ligand binding activates GCPRs by activating G protein (replacing GDP by GTP) which can then phosphorylate the downstream targets.  Intracellular receptors can be translocated into nucleus upon signal binding and activate gene expression directly. 

Signal Transduction
Signal transduction is often achieved by phosphorylation and de-phosphorylation, and therefore involves kinase and phosphotases.  Protein kinases are often involved in cell proliferation and phosphotases play antagonized roles.

Second messenger and signal amplification
Cell signals can be amplified during transduction because one kinase can phosphorylate multiple copies of downstream targets.  Second messengers also play important roles in signal amplification.  There are three major types of second messengers: cAMP/cGMP, IP3 and DAG, calcium ions.  cAMP activates gene expression via CREB or PKA which further activates downstream targets.  IP3 and DAG activate PKC and releases calcium ions.  Calcium ions can also activate PKC which further activates the downstream targets.  Calcium ions play multiple roles in cells in addition to second messenger.

Cell Cycle
Proliferating cells undergo cell cycle which is composed of G1, S, G2 and M phases.  Resting cells are in G0.  Cell cycle is controlled by cyclins and CDKs, when circumstances are not right, cell cycle checkpoints can be activated to restrain cell cycle.  There are 4 major cell cycle checkpoints: G1 checkpoint, intra-S phase checkpoints, G2 checkpoints and spindle checkpoints.  When cell cycle checkpoints are broken or cell cycle goes wrong, cells may undergo apoptosis or become cancerous. 

Rapid Study Kit for "Title":
Flash Movie Flash Game Flash Card
Core Concept Tutorial Problem Solving Drill Review Cheat Sheet

"Title" Tutorial Summary :

Cell-cell communication is critical for organism survival and homeostasis.  All cell signals are chemical signals.  Chemical signals are received by signal receptors on cell surface or inside cells.  Three major types of receptors are RTKs, GCPRs and intracellular receptors.  RTKs have intrinsic tyrosine kinase activities which are activated upon signal binding; GCPRs are coupled to G proteins which are activated by signal binding.  Intracellular receptors can bind to signal molecules and then trans-locate into nucleus for activating gene expression.  RTK and GCPR can activate downstream targets and initiate cascade signal transduction.  Signals can be amplified through transduction, especially through second messengers such as cAMP/cGMP, DAG and IP3, and calcium ions.  Dividing cells undergo cell cycle which includes G1, S, G2 and M phases.  Cell cycle are controlled and checked at certain points to ensure proper DNA inheritance. 

Tutorial Features:
  • Pictorial description of cell-cell contacts.
  • Easy to understand classification of receptors and how they work
  • Detailed analysis of second messengers.
  • Diagram of cell cycle
  • Logical link of cell cycle control to tumorigenesis

"Title" Topic List:

Cell-cell contact and signal type

  • Tight junction
  • Adherens junction
  • Gap junction
  • Desmosomes
  • Paracrine and endocrine signals

Signal Reception

  • Key-lock model
  • RTKs
  • GCPRs
  • Intracellular receptors

Signal Transduction

  • Protein kinase
  • Protein phosphotase
  • Signal amplification

Second Messenger

  • cAMP
  • DAG and IP3
  • Calcium ion

Cell Cycle

  • Cell cycle phases
  • Cyclins and CDKs
  • Cell cycle checkpoints
  • Cancer and cell cycle control

See all 24 lessons in College Biology, including concept tutorials, problem drills and cheat sheets:
Teach Yourself College Biology Visually in 24 Hours

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