Download Diapositive 1

The cell and its
environment
The cell within the organism
The cell and its organelles
How cells communicate with their environment
and vice versa
Three modes of distribution of first messengers
Different types of first messengers
Different types of cell membrane receptors
Different types of intracellular (nuclear) receptors
the phospholipid bilayer
Headgroups of phospholipids and non-bilayer arrangements
of (phospho)lipids in an aqueous environment
Phospholipid bilayers are efficient barriers that allow
for a « privileged » intracellular environmont
Because of the impermeable membrane, cells require
transmembrane proteins in order to communicate and
interact with their environment
Epithelial cells in particular make extensive contacts with
adjacent cells via specialized cellular junctions
Tight junctions seal the
intercellular space of
epithelial cellular
sheets (selective
barrier), an essential
function for selective
transport of solutes
(for instance nutrient
uptake in the intestine)
Adherens junctions protect the cell against physical agression (tension
forces in particular). They play an important role in the maintenance of
tissue integrity
Adhesion molecules, in particular the integrins, also interact with
cellular matrix. Collagen is an important component with both
structural and cell interaction functions
Fibronectin is an important ligand for integrins, it has a prime role in
connecting cells with the extracellar matrix.
Laminin, an important component of the basal lamina (basement
membrane) plays a bridging role between cells (through binding with
integrins) and their matrix (through binding with other components).
This drawing nicely illustrates how the different components of the
extracellular matrix form a dense matrix to which cells firmly attach
Integrins bind to proteins of the extracellular matrix. This often
occurs in focal adhesion complexes, where numerous proteins attach
to each other, and importantly, to the actin cytoskeleton
Glycosaminoglycans also have their place in the extracellular matrix.
These long and highly charged sugar chains attract water and have the
important capacity, unlike collagens, to resist compression
Cartilage of the synovial joint is a beautiful example of how proteins (collagen
and aggregan) and glycosaminoglycans (hyaluronan, KS and CS) act together
to resist to both tension (during flexion of the joint) and compression (static
weight bearing of the joint). The importance of all this is best explained by people
who suffer from rhumatoid arthritis or arthrosis.
Finally, cell-cell and cell-matrix interactions are important
- to maintain tissue integrity
and because adhesion molecules act like « classic » receptors and signal
into the cell, they also play a role in
- maintaining the cell in a differentiated state
- providing a survival signal that protects the cells against apoptosis
DNA versus RNA, a better way to stock genetic information (less
prone to alterations)
Coding sequence and non-coding (template) sequence
Transcription and translation,