General Biology/Cells/Cell-Cell Interactions
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Cell-cell interactions edit
Cells interact with the environment and with each other.
Cell signaling edit
- Signaling requires
- Signal
- Cell receptor (usually on the surface of a membrane)
- Signaling is important in:
- Response to environmental stimuli
- Sex
- Development
- Major area of research in biology today
Types of signaling edit
- Direct contact (e.g., gap junctions between cells)
- Paracrine: Diffusion of signal molecules in extracellular fluid; highly local
- Endocrine: Signal (hormone) molecule travels through circulatory system
- Synaptic: neurotransmitters
Types of signal molecules edit
- Hormones: chemically diverse
- Steroid
- Polypeptide
- Vitamin/amino acid derived
- Cell surface proteins/glycoproteins
- Ca2+, NO
- Neurotransmitter
- Several hundred types
- Some are also hormones e.g. Estrogen, progesterone
Receptor molecules edit
- Intracellular
- Protein that binds signal molecule in cytoplasm
- Bound receptor may act as:
- Gene regulator
- Enzyme
- Cell surface
- Gated ion channels (neurotransmitter receptor)
- Enzymic receptors
- G protein-linked receptors
Cell surface protein edit
- Tissue identity
- glycolipids
- MHC proteins
- Immune systems
- distinguish self from not-self
- Intercellular adhesion
- permanent contact
- help form sheets of cells, tissues
- may permit signaling
Example: G proteins edit
- Transmembrane surface receptor binds signal molecule
- Conformational change allows binding of G protein on cytoplasmic side
- G protein binds GTP, becomes activated
- G protein activates intracellular signal cascade
- Change in gene expression
- Secrection
- Many other possible consequences
Communicating junctions edit
- Gap junctions
- animals
- small molecules and ions may pass
- Plasmodesmata
- plants
- lined with plasma membrane
- permit passage of water, sugars, etc.
Gap junctions edit
This text is based on notes very generously donated by Dr. Paul Doerder, Ph.D., of the Cleveland State University.