Transcript Cell Communication

Cell Communication
Ch. 11
How are signals sent locally?
• Cell Junctions: Animals and Plants pass
molecules through the plasma membrane.
• Cell-cell Recognition: Receptor sites on
animal cells protrude from its surface and attach.
– Composed of the glycocalyx. Also responsible for
contact inhibition.
• Paracrine Signaling: Local regulatory
molecules are sent to neighboring target cells.
• Synaptic signaling: neurotransmitters
across the synapse.
Membrane carbohydrates:
Glycocalyx ( integral protein)
• Play a key role in cell-cell recognition
– ability of a cell to distinguish one cell from another
• antigens
– important in organ & tissue development
– basis for rejection of foreign cells by
immune system
How are signals sent long
distances?
• Hormone Signaling: Endocrine systems
sends signals through body fluids, often
through the blood.
– target cell : any cell that has a specific
receptor for an antigen or antibody or
hormone or drug, or is the focus of contact by
a virus or phagocyte or nerve fiber etc.
The Signal Transduction Pathway
• Small number of extracellular signal
molecules produce a major cellular
response.
Sutherland’s
epinephrine STP
• Three stages:
– Reception: The protein binds to a cells surface
receptor. This protein is often called a ligand.
– Transduction: Signal molecule changes the
receptor protein, the change is relayed to a secondary
messenger.
– Response: Secondary messenger induces the
cellular response.
G Protein
Point of the two pathways?
• Sutherlands Epinephrine pathway:
epinephrine does not directly break down
glycogen for fuel reserve. It does this through
intermediate steps.
• G Protein receptors
– Used in yeast for mating, by hormones such as
epinephrine, neurotransmitters, vision and smell.
– G protein when active picks up GTP sends it to an
enzyme and causes conformational shape which
allows for the cellular response.
– Botulism, cholera, pertussis (whooping cough)
intefeer with the G-Protein funcion.
– 60% of all medicines used today influce the G- protein
pathway.