Chapter 11:
Cell Communication
Cell to cell recognition:
Yeast cells: secrete
chemical signals
which bind to specific
receptors
Start to grow
towards each other
Forms new cell that
contains all genes
from both cells
Signal Transduction
Pathways:
process by which a signal on a
cell’s surface is converted into
a specific cellular response in a
series of steps
Phosphorylation Cascade
Protein kinase is activated by a relay molecule
Transfer of phosphate group from an active
protein kinase to an inactive protein kinase
Ultimately brings about a cellular response
Protein phosphatase- enzyme
Dephosphorylates protein kinases
Secondary Messengers
Carry signal to cells interior
Small, non protein, water soluble
Diffuse through out the cell
Examples:
cAMP
Ca++
Signal Molecules:
Cell
Bacteria
Proteins
Local and Long-Distance
Signaling:
cells communicate via chemical
messengers
Local Signaling:
paracrine signaling
Involves secreting cell and target cell
Example: growth factors
synaptic signaling
Involves neurons as the secreting cell
Neurotransmitters
Target cell- could be another nerve
cell, muscle cell etc…
Long distance signaling:
Hormones
Released by endocrine system
Pancreas releases insulin
Travels to different parts of the body via the
circulatory system
Another example in plants:
Ethylene: gas secreted by fruits speeds up
ripening process in other fruits
Auxins
Three stages of cell
signaling:
1. reception- detection of the
signal molecule by the target cell
Signal Molecules (ligand)
Surface Receptors
G- Protein Linked Receptors
Tyrosine- Kinase Receptors
Ion Channel Receptors
Intracellular Receptors
Three stages of cell
signaling:
2. transduciton- signal converted to
a specific cellular response
Involves conformational change of
proteins
Can be single step but usually
involves multiple steps
Three stages of cell
signaling:
3. response: a multitude of cellular
activity including: enzyme
catalysis, rearrangement of the
cytoplasm, activation of specific
genes
Three stages of cell
signaling:
This three step process ensures
the right cells and cell processes
are activated at the right time
The Role of membrane
carbohydrates in Cell- Cell
recognition
Glycolipids : short carbohydrate chain covalently
bound to proteins
Amphipathic
Receptor site
Glycoproteins: short carbohydrate
chain covalently bound to lipids
Cell to cell contact and communication