SGS 141- Zoology
CELL SIGNALING AND STEM CELLS
The routes of biological processes must be regulated so that energy
generation or end product synthesis fulfils the demands of the cell.
• Furthermore, individual cells do not function in isolation but rather as
part of a network of interconnected tissues.
• To coordinate the functioning of the body, a complex communication
system has evolved.
• Hormones
• Neurotransmitters
• Nutrient availability are examples of regulatory signals that tell an
individual cell about the metabolic condition of the organism as a whole.
Transduction is the process of converting next-acellular signals into intra-
cellular responses, and involves the binding of specific ligands to receptors
which transmit signals to intracellular targets. Different receptors can
respond differently to the same ligand, and each individual receptor binds
to a different ligand.
Extracellular signal
Receptor protein
intracellular signaling proteins
metabolic enzyme
gene regulatory protein
cytoskeletal protein
Types of signals
Intracellular
, Intercellular
Second messenger systems
The second messenger systems are molecules that act as a bridge
between the initial messenger (neurotransmitter or hormone) and
the effect on the cell (response) - an example of a second messenger
system is calcium/phosphatidylinositol or Adenylyl cyclase enzyme
system.
Types of signals
Signals are classified as dependent or independent of cellular
connectivity. The four forms of contact independent signals are as
follows: Autocrine (through growth factors, the signal is released by
the cell that is also the target cell). Paracrine (effect on nearby target
cells via neurotransmitters and cytokines). Endocrinology (via
hormones, action on distant target cells). Synaptic (action on post-
synaptic cells in response to electrical stimuli via neurotransmitters).
Types of signaling molecules (ligands)
(A) Ligands that bind to cell surface receptors, such as
neurotransmitters (such as acetylcholine)
Peptide hormones (such as insulin)
Growth factors
Prostaglandins (pain creators) (pain producers)
(B) Ligands that bind to intracellular receptors, such as lipid-soluble
hormones that may penetrate the plasma membrane, such as
steroids
CELL SIGNALING AND STEM CELLS
The routes of biological processes must be regulated so that energy
generation or end product synthesis fulfils the demands of the cell.
• Furthermore, individual cells do not function in isolation but rather as
part of a network of interconnected tissues.
• To coordinate the functioning of the body, a complex communication
system has evolved.
• Hormones
• Neurotransmitters
• Nutrient availability are examples of regulatory signals that tell an
individual cell about the metabolic condition of the organism as a whole.
Transduction is the process of converting next-acellular signals into intra-
cellular responses, and involves the binding of specific ligands to receptors
which transmit signals to intracellular targets. Different receptors can
respond differently to the same ligand, and each individual receptor binds
to a different ligand.
Extracellular signal
Receptor protein
intracellular signaling proteins
metabolic enzyme
gene regulatory protein
cytoskeletal protein
Types of signals
Intracellular
, Intercellular
Second messenger systems
The second messenger systems are molecules that act as a bridge
between the initial messenger (neurotransmitter or hormone) and
the effect on the cell (response) - an example of a second messenger
system is calcium/phosphatidylinositol or Adenylyl cyclase enzyme
system.
Types of signals
Signals are classified as dependent or independent of cellular
connectivity. The four forms of contact independent signals are as
follows: Autocrine (through growth factors, the signal is released by
the cell that is also the target cell). Paracrine (effect on nearby target
cells via neurotransmitters and cytokines). Endocrinology (via
hormones, action on distant target cells). Synaptic (action on post-
synaptic cells in response to electrical stimuli via neurotransmitters).
Types of signaling molecules (ligands)
(A) Ligands that bind to cell surface receptors, such as
neurotransmitters (such as acetylcholine)
Peptide hormones (such as insulin)
Growth factors
Prostaglandins (pain creators) (pain producers)
(B) Ligands that bind to intracellular receptors, such as lipid-soluble
hormones that may penetrate the plasma membrane, such as
steroids
