Cell Signalling 1 Flashcards
Communication: from
source to receiver
Source—Encoding—Channel—-Decoding—–Reciever
Diabetes: abnormal Cell-Cell Communication
Type 1 Diabetes – Autoimmune Destruction of Beta Cells
In type 1 diabetes, immune cells (T-cells) mistakenly attack pancreatic beta cells, leading to their destruction.
This disrupts cell-cell communication between beta cells and other pancreatic cells, preventing insulin production.
Type 2 Diabetes – Insulin Resistance & Beta Cell Dysfunction
In type 2 diabetes, cells (muscle, fat, and liver) become resistant to insulin, reducing glucose uptake.
Beta cells initially compensate by overproducing insulin but eventually fail due to chronic stress and dysfunction.
Defective Pancreatic Communication
In both types, disrupted signaling between beta cells and other pancreatic cells (alpha cells producing glucagon) leads to imbalanced glucose regulation.
In type 2, glucagon secretion remains high, worsening hyperglycemia.
Inflammation & Miscommunication in Other Organs
Inflammatory signals disrupt insulin signaling in muscles, liver, and fat cells, reducing glucose uptake.
In type 2 diabetes, fat cells release pro-inflammatory cytokines, worsening insulin resistance
Direct Signalling
contact-dependent signalling
(Juxtacrine)
cell-surface-bound
signal molecule binds to a receptor
protein on an adjacent cell.
Direct Signalling
Gap Junction
Plasmodesmata
Gap junctions in animals and plasmodesmata in plants are connections between the plasma
membranes (and cytoplasms) of neighboring cells.
These fluid-filled channels allow small signalling molecules to
diffuse between the two cells
Paracine Signalling
Paracrine signals are released
by cells into the extracellular fluid in
their neighbourhood and act locally
Paracine- Autocrine Signals
Autocrine signals are produced by signalling cells that themselves can also bind to the ligand that is released.
Paracrine-Neuronal Signalling
transfer of signals
between a neuron and its target cell.
Endocrine (Long distance signalling)
Hormones produced in endocrine glands are
secreted into the bloodstream and are
distributed widely throughout the body.
Cell Signalling Elements
Many different kinds of molecules transmit information between the
cells of multicellular organisms.
Although all these molecules act as
ligands that bind to receptors expressed by their target cells
Cell dependent response
The same signal molecule
can induce different
responses in different
target cells
Cell Signalling
An animal cell depends on
multiple extracellular signals.
Extracellular signals can act slowly or rapidly.
Signalling by Small Molecules: Hormones
Testosterone
Oestrogen
Progesterone
Cortisol
Thyroid Hormones
Vitamin D3
Retinoic Acid
Signalling by other small
molecules
-Nitric Acid
-Acetylcholine
-GABA
-Auxins
Peptide hormones and growth factors
Short (EGF) and Long range action (insulin)
Cell Signalling Elements
Target cells possess proteins called
receptors that recognize and respond specifically to the signal
molecule.
Cell Membrane
A) Cell surface receptors
B) Intracellular receptors
Four general types of
Receptors
1) G protein-coupled receptor
2a) Receptor Enzyme (Tyrosine Kinase)
2b) Kinase Activates Transcription Factors
3) Gated Ion Channel
4) Nuclear Receptor
G-Protein Complex
G protein–coupled
receptors that indirectly
activate (through GTP
binding proteins, or G
proteins) enzymes that
generate intracellular
second messengers.
Protein Kinase Receptors
Some eukaryotic receptor proteins,
called protein kinases, catalyse the
phosphorylation (adding phosphate) of
themselves or other proteins, thus
changing their shapes and therefore
their functions.
Nuclear Receptors
Nuclear receptors that bind specific
ligands (such as the hormone cortisol)
and alter the rate at which specific genes are transcribed and translated into cellular proteins.
