Cell Communication Flashcards
Quorum Sensing
Method of communication that allows bacteria to detect population density
Local Signalling
- Signalling that occurs in near by cells
- Includes direct contact via cell junctions and cell-to-cell recognition
Long-distance signalling
Signalling that occurs between different parts of the body
How does long-distance signalling work?
Based on the secretion of hormones produced by plants and animals
Endocrine Signalling
Long-distance signalling in animals
What are the 3 stages of cell signalling?
- Reception
- Transduction
- Response
What does reception require?
A protein with the correct binding site to recognize a signalling molecule
Ligand
Molecule that specifically binds to another often larger molecule
What happens when a signalling molecule binds to a receptor?
- Its binding impacts the shape and function of the receptor
- Activates it
2 different types of receptors
- Cell-surface receptors
- Intracellular proteins
What are cell-surface receptors?
- Integral membrane proteins
- 3 main types exist
G protein-coupled receptors (GPCRs)
- First type of cell-surface receptor
- Work with a G protein that binds to GDP/GTP
- Activate or inhibit GDP/GTP
Receptor tyrosine kinases (RTKs)
- Second type of cell-surface receptor
- Self-phosphorylates, dimerizes and structurally modifies relay proteins
- Can activate up to 10 signal transduction pathways
Dimerization
Process of joining molecular entities by bonding
Ligand-gated ion channel receptors
- Third type of cell-surface receptor
- Channel that opens in response to a signalling molecule
- For signal molecules and transported metabolite
- Can be voltage-gated
Histidine Kinases (HKs)
- Cell-surface receptor in bacteria
- Self-phosphorylates, then phosphorylates a response regulator protein
- For signal molecule and response regulator
Signalling Molecules
Molecules that are hydrophobic and small enough to pass through the plasma membrane
Examples of signalling molecules
Steroids and NO gas
Where are intracellular receptors found?
In the cytoplasm and nucleus
Functions of intracellular receptors
- Increase or decrease the rate of transcription
- DNA binding protein that influences gene expression
Signal Transduction
- Conversion of a signal into a form that can cause a specific cellular response
- Can be a single step but more often is a multistep process
Multistep signal transduction pathway
- Enable amplification of the signal and more opportunities for regulation
- Involves relay molecules
Protein Phosphorylation and dephosphorylation
- Method of regulating protein function
- Through addition or removal of phosphates
Protein Kinase
- Enzyme that adds a phosphate group to a protein from ATP
Protein phosphatase
Enzyme that removes a phosphate group from a protein
Phosphorylation cascade
Signalling pathway involving a series of phosphorylation events
What are second messengers?
- Small, nonprotein, water-soluble molecules
- Can diffuse through cytoplasm
Second messenger functions
- Involved in signal transduction
- Influence activity of relay proteins
What is cyclic AMP (cAMP)
- Second messenger
- Activates other proteins, usually protein kinase A
How is cyclic AMP synthesized?
- Synthesized by adenylyl cyclase, which is activated and inhibited by G protein-coupled receptors
What are calcium ions?
- Second messenger
- Act as allosteric regulators of proteins involving G protein-coupled receptors and receptor tyrosine kinases
Where are calcium ions found in the cell?
- Higher concentrations in extracellular fluid and ER lumen than in cytosol
- Release of calcium ions from ER lumen are mediated by IP3
What is a response?
- Final stage of cell signalling
- Involves changes in gene expression
- Can also involve regulating the rate of a protein’s activity
How does a response change gene expression?
Through the activation or repression of the transcription of specific genes
What is a proteome?
Complete set of proteins present in a cell
What is signal specificity?
Different cells have different responses to the same signal based on their collection of proteins
What is signal termination?
- Once the signal is removed everything inactivates
- Based on reversibility of the changes produced by a signal
