Cell Signalling Flashcards
How do cells communicate?
By sending chemical signals to neighbouring or far away cells.
Briefly explain the 4 steps of the signalling system.
- Detection of stimuli (signalling molecule/ligand) on the surface of CM of target cell.
- Transfer of signal to cytoplasmic side.
- Transmission of signal to effector molecule and down a signalling pathway.
- Cellular response- specific cellular effect brought about by signalling molecule.
What are ligands and give some examples of types of ligands.
They are molecules that bind to receptors and causes change in cell signalling. Cells communicate via chemical signalling molecules which are produced and released by signalling cells (sending cells).
Examples of types of ligands:
- peptide hormones like insulin and glucagon
- AA derivatives like adrenaline and histamine
- steroids and prostaglandins
- gases like nitric oxide (NO)
Name 5 types of cell signalling.
-
1. Autocrine
2. Paracrine
3. Neutral
4. Direct contact
5. Endocrine
Describe autocrine cell signalling.
Cell responds to chemical they produce themselves. Eg, growth factors and prostaglandins.
Describe paracrine cell signalling.
- Signalling molecules are released from signalling cell into surrounding area.
- Signalling molecules then interact with target neighbouring cells.
Eg. Cells involved in inflammation during infection; cells that regulate cell differentiation.
Describe neutral cell signalling.
(What happens during synapses).
- Nerve cells send signalling molecules NT to target cells.
- NT are detected by receptors on the CM of target cells.
Eg. Conduction of electrical signals from one nerve to another or to a muscle cell.
Describe direct contact cell signalling.
Physical contact between both cells CM. No molecules are secreted.
Eg. Cell differentiation during embryonic development.
Describe endocrine cell signalling.
Common. Endocrine cells send signalling molecules like hormones via the bloodstream to distant cells in the body. Binding of hormone-target cells lead to cellular responses.
Name and explain two types of hormones involved in endocrine cell signalling.
- Hydrophilic hormones bind to receptor on Cm of target cell. Eg. Insulin and adrenaline.
- Lipophilic hormones diffuse through Cm to reach cytosolic/nuclear receptors inside target cell. Eg. Sex hormones and thyroid hormones.
Where are the 2 places target cell signalling receptors can be found?
Cells respond to signalling molecules it has receptors for and ignores the ones with no receptors.
- Intracellular receptors- inside cytoplasm/nucleus of target cells. Bind to lipid soluble signalling molecules. Eg. Steroid hormones/ v.small ligands like NO.
- Cell surface receptors- protein embedded on plasma membrane of target cells. Bind to water soluble signalling molecules. Eg. NT and peptide hormones.
Intracellular receptors can act as a …
- As a gene regulator. Eg receptors for steroid hormones (coristol, oestrogens and progesterone), vitamin D and thyroid hormone.
- As an enzyme. Eg. NO diffuses into smooth muscle cell in blood vessel wall and binds to guanylyl cyclase enzyme activating cAMP resulting in muscle relaxation.
Where are cell surface receptors found and what are the two main domains.
Embedded on the CM of target cells.
2 main domains are:
- the signaling molecule binding domain which exposed to exterior of cells.
- intracellular domain which is in contact with the cytoplasm.
Name the 3 important cell surface receptor classes which are used in different signalling pathways.
- ligand gated ion channels coupled receptors
- Enzyme coupled receptors
- G protein coupled receptors (GPCRs)
What is ment by ‘second messenger?’
Relay molecules that transmit signals received at receptors on cell surface to target molecules in the cytoplasm and/or nucleus.
It amplifies strength of original signalling molecules.
Some enzyme coupled receptors and G protein coupled receptors (GPCRs) are used as second messengers in the cytoplasm to carry out signal molecules message.
3 major classes of second messengers.
- Cyclic nucleotides (cAMP+cGMP)
- inositol triphosphate (IP3) and diacylglycerol (DAG)
- Calcium ions
Describe the cAMP pathway briefly.
- Signal molecule attaches to cell surface receptor.
- G protein from cell surface receptor to (activated) adenyly cyclase.
- ATP to cAMP
- cAMP to target protein
Briefly describe the calcium ion pathway.
- Signal molecule to cell surface receptor (GPCR)
- G protein from receptor to phospholipase C
- Phospholipase C to inositol triphosphate intermediary to ER
- Calcium ions out of ER to target protein
