cell signalling Flashcards
cover content
what the helllll is homeostasis`
Maintenance of a stable internal environment independent of fluctuations in the external environment by self-regulating and negative feedback mechanisms so that the organism functions optimally.`
WOT are HORMONES
hint: location it effects; what amt needed for a response; level of specificity
what type of response elicited; 2 examples?`
they are chemicals secreted by endocrine glands directly into the bloodstream
effective in small quantities
act on specific target cells which have specific cell surface receptors
elicits different cellular responses and rapidly break down once served their function
insulin and glucagon are hydrophilic peptide hormones that bind to specific receptors on the cell membrane (RTK and GPCR`
function of pancreas
hint: what secretes what`
endocrine and exocrine gland
the islets of langerhans contain ALPHA cells that secrete glucagon and beta cells that secrete insulin directly into the bloodsteam ; they work in an antagonistic fashion --> normal blood glucose levels is around 90mg/dL
function of insulin and glucagon`
insulin triggers the conversion of glucose to glycogen
glucagon triggers the conversion of glycogen to glucose
what are the 3 stages of cell signaling`
Ligand-receptor interaction
Signal transduction
cellular response`
process of the negative feedback mechanism 6 steps`
1. stimulus
2. detection
3. sends out a signal
4. binds to CSR of the cells
5. effects response
6. negative feedback to detectors
signal transduction in detail
binding of the ligand to the protein receptor causes a conformational change in the intracellular domain of the protein receptor which initiates the signal transduction
LRI in detail`
Ligand binds to a specific, ligand-binding site which is complementary in shape and charge to the ligand on the extracellular domain of the CSR to form a ligand-receptor complex`
cellular response in detail
changes gene expression by targeting proteins such as gene regulatory proteins, ion channels etc etc
advantages of cell sig pathway (6)
1.facilitates amplification of signal
2.a signal molecule can trigger multiple signal transduction pathways in a cell and elicit many different cellular responses
3.provides many checkpoints for regulation as cellular responses can be terminated/regulated at reception or during signal transduction pathway
4. can allow the coordinated activation of man different cells simultaneously
5. ensures specific reactions are triggered as specific signals bind to specific receptors
6. activate genes in nucleus without the need to move into the nucleus
RTK pathway example: MUST KNOW
- insulin secreted by beta cells of islets of langerhans of pancreas
- recognises and binds to ligand binding site of CSR as they are complementary in shape. the insulin receptor is a RTK which exists as a linked dimer on the liver or muscle cell
- undergo changes in conformation in its intracellular cytoplasmic domain
- the conformational change activates tyrosine kinases in each of the subunits of the receptor and triggers crossphosphorylation of tyrosine residues
5.phosphorylated tyrosine residues serve as docking sites for other relay proteins
results in cellular responses ( i. translocation of glucose transporters from the membrane of cytoplasmic vesicles to the CSM, increasing glucose intake by increasing permeability of the cell to glucose
ii. activates glycogen synthase which catalyses glycogen synthesis from glucose
iii) increases rate of glycolysis
GPCR pathway example MUST KNOW
- alpha cells secrete glucagon
- recognises and binds to ligand binding site of CSR as they are complementary in shape. the insulin receptor is a RTK which exists as a linked dimer on the liver or muscle cell
- undergo changes in conformation in its intracellular cytoplasmic domain
- the conformational change causes an inactive G protein to bind to the GPCR, and release its bound GDP and allow GTP to bind in its place. the binding of GTP causes a conformational change in the g protein, activating it
- activated G protein dissociates from the receptor and translocates along the cytoplasmic side of the cell membrane to bind to and activate adenylyl cyclase.
- adenylyl cyclase converts ATP to cAMP which activates protein kinase A
- the PKA initiates a phosphorylation cascade which eventually activates glycogen phosphorylase which catalyses the breakdown of glycogen to glucose
Role and nature of 2nd messengers
`small, non-protein, water-soluble molecules or ions that can readily spread throughout the cell by diffusion and activate cellular proteins. can participate in both pathways
Molecular structure of GPCR and how its structure is related to function
5 points total, have fun
1.consists of a single polypeptide folded into a globular protein with an extracellular N terminus and an intracellular C-terminus.
2. globular seven pass transmembrane protein with a tertiary structure.
3. consists of 7 alpha-helices connected by 3 intracellular and extracellular peptide loops.
4. it is folded such that its amino acid residues with hydrophobic R groups are interacting with the hydrophobic core of the ppL bilayer of the plasma membrane
5. aa with hydrophilic R groups are arranged within the interior of the protein and also interact with the aqueous interior and exterior of the cell as well as the hydrophilic phosphate heads of the ppl bilayer.
