very last minute points to understand Flashcards
other than vital staining, what is another technique that can be used to determine cell counts
colony counts using serial dilution
what are the different forms of electrophoresis
native gel (does not denature, separates by size shape and charge)
sds-page (does denature by applying an equally negative charge, separating by size alone)
how can you separate proteins by size alone
sds page electrophoresis
how do you separate proteins by size shape and charge
native gel electrophoresis
how do you separate different substances
tlc
how do you separate proteins
affinity chromatography
how can you separate proteins based on pH
if a solution is buffered to a specific pH, only the proteins with an isoelectric point at that pH will precipitate out of solution.
can also use isoelectric points in electrophoresis, because the protein will stop migrating once it has reached its iep.
what is the principle of electrophoresis
charged macromolecules move through an electric field applied to a gel matrix
what are transcription factors
these are the receptors for hydrophobic signalling molecules. they are proteins that when bound to DNA can stimulate or inhibit the initiation of transcription.
what is the process of hydrophobic signalling
signalling molecule passes directly across the phospholipid bilayer and binds to an intracellular receptor known as a transcription factor.
the hormone receptor complex moves to the nucleus where it binds to specific DNA sequences called hormone response elements. binding at these sites influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes.
what is the process of hydrophilic signalling
the molecules bind to transmembrane receptors without entering the cell.
the receptors change conformation when the ligand binds to the extracellular face, transducing the signal across the membrane. this is done by converting the binding of the signal molecule into intracellular signals, which alter the behaviour of the cell.
how can signals be transduced in the cell
g proteins, which will relay signals from these activated receptors to target proteins like enzymes and ion channels
phosphorylation cascades, which involve a series of events where one kinase activates the next in the sequence and so on - many proteins are phosphorylated as a result of the original signalling event.
how is neurotransmitter released
when the action potential reaches the end of a neuron, it causes vesicles containing neurotransmitter to fuse with the membrane
explain the process of a nerve impulse in eye.
- retinal absorbs photon and rhodopsin becomes photoexcited rhodopsin
- this signal is amplified by a cascade of proteins
- the photoexcited rhodopsin actives hundreds of the g protein transducin which activates the enzyme PDE
- each g protein activates one molecule of PDE
- each PDE catalyses the hydrolysis of thousands of cGMP molecules per second
- reduction of cGMP concentration closes the ion channels in the membrane of rod cells and triggers nerve impulses in neurons in the retina
discuss retinoblastoma
found at the g1 checkpoint, acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for dna replication.
to allow the transcription of genes and therefore to allow progression through the cell cycle, it must be inhibited by g1 cyclin dependent kinases phosphorylation.
