Summary Slides Flashcards
Lecture 38
Proteins need signals to travel to their correct intracellular destination.
-Sorting signals are found within the protein and need to be exposed.
-E.g. nuclear proteins require NLS.
Cytoplasm- nucleoplasm traffic:
-Occurs through the nuclear pore complexes (NPCs).
-Uses receptors called importins (into the nucleus) or exportins (out of the nucleus).
-Directionality of movement is provided by the Ran GTPase switch.
-Asymmetric diffusion of Ran GTP (nucleus) and Ran GDP (cytosol) depends on the Ran GAO (cytosol) and ran GEF (nucleus).
-Asymmetric distribution of Ran GAP and Ran GEF depends on their preferential association with the cytosolic skeleton and nuclear chromatin, respectively.
Lecture 39
-The ER imports proteins from the cytosol via protein translocation.
-The secretory pathway is a functional array of membrane-bound organelles. Interconnected via vesicle trafficking.
-Proteins need a signal peptide to enter the secretory pathways and be secreted.
-To reach the lysosomes, they need an extra signal: a modified glycan (M6P), seen by a specific receptor- which sorts the lysosomal proteins into vesicles destined to the LE/lysosome in a pH dependent manner, yet another signal (a 3D patch) is required for lysosomal proteins to acquire the M6P.
-Any defect in lysosomal sorting leads to major diseases.
Lecture 41
-Multicellularity requires cells connecting to each other: this requires the cytoskeleton and the formation of cell-cell junctions.
-Three major cytoskeletal elements: microtubules, actin microfilaments, intermediate filaments. These provide the internal scaffold for the formation of cell-cell junctions or cell-extracellular matrix junctions.
-Adherens junctions use cadherins to link neighbouring cells.
-Focal adhesions use integrins to link cells to the ECM.
-Tight junctions use claudins/occludins to maintain cell polarity and prevent leakage between cells.
-Gap junctions use connexins to form passageways between cells.
-Proteins involved in cell-cell junctions are also active in intracellular signalling and developmental interactions.
Lecture 46
-Bacteria evolve through mutation.
-Evolution is caused by selection of the fittest.
-Traits survive, rather than _ evolved this trait.
-Note the scientific method of gathering evidence from multiple experiments.
Lecture 47
-Chemical and radiation can alter the chemistry of the bases, which often results in altered base pairing and hence mutations.
-Point mutations involve single base pairs. Large scale mutations can involve a few several kbp.
-Reversions: restoring the original genotype.
-Suppression: another mutation happens to suppress the phenotype.
-Selecting for mutations based on phenotype and studying these mutations has taught us much of the fundamental biochemistry and cell biology.
-Ames test is an example of how bacterial mutants can be exploited. In this case to asses whether chemicals are carinogenic.
Lecture 48
-Operons are groups of genes regulated together and transcribed off a single promotor.
-The Iac operon is normally repressed. Presence of lactose leads to de-repression.
-Catabolite repression means that bacteria prefer to grow on glucose and will not express genes to grow on other carbon sources if glucose is present.
-The Iac promoter is one of the most used promoters in biotechnology.
Lecture 50
-Plasmids exist outside of the chromosomal DNA, they control their own replication and copy number.
-Conjugation requires cell-to-cell contact to transfer plasmid.
-HFr strains have high frequency of recombination as they can transfer part of their genome to another cell.
Lecture 35
-Amphipathic lipids generating the membrane bilayer, which is semi-fluid.
-There are three main types of lipids in membranes: phospholipids (phosphoglycerides and sphingolipids), glycolipids and cholesterol.
-Membrane composition differ in terms of which lipids it contains and which & how many proteins it contains, reflecting the function.
-Lipids are not just structural but have functions in signalling as well.
