Organisation and function of membranes Flashcards
What are some of the functions of membranes?
-barrier (all cells)
-signalling (all cells)
-cell recognition (euks and proks)
-membrane trafficking (euks)
-compartmentalisation (euks)
-nerve transmission (euks)
-converting membrane potential/gradient to energy
What are the functions of membranes from an evolutionary perspective?
-initially all membranes as barriers
-developed channels, and later pumps, for transport -found across all species
-other functions developed later
-functions such as signalling and cell recognition developed in multiple types of organisms but have different systems in place
Why do eukaryotes have a larger cell size?
-need for internal compartmentalisation and transport systems
(more internal membranes than plasma membrane!)
What happens in membrane trafficking?
-ER makes and processes proteins, checking them and preparing them for secretion.
-proteins are tagged with a marker (oft added at N-terminal) (indicating where it is needed) and those with the same markers are packaged into the same vesicle (also with a marker for that location!)
-vesicles are moved along microtubules (protein structures which run from the nucleus to the outside of the cell)
How are the golgi, ER and mitochondria held in place?
-by kinesis (ATPase proteins that “walk” along the microtubules)
-on microtubules
What is the experimental evidence of the importance of microtubules for cell organisation?
-colchicine (chemical) disrupts microtubules
-when microtubules are disrupted, the golgi collapses and mitochondria move (cell contents becomes random)
How is vesicular transport checked?
-repeated checks
-not restrictive control, so it requires less energy
-retrograding (vesicles transporting backwards) when things have gone too far
-tightly regulated
What does FRAP show about membrane structure?
-shows that not all membrane proteins are mobile (not a true fluid mosaic model)
-not complete recovery after bleaching
