plasma membrane, cytosol and inclusions Flashcards
1
Q
cell membrane (plasmalemma)
A
- defines cell boundaries and retains contents
- semipermeable lipid bilayer
- bacteria and plant cells: cell wall attached to membrane
2
Q
plasma membrane below TEM
A
- two electron dense layers separated by an intermediate electron transparent layer
- each layer is 2.5-3 nm thick
3
Q
biochemical analysis of the membrane
A
- mainly of lipids and (glycosilated) proteins
4
Q
Singer and Nicolson fluid-mosaic model (1972)
A
- amphipathic
- inner is hydrophobic, external surfaces are hydrophilic
- protein:lipid = 1: 1
5
Q
scRNAseq experimental setup
A
- tissue collection, sorting, smart-seq2, clustering
- ratios of ISC populations change drastically in dystrophic muscle
6
Q
modified fluid-mosaic model
A
- dynamic (fluid) and multipartite (mosaic)
- protein distribution and movement is not as random
- glycoproteins and glycolipids form the glycocalyx at the outer surface of the cell
- peripheral proteins adhere, often temporarily to the lipids of integral proteins
- variable amount of lipids (e.g. cholesterol) in time and space
7
Q
distribution of phospholipids in membrane
A
- asymmetric and irregular
- outer leaflet: mainly phosphatidylcholine and sphingomyelins
- inner leaflet: mainly pshopatidylserine and phosphatidylethanolamine
8
Q
micro-domains of the plasmamembrane
A
- lipid rafts
- specific glycosphingolipids and high concentrations of cholesterol
- a variety of proteins involved in signalling
- become evident in the form of caveolar drafts (caveolae)
- proposed functions: endothelial transcytosis, signalling, tumour repression, lipid regulation
9
Q
microscope labelling
A
- glycocalix sugars can be stained to indicate membrane on light microscope images
- specific membrane molecules can be labelled making the membrane visible
10
Q
atomic force microscope image of lipid bilayer
A
- sphingomyelin and cholesterol molecules form lipid rafts thicker than non-raft areas
- white particles represent toxins which bind to a receptor present in rafts
11
Q
freeze-fracture image of plasma membrane
A
- scheme of the fracture and corresponding TEM of protoplasmic and exoplasmic leaflets
12
Q
specialisation of cell membrane
A
- microvilli,stereo cilia and cilia
- micro-ridges, flagella
13
Q
cytoplasm
A
- interior of cell but nucleus
- cytosol: liquid or aq part (cytoplasmic matrix)
- organelles and particles remain suspended
14
Q
EUK cell
A
- mini organs mostly surrounded by membrane, which have unique structures and functions
- cytoskeleton
- inclusions: glycogen, lipids, pigments…
15
Q
inclusions
A
- metabolic by-products, storage forms of various nutrients, inert crystals and pigments
- aggregates of (macro)molecules not membrane bound
- have no metabolic activity themselves
- temporary storage
- useful to identify cell types as are not presents in all cells
