Introduction: Cell Membranes Flashcards
What are the functions of membranes
Highly selective permeability Barriers which embody carriers and transporters etc
Maintain differences in ion concentrations inside and outside of the cell
Contain receptors for stimuli external and internal to the cell
Cen generate electrical and chemical signals
Are essential for energy conv
Cell cell adhesion
What does the lipid bilayer consist of
Lipids (phospholipids, glycolioids, cholesterol) and proteins
Bilateral with a trilaminar appearance
What is the structure of a phospholipid
Choline
Phosphate
Glycerol
Hydorarbons
( hydrophillic head and hydrophobic head)
What are lipid bilayers
Non covalent assemblies
Asymmetric
Fluid
What su the fluidity of the lipid bilayer like
Fluid
Phospholipids in constant motion where they rotat,vibrate
How does cholesterol effect the membranes
Cholesterol is s rigid steroid
Intercalated between phospholipids
Decreases fluidity of mem at warm temp
Maintains fluidity at cold temps prevent crystallisation of phospholipids
Reduces mem perm to hydrophillic molecules
What are the different kind of membrane proteins
Integral proteins embedded
Transmem proteins span mem
Peripheral proteins don’t penetrate mem
Lipid anchored protiens possess lipid modificicatins that hold them in association with the mem
What is membrane carbohydrate
A small amount of mem carb located on outer surface of cells
Short carb chains found bound to mem proteins and to a lesser extent lipids
- glycoproteins and glycolioids
- together form layer - glycocalyx
What is the overall structure phrased as for a lipid bilayer
Fluid mosaic model structure
What are some of the functions of the lipid bilayer
Forms basic structure of mem
Hydrophobic interior serves as a barrier to polar and charged subs
Responsible for fluidity of mem
Enable cell to change shape
Certain of phospholipids are precursors for signalling mols
What are ion channels
Some transmem proteins form water filled highly selective ion channels regulated by chemicals (neurotransmitters) transmem voltage or physical stimuli
Some drugs target sodium channels to block and give anaesthesia
Some ion channels may be abnormal
What are carrier transport proteins
Spam mem
Exhibit substrate selectivity
Diff cell types express diff kinds of carriers
Docking marker acceptors- located inner surface and interact with sec vesicle leading to exocytosis
What are some other types of mem proteins
Mem bound enzymes - either side of mem such as phospholipase C
Receptors - most transmem with binding site bind specific mols
Call adhesion molecules (CAMS) - cadherins which help hold cells in tissues together or integrins which span plasma mem acting as a link between extra and intra cellular enviro
How do some carbs serve as self identifying markers
Short carb chains on outer mem surface serve as self identifying markers
Diff cell types have diff markers
Imp for cell - cell interactions
Role in tissue growth - so cells do not overgrow
What are some examples of specialised cell junctions
Link cells directly
Tight junctions - join lateral edges of epi near luminal surface LEAKY
Desmosomes - adhering junctions that anchor cells together especially in tissues subject to stretching
Gap junctions - communicating junctions, allow move of ions and small mols between cells in heart as eg
