69. The Membrane Flashcards
what is a plasma membrane
phospholipid bilayer making the outer boundary of each cell
key features of plasma membrane
selectively permeable, maintains ion conc., participates in joining of cells to form tissues, enables cells to respond to signals of the environment
what is the cell membrane composed of
(phospho)lipid and protein
Head and tail- which is polar/non-polar etc
head is polar - hydrophilic
tail is non polar - hydrophobic
do phospholipid bilayer move
yes. they twirl and vibrate
what does cholesterol do in the membrane
aids in the stiffening of the membrane
what are phospholipid bilayer impermeable to
charged molecules
what can pass through the phospholipid membrane
O2, CO2, NH3 and H20
what are the 3 functions of the bilayer
- forms basic structure
- served as a barrier
- responsibility for fluidity of the membrane
what are the 2 types of membrane proteins
peripheral and integral
describe peripheral proteins
not embedded within the membrane.
Adhere tightly to the cytoplasmic surfaces of the PM
what are the 3 types of integral membrane protein
- transmembrane - span the bilayer once or several time
- some are embedded but do not cross the bilayer
- some are linked to a lipid component
what are the 2 functions of integral proteins
ligand binding receptors and adhesion molecules
what are ligand binding receptors
bind extracellular signalling molecules eg Hormone receptors
what are adhesion molecules
- Form contact with the extracellular matrix or cellular neighbours
- Important in regulating cell shape, growth and differentiation, allowing the cell to adapt to its immediate surroundings
what are examples of adhesion molecules
integrins (cell-matrix adhesion molecules)
cadherins (cell adhesion molecules) etc.
what are integrins
cell-matrix adhesion molecules
what are cadherins
cell adhesion molecules etc.
what are the 3 ways Integral membrane proteins can carry out the transmembrane movement of water-soluble substances
Pores and channels
Carriers
Pumps
describe integral protein pumps
Use energy that is released through the hydrolysis of ATP to drive the transport of substances into or out of cells against energy gradient
describe integral protein carriers
Either facilitate the transport of a specific molecule or couple the transport of a molecule to that of other solutes
describe integral protein Pores and Channels
Serve as conduits that allow water or specific ions to flow passively through the lipid bilayer
Integral membrane proteins can also be …. can …..
enzymes and participate in intracellular signalling
name another type of membrane protein
docking- marker acceptors
where can you find docking marker acceptors
inner membrane surface
what do docking marker acceptors interact with?? which leads to???
interact with secretory vesicles leading to exocytosis of vesicle contents
where are docking marker acceptors important
nervous system
when using the term ‘sugar coating’ what do we mean
A small amount of membrane carbohydrate is located on the outer surface of cells
Short carbohydrate chains are often bound to membrane proteins and to a lesser extent lipids. What are they called.
Glycoproteins and Glycolipids
Glycoproteins and Glycolipids form a layer called…?
Glycocalyx- which coats cells
what are Glycoproteins and Glycolipids
Short carbohydrate chains are often bound to membrane proteins and to a lesser extent lipids
Glycocalyx is made up of what
Glycoproteins and glycolipids
some cells are linked by 3 specialized cell junctions
- tight junctions
- desmosomes
- Gap junctions
what is a tight junction
Join the lateral edges of epithelial cells near their luminal (apical) membranes (tight or leaky)
what is desmosomes
Adhering junctions that anchor cells together, especially in tissues subject to stretching (e.g. skin, heart, uterus)
what is a gap junction
‘Communicating’ junctions that allow the movement of charge carrying ions and small molecules between two adjacent cells.
Carbohydrates have a 2 roles
self recognition
cell to cell interactions
what is the ‘bigger picture’ diagram where you see everything
fluid mosaic model
