Cell Membranes Flashcards
what causes the separation that is crucial for selective permeability,
ion gradients, signal transduction in cells?
cell membranes
Phospholipids are predominant class of lipid in the cell/plasma membrane and are comprised of:
— Phosphatidyl???
— Phosphatidylserine (cytosolic)
Phosphatidylcholine
TRUE or FALSE: Amphiphilic nature of lipids leads to spontaneous
assembly into self-sealing compartments
TRUE
Typically of the two hydrophobic tails of the glycerol backbone, one is ‘saturated’ (with hydrogen; only ???-bonds) whilst the other contains one double-bond (unsaturated)
single
What prevents tight packing of lipids, which results in more fluidity and flexibility of the membrane?
the unsaturation of phospholipids
Higher abundances of cholesterol within phospholipid bilayer of plasma membrane will result in more ‘packed’ membranes, increasing or decreasing (?) rigidity
increasing rigidity
TRUE or FALSE: High fluidity means lipids and proteins can move more freely within the plane of the membrane
TRUE
Movement of molecules is interrupted by ??? junctions
tight junctions
Membrane lipids are primarily synthesised by enzymes in the smooth ???
endoplasmic reticulum
membrane lipids are assembled from glycerol, fatty acids, phosphate
groups, other small molecules on the ??? surface of the ER. Flippases then selectively transfer some molecules to achieve both even growth and deliberate asymmetry
cytosolic
The lipid bilayer is asymmetrical i.e Interior (cytosolic) face is different to the side protruding into the ??? space
extracellular
??? also adds glycans (sugars) to lipids, but only on the ‘exterior’ face of the membrane
Golgi apparatus
Phosphatidylserine is predominantly found on the cytosolic face in most cell types, due to activity of ATP-dependent ???
flippases
phosphatidylserine facilitates signal transduction by providing a docking site for ??? enzymes such as protein kinase C
cytosolic
which lipid provides membrane curvature, phosphatidylcholine or phosphatidylserine?
phosphatidylserine
Phosphatidylserine is translocated to the other side of membrane during ???. Scramblase enzymes redistribute PS
apoptosis
what serves as a specific ‘eat me’ signal for phagocytes and enables rapid, controlled clearance of dying cells?
phosphatidylserine translocating to the other side of membrane
membrane glycosylation occurs when the ??? receives lipids from ER, Glycosyltransferases sequentially add sugar moieties to the lipid backbone (both simple and complex sugars are added ONLY to the non-cytosylic face)
Golgi apparatus
membrane ??? plays an important role in cell-cell communication such as host-recognition and Blood group antigens
membrane glycosylation
TRUE or FALSE: membrane glycosylation provides protective glycocalyx: Mechanical and environmental protection and prevents non-specific adhesion by other molecules
TRUE
Concentrations of important ions are
maintained at different levels via active transport = concentration ???
gradients
Non-polar molecules are permeable
through the mostly hydrophobic
bilayer, exception = ??? because it is small and also due to aquaporins
H2O
Glucose, to be absorbed across the gut, requires sodium electrochemical gradient (actively maintained via Na+/K+ pumps)
▪ This gradient is implemented to drive Na+ into the cell (??? its gradient) along with glucose
— Via glucose-Na+ symporter
— This occurs at the apical side
▪ At the luminal face, glucose exits via passive diffusion
— Via facilitated diffusion
— Known as glucose uniporter
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