exam 1 plasma membrane and plant cell wall Flashcards
what is the cell bounded by
plasma membrane
what is the plasma membrane composed of
phospholipids and sterols (cholesterols in animal cells)
what is the basic structure of cellular membranes
bilayers composed on phospholipids
what are lipid bilayers
2D fluids that allow lateral diffusion of constituents
what are the microdomains of the plasma membranes called
lipid rafts
what are leaflets
layers of the bilayer
what do they two leaflets have
an asymmetric distribution of phospholipids
what is the plasma membrane
a regulated cell boundary - “wall” with windows and doors that can be opened/closed in regulated fashion
what is the main purpose of the plasma membrane
prevent water from getting from one side to another
why can steroid hormones diffuse freely through the plasma membrane
highly hydrophobic
how can water pass through membrane
channels
what are the most abundant lipids in plasma membranes
phospholipids
what is the polarity of phospholipids
amphipathic - polar head group and two nonpolar hydrocarbon tails
what increases membrane fluidity of phospholipids
one tail is saturated (no double-bonds) and the other is unsaturated (one cis double-bond = bent fatty acid tail)
what is the charge of phospholipids
net charges are zero
what are sterols
important lipid component of membranes
why are sterols important for structural stability of membrane
contain rigid ring structures that stiffen portions of phospholipids
what is the major sterol of animal cell membranes
cholesterol
what are the major sterols of plant cell membranes
phytosterols
what is the major sterol of fungi
ergosterol (useful target for antifungal drugs)
why can phospholipids spontaneously self-assemble into lipid bilayer membranes
because they are amphiphilic
what do polar head groups of phospholipids associate with
water on the “outsides” of the membrane
what do hydrocarbon tails of phospholipids associate with
each other on the “inside” of the membrane
what is a lipid micelle
a lipid molecule in a conical shape
what is a lipid bilayer
the shape of the lipid is planar/cylindrical
what form of phospholipid bilayer is energetically favorable
a sealed (sphere-looking) compartment formed by phospholipid bilayer
what does the Fluid Mosaic Model describe
the properties of the plasma membrane
what does it mean that the plasma membrane is a fluid
molecules are able to move past each other
what does it mean that the plasma membrane is a mosaic
it’s made up of lots of little pieces (i.e. not continuous)
it has discrete regions (neighborhoods)
why is it difficult for molecules to diffuse from one region to another
regions have different lipid and protein compositions
what are lipid rafts
a type of microdomain that is a region highly concentrated in cholesterol, which makes them stiffer
what is lateral diffusion
molecules can move past each other
what is the plasma membrane derived from
the ER membrane
what is the symmetry of the plasma membrane
asymmetric, which provides voltage across the membrane
what do the proteins in the plasma membrane allow for
molecules to cross the membrane (molecular transport)
signal transduction
anchorage to cytoskeleton
interaction with other cells/extracellular matrix
what are peripheral membrane proteins
proteins bound to the membrane surface
what are integral membrane proteins
proteins inserted into membrane interior
how do integral membrane proteins interact with leaflets
may span both leaflets via a transmembrane region, or may be anchored via attachment of lipid groups that insert into one leaflet
what are plant cells surrounded by
the plant cell wall
what does the plant cell wall do
separates inside and outside of plasma membrane of plant cell
what is the major component of the plant cell wall
cellulose, a polymer of glucose that provides tensile strength comparable to steel
what is tensile strength
resistance to stretching
what is lignin
waterproofing
what is pectin
provides resistance to compression
what are components of the plant cell wall
pectin and lignin
Animals lack a cell wall. What will happen if animal cells are placed in a highly hypotonic environment?
they will expand until they burst OR nothing - animal cells are capable of regulating water flow in and out
what is turgor pressure
the hydrostatic pressure resisted by the cell wall, which builds up when water flows into a cell
what is the purpose of turgor pressure
allows plant cells to be rigid
how does turgor pressure help with growth
it can force the cell to elongate and grow in specific directions
