9/9/24 Membrane Structure and Composition Flashcards
what membranes wrap the cell, separating it from the outside and dividing it into compartments?
lipid (=”oily”) membranes
how are liposomes prepared in the lab?
prepared in
the lab by assembling
synthetic lipids or breaking
cell membrane
what are vesicles?
naturally occurring cell
organelles with aqueous cavities
the cell envelope is a biological membrane made of __________
molecules
amphiphilic phospholipid
A biological membrane is an
enclosing or separating thin layer
of material that acts as a ________________________________________________________________
selectively permeable barrier
describe the thin lipid layer that is trapped by the biological membrane
not
permeable to many small
compounds and large molecules
the phospholipid monolayer consists of what liquid
oil
the phospholipid bilayer
water
what are examples of small molecules that diffuse across lipid bilayer:
Co2, 02, H20
what are molecules that the lipid bilayer cannot diffuse across ?
Ions, and larger uncharged molecules such as glucose,
can not diffuse across.
what are the characteristics of the amphiphilic molecules in the phospholipid double layer
they have hydrophilic and hydrophilic sides
what are the role of proteins in the membrane?
control its permeability to
different compounds, sense the outside, and trigger intracellular
response signals.
what are the roles of sterols in the membrane?
control membrane properties
True or False: Lipids are the only components of the membrane.
False. Lipids are not the only components of the membrane.
other components include:
-proteins & sterols
-carbohydrates
what roles do lipids play in the membrane?
-compartmentalization
- metabolic energy conversion via oxidation
- control of metabolic processes (steroid hormones & prostaglandins)
What does the consistency of the membrane depends on?
composition and temperature
ex: when membrane undergoes heat it transforms from a gel-like consistency to a fluidlike consistency
define micelle
cone-shaped amphiphilic molecules forming curve structures
define bilayer
Cylinder-shaped amphiphilic molecule
ex: phospholipids
Bilayer thickness & curvature are affected by what?
Liquid composition
what are the building blocks of lipids?
fatty acids
what structural lipid is primarily found in membranes?
sterols
what are the simplest lipids ?
fatty acids
describe a hydrocarbon long hydrocarbon chain
16-18 carbons ending with a carboxyl group
the saturated chain adopts ________ conformations
extended
unsaturated fatty acids have one or more _______________
double bonds
double bonds in natural
unsaturated fatty acids
introduce
a kink
double bonds in natural
unsaturated fatty acids are commonly in what configuration
cis config
what is an essential polyunsaturated fatty acid (PUFA) needed in the diet for synthesis of critical signaling molecules like Arachidonic Acid
Omega-3
the extent of packing depends on the degree of _________
saturation
the longer the chain…..
the more organized
the less fluid
the more (cis) double bonds…..
the more disorganized
the more fluid
how do trans fatty acids form
by partial
breakdown of unsaturated fatty
acids (usually industrial)
a trans double bond allows a
given fatty acid to adopt what
extended conformation
trans fatty acids can pack
more regularly, show higher
melting points than cis forms
trans fatty acids have
higher melting points than cis forms
True or False: trans unsaturated fatty acids raise your “good” cholesterol
it raises your “bad” cholesterol
which double bond forms a kink
cis double bond
how can fatty acids be linked through Glycerol
triacyclglycerols (TAG)
what does TAG consist of
glycerol + 3 fatty acids
what form are majority of the fatty acids found in
TAGs
what are solid TAGs called?
fats
what are liquid TAGs called?
oils
what are the primary storage forms of lipids (body fat)?
TAGs
where do TAGs exist?
in the cytoplasm as droplets/deposits
why are TAGs less soluble in water than fatty acids?
lack of charge carboxylate group
Mixtures of TAGs differ in their _____________
fatty acid composition
fatty acid composition of which three food fats?
olive oil, butter, and beef fat
Why do fats and oils float?
because TAGs are less dense than water
How are cell membrane lipids formed?
fatty acids combine through scaffold to a head group
What are Glycerol and Sphingosine used by?
the scaffold to connect 1-2 hydrophobic fatty acids + polar head group
True or False: in the phospholipid bilayer the head is hydrophilic.
True. Hydrophilic head
True or False: in the phospholipid bilayer the tail is hydrophobic
True. hydrophobic tail
