BIOL 331 QUESTIONS AND
VERIFIED CORRECT
ANSWERS [LATEST] GRADED
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3 main components of sphingolipids
-important property - CORRECT ANSWER-Sphingosine backbone, only one fatty acid and a polar
head group
-all are neutral
Name of sphingolipid when polar head group is "H" - CORRECT ANSWER-Ceramide
Name of sphingolipid when polar head group is "phosphocholine" - CORRECT ANSWER-
Sphingomyelin (SM)
- major component of myeline sheaths surrounding nerve cells
X=choline
Myelin sheaths - CORRECT ANSWER-Insulates nerve cell from surrounding environment
-increases velocity at which impulses travel along axon
,-high lipid content
Name of sphingolipid when polar head group is a sugar "glycosphinglipid" - CORRECT ANSWER-
One sugar: cerebroside
More than one sugar: ganglioside
-found in cell surfaces and plat a role in cell recognition
How does cholesterol fit into bilayer? - CORRECT ANSWER-It fits into one leaflet
Why is cholesterol present in membranes?
-abbreviation - CORRECT ANSWER-Serves to rigidify membranes
-concentration ranges
-amphipathic
abbreviated as Cl
Why are membrane lipids asymmetrical? (3) - CORRECT ANSWER-Inner and outer leaflets have
different compositions
Provides different physicochemical properties appropriate for different interactions
Membrane lipids move easily within a leaflet but rarely flip-flip
What is the charge of the cytoplasmic leaflet of plasma membrane? - CORRECT ANSWER-
Negative charge
Floppase - CORRECT ANSWER-Keeps most PC, SM, and Cl in exoplasmic leaflet
,Flippase - CORRECT ANSWER-Keeps most PS, PE and PI in cytoplasmic leaflet
Scramblase - CORRECT ANSWER-Disrupt membrane asymmetry by randomizing phospholipids
Why don't membrane lipids flip? - CORRECT ANSWER-The polar head group would have to
travel through non-polar region which is energetically favourable
Fluidity - CORRECT ANSWER-A measure of the ease of flow
Viscocity - CORRECT ANSWER-A measure of the resistance of flow
Importance in maintaining fluidity? (3) - CORRECT ANSWER-1. Allows for membrane
components to orient in specific ways and move
-structural organization, mechanical support, cell growth etc
2. Allow for protein clusters to form
-synapses, energy production, intercellular junctions, energy production
3. Membrane assembly
Phases of lipids membranes - CORRECT ANSWER-Liquid-disordered (too fluid): lots so water can
enter
Solid gel: too solid
Liquid-ordered: "raft"
ex. sterol
, 4 factors influencing fluidity of lipid bilayers - CORRECT ANSWER-1. Temperature
2. Acyl chain length
3. Acyl chain saturation
4. Cholesterol content
How does temperature affect fluidity?
-what interactions assist with this? - CORRECT ANSWER-Bilayers are more fluid at high
temperatures due to "melting" of lipid-lipid interactions
VDW: if temperature is increased, then there is more more VDW interactions between tails
(have to be close but not too close)
Transition temperature (Tm) - CORRECT ANSWER-Temperature at which phase transition occurs
-is dependent upon the lipids present in the bilayer
How does acyl chain length affect fluidity? - CORRECT ANSWER-Bilayers made up of lipids
containing fatty acids with long chains are LESS fluid (more VDW interactions = more energy
required to break)
Bilayers made of lipids containing fatty acids with short chains are MORE fluid
Melting point and chain length - CORRECT ANSWER-The longer the chain, the greater the
number of VDW forces and the greater the energy required to break them apart, and therefore
the higher the melting point
How does acyl chain saturation affect fluidity? - CORRECT ANSWER-Bilayers made of lipids
containing saturated fatty acids with long chains are LESS fluid
VERIFIED CORRECT
ANSWERS [LATEST] GRADED
A+ 100% GUARANTEES
SUCCESS
3 main components of sphingolipids
-important property - CORRECT ANSWER-Sphingosine backbone, only one fatty acid and a polar
head group
-all are neutral
Name of sphingolipid when polar head group is "H" - CORRECT ANSWER-Ceramide
Name of sphingolipid when polar head group is "phosphocholine" - CORRECT ANSWER-
Sphingomyelin (SM)
- major component of myeline sheaths surrounding nerve cells
X=choline
Myelin sheaths - CORRECT ANSWER-Insulates nerve cell from surrounding environment
-increases velocity at which impulses travel along axon
,-high lipid content
Name of sphingolipid when polar head group is a sugar "glycosphinglipid" - CORRECT ANSWER-
One sugar: cerebroside
More than one sugar: ganglioside
-found in cell surfaces and plat a role in cell recognition
How does cholesterol fit into bilayer? - CORRECT ANSWER-It fits into one leaflet
Why is cholesterol present in membranes?
-abbreviation - CORRECT ANSWER-Serves to rigidify membranes
-concentration ranges
-amphipathic
abbreviated as Cl
Why are membrane lipids asymmetrical? (3) - CORRECT ANSWER-Inner and outer leaflets have
different compositions
Provides different physicochemical properties appropriate for different interactions
Membrane lipids move easily within a leaflet but rarely flip-flip
What is the charge of the cytoplasmic leaflet of plasma membrane? - CORRECT ANSWER-
Negative charge
Floppase - CORRECT ANSWER-Keeps most PC, SM, and Cl in exoplasmic leaflet
,Flippase - CORRECT ANSWER-Keeps most PS, PE and PI in cytoplasmic leaflet
Scramblase - CORRECT ANSWER-Disrupt membrane asymmetry by randomizing phospholipids
Why don't membrane lipids flip? - CORRECT ANSWER-The polar head group would have to
travel through non-polar region which is energetically favourable
Fluidity - CORRECT ANSWER-A measure of the ease of flow
Viscocity - CORRECT ANSWER-A measure of the resistance of flow
Importance in maintaining fluidity? (3) - CORRECT ANSWER-1. Allows for membrane
components to orient in specific ways and move
-structural organization, mechanical support, cell growth etc
2. Allow for protein clusters to form
-synapses, energy production, intercellular junctions, energy production
3. Membrane assembly
Phases of lipids membranes - CORRECT ANSWER-Liquid-disordered (too fluid): lots so water can
enter
Solid gel: too solid
Liquid-ordered: "raft"
ex. sterol
, 4 factors influencing fluidity of lipid bilayers - CORRECT ANSWER-1. Temperature
2. Acyl chain length
3. Acyl chain saturation
4. Cholesterol content
How does temperature affect fluidity?
-what interactions assist with this? - CORRECT ANSWER-Bilayers are more fluid at high
temperatures due to "melting" of lipid-lipid interactions
VDW: if temperature is increased, then there is more more VDW interactions between tails
(have to be close but not too close)
Transition temperature (Tm) - CORRECT ANSWER-Temperature at which phase transition occurs
-is dependent upon the lipids present in the bilayer
How does acyl chain length affect fluidity? - CORRECT ANSWER-Bilayers made up of lipids
containing fatty acids with long chains are LESS fluid (more VDW interactions = more energy
required to break)
Bilayers made of lipids containing fatty acids with short chains are MORE fluid
Melting point and chain length - CORRECT ANSWER-The longer the chain, the greater the
number of VDW forces and the greater the energy required to break them apart, and therefore
the higher the melting point
How does acyl chain saturation affect fluidity? - CORRECT ANSWER-Bilayers made of lipids
containing saturated fatty acids with long chains are LESS fluid
