Bio 201 UNCW - test 2 UPDATED ACTUAL
Exam Questions and CORRECT Answers
membrane mosaic structure - CORRECT ANSWER - enables membrane function
phospholipid organization - CORRECT ANSWER - organize spontaneously in aqueous
solutions
tails form a hydrophobic barrier that will keep hydrophilic areas from going into the center of the
membrane
hydrophobic interactions - CORRECT ANSWER - cage-like structure of water forms
around the hydrophobe
hydrophobic exclusion
making a fluid membrane - CORRECT ANSWER - 1. hydrophobic exclusion pushes the
fatty acid tails of phospholipids together
2. hydrogen bonds and hydration spheres form between water and the hydrophobic heads
3. van der waals interactions among the hydrophobic portions of molecules determines the
membrane fluidity
more van der waals forces - CORRECT ANSWER - less fluidity
why is it important to maintain a constant body temperature? - CORRECT ANSWER - to
maintain van der waals forces and membrane fluidity
cell membranes are semi fluid - CORRECT ANSWER - non covalent bonds are made and
broken a lot
molecules must be able to move in the membrane
,what makes the membrane fluid? - CORRECT ANSWER - hydrophobic portions of
membrane molecules interact with each other by van der waals forces
cholesterol - CORRECT ANSWER - only found in animals
can fill gaps between acyl chains (tails on the phospholipid) and create van der waals forces
what happens if a membrane is less fluid? - CORRECT ANSWER - you will not function
as well
fevers - CORRECT ANSWER - heat separates acyl chains and breaks van der waals forces
leaflet - CORRECT ANSWER - describes one half (layer) of a phospholipid bilayer
types of movement in a leaflet - CORRECT ANSWER - 1. lateral (side to side)
2. rotational (spin in a circle)
movement from one leaflet to another - CORRECT ANSWER - called a flip flop
flippase - CORRECT ANSWER - the protein enzyme required to flip flop
lipid structures - CORRECT ANSWER - determines membrane fluidity
unsaturated carbon tails - CORRECT ANSWER - enhance fluidity and resist solidification
of the membrane at colder temperatures
reduces van der waals forces
saturated carbon tails - CORRECT ANSWER - sold at room temperature and liquid when
heated
, less fluidity, increase of van der waals forces
cholesterol embedded in the plasma membrane acts as a buffer - CORRECT ANSWER -
stabilizes the membrane at higher temperatures and resists lower temperatures
increased cholerstol = increased fluidity - CORRECT ANSWER - increased van der waals
forces at high temps by filling holes made by fast moving phospholipids
decreased van der waals forces at low temps by breaking van der waals and pushing slow
moving phospholipids apart
2 classes of proteins associate with cell membranes in 2 different ways - CORRECT
ANSWER - integral proteins and peripheral proteins
integral proteins - CORRECT ANSWER - have one or more regions embedded in or
transversing through the membrane
7 hydrophobic alpha helices = 7TMD
peripheral proteins - CORRECT ANSWER - stick to other proteins
do not integrate in hydrophobic plasma membrane
main functions of proteins associated with the cell membrane - CORRECT ANSWER - 1.
transport of molecules across the plasma membrane
2. enzymatic activity
3. signal transduction (ex: salmonella makes a signaling molecule and more actin cytoskeleton
brings it in)
4. cell-cell recognition (ex: blood type)
5. intercellular junctions
6. attachment of the cell to the cytoskeleton or extracellular matrix
unity - CORRECT ANSWER - all organisms have shared cell features
Exam Questions and CORRECT Answers
membrane mosaic structure - CORRECT ANSWER - enables membrane function
phospholipid organization - CORRECT ANSWER - organize spontaneously in aqueous
solutions
tails form a hydrophobic barrier that will keep hydrophilic areas from going into the center of the
membrane
hydrophobic interactions - CORRECT ANSWER - cage-like structure of water forms
around the hydrophobe
hydrophobic exclusion
making a fluid membrane - CORRECT ANSWER - 1. hydrophobic exclusion pushes the
fatty acid tails of phospholipids together
2. hydrogen bonds and hydration spheres form between water and the hydrophobic heads
3. van der waals interactions among the hydrophobic portions of molecules determines the
membrane fluidity
more van der waals forces - CORRECT ANSWER - less fluidity
why is it important to maintain a constant body temperature? - CORRECT ANSWER - to
maintain van der waals forces and membrane fluidity
cell membranes are semi fluid - CORRECT ANSWER - non covalent bonds are made and
broken a lot
molecules must be able to move in the membrane
,what makes the membrane fluid? - CORRECT ANSWER - hydrophobic portions of
membrane molecules interact with each other by van der waals forces
cholesterol - CORRECT ANSWER - only found in animals
can fill gaps between acyl chains (tails on the phospholipid) and create van der waals forces
what happens if a membrane is less fluid? - CORRECT ANSWER - you will not function
as well
fevers - CORRECT ANSWER - heat separates acyl chains and breaks van der waals forces
leaflet - CORRECT ANSWER - describes one half (layer) of a phospholipid bilayer
types of movement in a leaflet - CORRECT ANSWER - 1. lateral (side to side)
2. rotational (spin in a circle)
movement from one leaflet to another - CORRECT ANSWER - called a flip flop
flippase - CORRECT ANSWER - the protein enzyme required to flip flop
lipid structures - CORRECT ANSWER - determines membrane fluidity
unsaturated carbon tails - CORRECT ANSWER - enhance fluidity and resist solidification
of the membrane at colder temperatures
reduces van der waals forces
saturated carbon tails - CORRECT ANSWER - sold at room temperature and liquid when
heated
, less fluidity, increase of van der waals forces
cholesterol embedded in the plasma membrane acts as a buffer - CORRECT ANSWER -
stabilizes the membrane at higher temperatures and resists lower temperatures
increased cholerstol = increased fluidity - CORRECT ANSWER - increased van der waals
forces at high temps by filling holes made by fast moving phospholipids
decreased van der waals forces at low temps by breaking van der waals and pushing slow
moving phospholipids apart
2 classes of proteins associate with cell membranes in 2 different ways - CORRECT
ANSWER - integral proteins and peripheral proteins
integral proteins - CORRECT ANSWER - have one or more regions embedded in or
transversing through the membrane
7 hydrophobic alpha helices = 7TMD
peripheral proteins - CORRECT ANSWER - stick to other proteins
do not integrate in hydrophobic plasma membrane
main functions of proteins associated with the cell membrane - CORRECT ANSWER - 1.
transport of molecules across the plasma membrane
2. enzymatic activity
3. signal transduction (ex: salmonella makes a signaling molecule and more actin cytoskeleton
brings it in)
4. cell-cell recognition (ex: blood type)
5. intercellular junctions
6. attachment of the cell to the cytoskeleton or extracellular matrix
unity - CORRECT ANSWER - all organisms have shared cell features
