BS 161 MSU Exam 2 UPDATED ACTUAL
Questions and CORRECT Answers
Identify the molecules that comprise a lipid - CORRECT ANSWER - Carbon, Hydrogen,
Oxygen, Glycerol
Explain the molecular difference between saturated and unsaturated fats - CORRECT
ANSWER - Saturated fats are solid, have the maximum number of Hydrogen molecules,
and no double bonds where as Unsaturated fats are liquid at room temp, have less than the max
number of Hydrogen molecules, and contain double bonds
Explain why, based on their properties, phospholipids spontaneously form a lipid bilayer -
CORRECT ANSWER - Because of their polar hydrophilic heads (which go towards
outside) and non-polar hydrophobic tails(more interior): they are amphipathic
Predict how changes in lipid structure related to the degree of saturation and polarity will impact
their behavior in biological systems - CORRECT ANSWER - Increasing amount of double
bonds (degree of unsaturation) increases the fluidity of the membrane because more double
bonds means more unsaturated and ability to flow
Increasing the amount of fatty acid saturation decreases the fluidity of the membrane
Increasing the temperature increases the likelihood for the membrane to flow
Describe the fluid mosaic model of a membrane structure - CORRECT ANSWER -a
membrane is a fluid structure with a "mosaic" of various proteins embedded in it
Explain how membrane fluidity is influenced by temperature and membrane composition -
CORRECT ANSWER - The higher the temp the more fluid
Explain how cholesterol resists changes in membrane fluidity as temps change - CORRECT
ANSWER - As the temperatures rise cholesterol restrains movement, as it lowers it
maintains fluidity
,At moderate temps it reduces fluidity by reducing movement at low temps it hinders
solidification by disrupting regular packing of phospholipids
Integral vs Peripheral Proteins - CORRECT ANSWER - Integral proteins penetrate the
hydrophobic core where as Peripheral bind to the surface of the membrane
The six roles of membrane proteins - CORRECT ANSWER - transporter, enzyme, cell-
surface receptor, identity marker, cell-to-cell adhesion, cytoskeleton anchor
Explain the role of membrane carbohydrates in cell-cell recognition - CORRECT
ANSWER - The ability of a cell to distinguish other cells based on recognition of
membrane carbohydrates. The glycolipids and glycoproteins attached to the outside of plasma
membranes varies.
Explain how the polarity of a molecule affects how it moved across a membrane - CORRECT
ANSWER - Non polar, hydrophobic molecules pass through more easily and vise versa bc
they are being pulled by non-polar tails
easiest 1.hydrophobic molecules
2. small, uncharged polar molecules
3.large uncharged polar molecules
hardest 4. ions (charged molecules)
Distinguish between channel proteins and carrier proteins - CORRECT ANSWER -
channel proteins only transport substances through membranes passively, career proteins can
transport ions and molecules either passively through diffusion or actively
Explain how aquaporins facilitate the passage of water through membranes - CORRECT
ANSWER - Aquaporins allow the transfer of water across a membrane 10x faster bc they
have polar regions of functional groups that interact with water
Define diffusion - CORRECT ANSWER - the tendency for molecules to spread out evenly
into the available space
, Explain why diffuse is a spontaneous and passive process - CORRECT ANSWER - It
requires no energy, is favorable bc substances naturally diffuse down their concentration gradient
Explain why a concentration gradient of a substance across a membrane represents P.E -
CORRECT ANSWER - The concentration gradient of a substance across a membrane
represents potential energy bc it drives the motion of diffusion
Distinguish between solutions that are hypertonic, hypotonic, and isotonic to cell contents -
CORRECT ANSWER - hypertonic: cell loses water, shrivels,a solution which contains
more solvent than solute
hypotonic: cell gains too much water and swells and possibly last (burst) a solution which
contains more solute than solvent
isotonic: equilibrium, cells don't gain or lose water
Define osmosis - CORRECT ANSWER - The diffusion of water across a selectively
permeable membrane
Define facilitated diffusion - CORRECT ANSWER - diffusion of polar molecules across a
membrane with the aid of transport proteins, wither channel proteins or carrier proteins
Define active transport - CORRECT ANSWER - the movement of a substance across a
membrane with the expenditure of energy, against it concentration gradient mediated with
specific transport proteins
Explain how transport proteins facilitate diffusion - CORRECT ANSWER - transport
proteins speed the passive movement of molecules across the plasma membrane down their
concentration gradient
Explain how solutes move against their concentration gradient - CORRECT ANSWER -
through active transport, carrier proteins, requires energy
Questions and CORRECT Answers
Identify the molecules that comprise a lipid - CORRECT ANSWER - Carbon, Hydrogen,
Oxygen, Glycerol
Explain the molecular difference between saturated and unsaturated fats - CORRECT
ANSWER - Saturated fats are solid, have the maximum number of Hydrogen molecules,
and no double bonds where as Unsaturated fats are liquid at room temp, have less than the max
number of Hydrogen molecules, and contain double bonds
Explain why, based on their properties, phospholipids spontaneously form a lipid bilayer -
CORRECT ANSWER - Because of their polar hydrophilic heads (which go towards
outside) and non-polar hydrophobic tails(more interior): they are amphipathic
Predict how changes in lipid structure related to the degree of saturation and polarity will impact
their behavior in biological systems - CORRECT ANSWER - Increasing amount of double
bonds (degree of unsaturation) increases the fluidity of the membrane because more double
bonds means more unsaturated and ability to flow
Increasing the amount of fatty acid saturation decreases the fluidity of the membrane
Increasing the temperature increases the likelihood for the membrane to flow
Describe the fluid mosaic model of a membrane structure - CORRECT ANSWER -a
membrane is a fluid structure with a "mosaic" of various proteins embedded in it
Explain how membrane fluidity is influenced by temperature and membrane composition -
CORRECT ANSWER - The higher the temp the more fluid
Explain how cholesterol resists changes in membrane fluidity as temps change - CORRECT
ANSWER - As the temperatures rise cholesterol restrains movement, as it lowers it
maintains fluidity
,At moderate temps it reduces fluidity by reducing movement at low temps it hinders
solidification by disrupting regular packing of phospholipids
Integral vs Peripheral Proteins - CORRECT ANSWER - Integral proteins penetrate the
hydrophobic core where as Peripheral bind to the surface of the membrane
The six roles of membrane proteins - CORRECT ANSWER - transporter, enzyme, cell-
surface receptor, identity marker, cell-to-cell adhesion, cytoskeleton anchor
Explain the role of membrane carbohydrates in cell-cell recognition - CORRECT
ANSWER - The ability of a cell to distinguish other cells based on recognition of
membrane carbohydrates. The glycolipids and glycoproteins attached to the outside of plasma
membranes varies.
Explain how the polarity of a molecule affects how it moved across a membrane - CORRECT
ANSWER - Non polar, hydrophobic molecules pass through more easily and vise versa bc
they are being pulled by non-polar tails
easiest 1.hydrophobic molecules
2. small, uncharged polar molecules
3.large uncharged polar molecules
hardest 4. ions (charged molecules)
Distinguish between channel proteins and carrier proteins - CORRECT ANSWER -
channel proteins only transport substances through membranes passively, career proteins can
transport ions and molecules either passively through diffusion or actively
Explain how aquaporins facilitate the passage of water through membranes - CORRECT
ANSWER - Aquaporins allow the transfer of water across a membrane 10x faster bc they
have polar regions of functional groups that interact with water
Define diffusion - CORRECT ANSWER - the tendency for molecules to spread out evenly
into the available space
, Explain why diffuse is a spontaneous and passive process - CORRECT ANSWER - It
requires no energy, is favorable bc substances naturally diffuse down their concentration gradient
Explain why a concentration gradient of a substance across a membrane represents P.E -
CORRECT ANSWER - The concentration gradient of a substance across a membrane
represents potential energy bc it drives the motion of diffusion
Distinguish between solutions that are hypertonic, hypotonic, and isotonic to cell contents -
CORRECT ANSWER - hypertonic: cell loses water, shrivels,a solution which contains
more solvent than solute
hypotonic: cell gains too much water and swells and possibly last (burst) a solution which
contains more solute than solvent
isotonic: equilibrium, cells don't gain or lose water
Define osmosis - CORRECT ANSWER - The diffusion of water across a selectively
permeable membrane
Define facilitated diffusion - CORRECT ANSWER - diffusion of polar molecules across a
membrane with the aid of transport proteins, wither channel proteins or carrier proteins
Define active transport - CORRECT ANSWER - the movement of a substance across a
membrane with the expenditure of energy, against it concentration gradient mediated with
specific transport proteins
Explain how transport proteins facilitate diffusion - CORRECT ANSWER - transport
proteins speed the passive movement of molecules across the plasma membrane down their
concentration gradient
Explain how solutes move against their concentration gradient - CORRECT ANSWER -
through active transport, carrier proteins, requires energy
