BIOL 112 UPDATED Questions and
CORRECT Answers
What properties of phospholipids determine if they will form micelles or bilayers when
mixed with water? - Whether there are one or two fatty acid tails
Which statements about proteins in biological membranes are true? - Hydrophobic
transmembrane regions of proteins are embedded in the fatty acid tails of the lipid bilayer
If bilayer-forming phospholipids are mixed with a hydrophilic dye, they form liposomes
suspended in the dye. What will happen to the dye once the liposomes are formed? - The dye
will interact with the phospholipid heads, surround the liposome, and fill the centre of the
liposome
Which of the following best describes the properties of a membrane according to the fluid
mosaic model?
- Hydrophobic tails on the phospholipids interact with polar protein domains to hold proteins
in place
- Intermolecular non-covalent interactions/ bonds that break and reform are required for the
movement of molecules within the membrane.
- This model applies only to human cells, but not to bacteria, fungi, or plants.
- Proteins and lipids can freely move laterally within the bilayer. - - Intermolecular non-
covalent interactions/ bonds that break and reform are required for the movement of
molecules within the membrane.
- Proteins and lipids can freely move laterally within the bilayer.
Hydrophilic - referring to a polar molecule
amphipathic - a molecule with both hydrophilic and hydrophobic components
, hydrophobic - referring to a non-polar molecule
bilayer self-assembly - spontaneous arrangment of lipids driven by the hydrophobic effect
phospholipid - an amphipathic molecule with a hydrophilic head group and hydrophobic fatty
acid tails
fluid mosaic model of biological membranes - The lipids and proteins form a dynamic two-
dimensional fluid held together by intermolecular non-covalent links
The property of phospholipids that drives bilayer formation for cellular membranes are: -
They are amphipathic, with both hydrophilic heads and hydrophobic tails
In secondary active transport, there are two concentration gradients used by membrane
proteins to transport a molecule X from an area of low to high concentration, which should be
energetically unfavourable. How does a cell do it? - Transport of the molecule X against the
concentration gradient is coupled to the 'downhill' movement of a second molecule, which is
moving from higher concentration to lower
What characteristics would increase the ability of a molecule to diffuse across a lipid bilayer -
- Small size
- Few polar functional groups
- No ionic charge
What is the difference between a membrane protein that is a channel and one that is a carrier?
- - The channel forms a tunnel for molecules of specific charge and shape to pass through the
membrane, the carrier has a binding site that is specific for the transporter molecule.
- The channel does not require a change in tertiary protein conformation to transport the
molecule, but the carrier does.
CORRECT Answers
What properties of phospholipids determine if they will form micelles or bilayers when
mixed with water? - Whether there are one or two fatty acid tails
Which statements about proteins in biological membranes are true? - Hydrophobic
transmembrane regions of proteins are embedded in the fatty acid tails of the lipid bilayer
If bilayer-forming phospholipids are mixed with a hydrophilic dye, they form liposomes
suspended in the dye. What will happen to the dye once the liposomes are formed? - The dye
will interact with the phospholipid heads, surround the liposome, and fill the centre of the
liposome
Which of the following best describes the properties of a membrane according to the fluid
mosaic model?
- Hydrophobic tails on the phospholipids interact with polar protein domains to hold proteins
in place
- Intermolecular non-covalent interactions/ bonds that break and reform are required for the
movement of molecules within the membrane.
- This model applies only to human cells, but not to bacteria, fungi, or plants.
- Proteins and lipids can freely move laterally within the bilayer. - - Intermolecular non-
covalent interactions/ bonds that break and reform are required for the movement of
molecules within the membrane.
- Proteins and lipids can freely move laterally within the bilayer.
Hydrophilic - referring to a polar molecule
amphipathic - a molecule with both hydrophilic and hydrophobic components
, hydrophobic - referring to a non-polar molecule
bilayer self-assembly - spontaneous arrangment of lipids driven by the hydrophobic effect
phospholipid - an amphipathic molecule with a hydrophilic head group and hydrophobic fatty
acid tails
fluid mosaic model of biological membranes - The lipids and proteins form a dynamic two-
dimensional fluid held together by intermolecular non-covalent links
The property of phospholipids that drives bilayer formation for cellular membranes are: -
They are amphipathic, with both hydrophilic heads and hydrophobic tails
In secondary active transport, there are two concentration gradients used by membrane
proteins to transport a molecule X from an area of low to high concentration, which should be
energetically unfavourable. How does a cell do it? - Transport of the molecule X against the
concentration gradient is coupled to the 'downhill' movement of a second molecule, which is
moving from higher concentration to lower
What characteristics would increase the ability of a molecule to diffuse across a lipid bilayer -
- Small size
- Few polar functional groups
- No ionic charge
What is the difference between a membrane protein that is a channel and one that is a carrier?
- - The channel forms a tunnel for molecules of specific charge and shape to pass through the
membrane, the carrier has a binding site that is specific for the transporter molecule.
- The channel does not require a change in tertiary protein conformation to transport the
molecule, but the carrier does.
