BIOL 1090: Exam 2
Comprehensive Questions and
Solutions Graded A+
The _____ _____ separates the living cell from its nonliving surroundings. - Answer: Plasma
membrane
The membranes of cells are composed mostly of a fluid mosaic of _____ and _____. - Answer: 1.
Lipids
2. Proteins
The lipids that make up the bilayer in the plasma membrane belong to a special category called
_____. - Answer: Phospholipids
The fatty acid chains that make up phospholipids are _____ whereas the phosphate group is
_____. - Answer: 1. Hydrophobic
2. Hydrophilic
Hydrophobic - Answer: Avoid water
Hydrophilic - Answer: Readily bonds with water
Plasma membranes are selectively permeable - Answer: -Hydrophobic molecules pass through
freely
,-Hydrophilic molecules do not pass through freely
Plasma membrane functions - Answer: -Structural support
-Recognition
-Communication
-Transport
Plasma membrane functions: structural support - Answer: Cell cytoskeleton attached and
provides an anchor to stabilize and give shape to cell
Plasma membrane functions: recognition - Answer: Identify friend from foe/self from non-self
Plasma membrane functions: communication - Answer: Signals pass between cells through cell
signaling
Plasma membrane functions: transport - Answer: Proteins in the plasma membrane form
channels known as microtunnels that allow molecules to move in and out of the cell
Diffusion - Answer: -Movement of molecules or ions from a region of their higher concentration
to a region of their lower concentration
-Through diffusion, compounds naturally move from higher to lower concentrations, meaning
they move down their concentration gradient
Concentration gradient - Answer: Difference between the highest and lowest concentrate of the
solute in the medium
Equilibrium - Answer: When a point is reached that the molecules are equally distributed
,A _____ _____ is one that allows some compounds to pass through freely while blocking the
passage of others. - Answer: Semipermeable membrane
Is the plasma membrane a semipermeable membrane/selectively permeable? - Answer: Yes
Osmosis - Answer: -Special case of diffusion that involves the movement of water through
membranes
-Osmosis is the net movement of water across a semipermeable membrane from an area of
lower solute concentration to an area of higher solute concentration
-Or: movement of water from its high concentration to its lower concentration
Because the plasma membrane is a semipermeable membrane, _____ operates in connection
with it. - Answer: Osmosis
_____ is a major force in living things; it is responsible for much of the movement of fluids into
and out of cells. - Answer: Osmosis
_____ _____ can cause cells either to dry out from losing too much water, or in the case of
animal cells, to break from taking too much water in (plant cells generally don not have this
problem because their cell walls limit their uptake of water). - Answer: Osmotic imbalances
Osmoregulation - Answer: The control of water balance
Cells will gain or lose water relative to their surroundings in accordance with what the _____
_____ is inside the cell as opposed to outside it. - Answer: Solute concentration
A cell will lose water to a surrounding solution that is _____ -- a solution that has a greater
concentration of solutes in it than does the cell's cytoplasm. - Answer: Hypertonic
, A cell will gain water when the surrounding solution is _____ to the cytoplasmic fluid. - Answer:
Hypotonic
Water flow is balanced between the cell and its surroundings when the surroundings fluid and
the cytoplasmic fluid are _____ to each other -- when they have the same concentration of
solutes. - Answer: Isotonic
_____ _____ is any movement of molecules or ions across a cell membrane that requires the
expenditure of energy. - Answer: Active transport
_____ _____ is any movement of molecules or ions across a cell membrane that does not
require the expenditure of energy. - Answer: Passive transport
Two types of passive transport - Answer: 1. Simple diffusion
2. Facilitated diffusion
For either form of passive transport to bring about a net movement of materials into or out of a
cell, a _____ _____ must exist. - Answer: Concentration gradient
Simple diffusion - Answer: -Concentration gradient is required to operate
-Small molecules without charge can pass through
-Exs: O₂, CO₂, and small non-polar molecules
Facilitated diffusion - Answer: -Requires both a concentration gradient and a protein channel
-Exs: too large (glucose and amino acids) and too charged ions (Na, Cl, and K)
In _____ _____, transport proteins function as channels for larger hydrophilic substances--
substances that, because of their size and/or electrical charge, cannot diffuse through the
hydrophobic portion of the plasma membrane. - Answer: Facilitated diffusion
Comprehensive Questions and
Solutions Graded A+
The _____ _____ separates the living cell from its nonliving surroundings. - Answer: Plasma
membrane
The membranes of cells are composed mostly of a fluid mosaic of _____ and _____. - Answer: 1.
Lipids
2. Proteins
The lipids that make up the bilayer in the plasma membrane belong to a special category called
_____. - Answer: Phospholipids
The fatty acid chains that make up phospholipids are _____ whereas the phosphate group is
_____. - Answer: 1. Hydrophobic
2. Hydrophilic
Hydrophobic - Answer: Avoid water
Hydrophilic - Answer: Readily bonds with water
Plasma membranes are selectively permeable - Answer: -Hydrophobic molecules pass through
freely
,-Hydrophilic molecules do not pass through freely
Plasma membrane functions - Answer: -Structural support
-Recognition
-Communication
-Transport
Plasma membrane functions: structural support - Answer: Cell cytoskeleton attached and
provides an anchor to stabilize and give shape to cell
Plasma membrane functions: recognition - Answer: Identify friend from foe/self from non-self
Plasma membrane functions: communication - Answer: Signals pass between cells through cell
signaling
Plasma membrane functions: transport - Answer: Proteins in the plasma membrane form
channels known as microtunnels that allow molecules to move in and out of the cell
Diffusion - Answer: -Movement of molecules or ions from a region of their higher concentration
to a region of their lower concentration
-Through diffusion, compounds naturally move from higher to lower concentrations, meaning
they move down their concentration gradient
Concentration gradient - Answer: Difference between the highest and lowest concentrate of the
solute in the medium
Equilibrium - Answer: When a point is reached that the molecules are equally distributed
,A _____ _____ is one that allows some compounds to pass through freely while blocking the
passage of others. - Answer: Semipermeable membrane
Is the plasma membrane a semipermeable membrane/selectively permeable? - Answer: Yes
Osmosis - Answer: -Special case of diffusion that involves the movement of water through
membranes
-Osmosis is the net movement of water across a semipermeable membrane from an area of
lower solute concentration to an area of higher solute concentration
-Or: movement of water from its high concentration to its lower concentration
Because the plasma membrane is a semipermeable membrane, _____ operates in connection
with it. - Answer: Osmosis
_____ is a major force in living things; it is responsible for much of the movement of fluids into
and out of cells. - Answer: Osmosis
_____ _____ can cause cells either to dry out from losing too much water, or in the case of
animal cells, to break from taking too much water in (plant cells generally don not have this
problem because their cell walls limit their uptake of water). - Answer: Osmotic imbalances
Osmoregulation - Answer: The control of water balance
Cells will gain or lose water relative to their surroundings in accordance with what the _____
_____ is inside the cell as opposed to outside it. - Answer: Solute concentration
A cell will lose water to a surrounding solution that is _____ -- a solution that has a greater
concentration of solutes in it than does the cell's cytoplasm. - Answer: Hypertonic
, A cell will gain water when the surrounding solution is _____ to the cytoplasmic fluid. - Answer:
Hypotonic
Water flow is balanced between the cell and its surroundings when the surroundings fluid and
the cytoplasmic fluid are _____ to each other -- when they have the same concentration of
solutes. - Answer: Isotonic
_____ _____ is any movement of molecules or ions across a cell membrane that requires the
expenditure of energy. - Answer: Active transport
_____ _____ is any movement of molecules or ions across a cell membrane that does not
require the expenditure of energy. - Answer: Passive transport
Two types of passive transport - Answer: 1. Simple diffusion
2. Facilitated diffusion
For either form of passive transport to bring about a net movement of materials into or out of a
cell, a _____ _____ must exist. - Answer: Concentration gradient
Simple diffusion - Answer: -Concentration gradient is required to operate
-Small molecules without charge can pass through
-Exs: O₂, CO₂, and small non-polar molecules
Facilitated diffusion - Answer: -Requires both a concentration gradient and a protein channel
-Exs: too large (glucose and amino acids) and too charged ions (Na, Cl, and K)
In _____ _____, transport proteins function as channels for larger hydrophilic substances--
substances that, because of their size and/or electrical charge, cannot diffuse through the
hydrophobic portion of the plasma membrane. - Answer: Facilitated diffusion
