BIOL 1201 EASLEY EXAM 2
QUESTIONS & ACTUAL CORRECT
ANSWERS
passive transport - Correct Answer ✔✔ of small molecules doesn't require energy; it
may involve transport proteins or diffusion
active transport - Correct Answer ✔✔ of small molecule requires energy and a transport
protein
exocytosis and endocytosis - Correct Answer ✔✔ large molecules move in and out,
using bulk transport
amphipathic - Correct Answer ✔✔ - duel headed
- hydrophobic tails and hydrophilic head
-phospholipids make up the cellular membrane bilayer
-hydrophilic regions of the protein are oriented towards the cytosol and the extracellular
fluid inside and outside the membrane
-hydrophobic regions are embedded in the bilayer
fluid mosaic model - Correct Answer ✔✔ depicts the membrane as a mosaic of protein
molecules bobbing in a fluid bilayer of phospholipids
The fluidity of membranes - Correct Answer ✔✔ - proteins are not randomly disrupted in
the membrane; they often form groups that carry out common functions
- membranes are held together mainly by hydrophobic interactions
- most of the lipids and some proteins can move sideways within the membrane
-rarely, a lipid may flip-flop across the membrane, from one phospholipid layer to the
other
membrane and fluidity - Correct Answer ✔✔ - as temperatures cool, membranes switch
from a fluid state to a solid state
- membranes rich in unsaturated fatty acids are more fluid than those rich in saturated
fatty acids
membrane in cold temperatures - Correct Answer ✔✔ - membranes with a higher
concentration of unsaturated fatty acids are going to be more ideal, because these
retain fluidity , and saturated tails will freeze
membrane in warm temperatures - Correct Answer ✔✔ -membranes with a higher
concentration of saturated fatty acids are going to be more ideal, because these retain
ideal fluidity, and unsaturated will be too fluid
,cholesterol in the membrane - Correct Answer ✔✔ - cholesterol is a membrane
component in animal cells that has variable effects on membrane fluidity at different
temperatures
- at warm temp(such as 37 degrees Celsius) cholesterol restrains movement of
phospholipids
- at cool temperatures, it maintains fluidity by preventing tight packing
membrane proteins and their function - Correct Answer ✔✔ - proteins, typically
clustered in groups, determine most of the membranes functions
-the protein composition of membranes varies among cells within an organism, and
among intracellular membranes within a cell
membrane proteins (2) - Correct Answer ✔✔ Peripheral proteins- bound to the surface
of the membrane
Integral proteins- penetrate the hydrophobic core
transmembrane proteins - Correct Answer ✔✔ integral proteins that span the
membrane
- hydrophobic regions of an integral protein consist of non-polar amino acids, often
coiled into a alpha helix
how are membranes held in place - Correct Answer ✔✔ - some membrane proteins are
held in place by attatchment to the cytoskeleton inside the cell
- other proteins, attach to materials outside the cell
- ex. proteins called intergirins attach to fibers of the extracellular matrix
cell-surface membrane proteins can carry out several functions - Correct Answer ✔✔ -
transport
-enzymatic activity
-signal transduction
-cell-cell recognition
-intercellular joining
-attachment to the cytoskeleton and extracellular matrix(ECM)
the role of membrane carbohydrates in cell-cell recognition - Correct Answer ✔✔ - cells
recognize each other by binding molecules to the surface of the membrane, which can
then be bonded to branched chains of carbohydrates which can function as markers for
cell ID
Glycolipids - Correct Answer ✔✔ carbohydrates bonded to lipids
glycoproteins - Correct Answer ✔✔ carbohydrates bonded to proteins
synthesis and sidedness of membranes - Correct Answer ✔✔ -membranes have
distinct inside and outside faces
, -the composition and distribution of proteins, lipids, and associated carbohydrates is
asymmetrical across the membrane
selective permeability - Correct Answer ✔✔ - the plasma membrane controls the
exchange of materials between the cell and its surroundings
-the fluid mosaic model explains how membranes regulate molecular traffic across the
membrane
permeability of the lipid bilayer - Correct Answer ✔✔ - small, hydrophobic (non-polar)
molecules dissolve in the lipid bilayer and pass through the membrane rapidly
-ex. hydrocarbons, CO2, and O2 pass easily
-the hydrophobic interior of the membrane impedes the passage of hydrophilic (polar)
molecules
-ex. sugars, waters, and ions pass through slowly if at all
channel proteins - Correct Answer ✔✔ - have a hydrophilic channel that certain
molecules or ions can use as a tunnel
Aquaporins - Correct Answer ✔✔ -a specific channel protein that greatly increase the
rate of passage of water molecules
carrier proteins - Correct Answer ✔✔ -bind to molecules and change shape to shuttle
the, across the membrane
-in facilitated diffusion move substances down their concentration gradients, no energy
is required
diffusion - Correct Answer ✔✔ -the movement of particles of any substance so that the
spread evenly into the available space
dynamic equilibrium - Correct Answer ✔✔ -as many molecules cross the membrane in
one direction as in the other
osmosis - Correct Answer ✔✔ -the diffusion of free(unbound) water across a selectively
permeable membrane
-free water molecules diffuse towards the are of higher solute concentration and will
keep moving until the concentration is equal on both sides
tonicity - Correct Answer ✔✔ depends on the concentration of solutes in the solution
that cannot cross the membrane on either side
isotonic - Correct Answer ✔✔ the solute concentration is the same outside and inside
the cell
-water molecules will still diffuse, but they will do so at an equal rate
hypotonic cell - Correct Answer ✔✔ the solute concentration is higher outside the cell,
than inside, the solution is hypertonic
QUESTIONS & ACTUAL CORRECT
ANSWERS
passive transport - Correct Answer ✔✔ of small molecules doesn't require energy; it
may involve transport proteins or diffusion
active transport - Correct Answer ✔✔ of small molecule requires energy and a transport
protein
exocytosis and endocytosis - Correct Answer ✔✔ large molecules move in and out,
using bulk transport
amphipathic - Correct Answer ✔✔ - duel headed
- hydrophobic tails and hydrophilic head
-phospholipids make up the cellular membrane bilayer
-hydrophilic regions of the protein are oriented towards the cytosol and the extracellular
fluid inside and outside the membrane
-hydrophobic regions are embedded in the bilayer
fluid mosaic model - Correct Answer ✔✔ depicts the membrane as a mosaic of protein
molecules bobbing in a fluid bilayer of phospholipids
The fluidity of membranes - Correct Answer ✔✔ - proteins are not randomly disrupted in
the membrane; they often form groups that carry out common functions
- membranes are held together mainly by hydrophobic interactions
- most of the lipids and some proteins can move sideways within the membrane
-rarely, a lipid may flip-flop across the membrane, from one phospholipid layer to the
other
membrane and fluidity - Correct Answer ✔✔ - as temperatures cool, membranes switch
from a fluid state to a solid state
- membranes rich in unsaturated fatty acids are more fluid than those rich in saturated
fatty acids
membrane in cold temperatures - Correct Answer ✔✔ - membranes with a higher
concentration of unsaturated fatty acids are going to be more ideal, because these
retain fluidity , and saturated tails will freeze
membrane in warm temperatures - Correct Answer ✔✔ -membranes with a higher
concentration of saturated fatty acids are going to be more ideal, because these retain
ideal fluidity, and unsaturated will be too fluid
,cholesterol in the membrane - Correct Answer ✔✔ - cholesterol is a membrane
component in animal cells that has variable effects on membrane fluidity at different
temperatures
- at warm temp(such as 37 degrees Celsius) cholesterol restrains movement of
phospholipids
- at cool temperatures, it maintains fluidity by preventing tight packing
membrane proteins and their function - Correct Answer ✔✔ - proteins, typically
clustered in groups, determine most of the membranes functions
-the protein composition of membranes varies among cells within an organism, and
among intracellular membranes within a cell
membrane proteins (2) - Correct Answer ✔✔ Peripheral proteins- bound to the surface
of the membrane
Integral proteins- penetrate the hydrophobic core
transmembrane proteins - Correct Answer ✔✔ integral proteins that span the
membrane
- hydrophobic regions of an integral protein consist of non-polar amino acids, often
coiled into a alpha helix
how are membranes held in place - Correct Answer ✔✔ - some membrane proteins are
held in place by attatchment to the cytoskeleton inside the cell
- other proteins, attach to materials outside the cell
- ex. proteins called intergirins attach to fibers of the extracellular matrix
cell-surface membrane proteins can carry out several functions - Correct Answer ✔✔ -
transport
-enzymatic activity
-signal transduction
-cell-cell recognition
-intercellular joining
-attachment to the cytoskeleton and extracellular matrix(ECM)
the role of membrane carbohydrates in cell-cell recognition - Correct Answer ✔✔ - cells
recognize each other by binding molecules to the surface of the membrane, which can
then be bonded to branched chains of carbohydrates which can function as markers for
cell ID
Glycolipids - Correct Answer ✔✔ carbohydrates bonded to lipids
glycoproteins - Correct Answer ✔✔ carbohydrates bonded to proteins
synthesis and sidedness of membranes - Correct Answer ✔✔ -membranes have
distinct inside and outside faces
, -the composition and distribution of proteins, lipids, and associated carbohydrates is
asymmetrical across the membrane
selective permeability - Correct Answer ✔✔ - the plasma membrane controls the
exchange of materials between the cell and its surroundings
-the fluid mosaic model explains how membranes regulate molecular traffic across the
membrane
permeability of the lipid bilayer - Correct Answer ✔✔ - small, hydrophobic (non-polar)
molecules dissolve in the lipid bilayer and pass through the membrane rapidly
-ex. hydrocarbons, CO2, and O2 pass easily
-the hydrophobic interior of the membrane impedes the passage of hydrophilic (polar)
molecules
-ex. sugars, waters, and ions pass through slowly if at all
channel proteins - Correct Answer ✔✔ - have a hydrophilic channel that certain
molecules or ions can use as a tunnel
Aquaporins - Correct Answer ✔✔ -a specific channel protein that greatly increase the
rate of passage of water molecules
carrier proteins - Correct Answer ✔✔ -bind to molecules and change shape to shuttle
the, across the membrane
-in facilitated diffusion move substances down their concentration gradients, no energy
is required
diffusion - Correct Answer ✔✔ -the movement of particles of any substance so that the
spread evenly into the available space
dynamic equilibrium - Correct Answer ✔✔ -as many molecules cross the membrane in
one direction as in the other
osmosis - Correct Answer ✔✔ -the diffusion of free(unbound) water across a selectively
permeable membrane
-free water molecules diffuse towards the are of higher solute concentration and will
keep moving until the concentration is equal on both sides
tonicity - Correct Answer ✔✔ depends on the concentration of solutes in the solution
that cannot cross the membrane on either side
isotonic - Correct Answer ✔✔ the solute concentration is the same outside and inside
the cell
-water molecules will still diffuse, but they will do so at an equal rate
hypotonic cell - Correct Answer ✔✔ the solute concentration is higher outside the cell,
than inside, the solution is hypertonic
