BIO 353 EVALUATION EXAM 2026 QUESTIONS AND
ANSWERS GRADED A+
✔✔Loss of the cell wall_________. - ✔✔occurs both for the endosymbiosis theory and
for the endomembrane system
✔✔The primitive proto-prokaryote likely acquired motility before it lost the cell wall. -
✔✔False
✔✔The endomembrane system supposedly resulted in the formation of the nuclear
envelope, endoplasmic reticulum, Golgi apparatus, and primary lysosomes. - ✔✔True
✔✔It is the proteins in the biological membrane that serve to partition water. - ✔✔False
✔✔If you had a phospholipid whose melting point was 12°C, what might happen if you
mixed it 1:1 with a lipid that had a melting point of 24°C. - ✔✔None of the above is
correct
✔✔Unsaturated sites in the fatty acid tails of phospholipids are places that water can
use to leak through the membrane. - ✔✔True
✔✔Phosphatidylserine influences a great deal of area primarily due to its large size. -
✔✔False
✔✔Transmembrane proteins _________. - ✔✔can move laterally and cannot flip 180˚
in the membrane
✔✔The presence of two disulfide bonds near each other is a good thing when a stretch
of protein is to be immobilized. - ✔✔True
✔✔The empty center of a single pass transmembrane protein provides a channel for
the transport of ions. - ✔✔False
✔✔Membrane anchors set up geography in a cell. - ✔✔True
✔✔Integrin receptor binding results in the recruitment of _________. - ✔✔actin
filaments
✔✔The sodium/potassium ATPase removes ___________ ions from the cell and
pumps ______________ ions into the cell against their respective concentration
gradients. - ✔✔3 sodium; 2 potassium
, ✔✔Actin filaments ______________. - ✔✔have a diameter of 7 nm and contain 375
amino acids
✔✔Actin filaments will ____________.
a. undergo treadmilling in a test tube
b. undergo treadmilling in a living cell
c. never reach equilibrium
d. Two of the above
e. None of the above
f. I don't know the answer - ✔✔Two of the above
✔✔Actin filaments associate with a nucleotide triphosphate. - ✔✔True
✔✔Treadmilling of actin filaments only occurs in a test tube. - ✔✔False
✔✔List the five steps of directional cell walking when starting with a cell in suspension. -
✔✔1) When most cell types are released from the surface of the culture dish (referred
to as "suspended"), they become spherical. This has a lot to do with disruption of the
cytoskeleton. Remember that cells, like you, are three dimensional and thus spherical;
the term "round or circular" is a two-dimensional term. 2) When cells are added to a
culture plate containing a fluid called "cell culture medium," they slowly settle to the
bottom of the plate at different rates. 3) When the cells reach the bottom of the plate,
they start to explore their environment, just like a rabbit, dog, or you would explore
its/your environment. The spherical cell initially sends out many filopodia radially from
the cell. A filopodium is 2-10 micrometers in length and 0.2 micrometers in diameter.
Note that the diameter is below the level of resolution of the light microscope. The
thousands of filopodia move around stirring the medium. These filopodia move much
like a cockroach's antenna as they sense their environment. These are cell extensions
whose outer edges are the plasma membrane filled with receptors - receptors are
molecules that sense the environment. 4) All of these receptor-encompassed filopodia
keep swirling (albeit very slowly) the cell culture medium looking for signals. When a
signal is received, the filopodia in the area that received the signal stop moving because
the area is undergoing a signal transduction biochemical cascade that is reorganizing
that part of the cell. From this area of the spherical cell, a lamellipodium extends a much
larger, irregularly-sized structure that pushes out against the plasma membrane; the
mechanism causing this is a new network of actin filaments. When the plasma
membrane of the lamellipodium comes in contact with substrate, three things happen in
succession.
(i) The part of the membrane tha
✔✔In the context of biomolecular machines and the above toys, what limits the size and
number of structures that can be constructed? - ✔✔It is limited by the number of
biomolecular machines that can be held within a single-celled organism. In other words,
within a single factory, the cell, you can only put so many biomolecular machines. If a
ANSWERS GRADED A+
✔✔Loss of the cell wall_________. - ✔✔occurs both for the endosymbiosis theory and
for the endomembrane system
✔✔The primitive proto-prokaryote likely acquired motility before it lost the cell wall. -
✔✔False
✔✔The endomembrane system supposedly resulted in the formation of the nuclear
envelope, endoplasmic reticulum, Golgi apparatus, and primary lysosomes. - ✔✔True
✔✔It is the proteins in the biological membrane that serve to partition water. - ✔✔False
✔✔If you had a phospholipid whose melting point was 12°C, what might happen if you
mixed it 1:1 with a lipid that had a melting point of 24°C. - ✔✔None of the above is
correct
✔✔Unsaturated sites in the fatty acid tails of phospholipids are places that water can
use to leak through the membrane. - ✔✔True
✔✔Phosphatidylserine influences a great deal of area primarily due to its large size. -
✔✔False
✔✔Transmembrane proteins _________. - ✔✔can move laterally and cannot flip 180˚
in the membrane
✔✔The presence of two disulfide bonds near each other is a good thing when a stretch
of protein is to be immobilized. - ✔✔True
✔✔The empty center of a single pass transmembrane protein provides a channel for
the transport of ions. - ✔✔False
✔✔Membrane anchors set up geography in a cell. - ✔✔True
✔✔Integrin receptor binding results in the recruitment of _________. - ✔✔actin
filaments
✔✔The sodium/potassium ATPase removes ___________ ions from the cell and
pumps ______________ ions into the cell against their respective concentration
gradients. - ✔✔3 sodium; 2 potassium
, ✔✔Actin filaments ______________. - ✔✔have a diameter of 7 nm and contain 375
amino acids
✔✔Actin filaments will ____________.
a. undergo treadmilling in a test tube
b. undergo treadmilling in a living cell
c. never reach equilibrium
d. Two of the above
e. None of the above
f. I don't know the answer - ✔✔Two of the above
✔✔Actin filaments associate with a nucleotide triphosphate. - ✔✔True
✔✔Treadmilling of actin filaments only occurs in a test tube. - ✔✔False
✔✔List the five steps of directional cell walking when starting with a cell in suspension. -
✔✔1) When most cell types are released from the surface of the culture dish (referred
to as "suspended"), they become spherical. This has a lot to do with disruption of the
cytoskeleton. Remember that cells, like you, are three dimensional and thus spherical;
the term "round or circular" is a two-dimensional term. 2) When cells are added to a
culture plate containing a fluid called "cell culture medium," they slowly settle to the
bottom of the plate at different rates. 3) When the cells reach the bottom of the plate,
they start to explore their environment, just like a rabbit, dog, or you would explore
its/your environment. The spherical cell initially sends out many filopodia radially from
the cell. A filopodium is 2-10 micrometers in length and 0.2 micrometers in diameter.
Note that the diameter is below the level of resolution of the light microscope. The
thousands of filopodia move around stirring the medium. These filopodia move much
like a cockroach's antenna as they sense their environment. These are cell extensions
whose outer edges are the plasma membrane filled with receptors - receptors are
molecules that sense the environment. 4) All of these receptor-encompassed filopodia
keep swirling (albeit very slowly) the cell culture medium looking for signals. When a
signal is received, the filopodia in the area that received the signal stop moving because
the area is undergoing a signal transduction biochemical cascade that is reorganizing
that part of the cell. From this area of the spherical cell, a lamellipodium extends a much
larger, irregularly-sized structure that pushes out against the plasma membrane; the
mechanism causing this is a new network of actin filaments. When the plasma
membrane of the lamellipodium comes in contact with substrate, three things happen in
succession.
(i) The part of the membrane tha
✔✔In the context of biomolecular machines and the above toys, what limits the size and
number of structures that can be constructed? - ✔✔It is limited by the number of
biomolecular machines that can be held within a single-celled organism. In other words,
within a single factory, the cell, you can only put so many biomolecular machines. If a
