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Mastering Biology Chapter 4 Questions and Answers 100% Accurate
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Mastering Biology Chapter 4
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Mastering Biology Chapter 4Which of the following choices correctly matches a tool and its proper application?
a. light microscopy to study the internal structure of cilia
b. scanning electron microscopy (SEM) to study the detailed movements of living cells
c. transmission electron microscopy (TEM) to study the surfaces of preserved cells
d. cell fractionation to study the function of specific organelles
e. transmission electron microscopy (TEM) to study the movement of organelles within
a living cell - answerd. cell fractionation to study the function of specific organelles
Which of the following clues would tell you if a cell is prokaryotic or eukaryotic?
a. whether or not the cell carries out cellular metabolism
b. whether or not the cell contains DNA
c. the presence or absence of ribosomes
d. whether or not the cell is partitioned by internal membranes
e. the presence or absence of a rigid cell wall - answerd. whether or not the cell is
partitioned by internal membranes
Prokaryotic cells lack any internal membranous compartmentalization.
Part A - Organelles of the endomembrane system
The various parts of the endomembrane system serve different functions in the cell. In
this activity, you will identify the roles of each part of the endomembrane system.
Drag each function to the appropriate bin. - answerSmooth ER: Lipid synthesis, Calcium
ion storage, Poison detoxification
Rough ER: Protein synthesis
Golgi apparatus: Protein modification and storage, Cisternal maturation
Lysosomes: Autophagy, Macromolecule digestion
The endomembrane system is critical for the synthesis, processing, and movement of
proteins and lipids in the cell. The smooth ER functions mainly in lipid synthesis and
processing. The rough ER is the site of secretory protein synthesis. These proteins are
processed further in the Golgi apparatus, from where they are dispatched in vesicles to
the plasma membrane. Lysosomes, whose enzymes and membranes are made and
processed by the rough ER and Golgi apparatus, function in the hydrolysis of
macromolecules, such as in phagocytosis and autophagy.
Part B - Sites of protein synthesis
All proteins are synthesized by ribosomes in the cell. Some ribosomes float freely in the
cytosol, while others are bound to the surface of the endoplasmic reticulum. Most
proteins made by free ribosomes function in the cytosol. Proteins made by bound
, ribosomes either function within the endomembrane system or pass through it and are
secreted from the cell.
Which of the following proteins are synthesized by bound ribosomes?
Select all that apply. - answeractin
x ER protein
ribosomal protein
DNA polymerase
x lysosomal enzyme
x insulin
Most proteins that function in the cytosol (such as actin) or in the nucleus (such as DNA
polymerase) are synthesized by free ribosomes. Proteins that function within the
endomembrane system (such as lysosomal enzymes) or those that are destined for
secretion from the cell (such as insulin) are synthesized by bound ribosomes.
As a protein destined for the endomembrane system is being synthesized by a
ribosome, the first amino acids in the growing polypeptide chain act as a signal
sequence. That signal sequence ensures that the ribosome binds to the outer
membrane of the ER and that the protein enters the ER lumen.
Part C - The pathway of secretory proteins
Proteins that are secreted from a eukaryotic cell must first travel through the
endomembrane system.
Drag the labels onto the diagram to identify the path a secretory protein follows from
synthesis to secretion. Not all labels will be used - answerProtein synthesis
a. endoplasmic reticulum
b. cis Golgi cisternae
c. medial Golgi cisternae
d. trans Golgi cisternae
e. plasma membrane
Extracellular space
As they are being synthesized, secretory proteins enter the lumen of the endoplasmic
reticulum. From the ER, vesicles transport these proteins to the Golgi, where they are
sequentially modified and concentrated in a cis-to-trans direction. Secretory vesicles
bud from the Golgi and move along cytoskeletal filaments to eventually fuse with the
plasma membrane, secreting their protein cargo. Each of these transport steps requires
specialized proteins to ensure that the cargo is sent to the proper location and is able to
fuse with the target membrane.
Part D - Pulse-chase experiments and protein location
Scientists can track the movement of proteins through the endomembrane system using
an approach known as a pulse-chase experiment. This experiment involves
• the "pulse" phase: Cells are exposed to a high concentration of a radioactively labeled
amino acid for a short period to tag proteins that are being synthesized.
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