Download 厦门大学细胞生物学课程试卷

厦门大学细胞生物学课程试卷
___________学院______系_______年级_______专业
主考老师：
试卷类型：
（A 卷）
1. Glossary (20)
1) Lipid raft (4)
2) Proteasome
(4)
3) Endomembrane system (4)
4) Anoikis (4)
5) Sorting signals (4)
2、
What roles are cholesterol thought to play in our cell membranes? （8）
3、
Name the various types of coated protein involved in vesicular transport and
expain their function respectively. (8)
4、
Describe the fate for an extracellular proteins that have been endocytosed (8)
5、
Summary the way that membrane protein associate with the lipid bilayer.(10)
6、
Identify several functions played by smooth endoplasmic reticulum. (8)
7、
Explain the mechanism of asymmetrical distribution of various phospholipids
in the lipid bilayer of a cell.(10)
8、
9、
Explain the physiological importance of Glycosylation （8）
Explain the mechanism for sorting lysosomal enzymes during the Vesicular
transport. (10)
10、 Describe the roles of the following in vesicular transport: A. SRP B.Signal
Sequence C. Bip (10)
Answer:
1. Glossary (20)
（1） Lipid raft (4)
A: Lipid rafts are membrane microdomains that are enriched in cholesterol and
glycosphingolipids. They have been implicated in processes as diverse as signal
transduction, endocytosis and cholesterol trafficking.
（2） Proteasome (4)
A: Large protein complex in the cytosol with proteolytic activity that is responsible
for degrading proteins that have been marked for destruction by ubiquitylation or by
some other means.
（3） Endomembrane system (4)
A: the structural and functional related intracellular membrane structures, including
Endoplasmic reticulum (ER),Golgi complex, lysosome, endosomes, secretory vesicles
（4） Anoikis (4)
A: a type of apoptosis that results from cell detachment from the extracellular matrix.
（5） Sorting signals (4)
A: Sorting signals are amino acid sequence that direct their delivery to targeting
locations.
2. What roles are cholesterol thought to play in our cell membranes? （8）
A: Cholesterol plays a important role in membrane mobility.
(1).Interaction with the relatively rigid cholesterol decreases the mobility of
hydrocarbon tails of phospholipids.
(2) the presence of cholesterol in a phospholipid membrane interferes with close
packing of fatty acid tails in the crystalline state, and thus inhibits transition to the
crystal state
(3) Phospholipid membranes with a high concentration of cholesterol have a fluidity
intermediate between the liquid crystal and crystal states.
3. Name the various types of coated protein involved in vesicular transport and expain
their function respectively. (8)
A: (A) Clathrin-coated vesicles: mediate transport from the Golgi apparatus to
lysosome and from the plasma membrane to endosome.
(B) COPI-coated vesicles: captures the escaped soluble ER resident proteins and
carries them in COPI-coated transport vesicles back to the ER.
(C) COPII-coated vesicles: mediate transport from ER to Golgi apparatus
4. Describe the fate for a protein that have been endocytosed (8)
A: (1) Recycling: proteins that are specifically retrieved are returned to the same
plasma membrane domain from which they came.
(2) Transcytosis: proteins that are specifically retrieved are returned to a
different domain of the plasma membrane
(3) Degradation: proteins that are not specifically retrieved from endosomes are
transported to lysosomes, where they are degraded.
5. Summary the way that membrane protein associate with the lipid bilayer. (10)
A: Most trans-membrane proteins are thought to extend across the bilayer as (1) a
single a helix , (2) as multiple a helices, or (3) as a rolled-upβsheet. Some of these
"single-pass" and "multipass" proteins have a covalently attached fatty acid chain
inserted in the cytosolic lipid monolayer (1). Other membrane proteins are exposed at
only one side of the membrane. (4) Some of these are anchored to the cytosolic
surface by an amphipathic a helix that partitions into the cytosolic monolayer of the
lipid bilayer through the hydrophobic face of the helix. (5) Others are attached to the
bilayer solely by a covalently attached lipid chain either a fatty acid chain or a prenyl
group in the cytosolic monolayer or, (6) via an oligosaccharide linker, to
phosphatidylinositol in the noncytosolic monolayer.
6. Identify several functions played by smooth endoplasmic reticulum. (8)
A: (1) Synthesis of steroids in endocrine cells.
(2) Detoxification of organic compounds in liver cells.
(3) Sequestration of Ca2+. Ca2+-ATPase
7. Explain the mechanism of asymmetrical distribution of various phospholipids in the
lipid bilayer of a cell.(10)
A: Asymmetrical distribution of various phospholipids in the lipid bilayer only occurs
in plasma membrane.
（1） phospholipids synthesis takes place in the cytosolic leaflet of the ER
membrane.some of the newly formed phospholipid molecules are transferred from
the cytosolic half of the ER bilayer to the lumenal leaflet by a phospholipid
translocator called a scramblase.
（2） The newly synthesized membrane is transported by vesicles from the ER to
plasma membrane.
（3） In plasma membrane, phospholipid translocators called flippases use the
energy of ATP hydrolysisto flip phosphatidylserine and phosphatidylethanolamine
directionally from the extracellular to the cytosolic leaflet.
Thus, the plasma membrane has a highly asymmetric distribution of phospholipids.
8. Explain the physiological importance of Glycosylation （8）
A:
(1) Mark the State of Protein Folding
(2) Limit the approach of other macromolecules to the protein surface, more
resistant to digestion by proteases.
(3) Regulatory roles in signaling through the cell-surface receptor Notch, to
allows these cells to respond selectively to activating stimuli.
9. Explain the mechanism for sorting lysosomal enzymes during the Vesicular
transport. (10)
A: （1）when lysosomal enzymes are transported from ER to cis Golgi network,
lysosomal enzymes are covalently modified by phosphorylation to the terminal
mannose residue to form mannose 6-phosphate (M6P) marker. Two enzymes act
sequentially to catalyze the addition of M6P groups to lysosomal hydrolases. The first
is a GlcNAc phosphotransferase that specifically binds the hydrolase and adds
GlcNAc-phosphate to one or two of the mannose residues on each oligosaccharide
chain .A second enzyme,N-Acetylglucosaminidase, then cleaves off the GlcNAc
residue, leaving behind a newly created M6P marker. Since most lysosomal
hydrolases contain multiple oligosaccharides, they acquire many M6P residues,
providing a high affinity signal for the M6P receptor.
(2) the lysosomal enzymes possessing the mannose 6-phophate(M6P) are recognized
and captured by M6P receptors in trans golgi network(TGN).
(3) the lysosomal enzymes are enclosed in clathrin-coated vesicles and transported to
late endosomes in which the M6P receptors are dissociated and the phosphates are
removed from the lysosomal enzymes.
(4) at last, the lysosomal enzymes are transported to lysosome.
10. Describe the roles of the following in vesicular transport: A.SRP B.Signal
Sequence C.Bip (10)
A. A:signal-recognition particle(SRP), which cycles between the ER membrane and
the cytosol and binds to the ER signal sequence, plays a role when secretory
proteins are synthesized in ER. The SRP binds to both the exposed ER signal
sequence and the ribosome, thereby inducing a pause in translation. The SRP
receptor in the ER membrane binds the SRP-ribosome complex and directs it to
the translocator.
B.
Signal sequences are short continuous amino acid sequence in proteins that direct
proteins from the cytosol into the ER, mitochondria, chloroplasts, and
peroxisomes, and they are also used to transport proteins from the nucleus to the
cytosol and from the Golgi Complex to the ER.
C. Bip (binding protein) are ER resident proteins.
During the cargo proteins are synthesized in ER, the molecular chaperone Bip
functions to recognize and bind to unfolded or misfolded proteins and give them
the opportunity to attain their correct three-dimensional structure. In addition, Bip
pulls the polypeptide chain into the ER lumen through the translocator.