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【单选题】
下列卤代烃在NaOH水溶液中进行水解，按SN1历程活性最大的是A.
3 –甲基– 1 –溴丁烷
B.
2 –甲基– 2 –溴丁烷
C.
2 –甲基– 3 –溴丁烷
D.
ABC三个化合物按 S N 1 历程反应活性相同
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举一反三
【判断题】There four general categories of cells: nerve cells, muscle cells, epithelial cells and connective tissue cells.
A.
正确
B.
错误
【多选题】How do cytoskeleton-linked junctions bind epithelial cells robustly to one another and to the basal lamina?
A.
The cell junctions that hold an epithelium together by forming strong mechanical attachments are of three main types.
B.
Adherens junctions and desmosomes bind one epithelial cell to another, while hemidesmosomes bind epithelial cells to the basal lamina.
C.
All of these junctions provide mechanical strength to the epithelium by the same strategy: the proteins that form the junctions span the plasma membrane and are linked inside the cell to cytoskeletal filaments.
D.
In this way, the cytoskeletal filaments are tied into a network that extends from cell to cell across the whole expanse of the epithelial sheet.
【多选题】How do adherens junctions form adhesion belts around epithelial cells?
A.
At an adherens junction, each cadherin molecule is tethered inside its cell, via several linker proteins, to actin filaments.
B.
Often, the adherens junctions form a continuous adhesion belt around each of the interacting epithelial cells; this belt is located near the apical end of the cell, just below the tight junctions.
C.
Bundles of actin filaments are thus connected from cell to cell across the epithelium.
D.
This network of actin filaments also contains myosin filaments and can thus contract, giving the epithelial sheet the capacity to develop tension and to change its shape in remarkable ways.
【单选题】which structure is located at the lateral surface of epithelial cells?
A.
zonula occludens
B.
cilia
C.
microvilli
D.
basement membrane
【单选题】The stomach produces acids, which denature protein, and pepsin that digests protein. The cell membranes of the epithelial cells lining the stomach contain protein. The protein in the epithelial cells ...
A.
the membranes contain a different type of protein that resists denaturation and digestion.
B.
mucus coats the epithelium.
C.
cell membranes are destroyed but mitotic activity replaces cells with new ones every few hours.
D.
hormones produced by the endocrine cells protect the cell membranes and neutralize the acid pH.
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