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【单选题】
( )是中国现已发现最早的城市遗址。A.
河南偃师二里头一号宫殿
B.
河南偃师二里头二号宫殿
C.
郑州商城
D.
陕西岐山凤雏村
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举一反三
【简答题】数组通常只有两种运算:______和______。
【多选题】How do transmembrane proteins form aqueous pores across the lipid bilayer to allow small, water-soluble molecules to cross the membrane?
A.
Some transmembrane proteins function as channels, forming aqueous pores across the lipid bilayer to allow small, water-soluble molecules to cross the membrane.
B.
Such channels cannot be formed by proteins with a single transmembrane α helix. Instead, they usually consist of a series of α helices that cross the bilayer a number of times.
C.
For many of these multipass transmembrane proteins, one or more of the membrane-spanning regions are amphipathic—formed from α helices that contain both hydrophobic and hydrophilic amino acid side chains. These amino acids tend to be arranged so that the hydrophobic side chains fall on one side of the helix, while the hydrophilic side chains are concentrated on the other side.
D.
In the hydrophobic environment of the lipid bilayer, α helices of this type pack side by side in a ring, with the hydrophobic side chains exposed to the hydrophobic lipid tails and the hydrophilic side chains forming the lining of a hydrophilic pore through the membrane.
【简答题】脂/水分配系数（lipid/water partition coefficient）