Continuity and Change D.7 Reproduction (id: 0f7300765)

本题目来源于试卷: Continuity and Change D.7 Reproduction，类别为 IB生物学

[单选题]
The diagram shows the transfer of a substance from v ky - emjk36llyu)37nsz/4jhnf x(c+ maternal blood to8 mostk +x (d:0lt ert(px6y)a foetal blood throxy m t0lspdatk (tr(ox)e6+8 :ugh the placenta. Which substance is being transferred?

A. Water
B. Antibodies
C. Glucose
D. Electrolytes


参考答案:  B


本题详细解析:

The diagram shows the transfer of a substance across the placenta by endocytosis. The substance from the maternal blood is transported into cells of the placenta through the invagination of the cell membrane and subsequent formation of a vesicle (endosome), which then empties its contents into the foetal blood. Of the answer choices, only antibodies require transport via endocytosis to reach foetal blood.

Water (Choice A) crosses the placenta through osmosis. Glucose (Choice C) crosses the placenta by facilitated diffusion through glucose transporters. Electrolytes (Choice D) are transported across the placenta by facilitated diffusion or active transport via carrier proteins.

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