- 作者: 謝昱暲
- 作者服務機構: 中央研究院植物研究所
- 中文摘要: 在正常狀態下,綠藻細胞積蓄高濃度的鉀離子,而維持一低含量的鈉離子。若細胞培養在缺鉀的溶液中,綠藻將積聚相當量的鈉。此睡富於鈉離子的細胞,一旦由外界供給鉀離子,將以相當快的速率吸收鉀離子,同時排出鈉離子。除了鉀和鈉的淨轉運外,還有一個依賴鉀離子的氫離子的向外轉運。 鉀和鈉的交換對光與溫度均甚敏感,可能由細胞內的代謝作用控制之。CCCP和DCCD的抑制作用暗示磷脂化作用和一個與細胞膜相結合的ATPase (membnane-bound ATPase)可能參於鉀鈉交換。進而,由DCMU,CO2-free N2和far-red light之作用推測循環式光磷脂化作用(Cyclic photophosphorylation)能夠支持鉀-鈉的交換作用。雖然偽循環式光磷脂化作用(psendocydic photophasphorylation )亦可能參於。 鉀一鈉交換的能量來源可能由光合作用或呼吸作用的磷脂化作用製成的ATP。 在黑暗條件下,鉀一鈉交換的速率仍相當高,略示呼吸作用產生的能量亦足有效的支持此一程序。 鉀一氫的交換在黑暗條件下完全被抑制,指出其依賴著光磷脂化作用。
- 英文摘要: Normally Chlorella cells accumulate potassium to a high concentration and main-tain a low internal sodium level. When grown in a K+-free culture medium lowor free of potassium, the cell will accumulate sodium. The addition of potassiumto a suspension of sodium-rich cells causes a relatively rapid uptake of K+ and aconcurrent extrusion of Na+. In addition to the net movements of K+ and Na+,there was also a K+-dependent hydrogen ion efflux from the Na+-rich cells. The K+/Na+ exchange is sensitive to light and temperature and seems to beunder metabolic control. Inhibition of the net cation fluxes with Carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and N,N'-dicyclohexylcarbodiimide (DCCD)implicates phosphorylation and a membrane-bound ATPase with the exchange. Theaction of 3-(3,4-dichlorophenyl)-1,1-dimethy1 urea (DCMU), anaerobic conditionsand fag-red light suggests that this process can be supported by cyclic photophos-phorylation although pseudocyclic photophorylation may also be involved. The energy source for k+/Na+ exchange process is probaly ATP producedfxom photosynthetic or oxidative phosporylation and the relative high rate of K+/Na+ exchange in the dark indicates that respiratory energy efftcienty supports thisprocess. The K+/H+ exchange is probably dependent on photophosphorylation since itis completely inhibited in the dark.
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