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5.11:

1์ฐจ ๋Šฅ๋™์ˆ˜์†ก

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– [๋‚˜๋ ˆ์ดํ„ฐ] ์ˆ˜๋™์  ์ˆ˜์†ก๊ณผ ๋‹ฌ๋ฆฌ,์ฃผ์š” ๋Šฅ๋™์  ์ˆ˜์†ก์€ ATP์˜ ์—๋„ˆ์ง€๋ฅผ ํ™œ์šฉํ•˜์—ฌ์„ธํฌ๋ง‰์— ๋‚ด์žฅ๋œ ๋‹จ๋ฐฑ์งˆ ํŽŒํ”„๋ฅผ ๊ตฌ๋™ํ•˜๋ฉฐ์ด๋ฅผ ํ†ตํ•ด ์ด์˜จ์ด ์ˆ˜์†ก์ด์ „๊ธฐ ํ™”ํ•™์  ๊ฒฝ์‚ฌ๋„์— ๋ฐ˜ํ•ด ์ง„ํ–‰๋˜๋Š”๋ฐ์ด๋Š” ํ™•์‚ฐ ์ค‘ ์ •์ƒ์ ์œผ๋กœ ์ด๋™ํ•˜์ง€ ์•Š๋Š” ๋ฐฉํ–ฅ์ž…๋‹ˆ๋‹ค๊ทธ๋Ÿฌํ•œ ์ˆ˜์†ก์ฒด ์ค‘ ํ•˜๋‚˜๋Š” ๋‚˜ํŠธ๋ฅจ ์นผ๋ฅจ ํŽŒํ”„์ด๋ฉฐ์ฒ˜์Œ์—๋Š” ์„ธํฌ๋ง‰์— ๊ฑธ์ณ ์žˆ๋„๋ก ๋˜์–ด ์žˆ๋Š”๋ฐ์„ธํฌ ์™ธ ์ธก๋ฉด์€ ํ์‡„๋˜์–ด ์žˆ๊ณ ์„ธํฌ ๋‚ด ์˜์—ญ์ด ๊ฐœ๋ฐฉ๋œ ์ƒํƒœ์ด๋ฉฐATP์˜ ๋ถ„์ž์™€ ๊ด€๋ จ์ด ์žˆ์Šต๋‹ˆ๋‹ค์ด ํ™•์ธ์— ์˜ํ•˜๋ฉด์ˆ˜์†ก์ฒด๋Š” ๋†’์€ ์นœํ™”์„ฑ์„์„ธํฌ์— ์ •์ƒ์ ์œผ๋กœ ์กด์žฌํ•˜๋Š” ๋‚˜ํŠธ๋ฅจ ์ด์˜จ์— ๋Œ€ํ•ด ๊ฐ€์ง€๋ฉฐ์ด๋“ค ์ค‘ 3 ๊ฐœ์˜ ์ด์˜จ์€ ํŽŒํ”„์— ๋“ค์–ด๊ฐ€ ๋ถ€์ฐฉ๋ฉ๋‹ˆ๋‹ค์ด๋Ÿฌํ•œ ๊ฒฐํ•ฉ์ฒด๋Š” ATP๊ฐ€ ์ˆ˜์†ก์„ ํ†ตํ•ด์ธ์‚ฐ๊ธฐ ์ค‘ ํ•˜๋‚˜๋ฅผ ์ˆ˜์†ก์ฒด์— ์ „๋‹ฌํ•˜๋ฉฐํ•„์š”ํ•œ ์—๋„ˆ์ง€๋ฅผ ์ œ๊ณตํ•˜๋Š”๋ฐํŽŒํ”„์˜ ์„ธํฌ ๋‚ด ์ธก๋ฉด์€ ํ์‡„๋˜๊ณ ์„ธํฌ ์™ธ ์˜์—ญ์„ ์—ด๊ฒŒ ๋ฉ๋‹ˆ๋‹ค์ด ์ƒˆ๋กœ์šด ํ™•์ธ ์‚ฌ์‹ค์€๋‚˜ํŠธ๋ฅจ ์ด์˜จ์— ๋Œ€ํ•œ ํŽŒํ”„์˜ ์นœํ™”์„ฑ์„ ๊ฐ์†Œ์‹œํ‚ต๋‹ˆ๋‹ค์ด๋“ค์€ ์„ธํฌ ์™ธ ๊ณต๊ฐ„์œผ๋กœ ๋ฐฉ์ถœ๋˜์ง€๋งŒ์นผ๋ฅจ์— ๋Œ€ํ•œ ์นœํ™”์„ฑ์„ ์ฆ๊ฐ€์‹œํ‚ค๊ณ 2 ๊ฐœ์˜ ์นผ๋ฅจ ์ด์˜จ์— ๊ฒฐํ•ฉ๋˜๋Š”๋ฐํ™˜๊ฒฝ์— ์กด์žฌํ•  ์‹œ ์ผ์–ด๋‚ฉ๋‹ˆ๋‹ค๊ทธ๋Ÿฐ ๋‹ค์Œ ํŽŒํ”„์˜ ์„ธํฌ ์™ธ ์ธก๋ฉด์ด ๋‹ซํžˆ๊ณ ATP ์œ ๋ž˜ ์ธ์‚ฐ๊ธฐ๊ฐ€์ˆ˜์†ก์ฒด์—์„œ ๋ถ„๋ฆฌ๋ฉ๋‹ˆ๋‹ค์ด๊ฒƒ์€ ์ƒˆ๋กœ์šด ATP ๋ถ„์ž๊ฐ€ํŽŒํ”„์˜ ์„ธํฌ ๋‚ด ์ธก๋ฉด๊ณผ ์ž‘์šฉํ•˜๊ฒŒ ํ•˜๋Š”๋ฐ๊ฐœ๋ฐฉ๋˜์–ด ์นผ๋ฅจ ์ด์˜จ์„ ์„ธํฌ ๋‚ด๋กœ ๋ฐฉ์ถœ์‹œํ‚ค๊ณ ์ˆ˜์†ก์ฒด๋ฅผ ์ดˆ๊ธฐ ํ˜•์ƒ์œผ๋กœ ๋ณต๊ท€์‹œํ‚ค๋ฉฐ์ฃผ๊ธฐ๊ฐ€ ๋‹ค์‹œ ์‹œ์ž‘๋ฉ๋‹ˆ๋‹ค

5.11:

1์ฐจ ๋Šฅ๋™์ˆ˜์†ก

์ˆ˜๋™์ˆ˜์†ก(passive transport)๊ณผ๋Š” ๋‹ฌ๋ฆฌ ๋Šฅ๋™์ˆ˜์†ก(active transport)์€ ๋ฌผ์งˆ์ด ๋†๋„๊ตฌ๋ฐฐ(concentration gradient) ๋˜๋Š” ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ(electrochemical gradient)์— ๋ฐ˜ํ•˜๋Š” ๋ฐฉํ–ฅ์œผ๋กœ ๋ง‰์„ ๊ฐ€๋กœ์งˆ๋Ÿฌ ์ด๋™ํ•˜๋Š” ๊ฒƒ์„ ๋œปํ•ฉ๋‹ˆ๋‹ค. ๋Šฅ๋™์ˆ˜์†ก์€ 1์ฐจ ๋Šฅ๋™์ˆ˜์†ก(primary active transport)๊ณผ 2์ฐจ ๋Šฅ๋™์ˆ˜์†ก(secondary active transport), ์ด ๋‘ ๊ฐ€์ง€ ์œ ํ˜•์ด ์žˆ์Šต๋‹ˆ๋‹ค. 1์ฐจ ๋Šฅ๋™์ˆ˜์†ก์€ ์•„๋ฐ๋…ธ์‹ ์‚ผ์ธ์‚ฐ(ATP)์˜ ํ™”ํ•™ ์—๋„ˆ์ง€๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ์„ธํฌ๋ง‰์— ๋‚ด์žฅ๋œ ๋‹จ๋ฐฑ์งˆ ํŽŒํ”„๋ฅผ ๊ตฌ๋™ํ•ฉ๋‹ˆ๋‹ค. ํŽŒํ”„๋Š” ATP์˜ ์—๋„ˆ์ง€๋กœ ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ๋ฅผ ๊ฑฐ์Šฌ๋Ÿฌ(์ผ๋ฐ˜์ ์œผ๋ก  ํ™•์‚ฐ์— ๋ฐ˜ํ•˜๋Š” ๋ฐฉํ–ฅ) ์ด์˜จ์„ ์ˆ˜์†กํ•ฉ๋‹ˆ๋‹ค.

๋†๋„๊ตฌ๋ฐฐ, ์ „๊ธฐ์  ๊ตฌ๋ฐฐ, ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ์˜ ๊ด€๊ณ„

๋Šฅ๋™์ˆ˜์†ก์˜ ์—ญํ•™์„ ์ดํ•ดํ•˜๋ ค๋ฉด ๋จผ์ € ์ „๊ธฐ์  ๊ตฌ๋ฐฐ(electrical gradient)์™€ ๋†๋„๊ตฌ๋ฐฐ๋ฅผ ์ดํ•ดํ•˜๋Š” ๊ฒƒ์ด ์ค‘์š”ํ•ฉ๋‹ˆ๋‹ค. ๋†๋„๊ตฌ๋ฐฐ๋Š” ๋ง‰ ๋˜๋Š” ๊ณต๊ฐ„ ์‚ฌ์ด์˜ ๋ฌผ์งˆ ๋†๋„ ์ฐจ์ด๋ฅผ ๋œปํ•˜๋ฉฐ ์ด๋Ÿฐ ๋†๋„ ์ฐจ์ด๋Š” ๋ฌผ์งˆ์ด ๋†’์€ ๋†๋„์˜ ์˜์—ญ์—์„œ ๋‚ฎ์€ ๋†๋„์˜ ์˜์—ญ์œผ๋กœ ์ด๋™ํ•˜๋„๋ก ์œ ๋„ํ•ฉ๋‹ˆ๋‹ค. ๋งˆ์ฐฌ๊ฐ€์ง€๋กœ, ์ „๊ธฐ ๊ตฌ๋ฐฐ๋Š” ๋ง‰ ์‚ฌ์ด์˜ ์ „๊ธฐํ™”ํ•™์  ์ „์œ„(electrochemical potential) ์ฐจ์ด๋ฅผ ๋œปํ•˜๋ฉฐ, ์ด ์ฐจ์ด๋Š” ๋ง‰ ์–‘์ชฝ์˜ ์ „ํ•˜๊ฐ€ ์œ ์‚ฌํ•  ๋•Œ๊นŒ์ง€ ์ด์˜จ์ด ๋ง‰์„ ๊ฐ€๋กœ์งˆ๋Ÿฌ ์›€์ง์ด๋„๋ก ์œ ๋„ํ•ฉ๋‹ˆ๋‹ค. ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ๋Š” ํ™”ํ•™์  ๊ตฌ๋ฐฐ์™€ ์ „๊ธฐ์  ๊ตฌ๋ฐฐ๊ฐ€ ๊ฒฐํ•ฉํ–ˆ์„ ๋•Œ ์ƒ์„ฑ๋ฉ๋‹ˆ๋‹ค.

๋‚˜ํŠธ๋ฅจ-์นผ๋ฅจ ํŽŒํ”„(Sodium-Potassium Pump)

์„ธํฌ์˜ ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ๋ฅผ ์œ ์ง€ํ•˜๋Š” ์ค‘์š”ํ•œ ์ˆ˜์†ก์ฒด(transporter) ์ค‘ ํ•˜๋‚˜๋Š” ๋‚˜ํŠธ๋ฅจ-์นผ๋ฅจ ํŽŒํ”„์ž…๋‹ˆ๋‹ค. ํŽŒํ”„์˜ 1์ฐจ ๋Šฅ๋™์ˆ˜์†ก์€ ๋ง‰ ์ „์ฒด์— ํผ์ ธ์žˆ๋Š” ํŽŒํ”„๊ฐ€ ์„ธํฌ ์™ธ๋ถ€๋ฅผ ํ–ฅํ•œ ๋ถ€๋ถ„์€ ๋‹ซ์•„๋‘๊ณ  ์„ธํฌ ๋‚ด๋ถ€๋ฅผ ํ–ฅํ•œ ๋ถ€๋ถ„์€ ์—ด์–ด๋‘” ์ƒํƒœ์—์„œ ATP ๋ถ„์ž์™€ ๊ฒฐํ•ฉํ–ˆ์„ ๋•Œ ๋ฐœ์ƒํ•ฉ๋‹ˆ๋‹ค. ์ด๋Ÿฐ ํ˜•ํƒœ์—์„œ ํŽŒํ”„๋Š” ์ผ๋ฐ˜์ ์œผ๋กœ ๋‚ฎ์€ ๋†๋„๋กœ ์„ธํฌ์— ์กด์žฌํ•˜๋Š” ๋‚˜ํŠธ๋ฅจ ์ด์˜จ์— ๋†’์€ ์นœํ™”๋„(affinity)๋ฅผ ๋ ๋Š”๋ฐ, ์ด๋•Œ 3๊ฐœ์˜ ๋‚˜ํŠธ๋ฅจ ์ด์˜จ์ด ํŽŒํ”„์— ๋“ค์–ด๊ฐ€ ํŽŒํ”„์— ๋ถ€์ฐฉํ•ฉ๋‹ˆ๋‹ค. ์ด๋Ÿฐ ๊ฒฐํ•ฉ์€ ATP๊ฐ€ ์ธ์‚ฐ๊ธฐ(phosphate group) ํ•˜๋‚˜๋ฅผ ํŽŒํ”„์— ์ „๋‹ฌํ•ด ํŽŒํ”„๊ฐ€ ์„ธํฌ ๋‚ด๋ถ€๋ฅผ ํ–ฅํ•˜๋Š” ๋ถ€๋ถ„์€ ๋‹ซ๊ณ  ์„ธํฌ ์™ธ๋ถ€๋ฅผ ํ–ฅํ•˜๋Š” ๋ถ€๋ถ„์€ ์—ด ์ˆ˜ ์žˆ๋Š” ์—๋„ˆ์ง€๋ฅผ ์ œ๊ณตํ•ฉ๋‹ˆ๋‹ค.

์ด๋Ÿฐ ํ˜•ํƒœ ๋ณ€ํ™”๋Š” ๋‚˜ํŠธ๋ฅจ ์ด์˜จ์— ๋Œ€ํ•œ ํŽŒํ”„์˜ ์นœํ™”๋„๋ฅผ ๊ฐ์†Œ์‹œ์ผœ ๋‚˜ํŠธ๋ฅจ ์ด์˜จ์„ ์„ธํฌ์™ธ ๊ณต๊ฐ„์œผ๋กœ ๋ฐฉ์ถœ์‹œํ‚ค๋Š” ๋ฐ˜๋ฉด, ์นผ๋ฅจ์— ๋Œ€ํ•œ ์นœํ™”๋„๋Š” ์ฆ๊ฐ€์‹œ์ผœ ์„ธํฌ์™ธ ํ™˜๊ฒฝ์—์„œ ๋‚ฎ์€ ๋†๋„๋กœ ์กด์žฌํ•˜๋Š” ์นผ๋ฅจ ์ด์˜จ ๋‘ ๊ฐœ๊ฐ€ ํŽŒํ”„์™€ ๊ฒฐํ•ฉํ•˜๊ฒŒ ๋งŒ๋“ญ๋‹ˆ๋‹ค. ์นผ๋ฅจ์ด ํŽŒํ”„์— ๊ฒฐํ•ฉํ•˜๋ฉด ํŽŒํ”„๋Š” ์„ธํฌ ์™ธ๋ถ€๋ฅผ ํ–ฅํ•œ ๋ถ€๋ถ„์„ ๋‹ซ๊ณ  ATP์—์„œ ์ „๋‹ฌ๋ฐ›์•˜๋˜ ์ธ์‚ฐ๊ธฐ๋ฅผ ๋ถ„๋ฆฌํ•ฉ๋‹ˆ๋‹ค. ์ด๋ ‡๊ฒŒ ๋˜๋ฉด ์„ธํฌ ๋‚ด๋ถ€์— ์žˆ๋Š” ATP ๋ถ„์ž๊ฐ€ ํŽŒํ”„์™€ ๊ฒฐํ•ฉํ•  ์ˆ˜ ์žˆ๊ฒŒ ๋˜๊ณ , ์ƒˆ๋กœ์šด ATP ๋ถ„์ž๊ฐ€ ํŽŒํ”„์™€ ๊ฒฐํ•ฉํ•˜๋ฉด ํŽŒํ”„๋Š” ์„ธํฌ ๋‚ด๋ถ€๋ฅผ ํ–ฅํ•œ ๋ถ€๋ถ„์„ ์—ด์–ด ํŽŒํ”„์— ๋ถ™์–ด์žˆ๋˜ ์นผ๋ฅจ ์ด์˜จ์„ ์„ธํฌ ๋‚ด๋ถ€๋กœ ๋“ค์ด๊ฒŒ ๋ฉ๋‹ˆ๋‹ค. ์ด ํ›„ ํŽŒํ”„๋Š” ์›๋ž˜ ๋ชจ์–‘์œผ๋กœ ๋Œ์•„๊ฐ€๊ณ  ํŽŒํ”„ ์ฃผ๊ธฐ๋ฅผ ๋‹ค์‹œ ์‹œ์ž‘ํ•˜๊ฒŒ ๋ฉ๋‹ˆ๋‹ค.

ํŽŒํ”„์˜ 1์ฐจ ๋Šฅ๋™์ˆ˜์†ก์œผ๋กœ ์ธํ•ด ๋ง‰์„ ๊ฐ€๋กœ์ง€๋ฅด๋Š” ์ด์˜จ์˜ ๋ถ„ํฌ์— ๋ถˆ๊ท ํ˜•์ด ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค. ์ด๋ ‡๊ฒŒ ๋˜๋ฉด ์„ธํฌ ์•ˆ์—๋Š” ๋” ๋งŽ์€ ์นผ๋ฅจ ์ด์˜จ์ด, ์„ธํฌ ๋ฐ”๊นฅ์—๋Š” ๋” ๋งŽ์€ ๋‚˜ํŠธ๋ฅจ ์ด์˜จ์ด ์žˆ๊ฒŒ ๋ฉ๋‹ˆ๋‹ค. ๋”ฐ๋ผ์„œ ์„ธํฌ์˜ ๋‚ด๋ถ€๋Š” ์™ธ๋ถ€๋ณด๋‹ค ๋” ์Œ์ „ํ•˜๋ฅผ ๋ ๊ฒŒ ๋ฉ๋‹ˆ๋‹ค. ์ด๋Ÿฐ ์ด์˜จ์˜ ๋ถˆ๊ท ํ˜•์€ ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ๋ฅผ ๋งŒ๋“œ๋Š”๋ฐ, ์ด ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ์—์„œ ์˜ค๋Š” ํž˜์ด 2์ฐจ ๋Šฅ๋™์ˆ˜์†ก ๋ฐ˜์‘์„ ์ด‰์ง„ํ•ฉ๋‹ˆ๋‹ค. ๊ณต์ˆ˜์†ก(co-transport)์œผ๋กœ๋„ ์•Œ๋ ค์ง„ 2์ฐจ ๋Šฅ๋™์ˆ˜์†ก์€ ์ถ”๊ฐ€ ATP๋ฅผ ํ•„์š”๋กœ ํ•˜์ง€ ์•Š๊ณ  1์ฐจ ๋Šฅ๋™์ˆ˜์†ก์— ์˜ํ•ด ํ™•๋ฆฝ๋œ ์ „๊ธฐํ™”ํ•™์  ๊ตฌ๋ฐฐ๋ฅผ ๋”ฐ๋ผ ๋ฌผ์งˆ์„ ๋ง‰์„ ๊ฐ€๋กœ์งˆ๋Ÿฌ ์ˆ˜์†กํ•ฉ๋‹ˆ๋‹ค.

Suggested Reading

Sahoo, Swagatika, Maike K. Aurich, Jon J. Jonsson, and Ines Thiele. “Membrane Transporters in a Human Genome-Scale Metabolic Knowledgebase and Their Implications for Disease.” Frontiers in Physiology 5 (March 11, 2014). [Source]

Yang, Nicole J., and Marlon J. Hinner. “Getting Across the Cell Membrane: An Overview for Small Molecules, Peptides, and Proteins.” Methods in Molecular Biology (Clifton, N.J.) 1266 (2015): 29–53. [Source]