4.10:_Chemiosmosis

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<p class="lt-bio-4636">Several kinds of evidence support the chemiosmotic theory of ATP synthesis in chloroplasts. When isolated chloroplasts are illuminated, the medium in which they are suspended becomes alkaline &mdash; as we would predict if protons were being removed from the medium and pumped into the thylakoids (where they reduce the pH to about 4.0 or so). The interior of thylakoids can be deliberately made acid (low pH) by suspending isolated chloroplasts in an acid medium (pH 4.0) for a period of time. When these chloroplasts are then transferred to a slightly alkaline medium (pH 8.5), that is, one with a lower concentration of protons and given a supply of ADP and inorganic phosphate (P<sub><font size="2">i</font></sub>), they spontaneously synthesize ATP. No light is needed.</p>

<figure><img class="internal" alt="Diagram showing a lab apparatus. (a) Incubator with dial connected to a beaker; a round object labeled Culture Dish beside it. (b) Two test tubes; one labeled Spores pointing to Germ Tube." loading="lazy" src="https://bio.libretexts.org/@api/deki/files/6327/chemiosmosis_demo.gif?revision=1" /><figcaption>Figure <mjx-container class="MathJax CtxtMenu_Attached_0" jax="SVG" overflow="linebreak" tabindex="0" ctxtmenu_counter="96" style="font-size: 85%; position: relative;"><svg width="5.783ex" height="1.581ex" role="img" focusable="false" viewbox="0 -677 2556 699" aria-hidden="true" style="vertical-align: -0.05ex;"><defs><path id="MJX-97-NCM-N-34" d="M353 677C344 677 336 672 330 663L28 199L28 163L289 163L289 81C289 63 285 51 278 46C271 41 252 39 219 39L194 39L194 0C223 2 269 3 331 3C393 3 439 2 468 0L468 39L443 39C410 39 391 41 384 46C377 51 373 63 373 81L373 163L471 163L471 202L373 202L373 660C373 670 366 677 353 677M295 553L295 202L67 202Z"></path><path id="MJX-97-NCM-N-2E" d="M192 53C192 82 168 106 139 106C110 106 86 82 86 53C86 24 110 0 139 0C168 0 192 24 192 53Z"></path><path id="MJX-97-NCM-N-31" d="M269 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data-semantic-level-number="0" data-speech-node="true"><mn data-latex="4" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:4" data-semantic-level-number="1" data-speech-node="true">4</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="10" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:10" data-semantic-level-number="1" data-speech-node="true">10</mn><mrow data-mjx-texclass="ORD" data-latex="{.}"><mo data-latex="." data-semantic-type="punctuation" data-semantic-role="fullstop" data-semantic-annotation="nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:{.};texclass:ORD" data-semantic-operator="punctuated" data-semantic-level-number="1" data-speech-node="true">.</mo></mrow><mn data-latex="1" data-semantic-type="number" data-semantic-role="integer" data-semantic-font="normal" data-semantic-annotation="clearspeak:simple;nemeth:number;depth:2" data-semantic-="" data-semantic-parent="5" data-semantic-attributes="latex:1" data-semantic-level-number="1" data-speech-node="true">1</mn></mrow></math></mjx-assistive-mml></mjx-container>: Chemiosmosis demo</figcaption></figure>

<p class="lt-bio-4636">This is a direct evidence that a gradient of protons can be harnessed to the synthesis of ATP.</p>

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<hr class="autoattribution-divider" /><div class="autoattribution"><p>This page titled <a target="_blank" class="internal mt-self-link" href="/Sandboxes/johnnyphung/biology/04:_Cell_Metabolism/4.10:_Chemiosmosis">4.10: Chemiosmosis</a> is shared under a <a rel="nofollow" href="https://creativecommons.org/licenses/by/3.0" target="_blank">CC BY  3.0</a>  license and was authored, remixed, and/or curated by <a rel="nofollow" target="_blank" href="http://www.biology-pages.info/">John W. Kimball</a> via <a rel="nofollow" href="https://www.biology-pages.info/" target="_blank">source content</a> that was edited to the style and standards of the LibreTexts platform.</p></div>

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