Energy pathways
Glycolysis, Krebs cycle, oxidative phosphorylation, and ATP yield logic.
Energy pathways are the cell's budget system. The MCAT expects you to know which pathway is fast, which is efficient, and which fails without oxygen. You do not need to memorize every intermediate, but you must be able to predict outcomes when oxygen, fuel availability, or enzyme function changes.
- Glycolysis is fast but low yield
- Krebs cycle harvests electrons for ATP production
- Oxidative phosphorylation provides the highest ATP yield
- Oxygen absence halts oxidative phosphorylation
- Low oxygen shifts reliance to glycolysis
Describe how ATP production changes when oxygen drops. Which tissues would be affected first, and why?
Generate a short quiz from this lesson. Choose the formats you want, then run it.
Use this for step-by-step support. This is learning-first and shows reasoning.
Official MCAT overview from AAMC (link-only).
Official free planning resources (link-only).
Register for the official free MCAT practice exam (link-only).
Official MCAT content outline (link-only).
External Khan Academy MCAT content. Link-only with attribution.
Some lessons include links to external educational resources such as Khan Academy® or other independent providers. These resources remain hosted on their own platforms under their original licenses. UnCram does not charge for or redistribute this content and does not imply partnership, sponsorship, or endorsement by any external provider.
MCAT® is a registered trademark of the Association of American Medical Colleges (AAMC). UnCram is not affiliated with or endorsed by the AAMC.