All Subjects



AP Bio



Unit 2

2.11 Origins of Cell Compartmentalization

1 min readseptember 25, 2020



The endosymbiotic theory is the current theory of how eukaryotic membrane-bound organelles existed in eukaryotic cells.
The endosymbiotic theory states that an early ancestor of eukaryotic cells engulfed a prokaryotic cell, and the prokaryotic became an endosymbiont, a cell living in another cell. These smaller cells were capable of producing extra energy for the other cell, leading to a selective advantage.
Overtime, cells with an extra cell inside were able to become more able to survive and reproduce quickly. The eukaryotic cell was born!
While prokaryotes generally lack internal membrane bound organelles, they still have internal regions with specialized structures and functions. These regions are just not defined by outer membranes.

Image courtesy of WikiMedia Commons.

Was this guide helpful?

🔍 Are you ready for college apps?
Take this quiz and find out!
Start Quiz
FREE AP bio Survival Pack + Cram Chart PDF
Sign up now for instant access to 2 amazing downloads to help you get a 5
Browse Study Guides By Unit
Big Reviews: Finals & Exam Prep
Free Response Questions (FRQ)
General Review
Multiple Choice Questions (MCQ)
Unit 1: Chemistry of Life
Unit 3: Cellular Energetics
Unit 4: Cell Communication and Cell Cycle
Unit 5: Heredity
Unit 6: Gene Expression and Regulation
Unit 7: Natural Selection
Unit 8: Ecology
Join us on Discord
Thousands of students are studying with us for the AP Biology exam.
join now
💪🏽 Are you ready for the AP Bio exam?
Take this quiz for a progress check on what you’ve learned this year and get a personalized study plan to grab that 5!
Hours Logo
Studying with Hours = the ultimate focus mode
Start a free study session
📱 Stressed or struggling and need to talk to someone?
Talk to a trained counselor for free. It's 100% anonymous.
Text FIVEABLE to 741741 to get started.
© 2021 Fiveable, Inc.