Rucete ✏ Campbell Biology In a Nutshell
Unit 2 THE CELL — Concept 6.5 Mitochondria and Chloroplasts Change Energy from One Form to Another
Mitochondria and chloroplasts are specialized organelles in eukaryotic cells responsible for energy transformation.
They convert energy from one form to another, powering life’s processes.
1. Mitochondria: The Powerhouses of the Cell
Structure: Mitochondria have two membranes. The inner membrane is highly folded into cristae, increasing surface area for reactions. Inside is the mitochondrial matrix, which contains enzymes, DNA, and ribosomes.
Function: They perform cellular respiration, converting energy from glucose and oxygen into ATP, the energy currency of the cell.
Location: Found in almost all eukaryotic cells, including animal, plant, fungal, and protist cells.
2. Chloroplasts: Solar Panels for Plants
Structure: Chloroplasts also have a double membrane. Inside are stacked thylakoid membranes (grana) where light is captured. The fluid around them is called the stroma, containing DNA and enzymes.
Function: Photosynthesis takes place here—light energy is transformed into chemical energy stored in sugars.
Location: Found in plant and algal cells, mostly in green parts like leaves.
3. Shared Traits and Evolutionary Origins
Double Membranes: Both organelles have two membranes—evidence they descended from engulfed prokaryotes.
Own DNA and Ribosomes: They produce some of their own proteins, supporting the endosymbiont theory.
Replication: They grow and divide similarly to bacteria—independently of the rest of the cell.
In a Nutshell
Mitochondria convert food into ATP via cellular respiration.
Chloroplasts convert sunlight into sugars via photosynthesis.
Both have double membranes, their own DNA, and likely originated from ancient symbiotic bacteria.
They are vital for providing energy that powers cellular activities.