Question

Name the two semi-autonomous double membraned organelles. State their characteristics and functions.

Answer 1

Mitochondria and chloroplasts are the two semi-autonomous organelles that have a double membrane.

Characteristics of the mitochondria

• The membrane of a mitochondrion is divided into the inner and outer membranes, distinctly divided into two aqueous compartments – outer and inner compartments. The outer membrane is very porous to allow easy passage of ions and molecules, while the inner membrane is deeply-folded.
• These folds of the inner membrane are known as cristae. Cristae increase the surface area inside the cell. They are the sites for ATP-generating chemical reactions. Mitochondria have their own DNA and ribosomes.

Characteristics of chloroplasts

• They are divided into outer and inner membranes, further divided into two distinct regions:
• (i) Grana are stacks of flattened discs containing chlorophyll molecules. The flattened membranous sacs are called thylakoids.
• (ii) Stroma is a homogenous mixture in which grana are embedded. It contains several enzymes that are used for the synthesis of carbohydrates and proteins. It also contains its own DNA and ribosomes.