Question

Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.

Answer 1

Double membrane-bound cell organelles:

The two cell organelles that are surrounded by a double membrane are: 
1. Mitochondria 
2. Chloroplast

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1. Mitochondria

Characteristics:

• Mitochondria are oval or rod-shaped organelles found in eukaryotic cells. 
• They are bounded by two membranes: an outer smooth membrane and an inner folded membrane. 
• The folds of the inner membrane are called cristae. 
• The space inside the inner membrane is called the matrix, which contains enzymes, mitochondrial DNA, and ribosomes.

Functions:

• Mitochondria are known as the powerhouse of the cell. 
• They are the site of cellular respiration and ATP production. 
• They supply energy required for various metabolic activities of the cell.

Labelled diagram of mitochondrion:

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2. Chloroplast

Characteristics:

• Chloroplasts are disc-shaped organelles found in green plant cells. 
• They are surrounded by an outer and inner membrane. 
• Inside the chloroplast is a fluid-filled matrix called the stroma. 
• Flattened membranous sacs called thylakoids are arranged in stacks known as grana. 
• Chloroplasts contain the green pigment chlorophyll.

Functions:

• Chloroplasts are the site of photosynthesis. 
• They convert light energy into chemical energy stored as glucose. 
• They help in the synthesis of food in green plants.

Labelled diagram of chloroplast:

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Conclusion:

Mitochondria and chloroplasts are double membrane-bound organelles essential for energy production and food synthesis, respectively, playing a vital role in the survival of living organisms.