Question

which type of organelle is not surrounded by a membrane?
a ribosomes
b endoplasmic reticulum
c lysosomes
d mitochondria

Explanation:

• Ribosomes are non - membrane - bound organelles. They are composed of RNA and proteins and are involved in protein synthesis.
• The endoplasmic reticulum (both rough and smooth) is a membrane - bound organelle. The rough endoplasmic reticulum has ribosomes attached to its surface, and the smooth endoplasmic reticulum is involved in lipid synthesis and detoxification.
• Lysosomes are membrane - bound organelles that contain hydrolytic enzymes for breaking down waste materials, cellular debris, and foreign particles.
• Mitochondria are double - membrane - bound organelles. They are the powerhouses of the cell, generating ATP through cellular respiration.

Answer:

A. ribosomes