Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Microbodies are minute, membrane-bound vesicles that contain various enzymes and are present in both plant and animal cells.
They are considered as part of the cytoplasm and are typically to in diameter.
Peroxisomes: These are microbodies involved in the metabolism of hydrogen peroxide (). They contain oxidative enzymes such as catalase and urate oxidase.
In green leaves of plants, peroxisomes carry out photorespiration (the cycle) in association with chloroplasts and mitochondria.
Glyoxysomes: These are specialized peroxisomes found in plant tissues, particularly in germinating fatty seeds (e.g., castor, peanut).
Glyoxysomes contain enzymes for the glyoxylate cycle, which converts stored lipids (fatty acids) into carbohydrates (sugar) to provide energy for the developing seedling.
Sphaerosomes: Found primarily in plant cells, these microbodies are involved in the synthesis and storage of lipids and are sometimes referred to as 'plant lysosomes'.
📐Formulae
💡Examples
Problem 1:
During the germination of a castor seed, which organelle is responsible for the conversion of stored fats into soluble sugars?
Solution:
The Glyoxysome.
Explanation:
Castor seeds are oil-rich seeds. During germination, they require carbohydrates for energy and growth. Glyoxysomes contain enzymes like isocitrate lyase and malate synthase which facilitate the conversion of fats into sugars through the glyoxylate cycle.
Problem 2:
What is the primary role of catalase enzyme found within peroxisomes?
Solution:
To decompose toxic hydrogen peroxide () into water () and oxygen ().
Explanation:
Many oxidative reactions in the cell produce as a byproduct, which is highly reactive and damaging. Catalase ensures the rapid breakdown of this toxin: .