Vacuoles: Study Notes

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Vacuoles, Peroxisomes, and Glyoxysomes

Vacuole

• Definition: Vacuoles are non-protoplasmic, liquid-filled cavities in the cytoplasm, surrounded by a membrane called the tonoplast.
• Occurrence: Vacuoles are prominent in plant cells and typically temporary in animal cells.
• Function: They store various substances, aid in plant defense, and contribute to cell growth and enlargement.
• Enzymatic Activity: Vacuoles are rich in hydrolytic enzymes, including proteases, ribonucleases, and glycosidases, which help break down cellular materials.

2. Peroxisome

• Definition: Peroxisomes are single membrane-bounded micro-bodies that play a crucial role in cellular metabolism.
• Occurrence: These organelles are found in cells that metabolize alcohol, and are present in yeast, protozoa, and many plant cells.
• Function: Peroxisomes detoxify alcohol and convert hydrogen peroxide (H₂O₂) into water (H₂O), thus protecting the cell from oxidative damage.
• Enzymatic Activity: Peroxisomes produce enzymes such as peroxidase and glycolic acid oxidase, which aid in breaking down harmful compounds.

3. Glyoxysome

• Definition: Glyoxysomes are micro-bodies covered by a single membrane, specialized for specific metabolic processes.
• Occurrence: These organelles are found in plant cells, especially in germinating seeds that are rich in lipids.
• Function: Glyoxysomes oxidize stored fatty acids, converting them into energy that supports new plant growth during germination.
• Enzymatic Activity: Glyoxysomes secrete enzymes that metabolize fatty acids, enabling the plant to generate energy from these stored compounds.

These organelles each perform unique and essential roles in cellular function, ranging from storage and detoxification to energy production, making them vital for the overall health and survival of the cell.

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