By Carolyn Csanyi
Updated Aug 30, 2022
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Plants and animals are composed of cells, the fundamental units of life. Each cell houses specialized structures—organelles—that carry out distinct functions essential for the cell's survival and the organism's health. While many organelles are shared across eukaryotes, plant cells possess unique features such as cell walls and chloroplasts.
All eukaryotic cells—plants and animals—contain a true nucleus surrounded by a nuclear envelope. The nucleus stores DNA and orchestrates cellular processes, ensuring that genetic information is accurately transmitted and regulated.
The ER is a vast, interconnected membrane network that spans the cytoplasm. Rough ER, studded with ribosomes, synthesizes proteins destined for secretion or membrane integration. Smooth ER, lacking ribosomes, specializes in lipid synthesis, detoxification, and calcium storage.
Often described as a stack of flattened cisternae, the Golgi complex modifies, sorts, and packages proteins and lipids originating from the ER. It generates secretory vesicles and contributes to the formation of lysosomes—organelles equipped with enzymes that degrade macromolecules.
Vesicles are small, membrane-bound carriers that shuttle molecules between organelles or to the plasma membrane. Vacuoles, particularly prominent in plant cells, maintain turgor pressure, store nutrients, and regulate water balance. Animal cells contain smaller vacuoles that participate in storage and waste disposal.
These peanut‑shaped organelles are the powerhouses of the cell, converting glucose and oxygen into ATP through cellular respiration. Mitochondria are present in nearly all eukaryotic cells and are believed to have originated from an ancestral symbiotic bacterium.
Exclusive to plant cells and some algae, chloroplasts house chlorophyll pigments that capture sunlight. Through photosynthesis, they transform CO₂ and H₂O into glucose, supplying energy for both the plant and the wider ecosystem. Chloroplasts, like mitochondria, are thought to have arisen from endosymbiotic bacteria.
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