A description of mitochondria tiny organelles found in nearly all eukaryotic cells

endoplasmic reticulum

For example, alcohol is detoxified by peroxisomes in liver cells. However, the level of organization varies within the cells of different organisms.


This compartment eventually evolves into a nucleus. They allow different functions to be compartmentalized in different areas of the cell. Most are membrane-bound structures that are the sites of specific types of biochemical reactions.

Prokaryotic cell

Individual mitochondria are capsule shaped, with an outer membrane and an undulating inner membrane, which resembles protruding fingers. For instance, some pancreas cells which make insulin for release into the bloodstream contain large numbers of storage granules that store insulin until the cell receives a signal to release it. Animal cells each have a centrosome and lysosomes, whereas plant cells do not. A prokaryotic host cell incorporates another prokaryotic cell. This organelle has an outer membrane and an inner membrane. Throughout the course of evolution, organelles such as mitochondria and chloroplasts a form of plastid may have arisen from engulfed prokaryotes. Fungal and protistan cells also have cell walls. Figure 9. Moreover, nearly all eukaryotic organelles are separated from the rest of the cellular space by a membrane, in much the same way that interior walls separate the rooms in a house. Mitochondria Mitochondria are rod-shaped organelles that can be considered the power generators of the cell, converting oxygen and nutrients into adenosine triphosphate ATP. Different organelles play different roles in the cell — for instance, mitochondria generate energy from food molecules; lysosomes break down and recycle organelles and macromolecules; and the endoplasmic reticulum helps build membranes and transport proteins throughout the cell. The nucleus stores the hereditary material of the cell: The nucleus is the control center of the cell. Eventually, according to this view, the larger organism developed into the eukaryotic cell and the smaller organism into the mitochondrion. However, the level of organization varies within the cells of different organisms. Enzymes within the lysosomes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles.

In addition, plant cells have a cell wall, a large central vacuole, chloroplasts, and other specialized plastids, whereas animal cells do not. However, water-soluble materials—such as glucose, amino acids, and electrolytes—need some assistance to cross the membrane because they are repelled by the hydrophobic tails of the phospholipid bilayer.

Microvilli, shown here as they appear on cells lining the small intestine, increase the surface area available for absorption.

mitochondria facts

The challenges associated with energy generation limit the size of prokaryotes.

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Eukaryotic Cell: Structure and Function