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The eukaryotic cell contains organelles, which are defined as membrane-bound structures such as nucleus, mitochondria, chloroplasts, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, peroxisomes, etc. Prokaryotic cells do not have organelles. For animal cells, the cell surface consists of the plasma membrane only, but plant cells have an additional layer called cell wall, which is made up of cellulose and other polymers.
The nucleus is the largest organelle in an eukaryotic cell. It is not part of the cytoplasm. By definition, cytoplasm is everything inside the plasma membrane except the nucleus. Under microscope, the nucleus shows two distinct areas. The darker area is called nucleolus, and the lighter area is known as nucleoplasm. Cytosol is the cytoplasm excluding organelles. It contains cytoskeleton, ribosomes, proteins and other smaller molecules.
Book Sections: The Dynamic Plant Cell Wall - From Molecular Cell Biology by Lodish et al. The Plant Cell - From Kimball's Biology Pages.
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