Interactive Animal and Plant Cells Nucleolus: The prominent structure in the nucleus is the nucleolus. The nucleolus produces ribosomes, which move out of the nucleus and take positions on the rough endoplasmic reticulum where they are critical in protein synthesis. Cytosol: The cytosol is the "soup" within which all the other cell organelles reside and where most of the cellular metabolism occurs. Though mostly water, the cytosol is full of proteins that control cell metabolism including signal transduction pathways, glycolysis, intracellular receptors, and transcription factors. Cytoplasm: This is a collective term for the cytosol plus the organelles suspended within the cytosol. Centrosome: The centrosome, or MICROTUBULE ORGANIZING CENTER (MTOC), is an area in the cell where microtubules are produced. During animal cell division, the centrioles replicate (make new copies) and the centrosome divides. Centriole (animal cells only): Each centriole is a ring of nine groups of fused microtubules.
Cell Size and Scale Some cells are visible to the unaided eye The smallest objects that the unaided human eye can see are about 0.1 mm long. That means that under the right conditions, you might be able to see an ameoba proteus, a human egg, and a paramecium without using magnification. Smaller cells are easily visible under a light microscope. To see anything smaller than 500 nm, you will need an electron microscope. Adenine The label on the nucleotide is not quite accurate. How can an X chromosome be nearly as big as the head of the sperm cell? No, this isn't a mistake. The X chromosome is shown here in a condensed state, as it would appear in a cell that's going through mitosis. A chromosome is made up of genetic material (one long piece of DNA) wrapped around structural support proteins (histones). Carbon The size of the carbon atom is based on its van der Waals radius.
A Science Odyssey: You Try It: DNA Workshop An embryonic cell divides again and again. Where there was one cell there are two, then four, then eight,... Each holds all the genetic information needed to create a human being. How, exactly, do these cells make copies of themselves? Hair grows from your head, nonstop, day in and day out. The answers to these questions are DNA replication and protein synthesis. Knowledge of the structure of DNA began with the discovery of nucleic acids in 1869. The activity in this section places you within the cell, involving you with the processes of DNA replication and protein synthesis. If you're interested in finding out more about DNA and protein synthesis, check out the other sections. Related People and Discoveries entries
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