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Section 3 Nucleus and Ribosomes

Section 3 Nucleus and Ribosomes. The Nucleus. Vacuoles store DNA and ribosomes Genes that are not in vacuoles are contained in the mitochondria and cytoplasm. Nucleus has a nuclear envelope to separate itself from the cytoplasm. Nuclear envelope has layers of membranes .

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Section 3 Nucleus and Ribosomes

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  1. Section 3Nucleus and Ribosomes

  2. The Nucleus • Vacuoles store DNA and ribosomes • Genes that are not in vacuoles are contained in the mitochondria and cytoplasm. • Nucleus has a nuclear envelope to separate itself from the cytoplasm. • Nuclear envelope has layers of membranes. • Nucleus contains most of the genes in a Eukaryotic cell.

  3. The Nucleus (cont.) • The two membrane layers in the nuclear envelope are made up of lipid bi-layers with associated proteins. • Each bi-layer is separated by a space of about 20-40nm. • The nuclear envelope has pores that are 100nm in diameter. • An intricate protein structure called a pore-complex lines each pore and plays an important role in the cell by regulating the entry and exit of most proteins and RNA as well as large complexes of macromolocules.   

  4. Chromatin • The chromosomes are made up of chromatin. • Chromatin look s like a dispersed mass in the nucleus until a cell gets ready to split. When it starts to split, the chromatin first coils up into separate chromosomes. Then they split. • Nucleolus- synthesizes RNA for ribosomes.

  5. Ribosomes • Ribosomes are complexes made of ribosomal RNA and protein. • Carry out protein synthesis • Cells with high rates of protein synthesis typically have a large number of ribosomes. • Cells active in protein synthesis also have prominent nucleoli.

  6. Ribosomes (cont.) • Ribosomes build proteins in two ways. 1) Free Ribosomes 2) Bound ribosomes

  7. Free Ribosomes • Free ribosomes- suspended in the cytosol • Most function inside the cytosol • Ex: Enzymes able to catalyze the first steps of sugar breakdown.

  8. Bound Ribosomes • Bound ribosomes- attached to the outside of the endoplasmic reticulum or nuclear envelope • Most create proteins made for packaging within organelles such as lysosomes or for secretion, which is an export from the cell. • Ex: The cells of the pancreas that secrete digestive enzymes

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