Flashcards- Ch 6 Part II- Cell Structures

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Nucleus

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A membrane-bound organelle in eukaryotic cells that contains most of the cell’s DNA. It is enclosed by a nuclear envelope and contains all of the information for the cell to function.

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Nuclear Envelope

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A double membrane that encloses the nucleus, consisting of a lipid bilayer with specific proteins. It is perforated by pores that regulate molecular traffic into and out of the nucleus.

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Chromosomes

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Compacted/supercoiled DNA, only visible under a microscope when the cell is about to divide.

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Nucleolus

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A spherical region in the nucleus that makes ribosomes.

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Ribosome

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-A cytoplasmic organelle that is made in the nucleolus;

-Ribosomes are the site of protein synthesis (makes proteins).

-Made of rRNA and protein.

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Ribosomes in High Protein Synthesis Cells

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Cells with high rates of protein synthesis have large numbers of nucleoli and ribosomes (e.g., human liver cells have millions).

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Location of Ribosomes

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May be free (suspended in cytosol) or bound (attached to the ER).

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Endoplasmic Reticulum (ER)

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An extensive network of lipid bilayer membranes that make up tubules and sacs.

2 types: smooth and rough ER

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Smooth ER function

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The function of the Smooth ER varies depending on the type of cell. It synthesizes lipids, phospholipids, and steroids.

In muscle cells, a special type of Smooth ER stores calcium ions, which are essential for muscle contraction.

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Rough ER function

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Folds and modifies proteins, especially those that need to be delivered to different organelles within the cell, or secreted from the cell.