Cell Structure and Organelle Function Pages 179-187

Basic Cell Structure Eukaryotic cells have a variety of internal, membrane-bound structures called organelles. Prokaryotic cells lack these organelles. Prokaryotic cells do contain cytoplasm, a cell membrane, ribosomes, a cell wall, and DNA.

Common Structures All cells contain certain structures. The ribosomes are the site of protein synthesis. They are found in the cytoplasm or attached to the endoplasmic reticulum. The cell (or plasma) membrane is the boundary of the cell. It controls what substances enter and leave the cell. The cytoplasm is the fluid-like substance found inside the cell.

The Control Center The DNA of eukaryotic cells is maintained in a membrane-bound structure called the nucleus. The membrane of the nucleus has pores that allow RNA to leave the nucleus. Prokaryotic cells do not have a nucleus. Their DNA is free-floating in the cytoplasm.

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Energy Transformers Chloroplasts are found only in plant cells. They contain the green pigment chlorophyll. They are the site of photosynthesis and transform light energy into chemical energy in the form of sugar.

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Energy Transformers contd. The mitochondria breaks down glucose to release energy in a form the cell can use. This energy is in the form of ATP. All eukaryotic cells contain mitochondria.

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Cell Boundaries The cell wall is a secondary boundary surrounding the cell membrane. It is only found in plants, fungi, and bacteria. The components of the cell wall vary based on organism.