3.1 The Cellular Level of Organization

• All organisms are composed of cells, which arise from preexisting cells.
• A microscope is usually needed to see a cell because most cells are quite small.

1. List three main ideas of the cell theory.
   Answer

2. Why are cells so small?
   Answer
   

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    Surface to Volume

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    Cell Size

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    Cell Size

3.2 Eukaryotic Cells

• All cells have a plasma membrane that regulates the entrance and exit of molecules into and out of the cell. Some cells also have a protective cell wall.
• Eukaryotic cells have a number of membranous organelles that carry out specific functions.
• The nucleus controls the metabolic functions and the structural characteristics of the cell.
• A system of membranous canals and vacuoles work together to produce, modify, transport, store, secrete, and/or digest macromolecules.
• Mitochondria and chloroplasts transform one form of energy into another. Mitochondria produce ATP and chloroplasts produce carbohydrates.
• The cell has a cytoskeleton composed of microtubules and microfilaments. The cytoskeleton gives the cell shape and allows it and its organelles to move.
• Centrioles are related to cilia and flagella, which enable the cell to move.

1. What are the components of the endomembrane system and what is its function?
   Answer
   
   
2. What are the three types of filaments and tubules that make up the cytoskeleton of a eukaryotic cell?
   Answer
   

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    Endomembrane
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Labeling Exercises
Animal Cell 1 (46.0K)
Animal Cell 2 (44.0K)
Plant Cell 1 (56.0K)
Plant Cell 2 (54.0K)
Anatomy of the Nucleus (31.0K)
Golgi Apparatus (48.0K)
Mitochondrion Structure (53.0K)
Chloroplast Structure (48.0K)
The Cytoskeleton (42.0K)

3.3 Prokaryotic Cells

• In contrast to the eukaryotic cell, the prokaryotic cell lacks a well-defined nucleus.

1. Explain the statement, "Although bacteria seem simple, they are metabolically diverse."
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2. What are plasmids?
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Nonphotosynthetic Bacterium (27.0K)
Cyanobacterium (55.0K)

3.4 Evolution of the Eukaryotic Cell

• The endosymbiotic hypothesis suggests that certain organelles of eukaryotic cells were once prokaryotic cells.

1. How did prokaryotic cells give rise to eukaryotic cells according to the endosymbiotic hypothesis?
   Answer
   

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    Eukaryotes