Describe the structure of a generalized eukaryotic animal cell. Indicate the ways in which a nonphotosynthetic prokaryotic cell would differ in structure from this generalized eukaryotic animal cell.
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Answer: A generalized eukaryotic animal cell has a complex structure with multiple organelles, each with specialized functions. The key features include:
1. Plasma Membrane: This is a semi-permeable membrane that encloses the cell, controlling the entry and exit of substances.
2. Cytoplasm: The interior of the cell, excluding the nucleus, is filled with a gel-like substance called cytoplasm where organelles are suspended.
3. Nucleus: Enclosed by the nuclear envelope, the nucleus houses DNA and is the control center of the cell. It contains the nucleolus, where ribosomal RNA is synthesized.
4. Mitochondria: Known as the powerhouses of the cell, mitochondria generate ATP through cellular respiration.
5. Endoplasmic Reticulum (ER): There are two types—rough ER, studded with ribosomes, plays a role in protein synthesis, and smooth ER, involved in lipid synthesis and detoxification.
6. Golgi apparatus: Functions in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.
7. Lysosomes: These contain digestive enzymes that break down waste materials and cellular debris.
8. Cytoskeleton: A network of protein fibers that maintains the cell's shape, secures some organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move independently.
9. Ribosomes: Sites of protein synthesis, they can be found either bound to the rough ER or floating freely in the cytoplasm.
10. Vesicles and Vacuoles: Membrane-bound sacs used for storage and transport. Vacuoles are larger and more common in plant cells.
11. Centrosomes and Centrioles: Involved in organizing microtubules and are important for cell division.
Differences between a nonphotosynthetic prokaryotic cell and a generalized eukaryotic animal cell include:
1. Nucleoid vs. Nucleus: Prokaryotic cells have a nucleoid region where their DNA is located, rather than a true nucleus with a membrane.
2. Cell wall: Most prokaryotes have a cell wall, while animal eukaryotic cells do not.
3. Size and complexity: Eukaryotic cells are generally larger and more complex than prokaryotic cells.
4. Organelles: Prokaryotic cells lack membrane-bound organelles. In contrast, eukaryotic cells have numerous organelles, each with distinct functions.
5. Ribosomes: Prokaryotic ribosomes are smaller (70S) than those in eukaryotes (80S).
6. Reproduction: Prokaryotes reproduce via binary fission, whereas eukaryotic cells generally undergo mitosis.