뒤로Eukaryotic Cell Structure and Function
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Eukaryotic Cells
Overview of Eukaryotic Cells
Eukaryotic cells are complex cells characterized by the presence of a nucleus and membrane-bound organelles. They are found in animals, plants, fungi, and protists. The internal organization of eukaryotic cells allows for compartmentalization of various cellular processes.
Plasma membrane: A selectively permeable barrier that surrounds the cell, controlling the movement of substances in and out.
Cytosol (cytoplasm): The fluid portion inside the cell where organelles are suspended and many metabolic reactions occur.
Ribosomes: Small complexes of RNA and protein that are the sites of protein synthesis.
Organelles: Specialized structures within the cell that perform distinct functions (e.g., nucleus, mitochondria, endoplasmic reticulum).
Example: Animal cells contain mitochondria for energy production, a nucleus for genetic information storage, and lysosomes for digestion of cellular waste.
The Nucleus
Structure and Function of the Nucleus
The nucleus is the control center of the eukaryotic cell, containing most of the cell's genetic material and coordinating activities such as growth, metabolism, and reproduction.
Nuclear envelope: A double membrane that encloses the nucleus, separating it from the cytoplasm.
Nucleoplasm: The semi-fluid substance inside the nucleus where chromatin and nucleolus are found.
Chromatin: DNA and associated proteins (histones) that condense to form chromosomes during cell division.
Nucleolus: A dense region within the nucleus where ribosomal RNA (rRNA) is synthesized and ribosome subunits are assembled.
Nuclear pores: Large protein complexes that span the nuclear envelope, allowing the regulated exchange of materials (such as RNA and proteins) between the nucleus and cytoplasm.
Nuclear lamina: A network of intermediate filaments (lamin proteins) that provides structural support to the nucleus and helps organize chromatin.
Example: The nucleolus is especially prominent in cells that are actively producing proteins, such as pancreatic cells that secrete digestive enzymes.
Key Terms and Concepts
Organelle: A specialized subunit within a cell that has a specific function and is usually separately enclosed within its own lipid bilayer.
Ribosome: A molecular machine, either free in the cytosol or bound to the endoplasmic reticulum, that translates mRNA into protein.
Chromatin: The complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells.
Summary Table: Major Components of the Eukaryotic Cell
Component | Structure | Function |
|---|---|---|
Plasma membrane | Phospholipid bilayer with embedded proteins | Controls entry and exit of substances |
Cytosol | Gel-like fluid | Site of metabolic reactions |
Nucleus | Double membrane, contains DNA | Stores genetic information, controls cell activities |
Ribosomes | RNA and protein complexes | Protein synthesis |
Organelles | Membrane-bound structures | Specialized cellular functions |
Additional info:
The nuclear envelope is continuous with the endoplasmic reticulum, facilitating transport between the nucleus and cytoplasm.
Ribosomes can be free in the cytosol or attached to the rough endoplasmic reticulum, depending on the destination of the proteins they synthesize.
