뒤로Chapter4: Cell Structure and Function: Study Notes for General Biology
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Chapter 4: Cell Structure
Overview
This chapter introduces the fundamental concepts of cell structure, including the cell theory, types of cells, and the organization of cellular components. Understanding these topics is essential for studying all aspects of biology, as cells are the basic units of life.
Cell Theory
Prokaryotic Cells
Eukaryotic Cells
Endomembrane System
Mitochondria
Chloroplasts
Cytoskeleton
Cell Theory
Foundations of Cell Theory
The cell theory is a cornerstone of modern biology, describing the properties and significance of cells in living organisms.
Historical Development: Cells were first observed by Robert Hooke in 1665 using a microscope. Later, Matthias Schleiden (1838) and Theodor Schwann (1839) conducted foundational studies and proposed the cell theory.
Principles of Cell Theory:
All organisms are composed of cells.
Cells are the smallest living things.
Cells arise only from pre-existing cells.
Cells today represent a continuous line of descent from the first living cells.
Example: All plants, animals, fungi, and microorganisms are made up of cells, whether unicellular or multicellular.
Scale of Cellular Components
Microscopy and Cell Size
Cells and their components vary greatly in size, requiring different types of microscopes for observation.
Visible without Microscope: Some cells (e.g., human egg) and multicellular organisms can be seen with the naked eye.
Light Microscope: Most cells and larger organelles (e.g., nucleus, mitochondria) are visible with a light microscope.
Electron Microscope: Smaller structures (e.g., ribosomes, viruses, macromolecules) require electron microscopy for visualization.
Additional info: The typical diameter of a eukaryotic cell is 10–100 μm, while prokaryotic cells are usually 1–10 μm.
Cells: Basic Unit of Life
Cell Structure and Types
The cell is the basic structural and functional unit of every organism. Cells can be unicellular or multicellular.
Prokaryotic Cells: Generally smaller, lack a nucleus, and have fewer organelles.
Eukaryotic Cells: Larger, possess a nucleus, and contain membrane-bound organelles.
Example: Escherichia coli is a prokaryotic bacterium; human skin cells are eukaryotic.
Comparison of Prokaryotic and Eukaryotic Cells
Key Differences
Prokaryotic and eukaryotic cells differ in structure, complexity, and organization.
Feature | Prokaryotic Cells | Eukaryotic Cells |
|---|---|---|
Nucleus | No (nucleoid region) | Yes (membrane-bound) |
Organelles | Few, not membrane-bound | Many, membrane-bound |
Size | Smaller (1–10 μm) | Larger (10–100 μm) |
Examples | Bacteria, Archaea | Plants, Animals, Fungi, Protists |
Additional info: Both cell types have a plasma membrane, cytoplasm, and ribosomes.
Cellular Components
Common Features of All Cells
Despite differences, all cells share certain structural features:
Plasma Membrane: A phospholipid bilayer that encloses the cell and regulates transport.
Cytoplasm: Semifluid matrix inside the cell.
Ribosomes: Sites of protein synthesis.
DNA: Genetic material located in the nucleoid (prokaryotes) or nucleus (eukaryotes).
Summary Table: Cell Structures in Prokaryotes vs. Eukaryotes
Structure | Prokaryotic Cell | Eukaryotic Cell |
|---|---|---|
Plasma Membrane | Present | Present |
Cell Wall | Usually present (peptidoglycan) | Plants (cellulose), Fungi (chitin), Animals (absent) |
Nucleus | Absent (nucleoid) | Present |
Organelles | Absent | Present (e.g., mitochondria, ER) |
Ribosomes | Present (smaller) | Present (larger) |
Additional info:
Cells may be unicellular (e.g., bacteria, protists) or multicellular (e.g., plants, animals). The organization and specialization of cells enable complex life forms.
