뒤로Cell Structure and Function: Microscopy, Prokaryotic & Eukaryotic Cells, and Organelles
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Microscopy and Cell Observation
Microscopes: Tools for Visualizing Cells
Microscopes are optical instruments used to visualize spatially small objects, such as cells, that cannot be seen with the naked eye. They are essential for studying cell structure and function in biology.
Light Microscopes: Use visible light to magnify small objects, typically up to 1000x. Suitable for viewing living cells and tissues.
Electron Microscopes: Use beams of electrons for much higher magnification and resolution, allowing visualization of subcellular structures.
Example: The range of the human eye, light microscopes, and electron microscopes covers different scales, from atoms to multicellular organisms.
Types of Electron Microscopes
Electron microscopes are used to study both external and internal cell structures.
Scanning Electron Microscope (SEM): Visualizes cell surfaces in high detail.
Transmission Electron Microscope (TEM): Visualizes internal cell structures by passing electrons through thin sections of specimens.
Example: SEM images show the surface of cells, while TEM images reveal organelles and internal architecture.
Classification of Cells: Prokaryotes and Eukaryotes
Domains of Life
All living organisms are classified into broad domains based on cell type:
Prokaryotic Cells: Lack a nucleus and membrane-bound organelles. Includes Bacteria and Archaea.
Eukaryotic Cells: Have a nucleus and other membrane-bound organelles. Includes Eukarya (plants, animals, fungi, protists).
Domain | Cell Type | Nucleus | Organelles | Cell Size | Cellularity |
|---|---|---|---|---|---|
Bacteria | Prokaryotic | Absent | Absent | Small (1-10 μm) | Unicellular |
Archaea | Prokaryotic | Absent | Absent | Small (1-10 μm) | Unicellular |
Eukarya | Eukaryotic | Present | Present | Large (10-100 μm) | Unicellular/Multicellular |
Features of Bacterial (Prokaryotic) Cells
Bacteria are among the most abundant and diverse organisms on Earth.
Bacterial DNA: Circular in shape, found in a region called the nucleoid.
Ribosomes: Small (70S), responsible for protein synthesis.
Cell Division: Occurs by binary fission, a simple splitting process.
Features of Eukaryotic Cells
Eukaryotic cells contain several membrane-bound organelles, each with specialized functions.
Nucleus: Contains linear DNA and is the site of genetic material storage.
Ribosomes: Larger (80S), responsible for protein synthesis.
Cell Division: Occurs by mitosis and cytokinesis.
Comparing Prokaryotic and Eukaryotic Cells
Key Differences and Similarities
Prokaryotic Cells | BOTH | Eukaryotic Cells |
|---|---|---|
No nucleus | Cell membrane | Has nucleus |
Smaller size (1-10 μm) | DNA as genetic material | Larger size (10-100 μm) |
Less complex | Ribosomes | More complex |
Binary fission | Major biomolecules: carbohydrates, proteins, nucleic acids, lipids | Mitosis/cytokinesis |
No membrane-bound organelles | Membrane-bound organelles |
Eukaryotic Cell Organelles
Animal vs. Plant Cells
Both animal and plant cells are eukaryotic, but they have some distinct organelles.
Animal Cells: Contain lysosomes, centrioles, and lack a cell wall.
Plant Cells: Contain chloroplasts, central vacuole, and a cell wall.
Example: Animal cells have mitochondria, rough and smooth ER, Golgi apparatus, and peroxisomes. Plant cells have all these plus chloroplasts and a large central vacuole.
Ribosomes
Ribosomes are non-membranous organelles found in all cells. They are molecular machines that build proteins by translating messenger RNA (mRNA).
Protein Synthesis: Ribosomes catalyze the formation of peptide bonds during translation.
Location: Ribosomes can be free in the cytoplasm or attached to the rough endoplasmic reticulum (ER).
Example: Ribosomes synthesize proteins, which are essential for cell structure and function.
Map of Eukaryotic Cell Organelles
Major Organelles and Their Functions
Endomembrane System: Includes the nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and vesicles. Responsible for protein and lipid synthesis, modification, and transport.
Energy-Related Organelles: Mitochondria (cellular respiration) and chloroplasts (photosynthesis in plants).
Cytoskeleton: Provides structural support, cell movement, and intracellular transport. Components include microtubules, microfilaments, and intermediate filaments.
Cell Junctions: Structures that connect cells to each other and facilitate communication.
Example: The cytoskeleton is composed of microtubules, microfilaments, and intermediate filaments, but not tight junctions (which are cell junctions).
Additional Info
Equations: Cell size is typically measured in micrometers ().
Classification Table: See above for domain comparison.
Practice Questions: The notes include practice questions to reinforce understanding of cell types, organelles, and microscopy.
