Chapter 1 - Introduction to Cells

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What are cells?

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Cells are the smallest living units that make up all organisms. They are self-contained, membrane-bound compartments that carry out the essential processes of life. Cells maintain internal environments, carry genetic information, convert energy, synthesize biomolecules, and reproduce. While some organisms are unicellular (e.g., bacteria), others are multicellular with cells that differentiate and specialize.

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What are the basic features of a cell?

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All cells share several fundamental features: Plasma membrane, Genetic material (DNA), Ribosomes, Cytosol, Metabolism & replication.

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How did cells evolve and what is the role of mutation?

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Cells evolved from a common ancestor 3.5–3.8 billion years ago. Random mutations during replication can alter protein function, affecting the organism’s fitness. Beneficial mutations are preserved through natural selection, leading to evolutionary adaptation.

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Why is microscopy important in cell biology?

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Microscopy allowed scientists to discover and study cells, revealing internal structures like organelles and helping relate form to function. Advances in microscopy have enhanced resolution and enabled dynamic studies of living cells.

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What are the advantages and disadvantages of light vs. electron microscopy?

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Light Microscopy: Advantages - Can visualize live cells in color, less expensive, easy to use. Disadvantages - Limited resolution (~0.2 µm). Electron Microscopy: Advantages - Much higher resolution (<1 nm). Disadvantages - Only dead, fixed samples can be used; costly and complex.

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How are features labeled in light microscopy?

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Features are labeled using Dyes/Stains, Fluorescent antibodies, and Genetic fusion with fluorescent proteins.

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How does fluorescence work in microscopy?

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Fluorophores absorb short-wavelength light and emit longer-wavelength visible light, allowing for specific visualization of cellular structures.

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What is the sensitivity of fluorescence microscopy?

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Fluorescence microscopy is highly sensitive because it measures emitted light, providing a stronger and more specific signal.

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What is resolution in microscopy?

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Resolution refers to the minimum distance between two distinguishable points. Super-resolution microscopy techniques can achieve up to 10x better resolution than conventional light microscopy.

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What are fluorescent proteins and their use?

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GFP and related proteins are naturally fluorescent and used in live-cell imaging. They fluoresce without needing additional cofactors.