Notes on Plant Cells (eg. of eukaryotic cells)
1. Introduction
- Definition: Plant cells are the basic structural and functional units of plants, categorized as eukaryotic cells with unique features like cell walls and chloroplasts.
- Key Characteristics over other cells:
- Presence of a rigid cell wall made of cellulose.
- Specialized plastids like chloroplasts for photosynthesis.
- Large vacuoles for storage and maintaining turgor pressure.
2. Historical Perspective
- Early Observations:
- Robert Hooke (1665) first described plant cells while observing cork tissue under a microscope.
- Advancements:
- Discovery of the nucleus by Robert Brown (1831).
- Schleiden and Schwann (1838-1839) developed the cell theory, emphasizing that all plants and animals are composed of cells.
3. Components and Their Functions
- Cell Wall:
- Provides structural support and protection.
- Composed of cellulose, hemicellulose, and lignin.
- Plasma Membrane:
- Regulates the transport of substances into and out of the cell.
- Cytoplasm:
- Medium for biochemical reactions and organelle suspension.
- Nucleus:
- Contains genetic material (DNA) and controls cell activities.
- Chloroplasts:
- Site of photosynthesis.
- Contains pigments like chlorophyll.
- Mitochondria:
- The powerhouse of the cell, responsible for ATP production.
- Vacuoles:
- Store nutrients, and waste products, and contribute to cell turgor.
- Endoplasmic Reticulum:
- Rough ER: Protein synthesis.
- Smooth ER: Lipid synthesis and detoxification.
- Golgi Apparatus:
- Modifies, sorts, and packages proteins and lipids.
- Ribosomes:
- Sites of protein synthesis.
- Peroxisomes:
- Detoxify harmful substances and break down fatty acids.
- Cytoskeleton:
- Provides a structural framework and facilitates intracellular transport.
4. Biochemical Composition and Biosynthesis
- Primary Biomolecules:
- Carbohydrates: Cellulose, starch, and sugars for structure and energy storage.
- Proteins: Enzymes, structural proteins, and signaling molecules.
- Lipids: Components of membranes and energy reserves.
- Nucleic Acids: DNA and RNA for genetic information and protein synthesis.
- Biosynthetic Pathways:
- Photosynthesis in chloroplasts synthesizes glucose.
- Protein synthesis occurs in ribosomes via transcription and translation.
- Lipid biosynthesis occurs in the smooth ER.
5. Degradation and Recycling
- Cellular Mechanisms:
- Autophagy: Vacuoles or lysosome-like organelles break down cellular debris.
- Enzymatic Breakdown:
- Cell wall components are degraded by cellulase and hemicellulase.
- Proteins are degraded by proteasomes.
- Programmed Cell Death:
- Essential for processes like leaf shedding and xylem differentiation.
Reference:
1. https://www.accessscience.com/highwire_display/entity_view/node/387129/focus_view
2. https://www.uou.ac.in/sites/default/files/slm/BSCZO-102.pdf
3. Courtesy: https://www.researchgate.net/profile/Alison-Ferguson-Sinclair/publication/237155186/figure/fig1/AS:281551578386433@1444138535287/Diagrammatic-representation-of-a-generalized-plant-cell-depicting-the-principal_W640.jpg
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