Lecture Notes on Cell Structure and Function
Summary
This lecture focuses on the structural and functional aspects of cells, the smallest living units in organisms. The discussion differentiates between the two main categories of cells: eukaryotic and prokaryotic. Special emphasis is placed on the various organelles within eukaryotic cells, their roles, and a comparison of plant and animal cells, detailing their unique structures.
Key Points
General Characteristics of Cells
- All cells share three principal components:
- Cell Membrane: Acts as a barrier between the inside of the cell and its environment.
- Cytoplasm: A gel-like fluid inside the cell.
- DNA: The genetic material of the cell.
Categories of Cells
- Eukaryotic Cells
- Contains organelles, including a nucleus.
- More complex and found in plants and animals.
- Organelles perform specific functions within the cell.
- Prokaryotic Cells
- Lack a nucleus and membrane-bound organelles.
- Genetic material is not enclosed in a nucleus.
- Always unicellular, e.g., bacteria.
Organelles and Their Functions
- Nucleus: Control center containing DNA.
- Chromatin: DNA in a tangled form inside the nucleus.
- Nucleolus: Site of ribosome synthesis.
- Ribosomes: Protein synthesis.
- Can be free in cytoplasm or attached to the ER.
- Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes, transports proteins.
- Smooth ER: No ribosomes, involved in lipid synthesis.
- Golgi Apparatus: Modifies, sorts, and packages proteins.
- Vacuoles: Storage sacs, prominent in plant cells for storing water.
- Lysosomes: Contain enzymes to breakdown waste (mainly in animal cells).
- Mitochondria: Powerhouse of the cell, produces ATP through cellular respiration.
- Cytoskeleton: Provides cell structure, made up of microfilaments and microtubules.
Additional Structures in Specific Cells
- Chloroplasts: Found in plant cells, site of photosynthesis.
- Cell Wall: Provides support and protection in plant cells.
- Cilia and Flagella:
- Cilia: Found in respiratory tract cells, aid in expelling particles.
- Flagella: Help in movement; e.g., bacteria have flagella; sperm cells in humans.
Unique Features
- Plant Cells:
- Have chloroplasts, cell wall, and large central vacuole.
- Animal Cells:
- Do not have a cell wall or chloroplasts.
- Presence of lysosomes and smaller vacuoles.
Conclusion
- Eukaryotic Cells: Complex, with nucleus and organelles, found in plants and animals.
- Prokaryotic Cells: Simpler, unicellular organisms without a nucleus or membrane-bound organelles.
- Core similarities include the presence of a cell membrane, cytoplasm, and genetic material.
- Distinct organelles within eukaryotic cells perform specialized functions vital for cell survival and function.