Overview
This lecture covers the basic structure and types of cells, with a focus on the similarities and differences between animal, plant, and bacterial cells.
What Are Cells?
- Cells are the basic building blocks of life and the smallest unit that can replicate independently.
- Multicellular organisms (animals, plants) have many cells for growth and repair, not individual reproduction.
- Unicellular organisms (like bacteria) consist of a single cell that acts as the whole organism.
- Humans have over 40 trillion cells of various types.
Structure of Animal and Plant Cells (Eukaryotic Cells)
- Both animal and plant cells are surrounded by a cell membrane that controls substance movement in and out.
- Both contain a nucleus, which stores DNA and controls cell activities.
- Cytoplasm is a jelly-like substance where chemical reactions occur and organelles are suspended.
- Mitochondria provide energy via aerobic respiration by breaking down glucose.
- Ribosomes are the site of protein synthesis.
Unique Features of Plant Cells
- Plant cells have a rigid cell wall made of cellulose for support and structure.
- A permanent vacuole contains cell sap (water, sugars, salts) for storage.
- Chloroplasts contain chlorophyll for photosynthesis, absorbing sunlight to make glucose.
Structure of Bacterial Cells (Prokaryotic Cells)
- Bacterial cells have a cell membrane, cell wall, cytoplasm, and ribosomes.
- No mitochondria or chloroplasts are present in bacterial cells.
- Genetic material is a single circular strand of DNA (nucleoid) floating in the cytoplasm.
- Some bacteria have plasmids (small rings of DNA with extra genes, e.g., antibiotic resistance).
- Flagella are thread-like structures for movement in some bacteria.
Key Terms & Definitions
- Cell membrane — controls entry and exit of substances in a cell.
- Nucleus — stores DNA and directs cell activities.
- Cytoplasm — jelly-like substance where reactions happen.
- Mitochondria — organelles that release energy from glucose.
- Ribosomes — structures where proteins are made.
- Cell wall — strong outer layer in plants and bacteria for support.
- Permanent vacuole — storage sac in plant cells filled with cell sap.
- Chloroplast — plant cell organelle for photosynthesis.
- Chlorophyll — pigment in chloroplasts for light absorption.
- Prokaryotic cell — cell without a nucleus (e.g., bacteria).
- Eukaryotic cell — cell with a nucleus (e.g., plants, animals).
- Plasmid — extra small DNA ring in some bacteria.
- Flagellum — tail-like structure for bacterial movement.
Action Items / Next Steps
- Practice labeling cell structures and describing their functions.
- Review the differences between animal, plant, and bacterial cells.