Cell Theory & Cell Structure (PDF)

## Cell Theory - **Leeuwenhoek** - First scientist to observe single-celled organisms (bacteria) he named animalcules. - **Schleiden** - Observed all plants were made of cells. - Proposed nucleus (center of cell) was responsible for development. - **Schwann** - Studied animal cells & observed the s...

## Cell Theory - **Leeuwenhoek** - First scientist to observe single-celled organisms (bacteria) he named animalcules. - **Schleiden** - Observed all plants were made of cells. - Proposed nucleus (center of cell) was responsible for development. - **Schwann** - Studied animal cells & observed the same characteristics. - **Schleiden/Schwann** reasoned where there's a nucleus, there's a cell. - Also determined cells are the basic unit of life. - **Virchow** - Observed bone cells develop from pre-existing cells. - Discovered cells divide to produce more cells, cells arise from cells. ## Parts of a cell - The basic unit of life & must perform: - Obtain food/energy. - Reproduction. - Convert energy. - Carry out chemical reactions. - Eliminate wastes. - Growth. ## Cell Theory - 3 Points of cell theory: - Cells are the smallest functional unit of life. - All organisms are composed of one or more cells. - All cells are produced from other cells. ## Abiogenesis & Spontaneous Generation - **Artistotle** created Abiogenesis & Spontaneous generation. - Abiogenesis - the idea that life could emerge from non-living matter. - **Redi** believed abiogenesis was not true. - Experiment: meat in jars, one sealed, one open. - Open had life, closed did not. - **Pasteur** also believed abiogenesis was not true. - Experiment: glass flask with an S-shaped neck. - Filled flasks with broth, then boiled broth. - The S-shaped neck allowed air to enter, but any micro-organisms would be stuck. - Both broth were clear after days. - Created Biogenesis - the idea that life could only emerge from living matter. ## Hooke - Used a compound light microscope, observed a cork cell, & noticed "tiny rooms" he named cells. ## Cell size and Function - **Why cells so small** - Diffusion over long distances is slow; minimizing distance for access to oxygen, substances, nutrients, etc., is faster. ## Plant structure & specialization - **Cell specialization in plants** - 4 organs in plants: roots, stems, leaves, flowers. - **Photosynthesis** occurs in chloroplasts of plant cells. - 6CO₂ + 6H₂O + Light (energy) -> C₆H₁₂O₆ + 6O₂ - **Cellular Respiration** occurs in mitochondria of cells. - C₆H₁₂O₆+ 6O₂ -> 6CO₂ + 6H₂O + Energy (ATP) ## Parts of a leaf cell - **Epidermal tissue** - Flat single layer of cells on upper/lower leaf. - Protects leaf, has no chloroplasts; the clear layer prevents evaporation through the leaf. - **Palisade tissue** - Long narrow columns of cells under epidermal tissue. - Main area of photosynthesis, has chloroplasts. - **Spongy tissue** - Round loosely packed cells under palisade tissue. - Main area of water/gas exchange, minor photosynthesis, some chloroplasts. - **Stomata** - Tiny openings on the bottom of the leaf; allows exchange of CO₂, O₂, H₂O - **Guard cells** - Cover stoma to allow substances in/out. - **Vascular tissue** - Tubes arranged in vascular bundles. - *Xylem* - Carries water/minerals from roots to leaves. - *Phloem* - Carries sugars from leaves to the rest of the plant.