Cells Unit Science Notes - PDF

1.A Cell Theory, Scientists, and Contributions Cell Theory states: 1.​ All living organisms are made of cells. 2.​ The cell is the basic unit of structure and function in living organisms. 3.​ All cells arise from pre-existing cells. Key Scientists and Contributions: ​ Robert Hooke (...

1.A Cell Theory, Scientists, and Contributions Cell Theory states: 1.​ All living organisms are made of cells. 2.​ The cell is the basic unit of structure and function in living organisms. 3.​ All cells arise from pre-existing cells. Key Scientists and Contributions: ​ Robert Hooke (1665): ○​ Discovered and named “cells” after observing cork under a microscope. ​ Anton van Leeuwenhoek (1670s): ○​ First to observe living cells (e.g., bacteria, protozoa) under a microscope. ​ Henri Dutrochet (1824) Concluded that cells are the basic unit of life. ​ Matthias Schleiden (1838): ○​ Proposed that all plants are made of cells. ​ Theodor Schwann (1839): ○​ Proposed that all animals are made of cells and co-developed the cell theory with Schleiden. ​ Rudolf Virchow (1855): ○​ Stated that “All cells come from pre-existing cells,” completing the modern version of cell theory. 2. Parts of a Cell Basic Cell Structure: ​ Cell Membrane: Semi-permeable membrane that controls what enters and exits the cell. ​ Cytoplasm: Gel-like substance where cell processes occur. ​ Nucleus: Contains genetic material (DNA) and controls cell activities. ○​ Nuclear Membrane: Surrounds the nucleus. ○​ Nucleolus: Produces ribosomes. ​ Ribosomes: Site of protein synthesis. ​ Mitochondria: Powerhouse of the cell; produces energy (ATP) through cellular respiration. ​ Endoplasmic Reticulum (ER): ○​ Rough ER: Has ribosomes; involved in protein synthesis. ○​ Smooth ER: No ribosomes; synthesizes lipids and detoxifies.  ​ Golgi Apparatus: Modifies, sorts, and packages proteins for secretion. ​ Lysosomes: Contain enzymes for digestion and waste removal. ​ Vacuole: Stores water, nutrients, and waste products (larger in plant cells). 3. Parts of a Microscope ​ Eyepiece (Ocular Lens): The lens you look through, typically 10x magnification. ​ Objective Lenses: Lenses of various magnifications (usually 4x, 10x, 40x, and 100x). ​ Stage: The platform where the slide is placed. ​ Stage Clips: Hold the slide in place. ​ Condenser Lens: Focuses light onto the specimen. ​ Diaphragm: Regulates the amount of light reaching the specimen. ​ Coarse Focus: Used for large adjustments in focus. ​ Fine Focus: Used for precise adjustments in focus. ​ Arm: Supports the body of the microscope. ​ Base: The bottom support structure. ​ Mirror/Light Source: Provides light for viewing the specimen. 4. Plant and Animal Cells Plant Cells: ​ Have a cell wall for extra structure and protection. ​ Contain chloroplasts for photosynthesis (contain chlorophyll). ​ Typically have one large vacuole that maintains turgor pressure. ​ Rectangular in shape. Animal Cells: ​ Lack a cell wall and chloroplasts. ​ Have smaller vacuoles (if any). ​ Usually round or irregular in shape. Common Structures in Both: ​ Nucleus ​ Cell membrane ​ Mitochondria ​ Ribosomes ​ Cytoplasm ​ Endoplasmic reticulum (rough and smooth)  ​ Golgi apparatus 5. Diffusion and Osmosis Diffusion: ​ The movement of molecules from an area of higher concentration to an area of lower concentration. ​ Example: Oxygen moving from the lungs into the bloodstream. Osmosis: ​ A specific type of diffusion that refers to the movement of water molecules across a semi-permeable membrane from an area of high water concentration to an area of low water concentration. 6. Unicellular and Multicellular Organisms Unicellular Organisms: ​ Made up of a single cell. ​ Examples: Bacteria, amoeba, paramecium. ​ All life functions (nutrition, respiration, reproduction) occur in one cell. Multicellular Organisms: ​ Made up of many cells that work together. ​ Cells are specialized for different functions. ​ Examples: Humans, plants, animals. ​ Cells in multicellular organisms are organized into tissues, organs, and organ systems. Definition: Prokaryotic cells are simpler and smaller cells that lack a nucleus and other membrane-bound organelles. Definition: Eukaryotic cells are more complex and larger cells that contain a nucleus and other membrane-bound organelles. 7. Viruses and Bacteria Viruses:  ​ Not considered living organisms because they cannot carry out life functions on their own. ​ Consist of a protein coat (capsid) and genetic material (DNA or RNA). ​ Reproduce only inside a host cell, hijacking the host's machinery. ​ Example: Influenza, HIV, COVID-19. Bacteria: ​ Prokaryotic organisms (no nucleus). ​ Can be beneficial (e.g., in the gut for digestion) or harmful (e.g., causing infections). ​ Reproduce asexually through binary fission. ​ Shape Types: ○​ Cocci (spherical) ○​ Bacilli (rod-shaped) ○​ Spirilla (spiral-shaped) ​ Can be treated with antibiotics.