Cell theory development_.pdf

Cell theory development: 1665 - Robert Hooke: Observed cells of a cork tree through a primitive microscope. 1674 - Anton van Leeuwenhoek: Improved the microscope and discovered living cells, observing microorganisms like bacteria and protozoa (called them "animalcules")....

Cell theory development: 1665 - Robert Hooke: Observed cells of a cork tree through a primitive microscope. 1674 - Anton van Leeuwenhoek: Improved the microscope and discovered living cells, observing microorganisms like bacteria and protozoa (called them "animalcules"). 1838 - Matthias Schleiden: Proposed that all plants are made of cells, forming the basis of cell theory. 1839 - Theodor Schwann: Stated that all animals are made of cells, extending the cell theory to all living things. 1855 - Rudolf Virchow: Concluded that all cells come from pre-existing cells, establishing the principle of cell division. 1931 - Ernst Ruska: Developed the electron microscope, allowing for greater magnification and study of cell structures. Modern Cell Theory: All organisms are composed of one or more cells. The cell is the smallest functional unit of life All cells are produced from other cells. Cells contain hereditary information (DNA) which is passed from the parent cell to the daughter cell during cell division All basic chemical and physiological functions are carried out inside the cell. All cells have the same basic chemical composition and metabolic activities. Cell activity depends on the activities of subcellular structures within the cell. How microscope led to the development of the cell theory: Discovery of Cells: - Robert Hooke (1665) used an early compound microscope to observe cork and coined the term “cell” to describe the box-like structures he saw. Observation of Living Cells: - Anton van Leeuwenhoek (1674) developed more powerful microscopes and was the first to observe living cells, such as bacteria and protozoa. He referred to these as "animalcules." Identification of Cell Structures: - Improved microscopes in the 1800s allowed scientists like Matthias Schleiden and Theodor Schwann to study plant and animal tissues, concluding that all living things are made up of cells. Understanding Cell Division: - Advanced microscopes allowed Rudolf Virchow to observe cell division, leading to the principle that all cells come from pre-existing cells. Refinement of Modern Cell Theory: - The invention of the electron microscope (1930s) enabled scientists to see cellular organelles in detail, supporting and expanding the modern cell theory with more accurate observations. Key components of scientific inquiry: - Manipulated Variable (Independent Variable): The variable that is intentionally changed or controlled in an experiment to test its effects. - Responding Variable (Dependent Variable): The variable that is measured or observed in response to changes in the manipulated variable. - Controlled Variables (Constants): All other factors that are kept constant throughout the experiment to ensure that any observed changes are due solely to the manipulated variable. Know how to identify whether if it’s living or not (must give reasoning) Microscopes: Bright Field Microscopes / compound light microscopes: The very first microscopes were simple microscopes, which used only one lens, similar to a magnifying glass. A compound microscope has two or more lenses, which increases the magnification. Using compound light microscopes, researchers can view living cells as well as some of the structures within cells. Advantages: see the true color of the specimen structure, to view specimens, easy to see, affordable to buy and repair. Disadvantages: has a limit of magnification to increase resolution, sometimes an oil immersion lens utilized because it prevents light refraction from occurring Simple microscope: magnifying device; uses single lens to enlarge the image of specimen. Has a double convex lens with a short focal length. Dark Field Microscopes: Ideal for observing pale objects, where only scattered light rays enter the objective lens. Advantages: Creates a bright specimen against a dark background, enhancing contrast for detailed observation. Phase Microscopes:Designed for examining living organisms that may be damaged by staining or slide preparation. Advantages: Uses in-phase and out-of-phase light rays to create contrast, enabling detailed observation of specimens. Fluorescent Microscopes:Utilizes UV light to excite specimens, causing them to emit longer visible wavelengths. Advantages: Increases resolution and contrast; can identify pathogens and visualize proteins, often used in immunofluorescence. Stereo Microscopes: Used for examining large specimens during dissection. Advantages: Provides a 3D view but has low magnification, making it unsuitable for individual cell examination. Confocal Laser Scanning Microscopes (CLSM): Suitable for thick specimens; uses a laser beam to scan in planes and create 2D images. Advantages: Stacks 2D images to produce detailed 3D representations, allowing for in-depth analysis. Electron microscope: uses a beam of electrons instead of a light wave and is able to produce images that provide fine detail. - High voltage - Uses for: microorganisms, cells, molecules, biopsy samples, metals, and crystals (for quality control and failure analysis.) Advantages: - High Resolution: Achieves greater magnifications and resolutions, revealing fine details at the nanometer scale. - Detailed Images: Provides highly detailed images not visible with light microscopes. - Variety of Techniques: Different types (TEM, SEM) allow for diverse applications, including internal structures and surface features. - 3D Imaging: SEM can create three-dimensional images of specimen surfaces. Disadvantages: - Cost: Significantly more expensive to purchase and maintain than light microscopes. - Complexity: Requires specialized training to operate. - Sample Preparation: Samples need specific preparation, often altering or limiting observation of live specimens. - Size and Portability: Typically large and not easily portable. - Vacuum Requirement: Operates in a vacuum, preventing observation of living specimens in their natural state. Electron Micrograph: A highly detailed image produced by an electron microscope. - Shows much finer details than light microscopes. Transmission Electron Microscope (TEM): Uses electrons that pass through a very thin specimen. - Produces a detailed, 2D image of the internal structure of cells. Scanning Electron Microscope (SEM): Electrons bounce off the surface of the specimen. - Produces a 3D image of the surface structure. - Uses a focused beam of electrons that scans the surface of a specimen. The interaction of the electrons with the atoms produces secondary electrons, which are collected to form an image. Scanning tunneling microscope: A fine metal probe is positioned close to a specimen, allowing electrons to flow between the probe tip and the specimen's surface atoms. This process generates a 3D image by mapping the surface contours. The scanning tunneling microscope (STM) offers even greater magnification than traditional electron microscopes, enabling researchers to produce detailed images of molecules like DNA. What is the difference between contrast and resolution? Contrast: the difference in colors and brightness between objects and their background in an image. - Importance: higher contrast makes it easier to distinguish between different stu=ructures within a specimen. - Enhancement: can improve using staining techniques or specific lighting conditions. - refers to the visual difference between objects and their background Resolution: The ability of a microscope to distinguish between two closely spaced objects as separate entities. - Importance: Higher resolution allows for finer details to be observed, revealing structures at a smaller scale. - Measurement: typically measured in nanometers; the better the resolution, the smaller detail that can be seen. - refers to the clarity and detail of the image, enabling the differentiation of closely spaced structures. Differences between Animal cell and Plant cell 1. Centrioles: Animal Cells: Have centrioles involved in cell division. Plant Cells: Lack centrioles. 2. Cell Wall: Plant Cells: Have a rigid cell wall. Animal Cells: Do not have a cell wall. 3. Chloroplasts: Plant Cells: Contain chloroplasts with chlorophyll for photosynthesis. Animal Cells: Do not have chloroplasts. 4. Energy Storage: Plant Cells: Store energy as starch. Animal Cells: Store energy as glycogen. 5. Vacuoles: Plant Cells: Have a large, permanent central vacuole. Animal Cells: Have small, temporary vacuoles. Animal and Plant cells Plant cells: Cell Wall: Appearance: Rigid, outer layer. Role: Provides structure, support, and protection. Chloroplasts: Appearance: Green, oval-shaped organelles. Role: Conduct photosynthesis to convert sunlight into energy. Large Central Vacuole: Appearance: Large, fluid-filled sac. Role: Maintains turgor pressure, stores nutrients, and wastes. Nucleus: Appearance: Round, membrane-bound structure. Role: Contains genetic material (DNA) and controls cell activities. Mitochondria: Appearance: Bean-shaped organelles with a double membrane. Role: Produce energy (ATP) through cellular respiration. Endoplasmic Reticulum (ER): Appearance: Network of membranes; rough ER has ribosomes, smooth ER does not. Role: Synthesizes proteins (rough ER) and lipids (smooth ER). Ribosomes: Appearance: Small dots, either free-floating or attached to the ER. Role: Synthesize proteins. Golgi Apparatus: Appearance: Stacked, flattened membranes. Role: Modifies, sorts, and packages proteins and lipids for transport. Animal Cells: Cell Membrane: Appearance: Thin, flexible layer surrounding the cell. Role: Controls the movement of substances in and out of the cell. Nucleus: Appearance: Round, membrane-bound structure. Role: Contains genetic material (DNA) and controls cell activities. Mitochondria: Appearance: Bean-shaped organelles with a double membrane. Role: Produce energy (ATP) through cellular respiration. Endoplasmic Reticulum (ER): Appearance: Network of membranes; rough ER has ribosomes, smooth ER does not. Role: Synthesizes proteins (rough ER) and lipids (smooth ER). Ribosomes: Appearance: Small dots, either free-floating or attached to the ER. Role: Synthesize proteins. Golgi Apparatus: Appearance: Stacked, flattened membranes. Role: Modifies, sorts, and packages proteins and lipids for transport. Centrioles: Appearance: Cylindrical structures located near the nucleus. Role: Involved in cell division and the formation of the spindle fibers. Lysosomes: Appearance: Small, round organelles filled with enzymes. Role: Digest waste materials and cellular debris. Five Kingdoms of life Monera: Single-celled organisms, including bacteria (prokaryotic). Protista: Mostly single-celled organisms, including amoebas and algae (eukaryotic). Fungi: Multicellular and unicellular organisms, including molds and yeasts, that absorb nutrients (eukaryotic). Plantae: Multicellular organisms that perform photosynthesis (eukaryotic). Animalia: Multicellular organisms that consume organic material for energy (eukaryotic). Role of the cell membrane in painting equilibrium while exchanging matter: Cell membrane: the cell membrane is vital for regulating material exchange, enabling communication, and ensuring cellular stability. Structure: Phospholipid Bilayer: Creates a semi-permeable barrier with hydrophilic heads and hydrophobic tails. Proteins: Embedded proteins facilitate transport, signaling, and communication. Key Roles Selective Permeability: Allows specific substances to enter and exit, maintaining internal balance. Transport Mechanisms: Passive Transport: Moves substances without energy (e.g., diffusion, osmosis). Active Transport: Requires energy to move substances against their gradient. Signal Transduction: Membrane proteins detect environmental changes, triggering cellular responses. Endocytosis and Exocytosis: Endocytosis: Uptake of particles or molecules by formation of a vesicle from the cell membrane’ requires energy and ATP. - Endo = taking things in - Taking small or longs things to take in particles or macromolecules - If microorganisms are too big, too charged, too polar, to pass through a biological membrane. It’s going to change the shape of the cell or some kind of membrane. Exocytosis: Process by which a variety of substances leave the cell getting stuff from the cell and could be needed to dispose of toxins, when not, could also be good stuff needed to go somewhere and do its job, - Made proteins are packaged into the vesicle inside the cell and transported to the cell membrane because cytoplasm is always squishing out by diffusion. - Vesicles and membranes fused together, and the contents of the vesicles spilled out. - Vesicle membrane smoothly incorporated into the cell membrane. Fluid Mosaic Model: description of the arrangement of protein molecules in the fluid double layer of phospholipids that make up the cell membrane. - A mosaic is a collection of different substances held together by a common material. - The membrane's flexible nature allows for adaptation and effective functioning. Chemical composition of cell structures: 1. Water: Composes about 70-90% of a cell mass. - Solvent for biochemical reactions, help maintain cell shape, and facilitate transport. 2. Macromolecules: - Proteins: Made of amino acids linked by peptide bonds. - Enzymes, structural components, transporters, and signaling molecules. - Nucleic Acids: DNA and RNA - Made of nucleotides (sugar, phosphate group, nitrogenous base). - Lipids: Phospholipids, cholesterol, triglycerides - Comprised of fatty acids and glycerol (for triglycerides) or phosphate group (for phospholipid) - Cell membrane structure, energy storage, and signaling molecules. - Carbohydrates: Monosaccharides (glucose), disaccharides (sucrose), and polysaccharides (starch, glycogen). - Energy storage, structural components (e.g., cellulose in plant cell walls), and cell recognition. 3. Ions and Small Molecules - Inorganic Ions: Sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl⁻), and bicarbonate (HCO₃⁻). - Vital for maintaining cellular homeostasis, electrical gradients, and enzymatic activities. 4. Vitamins and Cofactors - Various organic molecules needed in small amounts. - Role: Essential for enzyme function and various metabolic processes. Fluid mosaic model: description of the arrangement of protein molecules in the fluid double layer of phospholipids that make up the cell membrane. - A mosaic is a collection of different substances held together by a common material. - The membrane is described as "fluid" because the phospholipids and proteins can move laterally within the layer, allowing for flexibility and movement. - Components: - Phospholipid Bilayer: Composed of two layers of phospholipids with hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward. - Proteins: Embedded within or attached to the phospholipid bilayer, serving various functions such as transport, signaling, and structural support. - Carbohydrates: Often attached to proteins (glycoproteins) or lipids (glycolipids), playing a role in cell recognition and communication. - Function: helps explain how cell membranes maintain a barrier while allowing the movement of substances in and out of the cell. It also illustrates how cells communicate and interact with their environment through proteins and carbohydrates. What is it meant by a “system”? System: Set of interconnected parts. In studies of work and energy transfer, the system is the object involved in the transfers. Everything else is considered the surroundings or the environment. - Components: A system is made up of individual parts or elements that interact with each other. - Interactions: The components within a system are interdependent, meaning the behavior or function of one part affects the others. - Boundaries: A system has defined limits or boundaries that separate it from its environment, allowing it to function as a distinct entity. - Purpose: A system typically has a specific goal or function that it aims to achieve, whether it's in nature, technology, or social structures. - Dynamic: Systems can be dynamic, meaning they can change and adapt over time based on internal and external influences. Surrounding: Everything that is outside a system. Different forms of passive and active transportation. Passive Transport: movement of substances along the concentration gradient; transport process that does not require ATP. - Movement of materials by the process of diffusion is considered to be passive transport. - Don’t need energy Types of passive transport: Diffusion: spontaneous movement of particles from an area of higher concentration to an area of lower concentration. - Net movement - water is away moving, streaming - Thing are always in motion - Stationary because of particle model of matter Osmosis: diffusion of water across a selectively permeable membrane - Water is going to move - Can move small particles, ex: sodium - Net movement of water - Requires semi permeable membrane to move Facilitated diffusion: diffusion of molecules across a membrane through binding to carrier proteins; does not require energy from ATP. - Same as diffusion but you’ve got to use some help to transport proteins. - Maybe always open - Feels cannot pass through the lipids layer of the membrane so will be needing transport proteins. Filtration: Movement of water and solutes forced through a membrane by hydrostatic pressure. Processes of diffusion and osmosis: Diffusion mechanisms: - Particles move randomly due to their kinetic energy. - They spread out evenly in the available space. - No energy (ATP) is required for this process. Factors affecting diffusion/factors that will affect the rate of diffusion:  - Concentration gradient: The larger the difference in concentration, the faster the rate of diffusion. - Temperature: Higher temperatures increase kinetic energy, speeding up diffusion. - Size of particles: Smaller particles diffuse faster than larger ones. Osmosis mechanisms: - Water moves to balance solute concentrations on either side of the membrane. - Like diffusion, osmosis does not require energy. Factors affecting Osmosis: - Concentration gradient of solutes: The greater the difference in solute concentration across the membrane, the faster the rate of osmosis. - Temperature: Increased temperatures can enhance the movement of water molecules. How different types of solution affects the rate of diffusion: 1. Isotonic solutions: has the same concentration of solutes as the inside of the cell. - Effect on diffusion: - There is no net movement of water into or out of the cell, as water moves in and out at equal rates. - Cells maintain their normal shape and function, and diffusion rates are balanced. 2. Hypertonic solution: has a higher concentration of solutes than the inside of the cell. - Effect on diffusion: - Water moves out of the cell to the area of higher solute concentration (hypertonic solution). - This can cause the cell to shrink (crenation in red blood cells) as it loses water, which may affect cellular function and diffusion rates negatively. 3. Hypotonic solution: has a lower concentration of solutes than the inside of the cell. - Effect on diffusion: - Water moves into the cell, following its concentration gradient to balance the solute concentrations. - This can cause the cell to swell and potentially burst (lysis) if too much water enters, affecting the cell's ability to function properly. Active transport: an energy-driven process where membrane proteins transport molecules across cells - The organisms the cells out actually has to use ATP - Something might be opening some kind of protein to get some solutes inside. Types of active transport: Primary Active Transport: Direct use of ATP to transport molecules. Example: Sodium-Potassium Pump (Na+/K+ pump), which moves sodium ions out of the cell and potassium ions into the cell. Secondary Active Transport (Cotransport): Utilizes the energy from primary active transport to move other substances. It includes: Symport: Both molecules move in the same direction (e.g., glucose and sodium ions). Antiport: Molecules move in opposite directions (e.g., sodium ions entering while calcium ions exit). Bulk Transport (Vesicular Transport): Movement of large particles or volumes of substances through vesicles. It includes: Endocytosis: Bringing substances into the cell (e.g., phagocytosis for solids and pinocytosis for liquids). Exocytosis: Releasing substances out of the cell (e.g., secretion of hormones or neurotransmitters). What semi-permeable membrane? Semi-permeable: a type of membrane which allows certain particles to pass through while others are excluded; can be natural or synthetically produced for industrial use. - Cell membrane is considered as semi permeable. - Allows some particles to pass through while other particles cannot (depending on the size of the particles) Particle model of matter : is a scientific theory that explains the structure and behavior of matter based on the idea that all matter is made up of tiny particles. 1. Composition of Matter: All matter is composed of small particles, which can be atoms, molecules, or ions. The type of particles determines the properties of the material. 2. Types of Particles: - Atoms: The basic units of elements, consisting of protons, neutrons, and electrons. - Molecules: Combinations of two or more atoms bonded together (e.g., water, H₂O). - Ions: Charged particles that can form when atoms gain or lose electrons 3. Movement of Particles: Particles are in constant motion. The amount of energy they possess affects their movement: - Solid: Particles are tightly packed and vibrate in place, giving solids a fixed shape and volume. - Liquid: Particles are close together but can slide past one another, allowing liquids to take the shape of their container while maintaining a fixed volume. - Gas: Particles are far apart and move freely, allowing gasses to fill their container and have neither a fixed shape nor volume. 4. Temperature and Energy: As temperature increases, particles gain kinetic energy and move faster. This can lead to changes in state (e.g., solid to liquid). 5. Interactions: Particles interact with each other through forces, such as attraction and repulsion, which influence the properties of materials (e.g., melting, boiling, and solubility). Concentration gradients. Which way solvents and solutes will travel across semi-permeable barriers? Concentration gradient: refers to the difference in the concentration of a substance between two areas. It plays a crucial role in processes like diffusion and osmosis. In a concentration gradient, substances tend to move from an area of higher concentration to an area of lower concentration. - Solutes: Are substances dissolved in a solvent  - Solutes will travel down their concentration gradient, moving from areas of higher concentration to areas of lower concentration until equilibrium is reached. - Solvents: Solvents are the substances in which solutes are dissolved - Movement in Osmosis: Water (the solvent) moves across a semi-permeable membrane toward the area with a higher concentration of solute (lower concentration of water) to balance the solute concentrations. - This means water moves from an area of lower solute concentration to an area of higher solute concentration. In a concentration gradient, solutes move from high to low concentration, while solvents (like water) move toward the area of higher solute concentration across semi-permeable barriers to achieve equilibrium. This process is essential for maintaining homeostasis in biological systems. Types of membranes: 1. Cell membrane: the outer boundary of a cell, composed of a lipid bilayer with embedded proteins. - Function: Regulates the movement of substances in and out of the cell, providing protection and structural support. 2. Biological membranes: Can refer to the membranes within cells that perform specific function. - Nuclear membrane - Endoplasmic Reticulum (ER) - Golgi apparatus - Mitochondrial membrane 3. Semi-permeable membrane: A membrane that allows certain substances to pass while restricting others, based on size or charge. - Function: Cruciaal for processes like osmosis and diffusion, maintaining homeostasis within cells. 4. Synthetic membranes: Man-made membranes used in various applications. - Types: - Reverse osmosis membrane: used for water purification, allowing water to pass blocking contaminants. - Dialysis Membranes: USed in kidney dialysis to separate waste from blood while allowing certain solutes to pass. 5. Artificial membrane: Membranes created for experimental or industrial use. - Applications: Used in research to study membrane properties and behavior or in technologies like drug delivery systems. 6. Transport membranes: Specialized membranes that facilitate the transport of specific substances. - Ex: - Aquaporins: Water channels that enhance water transport. - Ion channels: Proteins that allow ions to pass through the membrane. Membranes play critical roles in cellular function and organization, with types ranging from cell membranes to synthetic membranes used in technology. Understanding their characteristics is essential for studying biological processes and developing various applications. How membranes can be used to transport matter? 1. Selective Permeability: - Membranes are selectively permeable, meaning they allow certain substances to pass while blocking others. This selective nature is essential for maintaining the internal environment of the cell. 2. By transport: - Passive: - Diffusion: Movement of molecules from an area of high concentration to low concentration. - Facilitated Diffusion: Similar to diffusion but involves specific transport proteins that help larger or polar molecules cross the membrane. - Osmosis: Diffusion of water across a semipermeable membrane. - Active: - Requires energy to move substances against their concentration gradient (from low to high concentration). - Involves specific transport proteins, such as pumps (e.g., sodium-potassium pump). 3. Vesicular Transport: - Endocytosis: Process by which cells engulf substances to bring them inside. Types include: - Phagocytosis: "Cell eating" for large particles. - Pinocytosis: "Cell drinking" for liquids. - Receptor-Mediated Endocytosis: Specific uptake of molecules via receptor binding. - Exocytosis: Process of expelling substances from the cell, where vesicles fuse with the cell membrane to release their contents outside. 4. Membrane Transport Proteins: - Channel Proteins: Form channels that allow specific ions or molecules to pass through. - Carrier Proteins: Bind to specific substances and change shape to shuttle them across the membrane. Membranes are integral to the transport of matter in biological systems, enabling cells to regulate their internal environment, communicate with their surroundings, and acquire essential nutrients while eliminating waste products. Necessary to maintain homeostasis Homeostasis: Homeostasis is the process by which living organisms maintain a stable internal environment despite changes in external conditions. It is essential for cells and organisms to function properly. - A state of balance among all the body systems needed for the body to survive and function correctly. Factors to Maintain Homeostasis: 1. Temperature Regulation: Keeping body temperature within a normal range. 2. pH Balance: Maintaining the right pH levels in blood and cells. 3. Water Balance: Regulating water content to prevent dehydration or overhydration. 4. Glucose Levels: Managing blood sugar levels for energy production.  5. Oxygen and Carbon Dioxide Levels: Balancing respiratory gasses to support cellular respiration. 6. Ion Concentration: Maintaining electrolyte balance (e.g., sodium, potassium) for nerve and muscle function. 7. Waste Removal: Eliminating toxins and metabolic waste from the body. How surface area and volume related to a cell’s metabolism Surface area to volume ratio is determining how efficiently a cell can exchange materials with its environment, impacting its metabolic rate. Surface area: - Represents the cell membrane’s size - Larger surface area allows more nutrients (e.g., oxygen) to enter and waste (eg., carbon dioxide) to leave the cell. Volume: - Represents the space inside the cell that contains organelles and cytoplasm - As volume increases, the cell’s demand for nutrients and production of waste increases. SA:V ratio: - As cells grow, their volume increases faster than their surface area. - This leads to a lower SA ratio, making it harder for the cell to meet its metabolic demands through diffusion alone. Higher SA ration: faster diffusion, higher metabolic rate. Lower SA ratio: slower diffusion, low metabolic rate, making it less efficient. Role of diffusion: - Diffusion is how nutrients and gasses enter and waste exits the cell. ; Cells with a higher SA ratio can exchange substances more efficiently, supporting higher metabolic activity. Know how to calculate SA:V Organs, tissue, and System. How they relate to multicellular organism Tissue: Groups of similar cells working together to perform a specific function (e.g., muscle tissue, nervous tissue). Organs: Structures made up of different types of tissues working together to carry out a particular function (e.g., the heart, lungs, or leaves in plants). System: Groups of organs that work together to perform complex functions for the body (e.g., digestive system, respiratory system). Relationship to multicellular organisms: Cells – tissue Tissues – organs Organs – systems Systems working together to support the entire organisms This organization allows multicellular organisms to perform more specialized and complex functions compared to single-celled organisms. Adaptations for nutrition: 1. Small cells  - Have a large surface area-to-volume ratio, which allows nutrients to quickly diffuse into the cell and waste to diffuse out efficiently. - This ratio supports quick and effective nutrient uptake. 2. Large cells - Have a smaller surface area-to-volume ratio, making nutrient exchange less efficient. - To adapt, large cells often develop structures like folds or projections (e.g., microvilli in intestinal cells) to increase surface area. 3. Multicellular organism - Develop specialized cells, tissues, and organs for nutrient absorption, transport, and digestion (e.g., roots in plants or intestines in animals). - Utilize complex systems (e.g., circulatory system) to distribute nutrients efficiently throughout the body. These ensure that cells and multicellular organisms can meet their nutritional needs, regardless of size. How gasses are moved in and out of multicellular organisms 1. Diffusion: Gasses like oxygen (O₂) and carbon dioxide (CO₂) move across cell membranes from areas of higher concentration to areas of lower concentration. 2. Respiratory Organs: - Animals: Use specialized structures like lungs, gills, or tracheae to increase surface area for gas exchange. - Plants: Use stomata (pores on leaves) and lenticels (pores on stems) to allow gas exchange with the environment. 3. Circulatory Systems: - In animals, oxygen is transported from the lungs to tissues and cells via the circulatory system, while CO₂ is transported back to the lungs for exhalation. 4. Ventilation: - Mechanisms like breathing (in animals) or transpiration (in plants) help maintain a concentration gradient, facilitating efficient gas exchange. These adaptations ensure that multicellular organisms can meet their oxygen needs and expel carbon dioxide efficiently. Energy conversions that takes place in the photosynthesis Photosynthesis: Means putting together light (“photo = light; “synthesis” = putting together): a chemical process in which carbon dioxide from the air and water from the soil, in the presence of light energy, produce glucose and oxygen. Energy Conversion: Light energy → Chemical energy (stored in glucose) Location: Occurs in the chloroplasts of plant cells. Equation: 6CO2​+6H2​O+light energy→C6​H12​O6​+6O2​ Main stages: - Light-dependent reactions: Convert light energy into ATP and NADPH. - Calvin cycle (Light-independent reactions): Uses ATP and NADPH to convert CO₂ into glucose. Cellular respiration Cellular respiration: - breakdown of glucose molecules to release chemical energy that a cell can use.  - The process by which cells break down glucose to release energy (ATP). Energy Conversion: Chemical energy (glucose) → Usable energy (ATP) Location: Occurs in the mitochondria of both plant and animal cells. Equation: C6​H12​O6​+6O2​→6CO2​+6H2​O+energy (ATP) Main stages: - Glycolysis: Breakdown of glucose into pyruvate in the cytoplasm. - Krebs Cycle: Produces electron carriers in the mitochondrial matrix. - Electron Transport Chain: Generates the majority of ATP in the inner mitochondrial membrane. Both processes are interconnected, with photosynthesis producing oxygen and glucose, which are used in cellular respiration to release energy (ATP). Xylem and Phloem in plants Xylem: - Function: Transport water and dissolved minerals from the roots to the other parts of the plants. - Structure: Composed of hollow, tube-like cells (tracheids and vessel elements) that are dead at maturity, allowing for efficient water movement. - Purpose: - Support: Provides structural support to the plant. - Water Transport: Ensures that water reaches leaves for photosynthesis and helps maintain turgor pressure. Phloem: - Function: transport the products of photosynthesis from leaves to non-photosynthetic cells. - Structure: Made up of living cells (sieve tube elements and companion cells) that facilitate the movement of nutrients. - Purpose: - Nutrient Distribution: Distributes the energy-rich sugars produced in the leaves to growing tissues, roots, and storage organs. - Growth Support: Provides the necessary components for growth and development throughout the plant. Xylem and phloem form the plant's vascular system, enabling the transport of essential water, minerals, and nutrients, thus supporting the plant's overall growth, development, and survival. The control systems in plants Phototropism: directional plant growth response to light (sun) - is the growth of a plant in response to light. Plants tend to grow toward the light source, which allows them to maximize their exposure to sunlight for photosynthesis. This movement is primarily regulated by the plant hormone auxin. Mechanism: - Auxin Hormones: When light shines on one side of a plant, auxins (plant growth hormones) accumulate on the shaded side. This causes cells on that side to elongate more than those on the light-exposed side. - Result: The plant bends towards the light, maximizing its ability to capture sunlight for photosynthesis. Gravitropism: directional plant growth response to gravity; may be positive or negative also called geotropism. - is the growth of a plant in response to light. Plants tend to grow toward the light source, which allows them to maximize their exposure to sunlight for photosynthesis. This movement is primarily regulated by the plant hormone auxin. Mechanism: - Statoliths: Specialized cells in plant roots contain statoliths (dense organelles) that settle at the bottom of the cell in response to gravity. - Auxin Distribution: In roots, auxins are redistributed towards the lower side, inhibiting growth on that side and promoting growth on the upper side, causing the roots to grow downward. Conversely, in stems, auxins promote growth on the lower side, causing the stem to bend upwards. phototropism, plants optimize light capture for photosynthesis, while gravitropism helps them orient their roots and shoots in relation to gravity. Both responses involve the action of auxins and demonstrate the complex control systems plants use to adapt to their environment.