Plant Cell Structure and Function: A Comprehensive Review - PDF

Here’s the organized version of your document while keeping all details intact: The Structure of a Plant Cell Levels of Biological Organization 1.​ Atoms 2.​ Molecules 3.​ Cells 4.​ Tissues 5.​ Organs 6.​ Organ Systems 7.​ Organism Levels of Biological Organiza...

Here’s the organized version of your document while keeping all details intact: The Structure of a Plant Cell Levels of Biological Organization 1.​ Atoms 2.​ Molecules 3.​ Cells 4.​ Tissues 5.​ Organs 6.​ Organ Systems 7.​ Organism Levels of Biological Organization 1.​ Atoms 2.​ Molecules 3.​ Cells 4.​ Tissues 5.​ Organs 6.​ Organ Systems 7.​ Organism The biological organization starts from the smallest unit, atoms, which combine to form molecules. These molecules make up cells, the basic unit of life. Groups of similar cells form tissues, which work together as organs. Multiple organs coordinate their functions in organ systems, which together sustain a complete organism. Structure of a Plant Cell A plant cell consists of the following organelles: ​ Cell Wall – Provides structural support and protection. ​ Plasma Membrane – Regulates entry and exit of substances.  ​ Cytoplasm – Contains organelles and cellular components. ​ Nucleus – Contains DNA, controls cell activities. ○​ Nuclear Envelope – Surrounds and protects the nucleus. ○​ Nucleolus – Produces ribosomes. ​ Vacuole – Stores nutrients, water, and waste. ​ Chloroplasts – Perform photosynthesis. ​ Mitochondria – Generate energy (ATP). ​ Golgi Apparatus – Packages and transports proteins. ​ Endoplasmic Reticulum (ER) ○​ Rough ER – Has ribosomes, aids in protein synthesis. ○​ Smooth ER – Lacks ribosomes, synthesizes lipids. ​ Ribosomes – Produce proteins. ​ Peroxisomes – Break down harmful substances. ​ Plasmodesmata – Channels between plant cells for communication. Anatomy of a Eukaryotic Plant Cell Similar to the general plant cell, a eukaryotic plant cell contains: ​ Cell Wall (Primary and Secondary) – Structural integrity. ​ Plasma Membrane – Selective permeability. ​ Cytoplasm – Holds organelles. ​ Nucleus – Controls genetic material. ​ Vacuole – Central storage and waste disposal. ​ Chloroplasts – Site of photosynthesis. ​ Mitochondria – Energy production. ​ Endoplasmic Reticulum (Rough & Smooth) – Protein and lipid synthesis. ​ Golgi Apparatus – Protein modification and transport. ​ Ribosomes – Protein factories. ​ Peroxisomes – Detoxification. ​ Microtubules – Cell shape and transport. ​ Middle Lamella – Holds adjacent cells together. These structures work together to maintain life functions in plant cells, allowing them to grow, develop, and sustain the ecosystem. 1. Introduction to Cells ​ Cells: Structural and functional unit of living organisms. ​ Key Scientists & Discoveries: 1.​ Robert Hooke – First observed plant cells. 2.​ Robert Brown – First observed the nucleus of cells. 3.​ Matthias Schleiden – Stated that plants are composed of cells. 4.​ Theodor Schwann – Stated that animals are composed of cells. Cell Theory ​ The bodies of plants and animals are composed of cells and their products. ​ Cells arise from pre-existing cells. 2. Fundamental Types of Cells A. Prokaryotic Cells (Before Nucleus) ​ Characteristics: 1.​ Lack a nucleus. 2.​ Simple/primitive cell type. 3.​ Lack some organelles. 4.​ Exist as independent, single-celled organisms. ​ Examples: Bacteria, algae. B. Eukaryotic Cells (After Nucleus) ​ Characteristics: 1.​ Have a nucleus. 2.​ Contain complex organelles. 3.​ Found in multicellular organisms. ​ Examples: Plants, animals, humans. Examples of Plant Cell Types & Specializations Cell Type Specialization Cells of shoot/root Cell division; produce new protoplasm. tips Epidermis Water retention; cutin and wax act as barriers against fungi and insects. Epidermal gland Protection; produce poisons that deter herbivores. cells Green leaf cells Collect solar energy through photosynthesis. Root epidermal cells Collect water and minerals from soil. Vascular cells Transport water, minerals, and organic molecules. Flower cells Various functions related to reproduction and pollination. Petal cells Contain pigments that attract pollinators. Scent cells Produce fragrances to attract pollinators. Nectary cells Produce sugars that attract pollinators. Stamen cells Indirectly involved in sperm cell production. Carpel cells Indirectly involved in egg cell production. Fruit cells Produce sugars, aromas, and flavors to attract seed-dispersing animals. SUMMARY OF PLANT CELL PARTS Structure of a Plant Cell Cell Wall ​ Provides structural support and protection. Protoplasm 1.​ Plasma Membrane (Cell Membrane) – Regulates material exchange between the cell and its environment. 2.​ Nucleus – Controls cell activities and contains genetic material (DNA). 3.​ Cytoplasm – Includes the cytosol and organelles. Fluid Part of Cytoplasm ​ Cytosol (Hyaloplasm/Ground Plasm) – The semi-fluid matrix where organelles are suspended. Organelles ​ Mitochondria – Powerhouse of the cell; site of ATP production.​ ​ Plastids (Three types):​ ○​ Chloroplasts – Contain chlorophyll; site of photosynthesis. ○​ Chromoplasts – Contain pigments that provide color to fruits and flowers. ○​ Leucoplasts (Three types): ​ Amyloplasts – Store starch. ​ Proteinoplasts – Store proteins. ​ Elaioplasts – Store lipids. ​ Endoplasmic Reticulum (ER)​ ○​ Rough ER – Studded with ribosomes; involved in protein synthesis. ○​ Smooth ER – Involved in lipid synthesis and detoxification. ​ Ribosomes – Synthesize proteins.​  ​ Dictyosome (Golgi Apparatus) with Vesicles – Modifies, sorts, and packages proteins and lipids.​ ​ Microbodies​ ○​ Peroxisomes – Break down hydrogen peroxide and fatty acids. ○​ Glyoxysomes – Convert stored lipids into carbohydrates in germinating seeds. ​ Cytoskeleton – Provides structural support and aids in cell movement.​ ​ Vacuole – Stores water, nutrients, and waste; maintains turgor pressure.​ 3. Plant Cell Parts & Functions A. Cell Wall ​ Function: Provides protection and structural support. ​ Composition or Made of: ○​ Carbohydrates (cellulose). ○​ All cells, except animal cells, have cell walls. Overview ​ Outermost part of a plant cell. ​ Present in almost all plants, except for the sperm cells of some seed plants. ​ Composed of a large amount of polysaccharides, mainly cellulose. Functions ​ Structural support – Provides strength and protection to the protoplasm inside. ​ Defense – Acts as a barrier against invading pathogens. ​ Communication – Facilitates pathways for signals and molecules between cells. ​ Dynamic & Active – Not just a rigid structure but plays an active role in cellular functions. Structural Components 1.​ Cellulose – The primary component, forming strong fibers. 2.​ Hemicellulose – Acts as glue, holding cellulose fibers together. 3.​ Pectin – Adds stiffness, known for its role in fruit jellies. 4.​ Proteins – Involved in various cell wall functions, including signaling and repair. This structure makes the cell wall a vital component for plant survival, growth, and communication. Cell Wall - Layers Cell Wall - non-living, rigid covering of plant cells that is porous and somewhat elastic. It consists of three main layers: 1.​ Middle Lamella (Intercellular Layer):​ ○​ Made of pectin (calcium pectate) which cements adjacent cells together. ○​ Contains a network of cellulose microfibrils and macrofibrils. 2.​ Primary Wall:​ ○​ Secreted against the middle lamella. ○​ Composed of cellulose and contains cutin, which forms the cuticle (impermeable to water). ○​ The cuticle protects leaves and stems against water loss. 3.​ Secondary Wall:​ ○​ Found inside the primary wall in cells with thick walls. ○​ Composed of cellulose, lignin (for hardness and decay resistance), and suberin (for water and gas impermeability). ○​ Provides additional strength and is thicker than the primary wall. The cellulose fibrils are arranged parallel to each other. 2. Special Features of the Cell Wall ​ Pits: Regions where no secondary wall is deposited, allowing diffusion of water and other substances. ​ Plasmodesmata: Pores that allow cytoplasmic strands to connect adjacent cells for material and impulse transfer. B. Protoplasm ​ Living part of the cell, living material that produces and is surrounded by the non-living cell wall. A) The Cell Membrane (Plasmalemma/Plasma Membrane): ​ Made up of three parts: 1.​ Phospholipids 2.​ Proteins 3.​ Carbohydrates II. Protoplasm:​ A) The Cell Membrane (Plasmalemma/Plasma Membrane): ​ Semi-fluid cell boundary (thick oil) that controls the passage of substances in and out of the cell. ​ It is impermeable to harmful substances, making it a semi-permeable membrane. ​ Composed of two layers of phospholipids with embedded proteins in between.  ​ The outer boundary of the living part of the cell, playing a vital role in regulating what substances enter and leave the cell (permeability) and in the production and assembly of cellulose for cell walls. ​ The chemical composition of the plasma membrane is crucial in the transport process. Made up of three parts: 1.​ Phospholipids 2.​ Proteins 3.​ Carbohydrates TABLE 3-4: Summary of Transmembrane Movement 1.​ Impermeable Membrane:​ ○​ Nothing passes through; no biological membrane is impermeable to everything. 2.​ Freely Permeable Membrane:​ ○​ Virtually anything can pass through. 3.​ Selectively Permeable (Differentially Permeable) Membrane:​ ○​ Certain substances pass through rapidly, while others pass through slowly. 4.​ Facilitated Diffusion:​ ○​ Large intrinsic membrane proteins allow hydrophilic, charged molecules to diffuse through the membrane. 5.​ Active Transport:​ ○​ Large intrinsic membrane proteins bind a molecule and force it through the membrane, consuming energy in the process. 6.​ Exocytosis:​ ○​ The fusion of a vesicle with the cell membrane, releasing the vesicle's contents to the exterior of the cell. 7.​ Endocytosis:​ ○​ The invagination of the cell membrane, forming a vesicle that pinches off and carries external material into the cell. C. Nucleus B. Nucleus: ​ Control Center: Stores genetic information as chromosomes and serves as a permanent storage place for the organism's genetic information. ​ The Genome: All the genetic material in a cell. ​ Nuclear Pores: Allow passage between the nucleus and the cytoplasm. ​ Spherical Organelle: Located either at the center or on one side of the protoplasm. Components of the Nucleus: 1.​ Nuclear Envelope: a.​ Two membranes. b.​ Nuclear Pores: Allow material exchange between the nucleus and cytoplasm. 2.​ Nucleoplasm: The substance within the nucleus. a.​ DNA: Genetic material. b.​ Enzymes: Proteins that facilitate chemical reactions. c.​ Histone Proteins: Proteins associated with DNA. d.​ Several Types of RNA: Involved in protein synthesis and gene expression. e.​ Water: Essential for cellular functions. f.​ Numerous Other Substances: Various molecules within the nucleus. 3.​ Nucleolus: The region of the nucleus responsible for ribosome production. a.​ Ribosomes: Found in the nucleolus, involved in protein synthesis. D. Cytoplasm ​ Cytosol/Hyaloplasm:​ A clear substance made up of water and enzymes. Cytoplasm: ​ If the nucleus and vacuole are excluded from the protoplasm, the remaining material is referred to as cytoplasm. ​ A rich "soup" of carbohydrates, proteins, fats, and nucleic acids. ​ Sometimes referred to as protoplasm. ​ Watery or gelatin-like substance in which all organelles are suspended. Cytosol/Hyaloplasm: ​ A clear substance made up of water, enzymes, and numerous precursors, intermediates, and products of enzymatic reactions. E. Mitochondria Mitochondria (Powerhouse of the Cell): ​ Double-layered outer membrane. ​ Energy-producing organelle. ​ Site of aerobic respiration, where energy (ATP) is generated for the cell. Different Kinds of Organelles: Mitochondria (Powerhouse of the Cell): ​ ATP production, responsible for energy generation. ​ Involved in cellular respiration (cell "breathing"), converting sugars to energy (ATP). ​ The mitochondrion has its own genome. ​ Matrix (Liquid Part): Contains enzymes and other molecules necessary for cellular respiration. ​ Have their own DNA and ribosomes. ​ Dynamic Organelles: Can grow larger, divide, or fuse together. Mitochondria: ​ Second largest organelle with a unique genetic structure. ​ Double-layered outer membrane with inner folds called cristae. ​ Energy-producing chemical reactions take place on the cristae. ​ Recycles and decomposes proteins, fats, and carbohydrates, and forms urea. ​ Found in ALL eukaryotic cells (even in plant cells). ​ Site of aerobic respiration, where sugars and oxygen are converted into ATP, carbon dioxide, and water:​ Sugars+O2→ATP+CO2+H2O\text{Sugars} + O_2 \rightarrow ATP + CO_2 + H_2O ​ Contain DNA which codes for mitochondrial proteins, ribosomes, etc. ​ Divide by a process similar to binary fission when the cell divides. ​ Inner Membrane forms the Cristae (invaginations into the interior region).  ​ The matrix is the liquid part inside the mitochondrion. ​ Mitochondria are dynamic organelles that: ○​ Can grow larger ○​ Can divide ○​ Can fuse together. F. Plastids 2. Plastids: ​ All plastids develop from proplastids and are interconvertible. ​ All plastids arise only from pre-existing plastids. ​ A group of dynamic organelles present in plants and algae, with 2 membranes. ​ Function: Diverse, depending on the type of plastid. ​ Contain pigments or storage products: Chloroplasts, Chromoplasts, Amyloplasts. Two Main Parts of Plastids: A. Chromoplasts: ​ Contain pigments like green, red, yellow, orange, or violet. ​ These pigments account for the color of plant parts, including flowers and fruits. B. Chloroplasts: ​ Function: Traps solar energy and makes food through photosynthesis. ​ Location: Found in plant cells. B. Chloroplasts: ​ Function: Traps sunlight energy and makes food through photosynthesis. ​ Location: Found in plant cells. ​ Vary in size and shape depending on the plant. Key Components: ​ Thylakoids: The site where photosynthesis takes place.​ ​ Stroma: The site of the Calvin cycle, where sugar synthesis occurs.​ ​ Genome: The chloroplast has its own genome, which is involved in photosynthesis, converting light energy to chemical energy (sugars).​ C. Amyloplasts: ​ Function: Store starch, a polysaccharide used as an energy reserve in plants. 2. Leucoplasts: ​ Colorless plastids found in roots and non-photosynthetic tissues of plants. ​ May specialize for bulk storage of starch, lipids, or proteins. ​ When specialized, they are known as amyloplasts, elaioplasts, or proteinoplasts. A) Amyloplasts: ​ Responsible for the synthesis and storage of starch granules. ​ Convert stored starch back into sugar when the plant needs it. ​ Large numbers can be found in fruit and underground storage tissues like potato tubers. ​ Amyloplasts are essentially starch grains. B) Elaioplasts: ​ Specialized for the storage of lipids in plants.  ​ House oil body deposits as rounded plastoglobuli (fat droplets). C) Proteoplasts/Proteinoplasts: ​ Contain crystalline bodies of protein and can serve as sites for enzyme activity involving those proteins. ​ Found in many seeds, such as Brazil nuts and peanuts. Table 3-7: Types of Plastids 1.​ Amyloplasts​ ○​ Function: Store starch. ○​ Considered a type of leucoplast. 2.​ Chloroplasts​ ○​ Function: Carry out photosynthesis. 3.​ Chromoplasts​ ○​ Function: Contain abundant colored lipids. ○​ Found in flowers and fruits. 4.​ Etioplasts​ ○​ Function: A specific stage in the transformation of proplastids to chloroplasts. ○​ Occur when tissues grow without light. 5.​ Leucoplasts​ ○​ Function: Colorless plastids that synthesize lipids and other materials. 6.​ Proplastids​ ○​ Function: Small, undifferentiated plastids that can develop into various types of plastids. Endoplasmic Reticulum (ER): ​ A tubular network fused to the nuclear membrane.​ ​ Extends through the cytoplasm and onto the cell membrane.​ ​ Functions: Stores, separates, and serves as the cell's transport system.​  ○​ Smooth ER or Type: Lacks ribosomes, involved in lipid synthesis and detoxification. ○​ Rough ER or Type: Ribosomes are embedded in the surface, involved in protein synthesis. Ribosomes: ​ The smallest organelle without a membrane. ​ Each cell contains thousands of ribosomes. ​ Known as the protein factories of the cell, involved in protein synthesis. ​ Composes about 25% of the cell's mass. Dictyosomes: ​ A stack of thin vesicles held together in a flat or curved array. ​ Rarely aggregate to form a cup-shaped structure. ​ Function in modifying, sorting, and packaging proteins and lipids, often related to the Golgi apparatus. Dictyosomes (Golgi Body/Golgi Apparatus): ​ A stack of thin vesicles held together in a flat or curved array. ​ Rarely aggregate to form a cup-shaped structure. ​ A membrane located or found near the nucleus and composed of numerous layers forming a sac. ​ Often referred to as the Golgi Body or Golgi Apparatus or/and Protein 'packaging plant'. Function: ​ Diverse processing activities, including: ○​ Modification of vesicle membranes/contents. ○​ Addition of sugars to proteins, forming glycoproteins. ○​ Packaging and sorting proteins and lipids for transport. Microbodies: ​ Numerous small, spherical bodies found in the cytoplasm. ​ Contain the enzyme catalase. Two Main Classes of Microbodies: 1.​ Peroxisomes: ○​ Function: Involved in detoxifying some products of photosynthesis. 2.​ Glyoxysomes: ○​ Function: Involved in converting stored fats into sugars in plants. ○​ Important during the germination of oily seeds such as peanuts and coconuts. Cytoskeletal Filaments: ​ A network of protein fibers that provides structure and shape to the cell. ​ Responsible for the movement of the cell and internal movement of organelles and other molecules. Functions: ​ Internal support and structure to the cell. ​ Transport of organelles and protein vesicles. ​ Cell motility (e.g., cilia and flagella). Types of Cytoskeletal Filaments: 1.​ Microtubules:​ ○​ Most abundant and easily studied structural elements of a cell. ○​ Made up of tubulin protein. ○​ Functions: Diverse ​ Means of motility for both organelles and whole cells. ​ Move chromosomes during cell division. ​ Assist in the formation of the cell plate during plant cell division. 2.​ Microfilaments:​ ○​ Made up of actin protein. ○​ Functions: ​ Move organelles and cytoplasm. ​ Assist in cell movement and shape changes. Vacuoles: ​ Membrane-bound organelles separated from the protoplasm by the tonoplast (vacuolar membrane). ​ Function as storage structures for a variety of substances, including water, nutrients, waste products, and pigments. ​ Play a role in maintaining turgor pressure, which helps in maintaining the cell’s shape and rigidity. Vacuoles: ​ Separated from the protoplasm by the tonoplast (vacuolar membrane).​ ​ Large central vacuole is typically found or usually in plant cells.​ ​ Function as storage containers for various substances, including:​ ○​ Water ○​ Food ○​ Enzymes ○​ Wastes ○​ Pigments ○​ Ions ○​ Nutrients ​ The central vacuole is highly selective in transporting materials through its membrane.​ ​ The chemical composition or chemical palette of the vacuole solution is referred or termed to as cell sap. Cell Sap: ​ The fluid part within vacuoles, which differs significantly from the surrounding cytoplasm. ​ Some vacuoles contain pigments that contribute to the characteristic colors of certain flowers. Crystals: ​ Waste products of metabolism, often found or associated in vacuoles, composed of calcium oxalate. Functions of Vacuoles: ​ Maintenance of cell pressure and pH. ​ Storage of various or numerous cell metabolites and waste products. ​ Frequently contains water-soluble pigments. ​ Contains dissolved substances such as: ○​ Salts ○​ Sugars ○​ Organic acids ○​ Small quantities of soluble proteins ​ Involved in the recycling of certain materials within the cell. ​ Aids in the breakdown and digestion of organelles.  ​ Crystals in Vacuoles: ​ Waste products of metabolism associated with vacuoles and composed of calcium oxalate. Types of Crystals: 1.​ Raphides:​ ○​ Needle-like crystals, which may occur singly or in bundles. 2.​ Prismatic:​ ○​ Prism-like or pyramid-shaped crystals. 3.​ Rosette:​ ○​ Aggregates of crystals that form a flower-like appearance. Note: ​ Calcium carbonate crystals can also be found within the cell, often grape-like in shape, and are known as Cystoliths, which may hang from the cell wall. Crystals in Vacuoles: ​ Waste products of metabolism associated with vacuoles and composed of calcium oxalate. Types of Crystals: 1.​ Raphides:​ ○​ Needle-like crystals, which may occur singly or in bundles. 2.​ Prismatic:​ ○​ Prism-like or pyramid-shaped crystals. 3.​ Rosette:​ ○​ Aggregates of crystals that form a flower-like appearance. Note: ​ Calcium carbonate crystals can also be found within the cell, often grape-like in shape, and are known as Cystoliths, which may hang from the cell wall. NOTE: AT THIS PART DON’T MIND THE DESCRIPTION JUST FOCUS ON WHAT AN PLANT CELL HAVE AND ANIMAL CELL HAVE. DESCRIPTION IS JUST AN EXTRA Plant Cell vs. Animal Cell Present in Plant Cell: 1.​ Cell wall – Provides structural support and protection. 2.​ Plastids – Including chloroplasts, chromoplasts, and amyloplasts. 3.​ Glyoxysomes – Involved in converting stored fats into sugars during seed germination. 4.​ Large central vacuole – Stores water, nutrients, and waste products, maintains cell pressure. Present in Animal Cell: 1.​ Centrioles – Involved in organizing the mitotic spindle during cell division. 2.​ Lysosomes – Contain enzymes that break down waste materials and cellular debris. 3.​ Small vacuole – Function in storing nutrients, waste products, and maintaining internal balance (much smaller than in plant cells). Common Parts (Found in Both Plant and Animal Cells): 1.​ Plasma membrane – Semi-permeable membrane that regulates what enters and exits the cell. 2.​ Nucleus – Control center, contains genetic information (DNA). 3.​ Cytosol – Fluid portion of cytoplasm where metabolic reactions occur. 4.​ Endoplasmic Reticulum (ER): ○​ Rough ER (RER) – Studded with ribosomes, synthesizes proteins. ○​ Smooth ER (SER) – Involved in lipid synthesis and detoxification. 5.​ Ribosomes – Sites of protein synthesis. 6.​ Dictyosome/Golgi complex – Involved in protein modification, packaging, and transport (Golgi apparatus in animal cells). 7.​ Microbodies – Small organelles with specific metabolic functions. 8.​ Peroxisomes – Involved in detoxification processes. 9.​ Vacuole – Stores various substances and helps with maintaining cell homeostasis (although larger in plant cells).