Plant and Cell Structure and Functions (Students) PDF

C ollege of N ursing P harmacy & A llied H ealth S ciences Pharmaceutical Botany with Taxonomy PHARM 100  Plant Structure Department of Pharmacy and Functions ...

C ollege of N ursing P harmacy & A llied H ealth S ciences Pharmaceutical Botany with Taxonomy PHARM 100  Plant Structure Department of Pharmacy and Functions  SPECIFIC LEARNING OBJECTIVES: Department of Pharmacy Describe the structures that all cells share in common. Summarize the functions of the major cell organelles.  Plants cells are complex structures with several organelles Department of Pharmacy lacking in animal cells. Among these are the cell wall, central vacuole, and plastids (the most familiar of which are chloroplasts). Plants have two organ systems: the ROOT SYSTEM and the SHOOT SYSTEM The root system is typically belowground and consists of roots, which specialized in water and nutrient absorption. The shoot system consists of stems and leaves and is typically aboveground.  Types of Plants Department of Pharmacy Non-vascular Plants Vascular Plants Seed Plants Gymnosperms Angiosperms Department of Pharmacy Non-vascular Plants The most primitive types of plants lack vascular tissue, the tube like structures through which water and other materials move inside a plant. Non-vascular plants, such as liverworts and mosses, take in water through osmosis, the process that allows water to diffuse across a cell membrane.  Liverworts and their relatives are small and Department of Pharmacy grow on the surface of wet soil. Mosses are the small plants that form a green carpet on the floor of many forests. Liverworts and mosses, like all non-vascular plants, lack true roots, stems, and leaves.  Vascular Plants Department of Pharmacy Vascular plants, known as tracheophytes, are true land plants. Vascular plants include seedless plants like club mosses (which are not true mosses, despite their name), horsetails, and ferns, as well as seed plants-for example, violets, potatoes, and pine trees.  Club mosses are small Department of Pharmacy evergreen plants with needle-like or scale-like leaves. The leaves of horsetails encircle the shoots. Horsetails may or may not be evergreens and can grow to be rather tall. Fern leaves look a great deal like green feathers.  Seed Plants Department of Pharmacy Seed plants are vascular plants that reproduce. They can be divided into two groups, gymnosperms and angiosperms.  Gymnosperms Department of Pharmacy Gymnosperms are vascular plants that produce seeds that are not enclosed within a fruit. Gymnosperms, such as pines, firs, redwoods, and sequoias, do not produce flowers but form seeds in cones. Department of Pharmacy Angiosperms Angiosperms, or flowering plants, include familiar plants such as roses, corn, bamboo, orchids, daisies, and fruit trees. In angiosperms, seeds are enclosed in fruits. The fruit protects the seeds as they develop.  Life Cycle of an Angiosperm Department of Pharmacy A life cycle is a continuous process and does not have a true beginning or end. One place to begin describing the process is at germination. The seed germinates, and a seedling begins to grow roots, stems, and leaves. An adult angiosperm grows flowers, which then go through the process of pollination.  Parts of Plants Department of Pharmacy All VASCULAR PLANTS have roots, stems, and leaves, but only gymnosperms and angiosperms have seeds, and only angiosperms have flowers. The FOUR MAIN ORGANS of angiosperms are roots, stems, leaves, and flowers. Department of Pharmacy Roots Roots give a plant the surface area it needs to absorb the water and minerals essential to its survival. The outermost cells of the roots absorb water and minerals. The more surface area, or outer part, the roots have, the more cells can absorb these essential substances.  A TAPROOT is a single Department of Pharmacy thick structure that grows straight into the ground. A taproot securely anchors a plant in the soil and serves primarily as a storage organ for starch and sugar made by the plant. Taproots generally grow deep into the soil and can absorb water and nutrients there.  FIBROUS ROOTS consist of Department of Pharmacy a great many thin, branching roots that grow from a central point. Fibrous roots serve primarily to hold the plant in the ground and provide a large surface area for water and mineral absorption. Department of Pharmacy Stems Stems support the leaves, cones, fruits, flowers, and even seeds of plants. They hold a plant’s leaves up toward the sunlight. Stems contain two types of vascular tissue. Department of Pharmacy Xylem is vascular tissue made up of tube-shaped cells that transport water and dissolved minerals through the roots to the rest of the plant. Lignin, a hard substance in xylem, helps give structure to the plant. Phloem is tube-shaped vascular tissue that transports organic molecules from the leaves throughout the plant.  There are two classifications of Department of Pharmacy stems: herbaceous stems and woody stems. HERBACEOUS STEMS are green, soft, and flexible. Cells in herbaceous stems contain chloroplasts that use light to make food for the plant. WOODY STEMS are hard, strong, and rigid. Trees, shrubs, and roses have woody stems. Department of Pharmacy Leaves Leaves are plant organs whose main functions include capturing the energy of sunlight, making organic molecules, and exchanging gases with the environment. Leaves have an outer layer of cells called the epidermis. The upper epidermis has a waxy, waterproof coating called the cuticle that prevents the plant from losing too much water. The lower epidermis has tiny pores, or openings, called stomata that allow molecules to move into and out of the plant.  The process by which most of the water passes out of leaves as water vapor through the stomata in the lower epidermis is called Department of Pharmacy TRANSPIRATION. Because water molecules attract other water molecules, water that exits the stomata by transpiration actually “pulls” water up from the roots.  Flowers Department of Pharmacy Flowers are the main reproductive organs of flowering plants. Most flowers have four main parts: petals, sepals, stamens, and a pistil.  Pollination is the transfer of pollen grains from stamen to pistil. With few exceptions, pollination must take place before seeds Department of Pharmacy can form. Department of Pharmacy Seeds Seeds that fall close to the parent plant often have to compete for available nutrients and other resources, such as light and water. Plants have evolved many ways to ensure that seeds are transported from where they are formed. This process is called SEED DISPERSAL.  Coconuts seeds are Department of Pharmacy encased in tough husks made of strong fibers with air spaces between them. Dandelion seeds have small fluffy threads attached to them. The threads help the wind carry the seeds aloft.  The process by which the embryo in a seed begins to develop into a Department of Pharmacy new plant is called GERMINATION. Seeds often undergo a period of inactivity called dormancy until the conditions are right for germination. Department of Pharmacy CELL STRUCTURE  SPECIFIC LEARNING OBJECTIVES: Department of Pharmacy 1. Contrast prokaryotic and eukaryotic cells. 2. Describe the functions of the following 10 parts of a plant cell: plasma membrane, nucleus, chloroplasts, mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, vacuole, cytoskeleton, and cell wall. 3. Summarize the similarities and differences between plant cells and animal cells. 4. Explain the basic structure of the fluid mosaic model of a membrane. 5. Define the following processes that are important to the cell: diffusion, osmosis, facilitated diffusion, and active transport.  BASIC TYPES OF CELLS Department of Pharmacy PROKARYOTIC CELLS EUKARYOTIC CELLS Department of Pharmacy PROKARYOTIC CELLS EUKARYOTIC CELLS eu = well or good. pro = before karyon = nucleus karyon = nucleus A eukaryotic cell is any A prokaryote is a cell with a true nucleus unicellular organism that and organelles. Organelles lacks a membrane-bound are membrane bound nucleus, mitochondria, or structures found inside any other membrane-bound eukaryotic cells and they organelle. play a similar role to the organs in our bodies. Example are Archae and Example is plant cell. Bacteria.  Cell OR PLASMA membrane Department of Pharmacy The plasma membrane is a physical boundary that confines the contents of the cell to an internal compartment. This regulation is selective: some substances pass through the plasma membrane unimpeded, other materials are allowed passage in a controlled fashion, and some substances are denied entrance or exit. Department of Pharmacy Cell OR PLASMA membrane consisted of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity under various temperature, in combination with proteins such as HEAD integral proteins, and peripheral TAILS Phospholipid proteins. Amphipathic - having both hydrophilic heads and hydrophobic tails Department of Pharmacy Cell membrane functions ✔ Protection ✔ Communication ✔ Selectively allow substances in ✔ Respond to environment ✔ Recognition Department of Pharmacy Nucleus- control center of the cell. ▪ Nuclear Envelope- double membrane with nuclear pores that encloses nucleus. ▪ Nucleoplasm- contains the DNA. ▪ Nucleolus- produces sub units of ribosomes. ▪ Nuclear pore- permits passage of proteins into nucleus and ribosomal subunits of nucleus. Department of Pharmacy PLASTIDS The plastid is a major double-membrane organelle found, among others, in the cells of plants and algae. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. Department of Pharmacy Chloroplasts Chloroplasts contain the enzymes necessary for photosynthesis plus the green pigment chlorophyll, a molecule with the vital role of absorbing light energy. Thylakoids, membranous stacks of thin, flat, circular plates; a stack of thylakoids is called a granum (pl., grana). Each chloroplast also contains a small amount of DNA and a few ribosomes. The presence of DNA and ribosomes in chloroplasts is significant because it indicates that they had free-living ancestors. Department of Pharmacy Leucoplasts Plant cells also contain leucoplasts, colorless plastids that form and store starch, oils, or proteins. Leucoplasts are common in seeds and in roots and stems modified for food storage. When leucoplasts are exposed to light, they can synthesize chlorophyll and function as chloroplasts; this happens, for example, when potato tubers are exposed to light.  Chromoplast Department of Pharmacy Chromoplast, contains pigments that provide yellow, orange, and red colors to certain flowers, such as marigolds, and to ripe fruit, such as tomatoes and red peppers. Chromoplasts often form from chloroplasts when chlorophyll breaks down; this happens, for example, when green tomatoes ripen and turn red. Department of Pharmacy Mitochondria It is known as the powerhouse of the cell. It generates most of the chemical energy needed to power the cell's biochemical reactions. An intracellular organelle associated with respiration; provides the cell with ATP. Department of Pharmacy Ribosomes - are tiny bodies that are visible with the aid of an electron microscope. - it carry out protein synthesis. - RIBOSOMES occur in the nucleus, plastids, and mitochondria, they are most numerous in the cytoplasm, where they are found free. Department of Pharmacy Endoplasmic Reticulum Facilitates cellular communication and channeling materials. Rough ER- studded with ribosomes Smooth ER- lacks ribosomes, synthesizes lipid molecules.  The ER is one of the major manufacturing centers of the Department of Pharmacy cell. ER that has ribosomes attached to it is called rough ER and is a site of protein synthesis; ER without ribosomes is known as smooth ER and is associated with lipid synthesis. ER also synthesizes the membranes for various organelles throughout the cell, including the nuclear envelope and other cellular organelles such as Golgi apparatus. Department of Pharmacy Golgi Apparatus DICTYOSOMES - also called as Golgi body or Golgi complex. It is made up of membrane-bound sacs. Golgi Apparatus- its job is to process and bundle macromolecules like proteins and lipids as they are synthesized within the cell.  The Golgi apparatus collects Department of Pharmacy and processes materials that are to be exported from the cell. In plant cells, for example, the Golgi apparatus produces and transports some of the polysaccharides that make up the cell wall. The Golgi apparatus also collects materials that are stored inside large, membrane-bounded sacs called vacuoles. Department of Pharmacy The manufacture and export of materials from the cell involve several cellular organelles. For example, consider the secretion of proteins. Proteins that are manufactured by the ribosomes along the rough ER are sealed in vesicles and transported to a Golgi body. The vesicle from the ER then fuses with the membrane of the Golgi body and deposits its contents inside. The finished products are then sealed inside a vesicle that pinches off the edge of the Golgi body. The vesicle from the Golgi body then migrates to the cell's plasma membrane, with it, and deposits its contents outside cell.  VACUOLES Department of Pharmacy Vacuolar Membranes (tonoplasts) - which constitue the inner bounderies of the living part of the cell, are similar in structure and function to plasma membrane.  One of the most significant is that the vacuole helps the cell maintain its shape by Department of Pharmacy making it turgid (from the Latin turg, "swollen"). A turgid cell is one that is swollen or firm due to water uptake. The large concentration of ions and other materials dissolved in the vacuole causes water to accumulate. The vacuole swells and presses against the cytoplasm, which in turn presses against the cell's plasma membrane and cell wall. The vacuole also serves as a temporary storage area; excess materials such as calcium ions are stored in the vacuole until the cell needs additional calcium.  Water-soluble pigments such as anthocyanins, which are blue, purple, or red, are often stored in the vacuole. Department of Pharmacy For example, anthocyanin is stored in the vacuoles of red onion cells, giving them their characteristic color. Waste products, malformed proteins, and the like also enter the vacuole, where they may be disassembled so that their component parts can be used again.  CYTOSKELETON Department of Pharmacy The cytoskeleton is a network of fibers that extends throughout the cytoplasm and provides structure to a eukaryotic cell. The cytoskeleton, which is also important in cell movement, includes TWO TYPES OF FIBERS, microtubules and microfilaments. Department of Pharmacy Microtubules Microtubules also make up the spindle, a special structure that moves chromosomes during cell division. Other microtubules are a part of flagella and cilia, hairlike extensions of certain cells that aid in locomotion. Flagella and cilia are never associated with the cells of flowering plants, but they are important structures in algae and in male reproductive cells of other plants. Department of Pharmacy Microfilaments Microfilaments, which are much thinner than microtubules, can contract and are responsible for cytoplasmic streaming, the movement of cytoplasm within the cell. Cytoplasmic streaming has a variety of purposes; for example, the movement of cytoplasm in leaf cells helps orient the chloroplasts for optimal exposure to light.  Cell Wall Department of Pharmacy The cell wall, which is a coating secreted by the cell, supports and protects each plant cell while providing routes for water and dissolved materials to pass to and from the cell. Collectively, cell walls provide strength to the entire plant; a massive tree stands tall and does not collapse on itself because of the combined strength of its cell walls.  Although animal cells do not have cell walls, the cells of many other organisms-prokaryotes, algae and some other protists, Department of Pharmacy and fungi-do. Plant cell walls are composed largely of cellulose, a long-stranded polysaccharide that consists of as many as several thousand linked glucose molecules. Cellulose and other cell-wall components are produced within the cell and transported out of the cytoplasm within vesicles from the Golgi apparatus. Microtubules appear to control the movement of these vesicles to the plasma membrane.  Cellulose forms bundles of fibers that are held together by other polysaccharides, including pectin Department of Pharmacy (the material that thickens jellies). A growing plant cell secretes a thin primary cell wall, which stretches and expands as the cell increases in size. After the cell stops growing, additional wall material may be secreted that thickens and solidifies the primary cell wall. The middle lamella, a layer of pectic compounds, cements the primary cell walls of adjacent cells together.  After growth ceases, multiple layers of a secondary cell wall with a Department of Pharmacy different chemical composition may form between the primary cell wall and the plasma membrane. In addition to cellulose, secondary cell walls usually contain lignin, a hard substance in which the cellulose fibers become embedded. (Lignin may also be found in primary cell walls.) Lignin gives wood, which consists largely of secondary cell walls, many of its distinctive properties.  Cells in a multicellular plant need to communicate among Department of Pharmacy themselves, a process that is known as cell signaling. For this reason, plant cells have connections called plasmodesmata (sing., plasmodesma), which are tiny channels through adjacent cell walls that connect the cytoplasm of neighboring cells. The plasma membranes of adjacent cells are continuous with each other through the plasmodesmata, which generally allow molecules and ions but not organelles to pass from cell to cell. Department of Pharmacy Plant cells and animal cells are more alike or Different? Department of Pharmacy Plasma membranes enclose both plant and animal cells, and BOTH have nuclei, mitochondria, ribosomes, ER, the Golgi apparatus, and a cytoskeleton. Plant cells have cell walls, plastids, and conspicuous vacuoles, whereas animal cells do not. In addition, animal cells contain centrioles that function in cell division and lysosomes that are involved in digestion; PLANT CELLS LACK BOTH OF THESE ORGANELLES.  FLUID MOSAIC MODEL Department of Pharmacy The fluid mosaic model characterizes the plasma membrane and other cell membranes as consisting of a double layer, or bilayer, of lipid molecules. A number of proteins are embedded in the lipid bilayer in a way that resembles a mosaic pattern. The membrane structure is fluid rather than motionless, and the lipids (and protein molecules, to a lesser extent) move laterally (sideways) within the membrane.  One of the important lipid components of membranes is Department of Pharmacy phospholipid, composed of a glycerol molecule to which are attached two fatty acids and a molecule containing a phosphate group. The phosphate end of the phospholipid molecule is polar-that is, slightly charged-whereas the fatty acid chains are nonpolar. The polar "head" is hydrophilic (from the Greek hydro,"water," and phil, "love"); that is, it has an affinity for water. The nonpolar "tail" is hydrophobic (from the Greek hydro, "water," and phobos, "fear"); that is, it has an aversion to water. Department of Pharmacy MEMBRANES PERFORM MANY FUNCTIONS First, membranes regulate the passage of materials because they are selectively permeable; that is, they prevent the entrance or exit of certain materials while permitting-and even helping-the entrance or exit of other materials. For example, the lipid bilayer is impermeable to ions and polar molecules. Thus, charged ions such as Na+ and Cl are not allowed to pass into or out of a cell on their own. The membrane's regulation of the passage of materials enables the cell to maintain homeostasis, a relatively constant set of internal conditions. Department of Pharmacy Second, membranes-particularly the plasma membrane-receive information from their surroundings, including other cells. Chemical messengers such as hormones often bind to special molecules in a membrane and set off some type of response in the cell. Membranes of other organelles, such as the are the sites of enzymatic activity.  TRANSPORT PROCESS Department of Pharmacy 1. Transport process involves the in and out movement of molecules, elements, and water across the cell. 2. In transport process, the required elements like oxygen, nitrogen, and water move inside, and the waste or toxic molecules are thrown out of the cell. 3. There are two types of transport processes: Mediated transport process and Non-mediated transport process.  Mediated transport process: Department of Pharmacy 1. In mediated transport process, a specific carrier protein is required. 2. Also, mediated transport process requires energy for the movement of molecules.  Non-mediated transport process: Department of Pharmacy 1. In non-mediated transport process, a simple diffusion process occurs. 2. The driving force of transportation of substance is dependent on carrier protein. Department of Pharmacy PASSAGE OF MATERIALS ACROSS BIOLOGICAL MEMBRANES Department of Pharmacy DIFFUSION The movement of a substance from a region of higher concentration to a region of lower concentration. During diffusion, atoms and molecules move along a concentration gradient- that is from where they are more concentrated to where they are less concentrated. Department of Pharmacy Diffusion occurs because atoms and molecules are in constant random motion that makes them collide with other particles. As a particle diffuses, it moves in a straight line until it collides with some other particle. This collision causes the original particle to rebound in another direction. Department of Pharmacy Diffusion is important to cellular function because it is responsible for the movement of many materials throughout the cytoplasm and into and out of cells. Oxygen, carbon dioxide, and water, for example, diffuse readily into and out of cells. Department of Pharmacy OSMOSIS Osmosis, a special kind of diffusion, is the movement of water through a selectively permeable membrane from a solution with a higher concentration of water to a solution with a lower concentration of water. In biological systems a solution is a mixture in which salts, sugars, and other materials are dissolved in water. The substances that are dissolved in water are referred to as solutes, and the water is referred to as the solvent.  A cell's plasma membrane is Department of Pharmacy relatively impermeable to sugars and salts, but water moves across the membrane freely in either direction. When a cell is placed in a solution with a solute concentration equal to that inside the cell, water molecules diffuse through the plasma membrane equally in both directions.  Such solutions are said to be Department of Pharmacy isotonic (from the Greek iso, "equal") -that is, they have a solute concentration equal to that in the cell. Department of Pharmacy When a cell is placed in a solution with a solute concentration higher than that within the cell, the solution is said to be hypertonic (from the Greek hyper, "over") to the cell. Department of Pharmacy When a cell is placed in a solution with a solute concentration lower than that within the cell, the solution is said to be HYPOTONIC (from the Greek hypo, "under") to the cell. In such a situation, water flows into the cell from the surrounding solution.  Normally, the roots of plants are exposed to soil water that is actually Department of Pharmacy a dilute solution of inorganic mineral salts. As water moves into the root cells, their cell walls enable them to withstand the building pressure caused by the incoming water. This internal pressure of water against the cell wall is known as TURGOR PRESSURE. As turgor pressure increases, an equilibrium is reached in which the turgor pressure forces water molecules out of the cell in numbers equal to that of the molecules coming in by osmosis. Department of Pharmacy Facilitated Diffusion In facilitated diffusion, materials diffuse from a region of higher concentration to a region of lower concentration through special passageways in the membrane. These passageways are actually membrane proteins called carrier proteins, which are channels in the membrane that function as conveyor belts. Department of Pharmacy Active transport Active transport is the assisted movement of a substance from a lower concentration to a higher concentration of that substance. Active transport occurs with the assistance of carrier proteins in the membrane that move the substance from one side of the membrane to the other. Department of Pharmacy THANK YOU!