Plant Cells and Tissues PDF

PRPM110L - Module 3 Aquino, Zuendie Pearl D. | BSP1E | Ms. Samantha Ocampo MODULE 3 Plant Cells and Tissues Plant cells - are eukaryotic cells or cells with a membrane-bound nucleus. Unlike prokaryotic...

PRPM110L - Module 3 Aquino, Zuendie Pearl D. | BSP1E | Ms. Samantha Ocampo MODULE 3 Plant Cells and Tissues Plant cells - are eukaryotic cells or cells with a membrane-bound nucleus. Unlike prokaryotic cells, the DNA in a plant cell is housed within the nucleus enveloped by a membrane. Organelles - tiny cellular structures that carry out specific functions necessary for normal cellular operation, including everything from producing hormones and enzymes to providing energy for a plant cell. Plastids -(e.g. chloroplasts) assist in storing and harvesting needed substances for the plant. These are round, oval, or irregularly shaped protoplasmic bodies which are of three main types: Chloroplasts or the green plastids, leucoplasts or colorless plastids, and chromoplasts. Plant Cell Animal Cell Larger than animal cells; more Various sizes and irregular shapes similar in size and typically Centrioles rectangular or cube-shaped. Lysosomes Cell wall Cilia and flagella Large vacuole Plastids LESSON 1: PLANT CELLS Cell (Plasma) Membrane: This thin, semi-permeable membrane surrounds the cytoplasm of a cell, enclosing its contents. Cell Wall: This rigid outer covering of the cell protects the plant cell and gives it shape. Chloroplast: the sites of photosynthesis in a plant cell. They contain chlorophyll, a green pigment that absorbs energy from sunlight. 1  Cytoplasm: The gel-like substance within the cell membrane. It contains water, enzymes, salts, organelles, and organic molecules. Cytoskeleton: This network of fibers throughout the cytoplasm helps the cell maintain its shape and supports the cell. Endoplasmic Reticulum (ER): an extensive network of membranes composed of both regions with ribosomes (rough ER) and regions without ribosomes (smooth ER). The ER synthesizes proteins and lipids. Golgi Complex or Dictyosomes: responsible for manufacturing, storing, and shipping certain cellular products, including proteins. Microtubules: These hollow rods, tubular fibrillar structures of indefinite length with cylindrical walls od highly organized globular protein primarily help support and shape the cell. Spindle fibers are also derived from here. Mitochondria: generate energy for the cell by converting glucose (produced by photosynthesis) and oxygen to ATP. This process is known as respiration. - a double-layered organelle of the plant cell. It has an inner membrane containing a series of tubular extensions or folds, the cristae. - These cristae are sparse and irregularly arranged and are the sites for cellular respiration. 2  Nucleus: a membrane-bound structure that contains the cell's hereditary information (DNA). ○ Nucleolus: darkly staining rounded bodies rich in ribosomal RNA. This structure within the nucleus helps in the synthesis of ribosomes. ○ Nucleopore: These tiny holes within the nuclear membrane allow nucleic acids and proteins to move into and out of the nucleus. ○ Nuclear membrane/envelope: semi-permeable membrane that regulates the passage of substance into and out of the nucleus. ○ Nuclear sap/nucleoplasm: fluid portion of the nucleus. ○ Chromatin: darkly staining material suspended within the karyoplasm or nucleoplasm. It is the portion of the chromosome visible only when the cell is dividing. Contains the genes determining the hereditary characteristics of the cell. Chromosomes also control the activity of the cell Peroxisomes: are tiny, single membrane-bound structures that contain enzymes that produce hydrogen peroxide as a by-product. These structures are involved in plant processes such as photorespiration. Glyoxysomes: play an important role in both catabolic and anabolic pathways in plants. It breaks the fatty acid into succinate in lipid-rich seeds like castor beans. Plasmodesmata: These pores or channels between plant cell walls allow molecules and communication signals to pass between individual plant cells. Ribosomes: Consisting of RNA and proteins, ribosomes are responsible for protein assembly. They can be found either attached to the rough ER or free in the cytoplasm. Vacuole: This plant cell organelle provides support for and participates in a variety of cellular functions, including storage, detoxification, protection, and growth. When a plant cell matures, it typically contains one large liquid-filled vacuole. Cell sap: contains dissolved substances such as the anthocyanins (water–soluble pigments) Crystals: form of waste products of metabolism in plants. It occurs in various shapes and size. They are differentiated based on their composition and shape. Calcium oxalate (CaC2O4): 1. RAPHIDE = fine, needle like crystals occurring singly or in cluster, scattered, or enclosed in a sac as in gabi or other succulent plants 2. PRISMATIC = prism-like or diamond-like crystals found in leaves of begonia or bangka bangkaan 3. ROSETTE = flowerlike appearance in santan and stem of kutsarita plant 4. STYLOID = knife-like, tapering at both ends. Calcium carbonate (CaCO3): 5. CYSTOLITH = grapelike as seen in hypodermal cell of leaf of an Indian rubber tree or ampalaya like plant. (Dc: Druse crystals; Pc: Prismatic crystals) 3  LESSON 2: PLANT TISSUES TISSUES - are different groups of cells that work together to perform a particular function. - A tissue system consists of one or more tissues organized into a functional unit connecting the organs of a plant. PLANT TISSUE SYSTEMS (1) Dermal Tissues - protects the soft tissues of plants and controls interactions with the plants' surroundings. - The epidermis is a dermal tissue that is usually a single layer of cells covering the younger parts of a plant. - covers the plant body consisting of the epidermis, usually made up of parenchyma cells in a single layer. (2) Ground Tissues - The three types of ground tissue include parenchyma, collenchyma, and sclerenchyma. - These tissues are involved in photosynthesis, storage, regeneration, support, and protection. (3) Vascular Tissues - Vascular tissue is composed of xylem and phloem, which function in the transport of water and dissolved substances. Two general types: meristematic tissue and permanent (or non-meristematic) tissue. I. Meristematic tissue - is analogous to stem cells in animals - undifferentiated continue to divide and contribute to plant growth. - produce cells that quickly differentiate or specialize and become permanent tissue. Three main tissue types: dermal, vascular, and ground tissue. 4 II. Permanent tissue - consists of plant cells that are no longer actively dividing. SIMPLE permanent tissues are composed of only one type of cell. 1. EPIDERMIS - is the outermost layer of any plant organ with primary growth. - Guard cells: (of stomata) specialized cells present in the epidermis. - Trichome (or epidermal hair): Outward growth of epidermal cells. - Cuticle: waxy material produced by the epidermis. Inhibits water loss - Transpiration - a process on stems and leaves that prevents water loss. 2. PARENCHYMA CELLS - are the least specialized permanent tissue composed of living thin-walled cells. - help to synthesize and store organic products in the plant. - Mesophyll: The middle tissue layer of leaves is composed of parenchyma cells, and it is this layer that contains plant chloroplasts. - Chlorenchyma: elongated cylindrical cells with a long axis at the right angle to the organ's surface. - Aerenchyma: specialized for gas exchange. They are irregular cells surrounded by large air space found in the stem of aquatic plants. 3. COLLENCHYMA CELLS - support function in plants, particularly in young plants. - help to support plants while not restraining growth. - elongated in shape and have thick primary cell walls composed of the carbohydrate polymers cellulose and pectin. - lacks secondary cell walls and the absence of a hardening agent in their primary cell walls, collenchyma cells can provide structural support for tissues while maintaining flexibility. They can stretch along with a plant as it grows. - found in the Cortex (layer between the epidermis and vascular tissue) of stems and along leaf veins. 4. SCLERENCHYMA CELLS - also have a support function in plants, but unlike collenchyma cells, they have a hardening agent in their cell walls and are much more rigid. - have thick secondary cell walls and are non-living once matured. 💜 - two types of sclerenchyma cells: sclereids and fibers. Sclereids: have varied sizes and shapes, and most of the volume of these cells is taken up by the cell wall. Sclereids are very hard and form the hard 💜 outer shell of nuts and seeds. Fibers: elongated, slender cells that are strand-like in appearance. Fibers are strong and flexible, found in stems, roots, fruit walls, and leaf vascular bundles. 5. CORK - the outer impermeable protective layer of a secondary plant body. - composed of compactly arranged dead lignified and suberized cells without intercellular spaces. 5  COMPLEX permanent tissue - composed of different kinds of cells but performs the same function. 1. XYLEM - Water-conducting cells that have a support function in plants. - has a hardening agent in the tissue that makes it rigid and capable of functioning in structural support and transportation. - Main function: transport water throughout the plant. T - Two types of narrow, elongated cells compose the xylem: tracheids and vessel elements. - Tracheids: have hardened secondary cell walls and function in water conduction. - Vessel elements: resemble open-ended tubes arranged end to end, allowing water to flow within the tubes. - Gymnosperms and seedless vascular plants contain tracheids - Angiosperms contain both tracheids and vessel members 2. PHLOEM - Sieve tube elements: conducting cells of phloem. - They transport organic nutrients, such as glucose, throughout the plant. - The cells of sieve tube elements have few organelles, allowing for easier passage of nutrients. - Sieve tube elements lack organelles, such as ribosomes and vacuoles. - Companion cells: specialized parenchyma cells that carry out metabolic functions for sieve tube elements. - Phloem also contains sclerenchyma cells that provide structural support by increasing rigidity and flexibility. Three main types of angiosperm: apical, intercalary, and lateral. LESSON 3: PLANT CELL DIVISION INTERPHASE ⁕ G1 phase: Metabolic changes prepare the cell for division. At a certain restriction point - the cell is committed to division and moves into the S phase. ⁕ S phase: DNA synthesis replicates the genetic material. Each chromosome now consists of two sister chromatids. ⁕ G2 phase: Metabolic changes assemble the cytoplasmic materials necessary for mitosis and cytokinesis. ⁕ M phase: A nuclear division (mitosis) followed by a cell division (cytokinesis). MITOSIS - although a continuous process is conventionally divided into five stages: ⚘ PROPHASE - occupies over half of the mitosis. - nuclear membrane breaks down to form a number of small vesicles - nucleolus disintegrates. - Centrosome: duplicates itself to form two daughter centrosomes that migrate to opposite ends of the cell. It organizes the production of; - Microtubules: forms the spindle fibers that constitute the mitotic spindle. - chromosomes condense into compact structures. 6  - Each replicated chromosome can now consist of two identical chromatids (or sister chromatids) held together by a structure known as the centromere. ⚘ PROMETAPHASE - The chromosomes, led by their centromeres, migrate to the equatorial plane in the midline of the cell - at right angles to the axis formed by the centrosomes. - Metaphase plate: region of the mitotic spindle - Kinetochore: spindle fibers bind to each chromosome on each side of the centromere. - The chromosomes continue to condense. ⚘ METAPHASE - The chromosomes align themselves along the metaphase plate of the spindle apparatus. ⚘ ANAPHASE - Shortest stage of mitosis - The centromeres divide, and the sister chromatids of each chromosome are pulled apart - or 'disjoin' - and move to the opposite ends of the cell, pulled by spindle fibers attached to the kinetochore regions - Daughter chromosomes: separated sister chromatids ⚘ TELOPHASE - final stage of mitosis and a reversal of many of the processes observed during prophase - nuclear membrane reforms around the chromosomes grouped at either pole of the cell, the chromosomes uncoil and become diffuse, and the spindle fibers disappear. ⚘ CYTOKINESIS - final cellular division to form two new cells. - In plants, a cell plate forms along the line of the metaphase plate - The cell then enters interphase - the interval between mitotic divisions. MEIOSIS - Meiosis results in gametes that have only half of chromosomes of the parent plant - When gametes form zygotes as they unite in pairs, the original chromosome # is restored - In sexual reproduction, sex cells called GAMETES - Two gametes called egg and sperm in higher plants and animals, unite to form a single cell called a ZYGOTE - Four main phases are recognized in each of the two divisions, and the first phase is further subdivided - It occurs in strawberry plants! - Accordingly, some have referred to ○ Division I as a reduction division ○ Division II as an equational division 7 DIVISION I 🎕 PROPHASE I - As the chromosomes become shorter and thicker, homologs become aligned in pairs, and eventually, two chromatids can be distinguished for each chromosome 🎕 METAPHASE I - The main features are: (1) The pairs of chromosomes become aligned at the equator of the cell. (2) The now complete spindle becomes more apparent 🎕 ANAPHASE I - The main features are: (1) Each chromosome, consisting of two chromatids, migrates to a pole (the region at each end of the cell, analogous to the poles of the earth) (2) Homologous chromosomes move to the opposite poles of the cell. 🎕 TELOPHASE I - Depending upon the species, the chromosomes now either partially revert back to interphase, becoming longer and thinner as they do so, - or proceed directly to Division II; two new cells will eventually form, each with half the chromosome number as the original cell; TWO DNA MOLECULE DIVISION II 🎕 PROPHASE II - chromosomes become shorter and thicker, and their two-stranded nature once more becomes apparent 🎕 METAPHASE II (1) The centromeres of the chromosomes become aligned along the equator. (2) New spindles become conspicuous and complete 🎕 ANAPHASE II - the centromeres and chromatids of each chromosome separate and migrate to opposite poles 🎕 TELOPHASE II (1) The coils of the chromatids (now called chromosomes again) relax so that the chromosomes become longer and thinner. ONE DNA MOLECULE (2) New nuclear envelopes and nucleoli appear for each group of chromosomes LESSON 4: DIFFUSION AND OSMOSIS DIFFUSION Diffusion is the random motion of particles from an area of high concentration to an area of low concentration through a semipermeable membrane. All molecules in liquids and gases characteristically tend to move or diffuse in all directions until they are distributed evenly throughout the available space. This idea is fundamental in understanding the mechanisms by which materials are exchanged between cells and the environment. Diffusion is the movement of molecules from a region of high concentration to a region of low concentration. 8  In a closed environment, the molecules will disperse themselves until the concentration is equal throughout – which is called equilibrium. The rate of diffusion is influenced by the: (1) temperature of the environment (2) density of the diffusing molecule (g/mL) (too dense - slower) (3) medium of diffusion (viscous - slower movement from high to low concen.) (rate low) (4) concentration gradient (same direction - faster diffusion) Increase in temperature increases the average kinetic energy of the particles, thus increasing their velocity. At a certain temperature, lighter atoms, such as H, C, O, and N, travel faster and are more mobile than larger atoms such as Cu or Fe. Thus, materials made of these lighter atoms diffuse faster than heavier materials. Diffusion rate also depends on the medium where the movement of molecules takes place. The particles present in the medium act as the barrier to diffusion e.g. adding sugar into water increases its viscosity. The particles present in the medium may collide with the diffusing molecules, thus reducing the diffusion rate. CONCENTRATION GRADIENT - pertains to the difference in concentration on either side of the membrane. - Molecules tend to move down the concentration gradient toward areas of lesser concentration. - The greater the concentration gradient, the greater the rate of diffusion. DIFFUSION (IN CELL MEMBRANES) rate of diffusion also depends on the membrane's thickness and the surface area. For molecules (e.g., drug molecules) to diffuse into the cell, they must traverse the cell membrane. The cell membrane is so thin that most molecules diffuse through it at a faster rate. The larger the area of diffusion, the greater the diffusion rate. Cell membranes allow some molecules to pass through, such as H2O and O, by diffusion However, other molecules do not freely move across the membrane. The selective permeability of the cell membrane is an important consideration in understanding the diffusion mechanism. OSMOSIS Osmosis is a diffusion process where water molecules move across the semipermeable membrane. Water molecules will move in the direction where there is a high concentration of solute and low concentration of water. Hence, concentrations on both sides of the membrane are equalize. Osmosis regulates hydration, the influx of nutrients, and the outflow of wastes. 9  ○ In plant or animal cells, if the medium surrounding the cell has a low solute concentration, water enters the cell, causing the cell to swell. In this case, there is high water concentration in the medium so that the cell will gain water by osmosis. ○ On the other hand, if the medium has lower concentration of water than the cell (hence high concentration of solute), it will lose water by osmosis. This time more water will leave the cell, this leads to shrinking of the cell. In most situations, water molecules move from the less-concentrated (HYPOTONIC) to the more-concentrated (HYPERTONIC) solution. This tends to reduce the difference in concentration, thus achieving equilibrium. Solvents are liquids in which substances dissolve Membranes through which different substances diffuse at different rates are described as SEMI-PERMEABLE. All plant cell membranes appear to be semi-permeable. In plant cells, osmosis is essentially the diffusion of water through a semipermeable membrane from a region where the water is more concentrated to a region where it is less concentrated. OSMOTIC POTENTIAL: (represented by Ψs) of a solution is a measure of the potential of water to move from one cell to another as influenced by solute concentration. Water enters a cell by osmosis until the osmotic potential is balanced by the resistance to the expansion of the cell wall PLANT SAMPLE: 1. Potato - Solanum tuberosum 2. Onion - Allium cepa 10