Cells: Structures and Functions PDF

Lesson 3: CELL STRUCTURES AND FUNCTIONS OPENING PRAYER Dear Lord and Father of all, Thank you for today. Thank you for ways in which you provide for us all. For Your protection and love we thank you. Help us to focus our hearts and minds now on what we are about to learn. Inspire us by Your Ho...

Lesson 3: CELL STRUCTURES AND FUNCTIONS OPENING PRAYER Dear Lord and Father of all, Thank you for today. Thank you for ways in which you provide for us all. For Your protection and love we thank you. Help us to focus our hearts and minds now on what we are about to learn. Inspire us by Your Holy Spirit as we listen and write. Guide us by your eternal light as we discover more about the world around us. We ask all this in the name of Jesus. Amen… Learning Competency: ▪ The learners shall be able to describe the structure and function of major and subcellular organelles ▪ (STEM_BIO11/12-Ia-c-2) Specific Objectives: At the end of the lesson, the learners should be able to: A. explain cell organelle functions. B. differentiate between plant, animal and bacterial cells in terms of structure and function C. describe the structure and function of major and subcellular organelles 5 A. Plasma Membrane ▪ Acts as the boundary between the outside and inside of a cell. ▪ The integrity and function of the plasma membrane are vital to a cell because this membrane acts much like a gatekeeper, regulating the passage of molecules and ions into and out of the cell. ▪ The plasma membrane is composed of a phospholipid bilayer. ▪ The polar heads of the phospholipids are at the surfaces of the membrane; the nonpolar tails make up the interior of the membrane. ▪ Proteins embedded in the membrane have various functions  B. Cytoplasm ▪ A semifluid interior, where chemical reactions occur. ▪ Consists of mainly water (80-85%). The remaining constituents are proteins (10-15%), lipids (2-4%), polysaccharides (1%) and nucleic acids (1%). C. DNA ▪ DNA = Deoxyribose nucleic acid ▪ Genetic material of all cellular organisms and most viruses. ▪ Made out of sugars (deoxyribose), phosphates and nitrogen bases ▪ DNA carries the information needed to direct protein synthesis and replication  D. Ribosomes ▪ Is a complex molecule made of ribosomal RNA molecules and proteins that form a factory for the protein synthesis in cells. ▪ Discovered by George E. Palade in 1955 – small particles in the cytoplasm that preferentially associated with the endoplasmic reticulum membrane. PROKARYOTIC CELL STRUCTURE BACTERIAL CELL ▪ A. FLAGELLA ▪ 3 parts □ filament – long, thin, helical structure composed of proteins □ hook- curved sheath □ basal body – stack of rings firmly anchored in cell wall ▪ rotates 360o ▪ 1-2 or many distributed over entire cell ▪ functions in motility BACTERIAL CELL ▪ A. FLAGELLA ▪ Flagellar arrangements ▪ monotrichous – single flagellum at one end ▪ lophotrichous – small bunches arising from one end of cell ▪ amphitrichous – flagella at both ends of cell ▪ peritrichous – flagella dispersed over surface of cell, slowest ▪ B. FIMBRIAE ▪ fine hairlike bristles from the cell surface ▪ function in adhesion to other cells and surfaces  C. PILI rigid tubular structure made of pilin protein found only in Gram negative cells Functions BACTERIALjoins bacterial cells for DNA transfer (conjugation) CELL adhesion ▪ D. GLYCOCALYX ▪ Coating of molecules external to the cell wall, made of sugars and/or proteins ▪ 2 types □ capsule - highly organized, tightly attached □ slime layer - loosely organized and attached ▪ functions □ attachment □ inhibits killing by white blood cells □ receptor ▪ E. CELL WALL Peptidoglycan ▪ unique macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments ▪ provides strong, flexible support to keep bacteria from bursting or collapsing because of changes in osmotic pressure Gram positive cell wall ▪ Consists of □ a thick, homogenous sheath of peptidoglycan 20-80 nm thick □ tightly bound acidic polysaccharides, including teichoic acid and lipoteichoic acid ▪ Retain crystal violet and stain purple Gram negative cell wall ▪ Consists of □ an outer membrane containing lipopolysaccharide (LPS) □ thin shell of peptidoglycan □ periplasmic space □ inner membrane ▪ Lose crystal violet and stain red from safranin counterstain ▪ F. CYTOPLASM ▪ dense gelatinous solution of sugars, amino acids, & salts ▪ 70-80% water ▪ serves as solvent for materials used in all cell functions ▪ G. CHROMOSOME ▪ single, circular, double- stranded DNA molecule that contains all the genetic information required by a cell ▪ DNA is tightly coiled around a protein, aggregated in a dense area called the nucleoid ▪ H. PLASMIDS ▪ small circular, double-stranded DNA ▪ free or integrated into the chromosome ▪ duplicated and passed on to offspring ▪ not essential to bacterial growth & metabolism ▪ may encode antibiotic resistance, tolerance to toxic metals, enzymes & toxins ▪ used in genetic engineering- readily manipulated & transferred from cell to cell I. RIBOSOMES ▪ site of protein synthesis ▪ have a small and large subunit EUKARYOTIC CELL STRUCTURE Basic Structure of a Eukaryotic Cell ✓ Plasma membrane ✓ Cytoplasm (semifluid) ✓ Cytoskeleton - microfilaments and microtubules that suspend organelles, give shape, and allow motion ✓ Presence of characteristic membrane enclosed subcellular organelles ✓ A membrane-bound nucleus PLANT CELL STRUCTURE Cell Wall ▪ Functions for protection and support for the entire cell ▪ Consists of the primary wall, middle lamella and secondary wall □ Middle lamella – intercellular layer composed of pectin. Pectin is a viscous and gelatinous substance which acts as a cementing material to hold the cells together. □ Primary wall – consists mainly of bundles of intertwined molecules of cellulose, cutin and waxes Cell Wall □ Secondary wall – produced and deposited between the primary wall and the protoplast after cell enlargement ceases and is composed mainly of cellulose and lignin. Lignin is a complex material responsible for hardness and decay-resisting qualities of many woods. Plasmodesmata ▪ Protoplasmic connections which aid in the movement of materials from one cell to another ▪ microscopic channels which traverse the cell walls of plant cells enabling transport and communication between them Plastids ▪ Essential in food making and storage of food □ Proplastid – young plastids capable of dividing, usually colorless □ Chromoplastid – colored plastids containing red, yellow or orange pigments □ Chloroplastid – contain the green pigment chlorophyll □ Leucoplastid – colorless plastid and usually functions for storage □ Amyloplastid – stores starch □ Elaioplastid – stores oil □ Aleurone plastid – stores protein Animal Cell Structures Diagram of a typical animal (eukaryotic) cell, showing subcellular components. ▪ Organelles: ▪ (1) nucleolus ▪ (2) nucleus ▪ (3) ribosome ▪ (4) vesicle ▪ (5) rough endoplasmic reticulum (ER) ▪ (6) Golgi apparatus ▪ (7) Cytoskeleton ▪ (8) smooth endoplasmic reticulum ▪ (9) mitochondria ▪ (10) vacuole ▪ (11) cytoplasm ▪ (12) lysosome ▪ (13) centrioles within centrosome Centrioles ▪ help to organize the assembly of microtubules during cell division. Organelles found in Most Eukaryotes MEMBRANE- BOUND ORGANELLES 1. Nucleus ▪ control center of the cell 56 Nuclear membrane ▪surrounds the nucleus. ▪ It is also called nuclear envelope. Nucleoplasm ▪ the liquid inside the nucleus. ▪ It is also called Karyoplasm Nucleolus ▪ produces ribosomes 2. ENDOPLASMIC RETICULUM ▪ transport system of the cell 2.1 Rough Endoplasmic Reticulum – has attached ribosomes and is involved in protein synthesis 2.2 Smooth Endoplasmic Reticulum – involved in synthesis and breakdown of lipid and carbohydrate (The word endoplasmic means "within the cytoplasm,~ and reticulum is Latin for "little net~) 62 3. Golgi Complex/Bodies/Apparatus ▪ also called dictyosome ▪ modifies, packages and distributes molecules made at one location of the cell and used at another. 64 4. Vacuoles ▪ serve as storage organelles within the cell. ▪ they are typically smaller and less prominent in animal cells. 67 4. VESICLE ▪ small, spherical, or irregularly shaped organelles that can be found in various eukaryotic cells, including both plant and animal cells. They are also membrane-bound, enclosed by a lipid bilayer. FUNCTIONS: ▪ Transport ▪ Secretion ▪ Endocytosis and Exocytosis 5. Mitochondrion ▪ powerhouse of the cell ▪ sites of cellular respiration, the metabolic process that generates ATP by extracting energy from sugars, fats, and other fuels with the help of oxygen. ▪ Surrounded by a DOUBLE membrane □ Folded inner membrane called CRISTAE (increases surface area for more chemical reactions) □ Interior called MATRIX 6. Lysosomes ▪ small membrane-bordered structures that contain chemicals and enzymes necessary for digesting certain materials in the cell. ▪ They are formed in the Golgi bodies. They are known as suicidal bags for they can destroy cell structures that have outlived their usefulness 7. Microbodies/cytosomes ▪ small membrane-bound organelle originating from the endoplasmic reticulum containing enzymes. ▪ For example, peroxisomes are a type of microbody with specific enzymes for detoxifying harmful substances. NON-MEMBRANE BOUND ORGANELLES 1. Ribosomes ▪ protein factories of the cell 2. CENTRIOLES ▪ are cylindrical, microtubule-based organelles found in animal cells, including human cells. ▪ They play a crucial role in cell division, particularly during the process of mitosis and meiosis. 3. Cytoskeleton ▪ composed of a variety of filaments and fibers that support cell structure and drive cell movement. ▪ Helps cell maintain cell shape ▪ Made of proteins □ Microtubules – contain long thin cylindrical fibrils that provide support for cell shape and help move organelles through the cell and during cell division. □ Microfilament – contains actin for movement and support of the cell. They also permit movement of the cytoplasm within the cell called cytoplasmic streaming.