Cell Structure and Function PDF

9/15/23 Theand Nature of Science Structure Function of the Cell Learning Goals/Objectives • Differentiate between prokaryotic vs. eukaryotic cells and plant vs. animal cells • List and describe the functions of each organelle • Explain the relationship between organelles in the endomembrane system...

9/15/23 Theand Nature of Science Structure Function of the Cell Learning Goals/Objectives • Differentiate between prokaryotic vs. eukaryotic cells and plant vs. animal cells • List and describe the functions of each organelle • Explain the relationship between organelles in the endomembrane system • Explain how the endosymbiotic theory explains the existence of eukaryotic cells • Describe how the structures of the cytoskeleton work together to produce movement 2 2 3 TheTypes Nature Science ofof Cells The Characteristics Nature of Science Common of Cells Cell theory states that all organisms consist of cells Cells are divided into two fundamental types based on morphology: All cells have: 1. Proteins—perform most of the cell’s functions 2. Nucleic acids—store, transmit, and process information 3. Carbohydrates—provide chemical energy, carbon, support, and identity 4. Plasma membrane—serves as a selectively permeable membrane barrier 1. Eukaryotes have membrane-bound nucleus 2. Prokaryotes lack membrane-bound nucleus Based on phylogeny, or evolutionary history, organisms are divided into three domains: 1. Bacteria—prokaryotic 2. Archaea—prokaryotic 3. Eukarya—eukaryotic 4 4 5 5 1 9/15/23 Prokaryotic Cell The Nature ofStructure: Science Distinctive Features The Nature of Science Prokaryotic cells have an array of distinctive structures and functions: • Contain at least one chromosome • Many protein-synthesizing ribosomes • Phospholipid components differ: Prokaryotic Cell Structure • Bacterial phospholipids consist of fatty acids bound to glycerol • Archaeal phospholipids used branched isoprenoid chains bound to glycerol Cytoplasm: All contents of cell inside membrane 6 6 7 7 Prokaryotic Cell The Nature ofStructure: Science Ribosomes Manufacture Protein Prokaryotic Cell The Nature ofStructure: Science DNA is free and supercoiled Prokaryotes also have ribosomes: • Macromolecular machines • Have large and small subunit • Consist of RNA molecules and protein • Used for protein synthesis • Ribosomes in bacteria and archaea similar in size and function but RNA and protein components are different • Similarly, Ribosomes in prokaryotes differ from those in eukaryotes Chromosome: • Most prominent structure inside prokaryotic cell • Most bacterial and archaeal species have single, circular chromosome: • Consists of large DNA molecule associated with proteins • DNA molecule contains information • Proteins give DNA structural support Prokaryotic cells may contain circular, supercoiled DNA molecules called plasmids 8 8 9 9 2 9/15/23 Prokaryotic Cell The Nature ofStructure: Science Cytoskeletal Structures Prokaryotic Cell The Nature ofStructure: Science Photosynthetic Membranes Bacteria and archaea contain long, thin protein filaments in cytoplasm: Many prokaryotes have internal photosynthetic membranes: • Convert energy in sunlight to chemical energy • Multiple membranes passing through internal region of cell observed in photosynthetic bacteria • Develop as infoldings of plasma membrane • Contain enzymes and pigment molecules required for reactions to occur • • • • Protein filaments form basis of cytoskeleton Serve variety of roles In bacteria, cytoskeleton essential for cell division Maintains cell shape 10 10 11 11 Prokaryotic Cell The Nature ofStructure: Science External Features Prokaryotic Cell The Nature ofStructure: Science Cell Wall Exoskeleton • Many prokaryotes interact with their environment via structures that grow from their plasma membrane • Flagella and fimbriae: • Cell wall forms protective “exoskeleton” • Most prokaryotes have cell wall: • Composed of tough, fibrous layer • Surrounds plasma membrane • Protects shape and rigidity of cell • Structures found on bacterial surfaces • Flagella—long filaments that rotate to propel cell • Fimbriae—needlelike projections that promote attachment to other cells or surfaces • In bacteria: • Primary structural component of cell wall is polysaccharide peptidoglycan • Some have outer membrane made of glycolipids 12 12 13 13 3 9/15/23 The Nature Science Eukaryotic CellofStructure The Nature of Science • Eukaryotes range in size from microscopic algae to 100-meter-tall redwood trees: • Includes protists, fungi, plants, and animals • Organisms may be multicellular or unicellular • Most eukaryotic cells are larger than most prokaryotic cells: (1-10um vs. 5-100um) Eukaryotic Cell Structure 14 14 • Organelles compartmentalize volume inside eukaryotic cells into small bins: • Fluid portion of cell, cytosol, has small volume • Compartmentalization offers two advantages: • Separation of incompatible chemical reactions • Increasing efficiency of chemical reactions 15 Eukaryotic CellofStructure: The Nature Science Benefits of Organelles Eukaryotic CellofStructure: The Nature Science Benefits of Organelles 16 16 15 17 17 4 9/15/23 Organelles work together to: Organelles in the Endomembrane System synthesize and move proteins 1. deliver proteins 2. remove wastes, 3. produce energy 4. provide storage 18 19 Eukaryotic CellofStructure: The Nature Science The Nucleus is the Control Center Nucleus and Ribosomes The Nucleus—Large, highly organized membrane bound compartment: • Surrounded by doublemembrane nuclear envelope: Chromatin • Studded with pore-like openings • Inside surface is linked to the nuclear lamina: • Lattice-like sheet of fibrous proteins • Has a distinct region called nucleolus: • Location where ribosomal RNA is synthesized and ribosome subunits are assembled 20 20 21 5 9/15/23 Eukaryotic CellofStructure: The Nature Science Ribosomes are the site of Protein Synthesis • Ribosomes are complex molecular machines that manufacture proteins: Eukaryotic CellofStructure: The Nature Science The Endoplasmic Reticulum- Protein and Lipid Synthesis • Endoplasmic reticulum—extensive membrane-enclosed factory: • Continuous with nuclear envelope • Lack membrane—not considered organelles • Two regions, distinct in structure and function: • Rough endoplasmic reticulum (rough ER) • Smooth endoplasmic reticulum (smooth ER) • Some ribosomes are free in the cytosol: • Manufacture proteins that remain in cytosol or are imported to other organelles (e.g., nucleus) • Some are attached to endoplasmic reticulum: • Manufacture proteins with other fates 22 22 23 23 Eukaryotic CellofStructure: The Nature Science Eukaryotic CellofStructure: The Nature Science The Endoplasmic Reticulum- Protein and Lipid Synthesis The Endoplasmic Reticulum- Protein and Lipid Synthesis • As proteins are manufactured on RER, they move to the lumen: Rough endoplasmic reticulum (rough E R, R E R): • Studded with ribosomes: • Dark, knobby looking structures • Synthesizes proteins that will be: • Shipped to another organelle • Inserted into plasma membrane • Secreted to the cell exterior • Lumen—inside of any saclike structure • In RER lumen, proteins are folded and processed • Proteins made on RER may: • Carry messages to other cells • Act as membrane transporters or pumps • Catalyze reactions 24 24 25 25 6 9/15/23 Eukaryotic Cell Structure: The Nature of Science Some Proteins Move From the ER to the Golgi The Golgi Apparatus is the Packaging and Shipping Plant Golgi apparatus • Golgi apparatus • Is formed by a series of stacked flat membranous sacs called cisternae • Function: • Processes, sorts, and ships proteins synthesized in the rough ER • cis side of a Golgi apparatus receives products from the rough ER • trans side ships them out to other organelles or the cell surface • Membranous vesicles carry materials to and from the organelle cis trans Vesicle s cleu s nu face side cis Lumen of Golgi apparatus Cisternae Vesicles ces e fa ne s sid bra tran a mem m s pla 100 nm 26 26 27 Golgi Apparatus Thewhen Nature of Science What happens vesicles leave the Golgi? Transport out of the cell is exocytosis 28 29 7 9/15/23 Eukaryotic CellofStructure: The Nature Science The Nature of Science Bringing Concepts Together: The Lysosome is the Recycling Center Lysosomes: What would the molecular consequence be if there was a mutation in a gene for an acid hydrolase protein? • Recycling centers found only in animal cells • Contain approximately 40 different enzymes that were made in the RER and shipped through the Golgi • Enzymes specialized for hydrolyzing different macromolecules What effect would this have on organelle function? • Digestive enzymes inside lysosomes are called acid hydrolases: • Work best at pH 5.0 • Proton pumps in membrane maintain low internal pH 30 31 30 31 Eukaryotic CellofStructure: The Nature Science Lysosomal Storage Diseases: The Endomembrane System Summary • Are due to genetic defects that destroy the function of one or more the the lysosomal enzymes that breakdown biomolecules . If a defective enzyme cannot digest its target material, that material will accumulate in the lysosome until it bursts The most severe form of lysosomal storage disease is inclusion cell-disease (I-cell disease). • Very rare, single gene, autosomal recessive, metabolic disorder • Nearly all lysosome enzymes are missing from the lysosomes all over the body. • As undigested material accumulates, lysosomes swell • Affects nearly all organ systems, skeletal integrity, and mental development. Individuals rarely live beyond 6-7 years old. 32 • Collectively, the ER, golgi, and lysosomes make up the endomembrane system: • Center for producing, processing, and transporting proteins, carbohydrates and lipids (Example) Acid hydrolases • Gene transcribed into mRNA • mRNA translated into a protein at ER • Processed in Golgi apparatus • Shipped to lysosomes But how do cells know where to direct proteins to go? 32 33 33 8 9/15/23 Experiments that Established The Presence The Nature of Science and Function of Molecular Zip Codes The Endomembrane System The Nature of Science Produces, Ships, and Recycles Cargo Nucleoplasmin Zip Code aka. Signal Sequence How do the proteins know where to go? Each protein has a specific amino acid zip code sequence embedded into it’s primary structure that is specific to it’s home organelle (signal 34 sequence) 34 NLS Pyruvate Kinase Pyruvate Kinase Fusion Protein NLS 35 35 Eukaryotic CellofStructure: The Nature Science The Mitochondria Makes ATP Energy Supplying Organelles • Mitochondria supplies ATP to cells: • Have two membranes: • Outer membrane defines organelle’s surface • Inner membrane is folded into series of sac-like cristae • Mitochondrial matrix—solution enclosed within inner membrane • Mitochondria’s morphology is dynamic in cells: • Prone to fusion and fission • Results in either elongated and branched structures called mitochondrial networks or multiple individual organelles • Mitochondria have their own mitochondrial DNA (mt DNA): • Grow and divide independently of cell division • Manufacture their own ribosomes 37 36 37 9 9/15/23 Eukaryotic CellofStructure: The Nature Science Eukaryotic CellofStructure: The Nature Science Endosymbiotic Theory Chloroplasts are Photosynthetic Most plant and algal cells have chloroplasts, where photosynthesis takes place: • Have three membranes: • Like mitochondria, chloroplasts contain their own DNA and manufacture their own ribosomes, and grow and divide independently of cell division • Endosymbiosis theory: • Proposes that mitochondria and chloroplast were once free-living bacteria • Bacteria were engulfed by ancestor of modern eukaryotes but were not destroyed • Mutually beneficial relationship evolved • Innermost membrane contains flattened sacs called thylakoids • Thylakoids are arranged in stacks called grana • Surrounding the thylakoids is the stroma which contains enzymes that use chemical energy to produce sugar 38 38 39 39 Relationship between chloroplasts and mitochondria The Nature of Science Storage and Structural Support 40 41 10 9/15/23 Vacuoles are storage oganelles in Plant and Fungal Cells Function: • Some vacuoles are specialized for digestion and contain digestive enzymes • Most are used for storage of water and/or ions, which helps the cell maintain its normal volume and structure • They may be packed with noxious compounds to protect leaves and stems from being eaten by predators • Inside seeds, they are filled with proteins. • In flower petals or fruits, they are filled with colorful pigments Eukaryotic CellofStructure: The Nature Science Vacuole Cytoskeleton • Cytoskeleton: • Extensive system of protein fibers • Gives cells shape and structural stability • Transports materials within cell • Organizes all organelles and other cellular structures into a cohesive whole • Allows whole cell movement Vacuole 1 µm 43 42 43 The Cytoskeleton The Nature of Science Actin Filaments The Cytoskeleton The Nature of Science Intermediate Filaments • Long Fibers that radiate throughout the cell to resist tension • Nuclear lamins are intermediate filaments: • Make up nuclear lamina layer • Defines shape of nucleus— stabilizes envelope • Form a dense mesh under nuclear envelope • Complete actin filament resembles two log strands that coil around each other • Individual actin protein subunits assemble via polymerization: • They assemble from head to tail through formation of covalent bonds • Grouped together into long bundles or dense networks • Usually found just inside plasma membrane 44 45 11 9/15/23 The Cytoskeleton The Nature of Science Microtubules The Cytoskeleton The Nature of Science Actin Filaments • Actin filaments are also involved in movement • Movement, with motor protein myosin: • Uses A T P to change shape and do work: • Cytokinesis: dividing cytoplasm during cell division • Cytoplasmic streaming— directed flow of cytosol and organelles • Cell crawling—groups of actin filaments grow causing bulges in plasma membrane 46 • Large, hollow tubes made of tubulin dimers (“two-parts”): • α-tubulin and β-tubulin • Tubulin dimers polymerize in polar head-to-tail fashion via noncovalent bonds • MT’s originate in centrioles • Serve as highways that motor proteins (kinesins) drag organelles across 47 The Cytoskeleton The Nature of Science Three Major Components The Cytoskeleton The Nature of Science Microtubules • Serve as structural components for flagella and cilia 48 49 12 9/15/23 Eukaryotic CellofStructure: The Nature Science To Recap Cytoskeleton Organelle Fungi, algae, and plants have stiff outer cell wall in addition to plasma membrane: • Cell wall is located outside of plasma membrane • Provides durable outer layer • Gives structural support to cell • Made of cellulose or chitin What’s it’s job? Nucleus Endoplasmic Reticulum Mitochondria Powerplant- produces energy Lysosomes Cell Membrane Cell Wall Vacuole Ribosomes Cells of animals lack a cell wall: • Supported by extracellular matrix (ECM) • Diffuse mixture of secreted proteins and polysaccharides 50 50 51 The Nature Science Animal Cells vs.ofPlant Cells The Nature of ScienceCells Eukaryotic vs. Prokaryotic Cell Membrane Cell Wall Chloroplasts Cytoplasm Cytoskeleton Genetic Material ER Lysosomes Mitochondria Nucleus Ribosomes Large/centralized Vacuole 53 Prokaryotes Eukaryotes Cell Membrane Cell Wall Chloroplasts Cytoplasm Cytoskeleton Genetic Material ER Lysosomes Mitochondria Nucleus Ribosomes Large centralized Vacuole Animal Plant 55 13 9/15/23 Eukaryotic Structure: Study Table TheCell Nature of Science 57 Eukaryotic Structure: Study Table TheCell Nature of Science 58 14