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Transcript
Unit Three Cell Structure, Function, and Membranes Chapters 4 and 5 Cell Structure Chapter 4 Cell Discovery Robert Hooke 1665 Called them “cellulae”, meaning small rooms Cell Discovery Anton van Leeuwenhoek Microscopist Called them“animalcules”, which means little animals Cell Discovery Matthias Schleiden Theodor Schwann 1838 1839 Botanist Physiologist “all plants are made of cells” “all animals are made of cells” Cell Theory All organisms are composed of one or more cells, and the life processes of metabolism and heredity occur within these cells Cells are the smallest living things, the basic unit of organization of all organisms Cells arise only by the division of a previously existing cell Limitations to cell size Cells remain small for reasons to do with diffusion Rate of diffusion can be affected Surface area Temperature Concentration gradient Distance over which diffusion must occur What do all cells have in common? Nucleoid region or nucleus where genetic material is housed Cytoplasm Ribosomes for protein synthesis Plasma membrane Cytoplasm and Plasma Membrane Cytoplasm Plasma Membrane Semifluid Phospholipid bilayer about 5 to 10 nm thick Contains sugars, amino acids, and proteins Proteins embedded May contain organelles Transport Cytosol Receptor Prokaryotic Cells Bacterial Cell wall Composed of peptidoglycan and short polypeptide cross-links Drugs such as penicillin and vancomycin interrupt bacterial cell wall formation by halting the short polypeptide crosslinks Some secrete a jelly-like capsule, which allows them to stick to other surfaces Flagella Eukaryotic Cells Much more complex Essentially they are compartmentalized Endomembrane system Organelles Nucleus Largest and most easily seen From the Latin meaning “nut” or “kernel” Houses the genetic material Most also have a nucleolus Nuclear Envelope Phospholipid bilayers Contains nuclear pores The pores allow ions and small molecules to diffuse freely Nuclear lamina provides structure and shape Know the Function of the Following Organelles Plasma membrane Lysosomes Nucleus Peroxisomes Nucleolus Microbodies Ribosomes Vacuoles Endoplasmic Reticulum Mitochondria Golgi apparatus Chloroplasts Flagella Cytoskeleton Cell wall Ribosomes Main function? Number of subunits? “Universal organelles?” Endoplasmic Reticulum What type of system is the ER part of? What does the name actually mean? Main function of the rough ER? What are some functions of the smooth ER? Golgi Apparatus What type of cells have large numbers of Golgi? What are the two faces of the Golgi? What is the job of each? What cell wall structures are made by the Golgi? Lysosomes How does a lysosome function? Phagolysosome? Peroxisomes What is the function? What do they produce? How is the toxicity of their product mitigated? Vacuoles Function? What is a tonoplast? Mitochondria What is the function of mitochondria? Do you remember the four steps of cell respiration? Be sure to know specific regions of mitochondria and the function. Chloroplast What are the steps of photosynthesis? Know the structures within the chloroplast Cytoskeleton Actin filaments, microfilaments—cell movements; pinching, contracting, crawling Microtubules—cytoplasm organization Intermediate filaments—structural components; ex. keratin Centrioles Barrel-shaped organelles in animals and some protists Centrosome—area surrounding the pair of organelles Help organize the microtubules Cytoskeleton and movement Actin filaments and microtubules aid in cellular division Chromosomes move to opposite poles because they are attached to shortening microtubules Muscle cells utilize the actin filaments to generate movement Molecular motors Eukaryotic cells must move materials ER sometimes does this Vesicles and microtubules also move materials Molecular motors Four components are needed to move materials Vesicle or organelle to be transported A motor protein to provide energy A connector molecule to attach the vesicle to the motor Microtubules that the vesicle will ride along like a train Directionality of movement is based on charges of the microtubules Crawling cells Actin filaments allow cells to crawl Inflammation, clotting, wound healing, and the spread of cancer all depend on crawling Ex. White blood cells Actin filaments rapidly polymerize at the leading edge of the cell, then myosin motors contract and pull the cell contents forward Flagella and Cilia Flagella Eukaryotic flagella have 9 + 2 structure Dyein motor protein movement cause ungulation Basal body Cilia More numerous than flagella Retain the same internal structure Plant cell walls Composed of cellulose Structure and support Primary wall, middle lamella, secondary walls Animal Cell ECM Extracellular matrix Composed of glycoproteins Proteoglycans Fibronectin and Integrin How do cells communicate? Formation of tissues, organs, and organ systems means cells need to communicate Cells need connections, cellular identifiers, and communication Membrane proteins are highly involved in this commnication Cell surface proteins Cell surface proteins allow cells to “read” each other and react accordingly Glycolipids Bloodtypes A, B, and O MHC proteins Major histocompatibility complex Recognizes “self” and “non-self” proteins Immune system Cell-to-cell connections Adhesive junctions Septate or tight junctions Communicating junctions Gap junctions Plasmodesmata Adhesive junctions Appear to be the first to have evolved, found in sponges Found in muscle and skin, areas of mechanical stress Based on the protein cadherin which is Ca+2 dependent Desmosomes Hemidesmosomes Septate or tight junctions Found in vertebrates and invertebrates Seal off sheets of cells Tight junctions are unique to vertebrates and use proteins called claudins, because they can occlude substances Cells of the digestive tract use tight junctions Communicating junctions Multicellular organisms Allow communication by diffusion through small openings Ions and other small molecules may pass Animals have gap junctions Plants have plasmodesmata Membranes Chapter 5 Fluid Mosaic Model Phospholipid bilayer Glycerol phospholipids Sphingolipids Singer and Nicholson developed new model in 1972 stating the proteins are in and on the membrane Fluid mosaic model Proteins float on and in the lipids Phospholipids Fatty acid tails Glycerol Phosphate head Choline Sphingolipids Similar structure Sphingomyelin found in animals Four Components Phospholipid bilayer Transmembrane proteins Interior protein network Scaffolding Can control movements and anchoring Cell-surface markers Glycoproteins glycolipids Membrane Fluidity Why does the membrane spontaneously form a bilayer? Can the fluidity of the membrane change? Membrane protein function Transporters Enzymes Cell-surface receptors Cell-surface identity markers Cell-to-cell adhesion Cytoskeleton attachment How do proteins anchor in the membrane? Non-polar regions embed in the membrane Chemical bonding domain regions in extracellular region If the protein moves, it gets shoved back into the membrane by water Blue areas are transmembrane domains Pore Proteins and β barrels Cellular Transport Passive Transport Active Transport Materials move from high to low concentration Materials move from low to high concentration Down the concentration gradient Up the concentration gradient No energy required Energy required Aquaporins Specialized channels for water Experimental demonstration Amphibian egg placed in hypotonic spring water Egg does not swell Aquaporin mRNA is injected into the egg and the proteins are expressed Egg swells Osmotic pressure Do you remember the following terms? Hypertonic Hypotonic Isotonic Sketch a cell in a hypertonic environment and show what would happen. Be sure to label salt and water concentrations inside and outside the cell. Extrusion Single-celled eukaryotes Contractile vacuole Pump out excess water Isosmotic regulation Marine organisms will adjust internal levels of solute to match external levels No net water movement Terrestrial animals bathe cells with an isotonic solution Example: blood contains high levels of albumin to match cell internal concentrations Turgor pressure Plants Most plant cells are hypertonic relative to their environment Water flows in and pushes the membrane against the cell wall Active Transport Energy is used to run pumps or change cell shapes Protein carriers can be any of the following Uniporter—carry a single type of molecule Symporter—carry two molecules in the same direction Antiporter—carry two molecules in opposite directions What is the energy used to complete these movements? Sodium-Potassium pump Directly uses ATP 3 Na+ leave 2 K+ enter Protein conformation changes rapidly, 300 Na+ transported per second Coupled Transport Indirect use of ATP The concentration gradient of the Na+ drives the action of the glucose transport
