Question: What are the three principles of cell theory?
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Question: What are the three principles of cell theory? Why is cell theory essential to understanding biology? CELL THEORY Every living organism is made up of one more cells The smallest living organisms are single cells and cells are the functional units of multicellular organisms All cells arise from preexisting cells CELL SIZE IS LIMITED Most cells are 1 to 100 micrometers Limited by need to exchange nutrients and waste through the plasma membrane through diffusion v v v v v v v v v CELL SIZE AND SHAPE As a spherical cell enlarges, its innermost parts get farther away from the plasma membrane Also, its volume increases more rapidly than its surface area A larger cell has a relatively smaller area of membrane for nutrition exchange than a small cell ALL CELLS HAVE A PLASMA MEMBRANE Phospholipid bilayer Hydrophilic head Hydrophobic tail Prevents movement of most ions and molecules Proteins Facilitate communication ALL CELLS CONTAIN CYTOPLASM All of the material inside the cell (but outside the DNA containing region) Cytosol Variety of structures ALL CELLS HAVE GENETIC MATERIAL DNA is the genetic blueprint RNA copies and translates DNA ALL CELLS OBTAIN ENERGY & NUTRIENTS FROM THE ENVIRONMENT Harness from sunlight Release from chemical bonds of energy carriers TWO BASIC TYPES OF CELLS Prokaryotic Eukaryotic REVIEW Table 4-1 Pro = before Eu = true Karyo = nucleus MAJOR CELLULAR FEATURES CELL WALLS Present in plants, fungi, some protists Non-living, relatively stiff coating Support and protect cells Usually porous for diffusion CYTOSKELETON Network of protein fibers Infuence Cell shape networks of intermediate filaments Cell movement microfilaments and microtubules assemble, disassemble, or slide Organelle movement microtubules and microfilament attachment Cell division microtubules form centrioles that apportion divided chromosomes and microfilaments contract to pinch daughter cells. CILIA AND FLAGELLA AID MOVEMENT Extensions of plasma membrane supported by microtubules Cilium Short, hairlike Flagellum Long whiplike EUKARYOTIC CELLS HAVE A NUCLEUS PARTS OF THE NUCLEUS Nuclear envelope Separates chromosomes from cytoplasm Studded with ribosomes Chromatin Diffuse in body of nucleus for DNA translation Compacted into chromosomes during replication Nucleolus Darker area within body of nucleus Ribosome synthesis PARTS OF THE NUCLEUS Nuclear envelope Separates chromosomes from cytoplasm Studded with ribosomes Chromatin Diffuse in body of nucleus for DNA translation Compacted into chromosomes during replication Nucleolus Darker area within body of nucleus Ribosome synthesis PARTS OF THE NUCLEUS Nuclear envelope Separates chromosomes from cytoplasm Studded with ribosomes Chromatin Diffuse in body of nucleus for DNA translation Compacted into chromosomes during replication Nucleolus Darker area within body of nucleus Ribosome synthesis WHAT IS A RIBOSOME? Cellular “workbench” - Site of protein synthesis Small particle composed of RNA and proteins Located on rough ER or on nuclear envelope membranes Proteins built depend on code of DNA that enters the ribosome CELLULAR MEMBRANES Includes the plasma membrane and the organelle membranes VESICLES ARE PART OF THE MEMBRANE SYSTEM Membranous sacs that transport substances among the separate regions of the membrane system ENDOPLASMIC RETICULUM Forms a series of enclosed, interconnected channels There are two forms of ER Smooth ER has no ribosomes Contains enzymes that detoxify drugs (in liver cells) or synthesizes lipids Rough ER is studded with ribosomes on outside Produces proteins and phospholipids destined for other membranes or for secretion (export) GOLGI APPARATUS Golgi Apparatus is a set of stacked flattened sacs Receives proteins from rough ER (via transport vesicles) and sorts them by destination Modifies some molecules (e.g. proteins to glycoproteins) Packages material into vesicles for transport WHAT HAPPENS TO SUBSTANCES IN THE MEMBRANE SYSTEM? Secreted proteins made in rough ER, travel through Golgi, then are exported through plasma membrane Membrane proteins and lipids made in rough ER, travel through Golgi, and replenish or enlarge organelle and plasma membranes Digestive proteins made in rough ER, travel through Golgi, and are packaged as lysosomes for use in cell Lysosomes fuse with food vacuoles and digest food into basic nutrients WHAT HAPPENS TO SUBSTANCES IN THE MEMBRANE SYSTEM? Secreted proteins made in rough ER, travel through Golgi, then are exported through plasma membrane Membrane proteins and lipids made in rough ER, travel through Golgi, and replenish or enlarge organelle and plasma membranes Digestive proteins made in rough ER, travel through Golgi, and are packaged as lysosomes for use in cell Lysosomes fuse with food vacuoles and digest food into basic nutrients LYSOSOMES ARE CELLULAR DIGESTIVE SYSTEM Membrane enclosed vesicles Merge with food vacuoles (bits of plasma membrane enclosing food particles) Lysosomal enzymes digest food VACUOLES Fluid filled sacs with a single membrane Contractile vacuoles in freshwater organisms used to collect and pump water out Plant central vacuoles used in several ways Maintain water balance Store hazardous wastes, nutrients, or pigments Provide turgor pressure on cytoplasm to keep cells rigid VACUOLES Fluid filled sacs with a single membrane Contractile vacuoles in freshwater organisms used to collect and pump water out Plant central vacuoles used in several ways Maintain water balance Store hazardous wastes, nutrients, or pigments Provide turgor pressure on cytoplasm to keep cells rigid MITOCHONDRIA Process food to release stored chemical energy CELLULAR POWERHOUSES Mitochondria extract energy from food molecules Extracted energy is stored in high-energy bonds of ATP (remember this molecule) Energy extraction process involves many reactions Anaerobic (cytosol) Aerobic (mitochondrion) CHLOROPLASTS Store energy in food ENERGY STORAGE BY CHLOROPLASTS The thylakoid membranes contain chlorophyll and other pigments that capture sunlight and make sugar, CO2, and water (photosynthesis) PLASTIDS PROVIDE STORAGE FOR PLANT CELLS PLASTID STORAGE Storage for photosynthetic products like starch Storage of pigment molecules giving color to ripe fruit PROKARYOTIC CELLS Smaller Usually with a stiff cell wall Can take the shape of rods, spheres, or helices PROKARYOTIC CELLS No nucleus Single, circular chromosome of DNA Chromosome found coiled in an area called the nucleoid Small rings of DNA (plasmids) located in the cytoplasm PROKARYOTIC CELLS No nuclear membrane or membrane-bound organelles present Some have internal membranes used to capture light Cytoplasm may contain food granules SPECIAL PROKARYOTIC FEATURES Some bacteria are propelled by flagella Infectious bacteria may have polysaccharide adhesive capsules and slime layers on their surfaces Pili and fimbriae are protein projections in some bacteria that further enhance adhesion REVIEW: What are the major parts of eukaryotic cells and their functions? How do plant cells differ from animal cells? How are prokaryotic cells different from eukaryotic cells? Question: What are the roles of the cell membrane? How does the structure of the membrane help it fulfill these roles? CELL MEMBRANE Also known as the plasma membrane Isolates the cell’s contents from the environment Regulates exchange of substances between cell and environment Communicates with other cells Creates attachments within and between other cells Regulates biochemical reactions FLUID MOSAIC MODEL OF PLASMA MEMBRANE Phospholipid bilayer foundation Proteins float in phospholipids in a fluid, constantly shifting mosaic Membranes are dynamic and changing WHAT ROLE DO PHOSPHOLIPIDS PLAY? Think back to biological molecules- what is special about phospholipids? THE PHOSPHOLIPID BILAYER THE PHOSPHOLIPID BILAYER Result from interactions with watery exterior and interior of cell Double row of phospholipids Polar heads face outward and inward Non-polar tails mingle within the membrane Cholesterol in animal membranes keeps them flexible Fluid layer Individual phospholipids do not bond to one another Unsaturated fatty acids in tails have kinks due to double bonds THE PHOSPHOLIPID BILAYER FORMS A FOUNDATION IN WHICH PROTEINS ARE EMBEDDED Some proteins float or drift Some proteins are anchored by cytoplasmic protein filaments Glycoproteins have attached carbohydrates CATEGORIES OF MEMBRANE PROTEINS Receptor proteins Bind specific molecules to trigger a cellular response CATEGORIES OF MEMBRANE PROTEINS Recognition proteins Are cellular identifiers CATEGORIES OF MEMBRANE PROTEINS Enzymes Promote chemical reactions Aid synthesis or breakdown of biological molecules CATEGORIES OF MEMBRANE PROTEINS Attachment proteins Provide anchorage for cell membrane Inner cytoskeleton External proteins Other cells CATEGORIES OF MEMBRANE PROTEINS Transport proteins Regulate transport of molecules through plasma membrane Include channel and carrier proteins THE FLUID MOSAIC ENABLES MOVEMENT INTO AND OUT OF THE CELL Molecules in fluids move in response to concentration gradients Molecules move from areas of high concentration to low concentration Dynamic equilibrium means concentrations are relatively equivalent and movement ceases (or decreases so that only a few molecules are moving back & forth) DIFFUSION Occur more quickly in extreme concentration gradients Can only move molecules rapidly over short distances CONCENTRATION GRADIENTS & THE PLASMA MEMBRANE Passive Transport Acts on concentration gradient Does not require energetic input Sites may be limited by location of membrane proteins Active Transport Substances move against the concentration gradient Does require energetic input Often assisted by cellular structures or membranes PASSIVE TRANSPORT Molecules move across at different rates and locations Simple diffusion Facilitated diffusion Osmosis SIMPLE DIFFUSION Molecules move directly across the lipid bilayer Very small molecules Lipid soluble molecules Fat soluble vitamins Gasses FACILITATED DIFFUSION Molecules transported via transport proteins Water soluble molecules Ions Amino acids Sugars OSMOSIS Water diffusion depends on concentration of water in internal and external solutions Dissolved substances reduce the concentration of free water molecules in a solution Water diffuses from high concentration (high purity) to low concentration (low purity) across a membrane OSMOTIC POTENTIAL Isotonic solutions have equal concentrations of water and of dissolved substances No net water movement across the membrane A hypertonic solution has lower water or higher dissolved particle concentration Water moves across a membrane towards the hypertonic solution A hypotonic solution is one with higher water or lower dissolved particle concentration Water moves across a membrane away from the hypotonic solution OSMOSIS IN FISHES No drinking Lots of drinking Glands concentrate salt Glands excrete salt Little concentrated urine Marine fish Lots of dilute urine Freshwater fish ACTIVE TRANSPORT Allows substances to move against a concentration gradient ATP provides energy to move molecules Protein “pumps” have a molecule binding site and an ATP binding site ENDOCYTOSIS AND EXOCYTOSIS Allow large molecules to enter and exit cells ENDOCYTOSIS Molecules are imported into the cell Plasma membrane pinches off to form a vesicle Pinocytosis Receptor-mediated endocytosis Phagocytosis PINOCYTOSIS “Cell drinking” brings in droplet of extracellular fluid RECEPTOR-MEDIATED ENDOCYTOSIS Moves specific molecules into the cell PHAGOCYTOSIS “Cell eating” moves large particles or whole organisms into the cell EXOCYTOSIS Molecules are exported from cell Vesicles join the membrane, dumping out contents JUNCTIONS ALLOW CELLS TO CONNECT & COMMUNICATE WITH ONE ANOTHER Why might cells need to connect or communicate? DESMOSOMES ATTACH CELLS TOGETHER Found where cells need to adhere tightly together under the stresses of movement (e.g. the skin or digestive tract) TIGHT JUNCTIONS MAKE THE CELL LEAKPROOF Found where tubes and sacs must hold contents without leaking (e.g. the urinary bladder) GAP JUNCTIONS ALLOW FOR COMMUNICATION IN ANIMAL CELLS Cell-to-cell channels allowing for passage of hormones, nutrients, and ions in animal cells PLASMODESMATA ALLOW PLANT CELL COMMUNICATION Plasmodesmata are cytoplasmic connections REVIEW What is the fluid mosaic model? How is this model influenced by the unique nature of phospholipids? What is the difference between passive and active transport and examples of each? How do cells connect and communicate?
