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Transcript
Ch. 7 Cellular Structure and Function p. 180 -207 7.1 Cell Discovery and Theory p. 182-186 Big Idea Cells are the structural and functional units of all living organisms 7.1 Cell Discovery and Theory p. 182-186 Essential Question What are the differences between prokaryotic and eukaryotic cells? Main Idea • The invention of the microscope led to the discovery of cells. Robert Hooke • Made a simple microscope • Observed small, box-shaped structures in a piece of cork • Most scientists observed tiny organisms using the first microscopes Cell • The basic structural and functional unit of all living organisms Anton van Leeuwenhock • Designed a microscope that allowed him to see living organisms in pond water, milk, and various other substances Cell Theory 1. All living organisms are composed of one or more cells 2. Cells are the basic unit of structure and organization of all living organisms 3. Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cell Microscopes • Compound light microscope - Utilizes a series of glass lenses and visible light to magnify an image • Magnifies up to 1000 times • Microscopes • Electron Microscopes uses magnets to aim a beam of electrons at an object to produce an image • Magnifies up to 500,000 times Pollen • Plasma Membrane • A special boundary that helps control what enters and leaves the cell Eukaryotic cells • Contain a nucleus and other organelles that are bound by membranes Prokaryotic cells • Cells without a nucleus or other membranebound oragnaelles Comparison of Eukaryotic and Prokaryotic cells • Eukaryotic Cells – True nucleus – Membrane-bound organelles – Usually larger in size – Example: cells that make up a human • Prokaryotic Cells – No true nucleus – No membrane-bound organelles – Smaller in size – Example: bacteria End of 7.1 7.2 The Plasma Membrane p. 187-190 Main Idea • The plasma membrane helps to maintain a cell’s homeostasis Essential Question What is the plasma membrane and what is its function? Homeostasis • Is maintaining balance in an organism’s internal environment Plasma Membrane • Responsible for maintaining homeostasis in a cell • A thin flexible boundary between a cell and its environment • Allows nutrients into the cell and allows waste and other products to leave the cell Selective permeability • When a membrane allows some substances to pass through while keeping others out p. 187, fig 7.5 (right) • What substances are allowed into the cell by the plasma membrane? • What substances are allowed out of the cell by the plasma membrane? • What is selective permeability? p. 187, fig 7.5 (right) • What substances are allowed into the cell by the plasma membrane? – Water, oxygen and glucose • What substances are allowed out of the cell by the plasma membrane? – Water, wastes and carbon dioxide • What is selective permeability? – When a membrane allows some substances to pass through, and keeps others out Phospholipid bilayer • 2 layers of phospholipids arranged tail-totail • This arrangement allows the membrane to exist in watery environments Phospholipid • Polar head – faces the watery environment – Is attracted to the water • Nonpolar tail – faces each other Find the polar head, and nonpolar tail Phospholipid bilayer • Functions to separate the environment inside the cell from the environment outside of the cell Transport Proteins • Move substances or waste materials through the plasma membrane Proteins • Transmit signals inside the cell • Act as a support structure • Provide pathways for substances to enter and leave Cholesterols • Prevent fatty acid tails from sticking together Carbohydrates • Identify chemical signals Fluid mosaic model The phospholipid bilayer allows other molecules to “float” in the membrane. End of 7.2 7.3 Structure and Organelles p. 191 - 200 Main Idea • Eukaryotic cells contain organelles that allow the specialization and the separation of functions within the cell Essential Question What are the component parts of a cell and what are their functions? Cytoplasm • The environment inside the plasma membrane that is a semifluid material Cytoskeleton • A supporting network of long, thin protein fibers that form a framework for the cell and provide an anchor for the organelles inside the cell • Made up of microfilaments and microtubules Nucleus • “manages” the cell • Contains DNA that stores genetic information • Nucleolus – where ribosomes are made Nuclear Membrane • Double membrane that surrounds the nucleus • Nuclear pore –opening that allows largersized substances to move in and out of the nucleus Ribosome • Help manufacture proteins • Made up of RNA and protein Endoplasmic Reticulum • Aka ER • A membrane system of folded sacs and interconnected channels that serves as the site for protein and lipid synthesis • Rough ER – area of ER where ribosomes are attached • Smooth ER – area of the ER where there are no ribosomes attached Golgi Apparatus • A flattened stack of membranes that modifies, sorts, and packages proteins for distribution into and outside of the cell Vacuole • A sac used to store food, enzymes, and other materials needed by a cell • Mostly found in plant cells Lysosomes • Vesicles that contain substances that digest excess or worn-out organelles and food particles Centrioles • Groups of microtubules • Function during cell division • We will learn more about these in ch. 9 Mitochondria • “energy generators” that convert fuel particles (sugars) into usable energy • Aka “powerhouse” of the cell Chloroplast • Organelles that capture light energy and convert it to chemical energy through a process called photosynthesis • Only found in plant cells Cell Wall • Thick, rigid mesh of fibers that surrounds the outside of the plasma membrane, protecting the cell and giving it support • Only in plant cells Cilia and Flagella • Structures that project outside the plasma membrane • Cilia – short, numerous projections that look like hairs • Flagella – long, less numerous projections that move in a whiplike motion End of 7.3 7.4 Cellular Transport p. 201 - 207 Main Idea • Cellular transport moves substances within the cell and moves substances into and out of the cell Essential Question How are substances moved into and out of a cell? Diffusion • The net movement of particles from an area where there are many particles of the substance to an area where there are fewer particles of the substance • Example: a drop of ink in water Dynamic equilibrium • The condition in which there is continuous movement but no overall change • Example: ink that has been dropped in water last hour Facilitated Diffusion • Substances move into the cell through a water-filled transport protein called a channel • The protein is “facilitating” the diffusion of the water Osmosis • Diffusion of water across a selectively permeable membrane • Look at fig 7.22 pg. 203 Isotonic solution • A solution that has the same concentration of water and solutes (ions, sugars, proteins) – Iso means same Hypotonic solution • A solution that has a lower concentration of solute – There is more water outside the cell than in it – Cell swells Hypertonic solution • The concentration of the solute outside of the cell is higher than inside – Cell shrivels Active Transport • The movement of substances across the plasma membrane against a concentration gradient • Requires energy • Example: sodium-potassium ATPase pump Endocytosis • The cell engulfs an object • Example: cellular eating in unicellular organisms Exocytosis • The secretion of materials at the plasma membrane • Example: to expel waste from a cell End of 7.4 End of ch. 7