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Transcript
Cell Structure and Function Chapter 7 Microscopes : windows to the world of the cell Cells are the basic unit of life. The invention and improvement of microscopes in the 17th century led to the discovery and early study of cells Robert Hooke observed “cells” in a slice of cork History of Cells 1800’s Schwann –Animal tissues are composed of cells Schleiden – Plant materials are composed of cells Virchow - All tissues from living organisms are composed of cells The Cell Theory All living things are composed of cells Cells are basic units of structure and function All cells come from pre-existing cells How Cells are Studied A. B. Microscopy Cell Fractionation Microscopes An instrument used observe minute objects Enlarges images of small objects Types of Microscope Light: uses light and lenses to magnify image Electron: uses magnets and electrons to magnify image Parts of a Microscope (Eyepiece) Magnification To calculate: Power of objective lens x Power of Eyepiece Do these calculations: Eyepiece = 10x Objective = 10x; 40x; 100x Electron Microscope Uses magnets and electrons to magnify images Magnifies 1000x better than a light microscope Specimen cannot be living Types of Electron Microscopes Transmission Electron Microscope: internal structures Scanning Electron Microscope: surface structures The Eukaryotic Animal Cell The Eukaryotic Plant Cell Major Type of Cells There are two basic types of cells Prokaryotic & Eukaryotic A major difference between prokaryotic and eukaryotic cells is the location of chromosomes. Prokaryotic Cells Lacks a nucleus and most other organelles DNA concentrated in nucleoid region Bacteria and Archae 1-10 micrometers Appear earliest in earth’s fossil record Nucleus Eukaryotic Cells surrounded by its membrane Internal organelles bounded by membranes 10 – 100 micrometers Protists, Fungi, Plants, Animals Cell Structure Section 7.2 Cell Organization Cytoplasm Cytoplasmic Nucleus inclusions / Nuclear region Cell Membrane/Wall Cytoplasm Fluid portion of the cell All cellular organelles are suspended in it Organelles specialized structures that perform various functions Nucleus & it’s Contents Nucleus & it’s Contents Chromosomes carry the cell’s genetic information Always remain in the nucleus RNA carries this message from the nucleus to the ribosomes moves through the nuclear pores Storage, Cleanup and Support Vacuolesstore water, salts, carbohydrates & proteins Lysosomes filled with enzymes breakdown of macromolecules Cytoskeleton maintains shape & helps in movement Microfilaments Threadlike structures made of actin Forms an extensive network Helps cells move Microtubule Centriole Hollow structures made of tubulin Maintain shape in many cells Centrioles in animals cells made of tubulin help organize cell division not present in plant cells Project from the surface cilia & flagella movement Cilia Building Protein Ribosomes Endoplasmic Reticulum Golgi Apparatus Ribosome Endoplasmic Reticulum (rough & smooth) Protein Synthesis Golgi Body Capture and Release Energy The cellular machinery constantly needs energy to function. Supplied by two organelles the Chloroplasts & Mitochondria Chloroplasts Sunlight to Chemical energy Mitochondria Convert chemical energy in food to a form that the cell can useATP All mitochondria come from the cytoplasm of the egg cell inherited from the mother Endosymbiosis Chloroplasts and mitochondria are similar to prokaryotes Lynn Margulis in 1960 evidence that chloroplasts and Mitochondria evolved as endosymbionts Both have DNA, RNA and Ribosomes that prokaryotic They replicate their own DNA Divide by binary fission RNA World Miller & Urey 1953, organic molecules necessary for life have arisen from simpler compounds Origin of life RNA evolved before DNA Cellular Boundaries Cell Walls Provides support Confers shape Protects the cell Present in plants and prokaryotes Cell Membranes Regulates what enters and leaves the cell Selectively Permiable Cell/Plasma Membrane Boundary that separates the interior of a living cell from it’s surroundings and regulates the traffic of chemicals into and out of the cell Phospholipid Protein Bilayer “icebergs” float in a “sea” of phospholipids Phospholipid Molecule Composed of proteins and a type of lipid called phosopholipid (glycerol+2 fatty acids) Protein “icebergs” in a “sea” of phospholipids Plasma Membrane Cell Transport Section 7.3 Function of Cell Membranes Materials need to move in and out of the cell Function like gatekeepers, letting some molecules through, but not others “Selectively Permeable” Types of Transport Passive Transport Diffusion Facilitated Active Transport Transport Diffusion The spread of molecules from areas of high concentration, to areas of low concentration. Equilibrium when the molecules are even throughout a space Concentration Gradient difference between concentrations in a space. Passive Transport Diffusion Some substances are allowed to move freely Facilitated diffusion transport proteins Osmosis The diffusion of water (across a membrane) Water will move in the direction where there is a high concentration of solute and low water concentration Osmosis Dissolved molecules ( ions, organic molecules, etc) are called solutes Most solutes cannot cross membranes As solute conc increases “free” H2O decreases Hypertonic high [solute] Hypotonic low [solute] Isotonic- means the same Hypotonic- less solute Hypertonic- high solute Water Balance in Animal Cells •Water flow equal in both directions •Net water flow into the cell which can burst (Hemolysis) Net water flow out of cell which shrinks (Crenation) Water Balance in Plant Cells Turgid Flaccid Plasmolysis Shrinking of cytoplasm in both plant and animal cells Active Transport Cell expends energy to move molecules or ions across the membrane A specific transport protein pumps solute across a membrane The chemical energy is supplied by the mitochondria Example Na+(Sodium) K+(Potassium) pump. Active Transport Transport of Large Molecules Large molecules have to be packaged to be transported in and out of the cell Vesicles (membranes sacs) are formed to move the substances Exocytosis Endocytosis Exocytosis & Ednocytosis More Exo & Endo