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Chapter 7 A view of the cell The History of the Cell Theory (p 172) •Compound Light microscopes •Invented by Anton van Leeuwenhoek •1500 x •Electron microscopes •Scanning electron microscope (SEM,扫描电镜) •Surface of 3D objects •Transmission electron microscope (TEM, 透射电镜) •Inside a cell •Scanning Tunneling microscope (STM) •Viewing atoms The History of the Cell Theory (p172) Robert Hooke- first to use the word “cells” The Cell Theory: 1. All organisms are composed of one or more cells. 2. The cell is the basic unit of structure and organization of organisms. 3. All cells come from preexisting cells. Two Basic Cell Types (p173) Prokaryotes (原核生物): Cells that do not contain any membrane- bound organelles Most unicellular (one cell) organisms; bacteria Two Basic Cell Types (p173) Eukaryotes (真核生物): Cells that do contain membranebound organelles Most multicellular (many cells) organisms; plants, animals, etc. Some unicellular organism too; algae Prokaryote Vs. Eukaryote Prokaryote Eukaryote No membrane-bound organelles Membrane-bound organelles No nucleus Nucleus Small (0.001-0.01 mm) Large (0.01-0.1mm) Small Ribosomes Large Ribosomes Small, normally circular DNA Large, chromosome DNA Maintaining a Homeostasis (p175) Homeostasis- stable state of a healthy functioning cell Plasma Membrane- “guard” of the cell; first step towards homeostasis Selective permeability (选择透过性)- a process in which a membrane allows some molecules to pass through while keeping others out. Transport proteins- special tunnels or doors that only let in specific molecules Structure of the Plasma Membrane (p177) Phospholipidshydrophilic heads and hydrophobic tails make a double layered wall Cholesterol- help keep membrane fluid and stable Carbohydrates- used in cell communication Structure of the Plasma Membrane Fluid Mosaic Model Cell Organelles Organelles- “tiny organs” inside the cell • have a specific job to maintain homeostasis (healthy cell) • Some are in all cells; membrane • Some are only found in either animal or plant cells Cellular Boundaries Animal Cell: Plasma membrane Plant Cell: Plasma membrane and Cell wall (cellulose) The Nucleus (细胞核) The “brain” of the cell; contains DNA (Chromatin) Making proteins! Ribosomes- take copy of DNA’s information (mRNA) and use it as a guide to create proteins Endoplasmic Reticulum- site of chemical reactions inside cell Smooth ER- no ribosomes Rough ER- ribosomes Transportation Center Golgi Apparatus- puts proteins into small membrane-bound packages called vesicles which are sent out and around the cell Vacuoles- storage compartments for food, enzymes, etc. In plant cells- they are very large and hold lots of water In animal cells- very small; transport things inside the cell Vacuoles Cellular Digestion Lysosomes- sacs of digestive enzymes that break down old organelles, food, and viruses/bacteria Making Energy in Plant Cells (p184) Chloroplasts- perform photosynthesis to make energy from sunlight in planets and some unicellular organisms Chlorophyll- chemical that absorbs wavelengths of sunlight, expect green Making Energy in Animal Cells (p185) Mitochondria- “power house” of the cell; produces ATP(energy unit for cells) by breaking down sugars and other organic compounds (cellular respiration) Organelles for Support (p 185) Cytoplasm- clear gel-like fluid inside cells; help holds organelles in place Cytoskeleton- “Bones” of the cell; crossing rods, filaments, and tubes, that hold the cells shape. Also act at a “railroad” system to move things around the cell The Cytoskeleton Organelles for Support Centrosome- move chromosomes during cell division in animal cells Locomotion Flagella- long, wipe-like tail that pushes and rolls the cell Cilia- short, hair-like paddles that push the cell along Animal Cells Vs. Plant Cells Organelle Plants only Animals only Plasma Membrane Cell Wall Both X X Nucleus X Ribosomes X Endoplasmic Reticulum X Gogi Apparatus X Lysosome X Vacuole (large) Centrioles X X Mitochondria Chloroplasts (small) X X Tour of an Animal Cell Tour of an Plant Cell P 192 Homework • Cell labeling practice sheet Cellular Transport • Cells must move things inside and outside to maintain homeostasis • What might they need to take in: – Food molecules – Signals – Ions • What might they need to release: – Waste material – Proteins – Signals Cellular Transport • 2 Types of transport: 1) Passive Transport – Does not require the cell to use energy to move 2) Active Transport – Does require the cell to use energy – Cell uses energy units (ATP) Passive Transport: Diffusion • Diffusion movement of molecules from areas High concentrations to areas of Low concentrations; down a concentration gradient • Food coloring in water, sugar in water, fart fills a room, etc… • Where does the energy come from for this movement? – Kinetic energy in molecules (random movement) Passive Transport: Facilitated Diffusion • Facilitated diffusion diffusion through a protein channel or carrier protein that is specific for 1 type of substance (Na+, Cl-, glucose, etc…) • Still follow concentration gradient • Can become saturated meaning the movement is at its maximum rate and can not go any faster Passive Transport: Osmosis • The diffusion of water across a selectively permeable membrane(选择 性透过膜) is called osmosis(渗透) • H2O is small enough to fit between phospholipids but moves very slow, why? – Hydrophobic center of membrane pushes it back • Aquaporins transport channels just for H2 O Osmotic Pressure: • Movement of water can increase and decrease pressure inside the cell • Hypotonic Solution – concentration of solute is low (high H2O) on the outside and high (low H2O) on the inside of the cell – Water moves into the cell causes it to swell Osmotic Pressure • Hypertonic Solution – concentration is high (low H2O) on the outside and low (high H2O) on the inside – Water rushes out of the cell causing it to shrink Osmotic Pressure • Isotonic solution – concentration inside and outside the cell are equal (equilibrium) – Movement of water in and out of the cell is at equal rates; best for animal cells Active Transport • Energy is required to move molecules AGAINST their concentration gradients • ATP must be used to make carrier proteins (pumps) move molecules to the other side • Cell uses active transport to create concentration gradients to be used later by passive transport; nervous system Active Transport: Large Particles • Endocytosis – Cell folds around large particle and pulls it in; plasma membrane makes vacuole • Exocytosis – Vacuole fuses with plasma membrane and release large particles Know The Difference! Homeostasis: Happy Cells • All strive to maintain homeostasis • In single-celled organisms this is not very difficult • In multi-celled, complex organisms there are many methods used: • Cell specialization • cells for different organs that do different jobs • Cell Communication • systems talk to each other • Organized levels CellsTissueOrgan System Homework • Read Ch. 8 and do Ch. 8 Vocabulary • Ch. 7 Apply Vocabulary and Questions #1-18 on p.187188