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Cellular Structure and Function Chapter 7 7.1: Cell Discovery and Theory MAIN IDEA: The invention of the microscope led to the discovery of cells. Types of Microscopes Light Microscopes Light waves pass through small organisms, or thin slices of larger ones Simple – one set of lenses (magnifying glass) Complex – more than one set of lenses Magnify up to 1500 times Dyes often used – kill/distort cells Types of Microscopes cont’d Phase contrast microscope Type of light microscope Increases contrast – difference btwn light/dark Cell structures more visible Can study living cells and processes Electron Microscopes Use electron beams instead of light beams High magnification View image on screen: micrograph 2 Types: Transmission electron microscope (TEM) – electron beam passed through thin slice of specimen; up to 1 million X magnification Scanning electron microscope (SEM) – views surface of specimen 2 1 3 4 1.Light 2.Phase contrast 3.TEM 4.SEM Compound Light Microscope Early Scientists… 1665 – Robert Hooke Also made microscopes Examined cork – discovered cells 1600s – Anton von Leeuwenhoek (Dutch lens maker) – made simple microscopes Observed tiny organisms (bacteria, insect structure, etc.) Scientists focused only on cell itself Cell Theory Discovered! 1700s – 1800s - 2 German biologists: Matthias Schleiden and Theodor Schwann discovered cell theory Schwann emphasized contents of cells, found similarities between plant and animal cells 1864 – Louis Pasteur disproved spontaneous generation By 1880s – scientists could show how cells divide Cell Theory 1. All living things are made of one or more cells. 2. Cells are the units of structure and function in all organisms. 3. All cells come from preexisting cells. Cells – Units of Life Cell – basic unit of life; in ALL organisms: Unicellular (one-celled) Multicellular (many cells, some with special functions) Complex organisms: cells tissues organs body systems organism 2 Main Cell Types Prokaryotes “Pro-” = early Simple cells No nucleus No membranebound organelles Eukaryotes “you” More complex cells Have a nucleus May have other organelles (other membrane-bound cell structures w/specific jobs) Prokaryotes Microscopic: .1 – 10 micrometers – billions in a spoonful of soil, or in your mouth! Can live in extreme environments Bacteria Has DNA, ribosomes, plasma membrane Some have cell walls, flagella Divide rapidly Will not form tissues Prokaryote Eukaryotes Larger – about 2-100 micrometers, some even larger (neurons, frog eggs) Contain membran-bound organelles: structures for organization Allow for different reactions to occur in cell at once b/c separate from each other All have different functions Cells can form tissues Eukaryote 7.2: The Plasma Membrane MAIN IDEA: A cell’s plasma membrane helps maintain homeostasis. Plasma Membrane Thin, flexible boundary between the cell and its environment Allows nutrients into the cell Allows waste to leave the cell Selective Permeability Ability of plasma membrane to control which substances, and how much of them, enter and leave a cell Composition of Membrane Made of phospholipids which form a double layer (phospholipid bilayer) One Phospholipid Phospholipid Bilayer Fluid Mosaic Model The phospholipid bilayer allows other molecules to “float” in the membrane. Proteins, cholesterol, carbohydrates Proteins Transmit signals inside the cell Act as support structures Provide pathways for substances to enter and leave the cell Cholesterol Prevent fatty acid tails from sticking together Carbohydrates Identify chemical signals 7.3: Cell Structures and Organelles MAIN IDEA: The eukaryotic cell contains organelles. 2 Main Eukaryotic Cell Types Animal and Plant cells Many of the same organelles, but some different from each other Main Differences Animal Cells Contain centrioles Contain lysosomes NO cell wall NO central vacuole (only small ones) NO chloroplasts Plant Cells NO centrioles NO lysosomes Contain cell wall Contain central vacuole Contain chloroplasts 7.4 – Cellular Transport MAIN IDEA: Cellular transport moves substances within a cell, and moves substances into and out of cells. Passive Transport Movement of particles across cell membrane without using energy 3 Types: Diffusion Facilitated Diffusion Osmosis Diffusion Movement of particles from an area of high concentration to an area of low concentration Concentration Gradient Diffusion Controlled By… Temperature Concentration Pressure ALL of the above, when increased, increase the amount of collisions particles have with each other, so diffusion occurs more rapidly. Diffusion and Cells Diffusion allows for… Some substances to pass into and out of cells Substances to spread out within cells Dynamic Equilibrium Diffusion into cell = diffusion out of cell Concentration on either side of membrane is equal, although movement of particles continues Diffusion in a Cell Facilitated Diffusion Movement of particles across a plasma membrane using proteins Proteins are specific to certain particles Channel Proteins – span membrane so particles do not come into contact with nonpolar tails; effective for ion transport Carrier Proteins – physically bind particles on one side of membrane, and release them on other, changing shape; used for ions, sugars, amino acids Cellular Structure and Function Facilitated Diffusion Channel Proteins Carrier Proteins Osmosis Diffusion of WATER across selectively permeable membrane, from high concentration to low concentration Osmosis 3 Types of Solutions Isotonic Hypotonic Hypertonic Isotonic Solution Water and dissolved substances diffuse into and out of the cell at the same rate.; concentrations equal; cell size, pressure stays the same Plant Cell Blood Cell Hypotonic Solution Solute concentration is higher inside the cell than in the solution Water diffuses into the cell; cell swells Plant cells don’t burst (b/c of cell wall) Plant Cell Blood Cell Hypertonic Solution Solute concentration is higher outside the cell than in the solution Water diffuses out of the cell (shrinks) Plant Cell Blood Cell Active Transport Movement of substances AGAINST the concentration gradient (____ to _____ concentration) Requires energy Helps cell maintain homeostasis Uses carrier proteins called pumps Some move substances only one way, some move them both ways Active Transport and Proteins Transport of Large Particles Endocytosis – cell surrounds substance outside of cells, encloses it in a sac/vesicle, and takes it into the cell Exocytosis – vesicle with a substance is released from the cell Endocytosis Exocytosis