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This article provides a comprehensive overview of cell structure and function, including the definition of a cell, cell theory, types of microscopes, examples of cells, and the structures and functions of different organelles.
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Definition of a Cell • A cell is the smallest unit that is capable of performing life functions.
Robert Hook • Credited for discovering cells. Viewed cork cells through a compound light microscope in the mid-1600’s
Cell theory • All living things are made up of cells. • The basic unit of living things is the cell • All cells come from preexisting cells through cell division.
Compound light microscope • Uses light and multiple objective lenses to look at objects • Can view a living organism • Magnifies to micrometers
Electron Microscope • Uses a beam of electrons to magnify objects • Usually kills organisms • Magnifies to nanometers so organelles can be seen
2 types of electron microscopes • Scanning electron microscope (SEM)-looks at the surface of the specimen • Transmission Electron Microscope (TEM)- looks at the interior of the specimen
Examples of Cells Amoeba Proteus Plant Stem Bacteria Red Blood Cell Nerve Cell
Two Types of Cells Prokaryotic Eukaryotic
Prokaryotic • No nucleus and no membrane bound organelles • Examples: bacteria (anything Kingdom Monera) http://library.thinkquest.org/C004535/prokaryotic_cells.html
Eukaryotic • Contains a nucleus and membrane bound organelles (ex: fungi, plants, animals) Plant Animal http://library.thinkquest.org/C004535/eukaryotic_cells.html
Plasma (Cell) Membrane • Found in both plant and animal cells • Boundary between the cell and it’s environment, allows a steady supply of nutrients to come into the cell http://library.thinkquest.org/12413/structures.html
Selectively Permeable • It allows only certain particles to enter and leave the cell
Structures of the cell membrane • Phospholipid bilayer- phosphorus head (hydrophilic) and lipid tail (hydrophobic) • Proteins- aids in transport of particles into and out of a cell • Carbohydrates • cholesterol
Fluid mosaic model • Called this because it contains a number of different compounds (mosaic) and many of the compounds move around in the membrane
Nucleus • Found in both plant and animal • Control center of the cell because it contains chromatin (DNA and protein) • Enclosed by a porous nuclear envelope
Nucleolus • Region within • nucleus that makes • ribosomes
Cytoplasm Watery/Gel-like mixture Found between nucleus an cell membrane Contains organelles
Cell Wall • Found in plant cells only • Strong/stiff nonliving layer outside of the cell • Not selectively permeable, very porous • Contains cellulose to provide support/protection
Ribosomes • Small grain like body made primarily of RNA. • Produced by nucleolus. Can be attached or floating free in the cytoplasm http://library.thinkquest.org/12413/structures.html
Ribosomes cont.. Function: make protein Found in plants and animals
Endoplasmic Reticulum Moves materials around in cell Smooth type: lacks ribosomes Rough type (pictured): ribosomes embedded in surface
Rough ER • Series of highly folded membranes that contain ribosomes • Produce proteins and transport them to the golgi. Releases proteins to be transported in the vesicle
Smooth ER • Series of highly folded membranes that do NOT contain ribosomes • Produce lipids and transports to golgi • Releases lipids to be transported into vesicle • Found in both plants and animals
Golgi Bodies • Flattened tubular membranes • Sorts, stores, modifies, packages, and transports materials.
Golgi cont.. • Releases materials into vesicle to be transported to other areas of the cell or to be released from the cell • Found in plant and animal cells
Chloroplast • Large green structures that contain chlorophyll (green pigment) • Captures light energy and converts it to chemical energy (glucose) Found in plants only http://library.thinkquest.org/12413/structures.html
Mitochondria • Rod-shaped. • Has a greatly folded inner membrane to increase surface area • Site for cellular respiration, converts chemical energy (glucose) to usable energy (ATP) • Found in plants an animals
Vacuoles • Sacs in the cytoplasm used for temporary storage • Stores food, water, wastes and other materials http://library.thinkquest.org/12413/structures.html
Plant cells have a large Central Vacuole that makes a plant turgid • Vacuoles are found in plant and animal cells
Lysosome • Small round sacs in cytoplasm that contain enzymes • Break down excess or worn out organelles, food, particles, old cells, viruses, and bacteria. • Found in animal cells only
Cytoskeleton • Support structure composed of tiny rods (microfilaments) and filaments • Forms framework for the cell. Maintains cells shape and assist organelles in moving from place to place. Microtubules that extend outside of the cell membrane cilia and flagella
Centriole • A cylinder shaped structure • Aids in cell division • Found in animal cells only