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1. Definition: a thin, flexible barrier between the cell and its environment 2. Function: regulates what enters and leaves the cell; is selectively or semi-permeable; known as the “gate keeper” 3. Is a lipid bilayer; contains “hydrophobic” (waterfearing) and “hydrophilic” (water-loving) ends 4. Known as the “fluid-mosaic model” 1. Definition: outer boundary of a plant cell, bacterial cell and fungal cell; not present in animal cells 2. Function: provides support, strength, and rigidity to the cell; composed of cellulose • Is a double-membrane structure that is the genetic control center of a eukaryotic cell • Known as the control center, brain, or boss of the cell • Surrounded by a nuclear envelope or membrane • Contains DNA in the form of chromatin Mass of fibers and granules, dark structure inside the nucleus; composed of chromatin DNA plus RNA and protein Function: produces ribosome Organelles which manufactures protein Interprets the code from RNA Are made of RNA and protein Are not bound by a membrane Is the area between the nucleus and the cell membrane Houses the organelles Site of most chemical reactions Breaks down molecules to release energy Gel-like fluid or substance Endoplasmic Reticululm(ER) Inter-related series of membranes forming a network of connected tubules Provides a delivery system for the cell Attached to the outer membrane of the nuclear envelope Endoplasmic Reticululm(ER) ► RER (Rough) is studded (covered) with ribosomes ► Function: makes proteins and more membranes ► SER (Smooth) does not have ribosomes; breaks down drugs and toxins in the liver ► Function: synthesizes lipids, fatty acids, phospholipids, and steroids A series of closely stacked, flattened membrane sacs Function: packages, collects, modifies, and secretes proteins and distributes them to other parts of the cell • Sacs of fluid-filled compartments surrounded by a membrane in plant and animal cells • Function: stores food, enzymes, and some waste • Contractile vacuole-collects excess water and pumps it out of the cell in some unicellular organisms • Central vacuole- a single, large vacuole in the plant cell that stores water and other substances “Clean-up Crew”; membrane bound organelles Contain digestive enzymes Destroy old, worn out cell parts, food particles, or invading viruses or bacteria Microtubules-straight, hollow tubes composed of tubulin Intermediate filaments-made of fibrous protein and have a rope-like structure Microfilaments-solid, helical rods composed mainly of actin (globular protein) important in amoeboid movement • Short, hair-like projections • Lines the trachea • Moves liquid over the surface of the cell and sweeps mucus with trapped debris out of our throat; aids in locomotion (movement) • Also found in kidney tubules and other structures in the body Long, whip-like structures used for locomotion Propels protists, most animals, and some plant cells Typically cilia and flagella have a core composed of microtubules connected to the plasma membrane arranged in what is known as a 9 + 2 pattern. The pattern is so named because a ring of nine microtubule "doubles" has in its center two singular microtubules. Known as the “powerhouse” of the cell Organelle in which food molecules are broken down to release energy Site of cellular respiration Produces large amounts of ATP (adenosine triphosphate); a high energy storing molecule Growing cells in areas of repair utilize energy (muscle cells) Cilia and flagella require large amounts of ATP Becomes ADP (adenosine diphosphate), when one phosphate (PO4-3), group breaks off during respiration ADP is a low energy storing molecule Found only in plant cells and some protists Contains the pigment, chlorophyll, which aids in the process of photosynthesis Consists of stacks of grana composed of single disc shaped structures called thylakoids Differences Between Plant and Animal Cells • Plant Cells – – – – – – Chloroplast Cell Wall Rectangular Shape Plastids Central Vacuole Nucleus location is off center • Animal Cells – – – – – Centrioles Flagellum Circular Shape Lysosomes Nucleus location is in the center Chapter 7 Cellular Structure & Function Cell Types • Prokaryotes-unicellular, cells that do not contain a nucleus or membrane-bound organelles (internal structures) but do have ribosomes (non-membranous structures). Ex. bacteria • Eukaryotes-unicellular or multicellular organisms that have a “true” nucleus and membrane-bound organelles; plants and animals • Eukaryotic cells evolved from prokaryotic cells (Endosymbiotic Theory) Light Microscopes • Most commonly used microscope; allows light to pass through the specimen and use two lenses to form an image; It produces magnified images by focusing visible light rays. Electron Microscopes Focus beams of electrons on specimens. - TEM(Transmission)shine a beam of electrons through a thick specimen; studies internal cell structure. - SEM(Scanning) runs a pencil-like beam of electrons back and forth Electron Microscopes - Produce 3D images of the surface of objects. - Cannot be used to study live specimen. Electron Microscope Cell Theory In the 1600’s, early investigators were curious about the quality of cloth. They used magnifying lens to observe this. The telescope was developed to view objects at a distance. Scientists • Anton Van Leeuwenhoek: credited with developing the 1st single lens microscope was the 1st to describe protozoa and bacteria that are in drops of water (Dutch scientist) • Robert Hooke: Coined the term “Cell”; viewed cork, wood, and plant stems. (Dutch Biologist) • Matthias Schleiden: 1838-all plants are made of cells (German Botanist). Scientists • Robert Brown: Observed what is now known as the nucleus (Scottish scientist). • Theodor Schwann: 1839, all animals are made of cells. • Rudolph Virchow: 1855, all cells arise from the division of pre-existing cells. Cell Theory 1. All living things are made of cells 2. Cells are the basic unit of structure and function 3. All cells arise from pre-existing cells • Anton Van Leeuwenhoek • Robert Hooke • Matthias Schleiden • Robert Brown • Theodor Schwann • Rudolph Virchow Cell Transport Membrane functions Membrane structure How molecules cross membranes Two mechanisms of Transport Transportation of Molecules • Passive Transport Movement of molecules across a semi-permeable membrane no energy required • Active Transport Movement of molecules across a semi-permeable membrane against a concentration gradient with a protein ENERGY – ATP • Facilitated Diffusion Movement of molecules across a semi-permeable membrane with a protein no energy required How Molecule Cross Membranes Diffusion Osmosis Osmosis Osmotic Effects on Cells Cellulose in cell wall Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic Effect of Water on RBC Osmosis in Plant Cells Plasmolysis Hypertonic Hypotonic Facilitated Diffusion Channel proteins help small polar or charged molecules cross membranes. Active Transport Proteins use energy to move solutes against gradient. Active Transport: Na+/K+ Pump ATPase pump protein gets phosphorylated by ATP. Protein’s conformation changes... causing binding & then release of ions. Active (vesicular) Transport 3 Kinds of Endocytosis Vesicular Transport: Exocytosis How Substances Move Across Membranes Passive Transport Simple diffusion Osmosis Facilitated diffusion Active transport Endocytosis Phagocytosis Pinocytosis Receptor-mediated endocytosis Exocytosis