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Transcript
Cell Structure and Function Chapter 7 Biology Miller • Levine The Scientists… Robert Hooke (1665) Viewed cork under a microscope Called the chambers he saw “cells” Anton van Leeuwenhoek (1674) First to see living organisms in a drop of water The Scientists… Matthias Schleiden (1838) Theodor Schwann (1839) All plants are made of cells All animals are made of cells Rudolf Virchow (1855) All cells come from preexisting cells The Cell Theory All living things are composed of cells Cells are the basic units of structure and function in living things New cells are produced from existing cells Unicellular vs. Multicellular Unicellular – single-celled organism Multicellular – many-celled organism Cell specialization – cells are specialized to perform certain functions Cells → Tissues → Organs → Organ systems → Organism Prokaryotes vs. Eukaryotes Prokaryotes Have a cell membrane & cytoplasm, but do not have a nucleus Ex. Bacteria such as E.coli Eukaryotes Have a nucleus, cell membrane, cytoplasm & organelles Ex. Plants, Animals, Fungi Prokaryotes vs. Eukaryotes Basic Cell Structures Cell membrane – thin, flexible barrier around the cell; protects the cell Present in all cells Cytoplasm – material inside the cell membrane (not including the nucleus) Prokaryotes & Eukaryotes Cell Wall Found in many organisms, including plants, algae, fungi and nearly all prokaryotes Not found in animal cells Lies outside the cell membrane Main function is to provide support & protection for the cell Nucleus Almost all eukaryotic cells, including plants and animals have a nucleus Prokaryotes do not have a nucleus Controls most cell process and contains the DNA Nucleolus and Nuclear Envelope Nucleolus: Inside the nucleus Where ribosomes are made Nuclear Envelope: Double-membrane layer around the nucleus Allows material to move into and out of the nucleus Nucleus Cytoskeleton Found in all eukaryotic cells Not found in prokaryotes A network of protein filaments that helps the cell maintain its shape It also is involved in cell movement Ribosomes Found in all cells Main function is to make proteins Can be found floating in the cytosol or attached to endoplasmic reticulum Endoplasmic Reticulum (ER) Found only in eukaryotic cells Where components of the cell membrane are assembled Two kinds: Smooth ER & Rough ER Smooth ER: no ribosomes; makes lipids Rough ER: has ribosomes; involved in making proteins Endoplasmic Reticulum Golgi Apparatus Found only in eukaryotic cells Enzymes attach carbohydrates & lipids to proteins Send proteins to their final destination Lysosomes Found in animal cells only Break down lipids, carbohydrates & proteins from food into particles that can be used by the cell Also break down “dead” organelles Vacuoles Not found in prokaryotes Animal cells have small or no vacuoles Plant cells have a large central vacuole Store materials such as water, salts, proteins & carbohydrates Chloroplasts Found in all plant cells Some prokaryotes have them, but most do not Use the energy from sunlight to make energy-rich food molecules during photosynthesis Chloroplasts Mitochondria Found in eukaryotic cells only Release energy from stored food molecules Cell Membrane Regulates what enters and leaves the cell (selectively permeable) Provides protection and support Lipid bilayer – two layers of lipids Proteins run through the layers Carbohydrates are attached to some of the proteins Fluid Mosaic Model Cell Membrane Diffusion Molecules move from an area of high concentration to an area of low concentration Movement continues until equilibrium is reached Many substances move across the membrane by diffusion Does not require energy (passive transport) Diffusion Osmosis The diffusion of water Isotonic – equal concentration Nothing Hypertonic – higher concentration Water moves out of the cell Hypotonic – lower concentration Water happens moves into the cell No energy is required Effects of Osmosis on Cells Osmotic Pressure In pure water, an animal cell would burst Plant cells are protected by their cell wall Some freshwater organism have special structures like contractile vacuoles to get rid of extra water Facilitated Diffusion Some molecules cannot cross the membrane without help Some of the proteins in the membrane form protein channels Materials still move from higher to lower concentrations No energy is required Facilitated Diffusion Active Transport Materials move from lower concentration to higher concentration Requires an input of energy Works kind of like a pump Transport of Large Amounts Endocytosis – movement into the cell Phagocytosis – “cell eating” – solid particles Pinocytosis – “cell drinking” – particles dissolved in water Exocytosis – movement out of the cell Phagocytosis Pinocytosis