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UNIT 2: CELL THEORY 7th Grade CELLS ARE EVERYWHERE!! Cells are the fundamental units of life. All living organisms are composed of and depend on cells to function normally. Scientists estimate that our bodies contain anywhere from 75 to 100 trillion cells. CELL THEORY Before 330+ years ago, there was no knowledge of cells. Cells were too small to be seen. But with the invention of the microscope, an entirely new world was discovered, where very large objects like humans are in fact made up of billions of tiny individual pieces called cells. 1665 – CELL FIRST OBSERVED Robert Hooke, an English scientist, discovered a honeycomb-like structure in a cork (tree) slice using a primitive compound microscope. He only saw cell walls as this was dead tissue. He coined the term "cell" for these individual compartments he saw. 1670 – FIRST LIVING CELLS SEEN Anton van Leeuwenhoek, a Dutch biologist, looks at pond water with a microscope he made lenses for. 1683 – MINIATURE ANIMALS Anton van Leeuwenhoek made several more discoveries on a microscopic level, eventually publishing a letter to the Royal Society in which he included detailed drawings of what he saw. Among these was the first protozoa and bacteria discovered. 150 YEAR GAP Between the Hooke/Leuwenhoek discoveries and the mid 19th century, very little cell advancements were made. This is due to the widely accepted, traditional belief in Spontaneous Generation. Examples: -Mice from dirty clothes/corn husks -Maggots from rotting meat 1833 – THE CENTER OF THE CELL SEEN Robert Brown, an English botanist, discovered the nucleus in plant cells. 1838 – BASIC BUILDING BLOCKS Matthias Jakob Schleiden, a German botanist, proposes that all plant tissues are composed of cells, and that cells are the basic building blocks of all plants. This statement was the first generalized statement about cells. 1839 – CELL THEORY Theodor Schwann, a German botanist reached the conclusion that not only plants, but animal tissue as well is composed of cells. This ended debates that plants and animals were fundamentally different in structure. He also pulled together and organized previous statement on cells into one theory, which states: 1 - Cells are organisms and all organisms consist of one or more cells 2 - The cell is the basic unit of structure for all organisms 1840 – WHERE DOES LIFE COME FROM? Albrecht von Roelliker discovers that sperm and eggs are also cells. 1845 – BASIC UNIT OF LIFE Carl Heinrich Braun reworks the cell theory, calling cells the basic unit of life. 1855 – RD 3 PART OF THE CELL THEORY ADDED Rudolf Virchow, a German physiologist/physician/pathologist added the 3rd part to the cell theory. The original is Greek, and states Omnis cellula e cellula. This translates as all cells develop only from existing cells. Virchow was also the first to propose that diseased cells come from healthy cells. COMPONENTS OF BASIC CELL THEORY 1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39) 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of preexisting cells. (Virchow)(1858) MODERN CELL THEORY Modern Cell Theory contains 4 statements, in addition to the original Cell Theory: - The cell contains hereditary information (DNA) which is passed on from cell to cell during cell division. - All cells are basically the same in chemical composition and metabolic activities. - All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc) - Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane) SINGLE OR MULTI-CELLED ORGANISMS PROKARYOTES a microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles. Prokaryotes include the bacteria DNA is free-floating in the cell Move thorough the use of flagella (tail) or cilia (little hairs) TYPES OF PROKARYOTES Paramecium Euglena Amoeba EUKARYOTES A eukaryote is any organism whose cells contain a nucleus and other organelles enclosed within membranes Are usually part of a greater organism DNA found in nucleus Not known to move by themselves ORGANELLES Means “little organ” and refers to a specialized cell part Found only in eukaryotic cells CELL MEMBRANE Two main purposes: 1. Boundary of the cell 2. Facilitates passage of items in and out of the cell NUCLEUS Control center of the cell Location of DNA Surrounded by a double membrane Easiest organelle to see under a microscope Usually only one per cell Nucleolus is found inside the nucleus and produces ribosomes CYTOSOL Empty space found between the organelles is considered the cytosol and is comprised of the jelly-like substance called the cytoplasm CYTOSKELETON Provides shape and structure Helps move organelles around the cell ENDOPLASMIC RETICULUM Also known as the “ER” Connected to the nuclear membrane (nucleus) Highway of the cell Two Parts: 1. Rough ER: studded with ribosomes (it makes proteins) 2. Smooth ER: no ribosomes (it makes lipids) RIBOSOMES Site of protein synthesis Found attached to the rough ER and floating in the cytosol Produced by the nucleolus GOLGI APPARATUS Stores, modifies and packages proteins Molecules transported to and from the Golgi by means of vesicles (containers or shipping boxes) LYSOSOMES Garbage disposal of the cell Contains digestive enzymes that break down waste and worn out or old cell parts MITOCHONDRIA Powerhouse of the cell Site of cellular respiration where energy is converted Bound by a double membrane Has its own DNA CHLOROPLAST Found only in plant cells Contains the green pigment Chlorophyll Site of food (glucose) production Bound by a double membrane Look like little stacks of pancakes! CELL WALL Found in plant and some bacteria cells Rigid, protective barrier Located outside the cell membrane Made of cellulose (fiber) VACUOLES Large central vacuole usually in plant cells. Animal cells have many smaller vacuoles called vesicles. Storage container for water, food, enzymes, wastes, etc. TAXONOMY Usually Unicellular ARCHAEA Cell Walls Autotroph & Heterotroph “Extremophiles”