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Cell Structure Chapter 7 Looking at cells Discovery of Cells Robert Hooke was the first person to see a cell in 1665. Hooke used a crude compound microscope to view a thin slice of cork. He called what he saw “cells” because the tiny squares reminded him of the rooms that monks lived in. Looking at cells A picture of the primitive microscope that Hooke used. Notice some of the parts we’ve discussed. A diagram of the “cells” that Hooke viewed under his scope. Expanding on Hooke’s work. Around 1670 another man named Anton Van Leeuwenhoek made a microscope a little different then Hooke’s that magnified 200x. Van Leeuwenhoek’s scope was a lot stronger than Hooke’s and he was able to see bacteria in pond water. Van Leeuwenhoek called what he saw “animalcules”. Measuring the sizes of cells Once again scientists use SI units to measure the length of microscopic organisms. Do you think they use meters, centimeters or even millimeters? Scientists use Micrometers and Nanometers to measure microscopic organisms. 1μm = 0.000001m 1nm = 0.000000001m Cell Theory In 1838 a German botanist named Mattias Schleiden noticed that cells make up every part of a living thing. Later a German zoologist named Theodore Schwann noticed that animals are also made of cells. In 1858 Rudolph Virchow a German physician noticed that all cells come from existing cells These observations formed the three parts of the cell theory. Three steps of the Cell Theory All living things are made of one or more cells. Cells are the basic units of structure and function in organisms. All cells arise from existing cells. Size of Cells How big is a cell? 2 μm – 2 mm. Most cells that we know of are very small. Why do you think cells are so small? Nutrients and water need to diffuse across the cell membrane and be distributed throughout the entire cell. Think about it… Is it easier to distribute nutrients throughout a big cell or a smaller cell? Surface-area-to-volume ratio. What is surface area? The cell membrane of a small cell has a small surface area and a small volume. The cell membrane of a large cell has a larger surface area and a very large volume. The cell with the highest ratio is the most efficient cell. What can we tell about the amount of time it would take for nutrients to make it to the nucleus of these cells? Simple cells The first cells appeared on earth about 3.5 billion years ago. The cells were very basic, they had very few organelles and its DNA was not surrounded by a nucleus. These cells are called prokaryotic cells. An example of a prokaryotic cell is bacteria. Prokaryotic cells Prokaryotic cells are very small, only one to two μm in diameter. Prokaryotic cells are filled with a fluid like substances called cytoplasm. These cells have a cell membrane and a cell wall. (The cell wall of the cork cell is what Hooke saw) Most bacteria move using a long threadlike structure that spins like a propeller called a flagellum. Some examples of bacterial cells. Larger cells The cells that make up our bodies are much more complex than prokaryotic cells. Our cells have many organelles that each have a specific function. Our cells also have a nucleus that protects our DNA. Our cells are called eukaryotic cells. Eukaryote- Cell that has a nucleus, internal compartments and appeared on earth about 1.5 billion years ago. Eukaryotic Cell Important Organelles (Phospholipid Bilayer) Phospholipid Bilayer- Double layer that makes up the cell membrane. Town Boundary Important Organelles (Nucleus) Nucleus- Controls most functions in a eukaryotic cell. Houses the DNA. Surrounded by a nuclear envelope. Nuclear Pores allow substances in and out of the cell. The nucleus acts like City Hall Important Organelles (Endoplasmic Reticulum) Endoplasmic Reticulum- Helps distribute proteins throughout the cell. Smooth & Rough. The rough ER is studded with ribosomes. The ER is like a factory. Important Organelles (Golgi) Golgi Apparatus- Packages and distributes proteins throughout the cells. The Golgi acts like a post office or a packaging plant. Important Organelles (Vesicle) Vesicle – A small membrane-bound sac that transports substance throughout a cell. A vesicle acts like a mail truck. Important Organelles (Lysosome) Lysosome – A small circular organelle that contains digestive enzymes. A lysosome acts like a garbage truck. Important Organelles Mitochondria – Organelle that harvests energy and makes ATP. “The powerhouse” The electric company. Comparing Plant and Animal Cells Plant cells contain everything that an animal cell has plus some. Animal cells are circular whereas plant cells are rectangular. Plant cells have three organelles that are not present in animal cells. - Cell Wall - Chloroplasts -Central Vacuole Important Organelles Cell Wall – The structure that surrounds the cell membrane and provide support for the cell. The cell wall is like a city wall. Important Organelles Chloroplast – Organelle that uses light energy to make carbohydrates from carbon dioxide and water. A chloroplast again is like the electric company. Important Organelles Central Vacuole – Cavity that is used for storage. The central vacuole takes up the most space of any organelle. Self storage facility.