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Lesson Overview 7.1 Life is Cellular Lesson Overview Life Is Cellular The Discovery of the Cell • The cell theory states: - All living things are made up of cells. - Cells are the basic units of structure and function in living things. - New cells are produced from existing cells. Lesson Overview Life Is Cellular Early Microscopes • Robert Hooke • 1st person to use the microscope to look at a nonliving specimen. • He looked at a thin slice of cork, a plant material. Lesson Overview Life Is Cellular Early Microscopes • He called the empty chambers he looked at “cells”. Lesson Overview Life Is Cellular Early Microscopes – Anton van Leeuwenhoek examined pond water and other things, including a sample taken from a human mouth. – He called the organisms bacteria. Lesson Overview Life Is Cellular The Cell Theory • Theodor Schwann stated that all animals were made of cells. Theodor Schwann • Matthias Schleiden concluded that all plants are made of cells. Matthias Schleiden Lesson Overview Life Is Cellular The Cell Theory • Rudolf Virchow concluded that new cells could be produced only from the division of existing cells. Rudolf Virchow Lesson Overview Life Is Cellular Exploring the Cell • Most microscopes use lenses to magnify the image of an object by focusing light or electrons. Lesson Overview Life Is Cellular Light Microscopes and Cell Stains • A typical light microscope allows light to pass through a specimen and uses two lenses to form an image. • The first set of lenses, located just above the specimen, produces an enlarged image of the specimen. Lesson Overview Life Is Cellular • The second set of lenses magnifies this image still further. • Light microscopes are able to produce images of objects only to a magnification of about 1000 times because light waves are diffracted or scattered as they pass through matter. Lesson Overview Life Is Cellular Light Microscopes and Cell Stains – It is difficult to see most living cells through a light microscope because they are nearly transparent. – Using chemical stains or dyes can usually solve this problem. Lesson Overview Life Is Cellular Light Microscopes and Cell Stains-R-Track – Fluorescence- when dyes give off light of a particular color when viewed under specific wavelengths of light. – Fluorescence microscopy makes it possible to see the locations of molecules and watch them move about in a living cell. Lesson Overview Life Is Cellular Electron Microscopes – Used to study objects smaller than 1millionth of a meter. – Use beams of electrons, not light, that are focused by magnetic fields. Lesson Overview Life Is Cellular Electron Microscopes There are two major types of electron microscopes: transmission and scanning. Lesson Overview Life Is Cellular Transmission Electron Microscopes – Used to explore inside the cell (ex. Cell structures and large protein molecules). – produce flat, twodimensional images. Lesson Overview Life Is Cellular Scanning Electron Microscopes – Used to scan the entire surface of a specimen without cutting them into thin slices. – produce threedimensional images of the specimen’s surface. ANTENNA OF AN ANT Lesson Overview Life Is Cellular Electron Microscopes – R-Track • Electron microscopy can be used to examine only nonliving cells and tissues because samples need to be dehydrated and chemically preserve first before placing them in the microscope. Lesson Overview Life Is Cellular Prokaryotes and Eukaryotes – All cells are surrounded by a thin, flexible barrier called a cell membrane. – Cells are prokaryotes or eukaryotes depending on whether they contain a nucleus. Lesson Overview Life Is Cellular Prokaryotes and Eukaryotes – Eukaryotes are cells that enclose their DNA in nuclei. – Prokaryotes are cells that do not enclose DNA in nuclei. Lesson Overview Life Is Cellular Prokaryotes – Prokaryotic cells are generally smaller and simpler than eukaryotic cells. – Example: bacteria. Lesson Overview Life Is Cellular Eukaryotes – Eukaryotic cells are generally larger and more complex than prokaryotic cells. – Examples: plants, animals, fungi, and organisms commonly called “protists.” Lesson Overview Life Is Cellular Differences & Similarities between Prokaryotes & Eukaryotes Prokaryotes Eukaryotes No nucleus Has nucleus No membrane-bound organelles Some ribosomes Has membrane-bound organelles Has ribosomes Very small (1-10 µm) Small (2-1000 µm) Has cytoplasm, DNA, cell membrane Has cytoplasm, DNA, cell membrane