Life is Cellular Chapter 7

Key Concept: Cells are the basic unit of life Macrophages engulfing bacteria © Eye of Science/Photo Researchers, Inc.

History Lenses and microscopes: ▫Late 1500s – Italy: merchants develop magnifying lenses to examine the quality of cloth ▫1600s – Holland: lenses combined to form microscopes and telescopes The cell theory grew out of the work of many scientists and improvements in the microscope.

History Lenses / Microscopes ▫1665 – Robert Hooke (England) built compound microscope – looked at thin sections of cork – called the small chambers that he saw “cells” © The Granger Collection, New York smithlifescience.com

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History Lenses and microscopes: ▫1674 – Anton van Leeuwenhoek used a single-lens microscope to observe pond water. To his amazement, he found a whole new world of microorganisms. l/collectie/e_voorwerpen/aalkijk er.html © The Granger Collection, New York

History Looking at cells ▫1838 – Matthias Schleiden: all plants made of cells ▫1839 – Theodor Schwann: all animals made of cells ▫1855 – Rudolf Virchow: observed onion root tip cells and concluded that new cells could only be produced by division of existing cells © The Granger Collection, New York

The Cell Theory The Cell Theory has three principles: All living things are made of cells. Nowicki

The Cell Theory The Cell Theory has three principles: All living things are made of cells. Cells are the basic units of structure and function in living things. Nowicki

The Cell Theory The Cell Theory has three principles: All living things are made of cells. Cells are the basic units of structure and function in living things. New cells are produced from pre-existing cells. Nowicki

Life is Cellular Most cells are 2-20 micrometers, about 1-10% of the diameter of a human hair. Mycoplasma bacterial cell: 0.1 micrometer Very large cells: human egg cell, amoeba proteus, skeletal muscles. lls/scale/ lls/scale/

Cell Types Cells fall into two broad categories, depending on whether they contain a nucleus Nucleus: a large membrane-enclosed structure that holds the cell’s genetic material (DNA) ProkaryotesEukaryotes Do not have nucleiContain nuclei

Cell Types Both Prokaryotes and Eukaryotes: ▫Come in a variety of shapes and sizes ▫Cells tend to be microscopic ▫All cells are enclosed by a membrane ▫All cells are filled with cytoplasm prokaryote cell © Dr. Kari Lounatmaa/Photo Researchers, Inc. cell membrane cytoplasm

Cell Types Eukaryotic cells ▫Have a nucleus ▫Have dozens of structures and internal membranes ▫Plants, animals, fungi, and protists are eukaryotes nucleus cell membrane organelles

Cell Types Prokaryotic cells ▫Do not have a nucleus ▫Do not have membrane-bound organelles ▫The organisms we call bacteria are prokaryotes Bacterium (colored SEM; magnification 8800x) cell membranecytoplasm

Cell Types – Summary ProkaryotesEukaryotes Genetic material is not contained in a nucleus Does not have membrane-bound organelles Bacteria Genetic material is contained in a nucleus Does contain membrane-bound organelles Plants, animals, fungi, and protists Both prokaryotic and eukaryotic cells : 1. Tend to be microscopic 2. Are enclosed by a membrane 3. Are filled with cytoplasm 4. Contain DNA Liver Cell

Plant and Animal Cells Both plant and animal cells contain a variety of organelles. ▫Organelles: specialized organs inside the cell, also called “little organs”

Plant and Animal Cells Some structures are specific to either plant cells or animal cells only ▫What structures do plant cells have that animal cells do not? Cell Wall Chloroplasts

Plant and Animal Cells Plant Cells ▫Plant cells have cell walls and chloroplasts

Plant and Animal Cells Plant Cells ▫A cell wall provides rigid support ▫Chloroplasts convert solar energy to chemical energy

Images Produced by Light Microscopes AmoebaStreptococcus bacteriaAnthrax bacteria Human cheek cells Plant cells Yeast cells

Images Produced by Electron Microscopes Cyanobacteria (TEM) Lactobacillus (SEM) Campylobacter (SEM) Deinococcus (SEM) House ant Avian influenza virus Human eyelash Yeast

Using Microscopes to Visualize the Three Shapes of Bacteria Cocci (round) Bacilli (rod) Spirilla (spiral) Light microscope: Three shapes of bacteria taken with an SEM Bacilli Cocci Spirilla