1. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The microscope was invented in the 17th century Using a microscope, Robert Hooke discovered cells in 1665 All living things are made of cells (cell theory) INTRODUCTION TO THE WORLD OF THE CELL

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The light microscope enables us to see the overall shape and structure of a cell 4.1 Microscopes provide windows to the world of the cell Figure 4.1A Image seen by viewer Eyepiece Ocular lens Objective lens Specimen Condenser lens Light source

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Illustration is an important way to represent what scientists see through microscopes The anatomist Santiago Ramón y Cajal (1852- 1934) was trained as an artist –He drew these retina nerve cells

4. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Electron microscopes were invented in the 1950s They use a beam of electrons instead of light The greater resolving power of electron microscopes –allows greater magnification –reveals cellular details

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Scanning electron microscope (SEM) Figure 4.1B Scanning electron micrograph of cilia

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Transmission electron microscope (TEM) Figure 4.1C Transmission electron micrograph of cilia

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Below is a list of the most common units of length biologists use (metric) 4.2 Cell sizes vary with their function Table 4.2

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell size and shape relate to function Figure 4.2

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings At minimum, a cell must be large enough to house the parts it needs to survive and reproduce The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes 4.3 Natural laws limit cell size

10. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A small cell has a greater ratio of surface area to volume than a large cell of the same shape 30 µm10 µm Surface area of one large cube = 5,400 µm 2 Total surface area of 27 small cubes = 16,200 µm 2 Figure 4.3

11. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings There are two kinds of cells: prokaryotic and eukaryotic Prokaryotic cells are small, relatively simple cells –They do not have a nucleus 4.4 Prokaryotic cells are small and structurally simple

12. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A prokaryotic cell is enclosed by a plasma membrane and is usually encased in a rigid cell wall –The cell wall may be covered by a sticky capsule Ribosomes Figure 4.4 Capsule Cell wall Plasma membrane Prokaryotic flagella Nucleoid region (DNA) Pili –Inside the cell are its DNA and other parts

13. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings All other life forms are made up of one or more eukaryotic cells These are larger and more complex than prokaryotic cells Eukaryotes are distinguished by the presence of a true nucleus 4.5 Eukaryotic cells are partitioned into functional compartments

14. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An animal cell Plasma membrane Figure 4.5A Golgi apparatus Ribosomes Nucleus Smooth endoplasmic reticulum Rough endoplasmic reticulum Mitochondrion Not in most plant cells Cytoskeleton Flagellum Lysosome Centriole Peroxisome Microtubule Intermediate filament Microfilament

15. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The plasma membrane controls the cell’s contact with the environment The cytoplasm contains organelles Many organelles have membranes as boundaries –These compartmentalize the interior of the cell –This allows the cell to carry out a variety of activities simultaneously

16. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A plant cell has some structures that an animal cell lacks: –Chloroplasts –A rigid cell wall

17. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 4.5B Nucleus Golgi apparatus Not in animal cells Central vacuole Chloroplast Cell wall Mitochondrion Peroxisome Plasma membrane Rough endoplasmic reticulum Ribosomes Smooth endoplasmic reticulum Cytoskeleton Microtubule Intermediate filament Microfilament