1. CHAPTER 4 A Tour of the Cell
Modules 4.1 – 4.5

2. The Art of Looking at Cells
Artists are often inspired by biology and biology depends on art
The paintings of Wassily Kandinsky ( ) show the influence of cellular forms

3. Illustration is an important way to represent what scientists see through microscopes
The anatomist Santiago Ramón y Cajal ( ) was trained as an artist
He drew these retina nerve cells

4. INTRODUCTION TO THE WORLD OF THE CELL
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)

5. 4.1 Microscopes provide windows to the world of the cell
The light microscope enables us to see the overall shape and structure of a cell
Image seen by viewer
Eyepiece
Ocular lens
Objective lens
Specimen
Condenser lens
Light source
Figure 4.1A

6. 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

7. Scanning electron microscope (SEM)
Scanning electron micrograph of cilia
Figure 4.1B

8. Transmission electron microscope (TEM)
Transmission electron micrograph of cilia
Figure 4.1C

9. 4.2 Cell sizes vary with their function
Below is a list of the most common units of length biologists use (metric)
Table 4.2

10. Cell size and shape relate to function
Figure 4.2

11. 4.3 Natural laws limit cell size
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

12. A small cell has a greater ratio of surface area to volume than a large cell of the same shape
Surface area of one large cube = 5,400 µm2
Total surface area of 27 small cubes = 16,200 µm2
Figure 4.3

13. 4.4 Prokaryotic cells are small and structurally simple
There are two kinds of cells: prokaryotic and eukaryotic
Prokaryotic cells are small, relatively simple cells
They do not have a nucleus

14. 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
Prokaryotic flagella
Ribosomes
Capsule
Cell wall
Inside the cell are its DNA and other parts
Plasma
membrane
Nucleoid region (DNA)
Pili
Figure 4.4

15. 4.5 Eukaryotic cells are partitioned into functional compartments
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

16. An animal cell Smooth endoplasmic reticulum Nucleus
Rough endoplasmic reticulum
Flagellum
Not in most plant cells
Lysosome
Centriole
Ribosomes
Peroxisome
Golgi apparatus
Microtubule
Plasma membrane
Cytoskeleton
Intermediate filament
Microfilament
Mitochondrion
Figure 4.5A

17. 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

18. A plant cell has some structures that an animal cell lacks:
Chloroplasts
A rigid cell wall

19. Rough endoplasmic reticulum
Nucleus
Ribosomes
Smooth endoplasmic reticulum
Golgi apparatus
Microtubule
Central vacuole
Not in animal cells
Intermediate filament
Cytoskeleton
Chloroplast
Microfilament
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
Figure 4.5B