1. A Tour of the Cell Figures 4.17 – 4.23
CHAPTER 4
A Tour of the Cell
Figures 4.17 – 4.23

2. CHLOROPLASTS AND MITOCHONDRIA: ENERGY CONVERSION
Cells require a constant energy supply to do all the work of life

3. CHLOROPLASTS
Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy
Inner and outer
membranes of
envelope
Space between
membranes
Granum
Stroma (fluid in
chloroplast)
Figure 4.17

4. Mitochondria
Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules
Outer
membrane
Inner
membrane
Cristae
Matrix
Space between
membranes
Figure 4.18

5. THE CYTOSKELETON: CELL SHAPE AND MOVEMENT
The cytoskeleton is an infrastructure of the cell consisting of a network of fibers

6. Maintaining Cell Shape
One function of the cytoskeleton
Provide mechanical support to the cell and maintain its shape
Figure 4.19A

7. The cytoskeleton can change the shape of a cell
This allows cells like amoebae to move
Figure 4.19B

8. Cilia and Flagella
Cilia and flagella are motile appendages

9. Flagella propel the cell in a whiplike motion
Cilia move in a coordinated back-and-forth motion
Figure 4.20A, B

10. Some cilia or flagella extend from nonmoving cells
The human windpipe is lined with cilia
Figure 4.20C

11. CELL SURFACES: PROTECTION, SUPPORT, AND CELL-CELL INTERACTIONS
Most cells secrete materials that are external to the plasma membrane

12. Plant Cell Walls and Cell Junctions
Plant cells are encased by cell walls
These provide support for the plant cells
Walls of two adjacent
plant cells
Vacuole
Plasmodesmata
(channels between cells)
Figure 4.21

13. Animal Cell Surfaces and Cell Junctions
Animal cells lack cell walls
They secrete a sticky covering called the extracellular matrix
This layer helps hold cells together

14. Animal cells connect by various types of junctions
Tight junctions
Adhering junctions
Communicating junctions

15. Extracellular matrix (a) Tight junctions (b) Anchoring junctions
(c) Communicating
junctions
Plasma membranes
of adjacent cells
Extracellular matrix
Figure 4.22

16. EVOLUTION CONNECTION: THE ORIGIN OF MEMBRANES
Phospholipids were probably among the organic molecules on the early Earth

17. When mixed with water, phospholipids spontaneously form membranes
Figure 4.23

18. SUMMARY OF KEY CONCEPTS
The Two Major Categories of Cells
Visual Summary 4.1

19. Membrane Structure and Function
A Fluid Mosaic of Lipids and Proteins
Outside cell
Phospholipid
Hydrophilic
Protein
Hydrophobic
Hydrophilic
Cytoplasm (inside cell)
Visual Summary 4.2