1. Chapter 6
Part A
A tour of The Cell

2. The Microscopic World of Cells
Organisms are either:
Single-celled, such as most bacteria and protists
Multicelled, such as plants, animals, and most fungi
The light microscope is used by many scientists.
Light passes through the specimen.
Lenses enlarge, or magnify, the image.

3. Microscopes as a Window on the World of Cells
glena

4. Magnification Resolving power
Is an increase in the specimen’s apparent size.
Resolving power
Is the ability of an optical instrument to show two objects as being separate.

5. The accumulation of scientific evidence since the cell discovery (1665) led to the cell theory.
All living things are composed of cells.
All cells are formed from previously existing cells.

6. The electron microscope (EM) uses a beam of electrons.
It has a higher resolving power than the light microscope (200 nm vs 2 nm).
The electron microscope can magnify up to 100,000X.
Such power reveals the diverse parts within a cell.

7. Figure 4.3

8. The scanning electron microscope (SEM) is used:
To study the detailed architecture of the surface of a cell.

9. The transmission electron microscope (TEM) is:
useful for exploring the internal structure of a cell.

10. The Two Major Categories of Cells
The countless cells on earth fall into two categories:
Prokaryotic cells
Eukaryotic cells
Prokaryotic and eukaryotic cells differ in several respects.

11. Figure 4.4

12. Prokaryotic cells Are smaller than eukaryotic cells.
Lack internal structures surrounded by membranes (organelles).
Lack a nucleus.

13. (b) A thin section through the
bacterium Bacillus coagulans
(TEM)
Pili: attachment structures on
the surface of some prokaryotes
Nucleoid: region where the
cell’s DNA is located (not
enclosed by a membrane)
Ribosomes: organelles that
synthesize proteins
Plasma membrane: membrane
enclosing the cytoplasm
Cell wall: rigid structure outside
the plasma membrane
Capsule: jelly-like outer coating
of many prokaryotes
Flagella: locomotion
organelles of
some bacteria
(a) A typical
rod-shaped bacterium
0.5 µm
Bacterial chromosome
Figure 6.6 A, B

14. Animal & Plant (Eukaryotic) Cells
A animal cell
Rough ER
Smooth ER
Centrosome
CYTOSKELETON
Microfilaments
Microtubules
Microvilli
Peroxisome
Lysosome
Golgi apparatus
Ribosomes
In animal cells but not plant cells:
Lysosomes
Centrioles
Flagella (in some plant sperm)
Nucleolus
Chromatin
NUCLEUS
Flagelium
Intermediate filaments
ENDOPLASMIC RETICULUM (ER)
Mitochondrion
Nuclear envelope
Plasma membrane
Figure 6.9

15. Ribosomes (small brwon dots)
A plant cell
Ribosomes (small brwon dots)
Central vacuole
Microfilaments
Intermediate
filaments
Microtubules
Rough
endoplasmic
reticulum
Smooth
Chromatin
NUCLEUS
Nuclear envelope
Nucleolus
Chloroplast
Plasmodesmata
Wall of adjacent cell
Cell wall
Golgi apparatus
Peroxisome
Tonoplast
Centrosome
Plasma membrane
Mitochondrion
CYTOSKELETON
In plant cells but not animal cells:
Chloroplasts
Central vacuole and tonoplast
Cell wall
Plasmodesmata
Figure 6.9

16. The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins
Plasma membrane separates cell living & nonliving surroundings.
Membranes composed mostly of lipids & proteins
Lipids belong to a special category (phospholipids)
Phospholipids form a two-layered membrane, the phospholipid bilayer.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

17. Figure 4.7a

18. Figure 4.7b

19. Membrane phospholipids and proteins:
Can drift about in the plane of the membrane.
Behavior why membrane described as a fluid mosaic:
Fluid: Molecules freely moving w/in membrane.
Mosaic: Diversity of proteins w/in membrane.

20. These extracellular coats help:
Cell Surfaces
Most cells secrete:
Coating materials of one kind or another
Coats are external to the plasma membrane.
These extracellular coats help:
Protect cells
Support cells
Facilitate cellular interactions in tissues.

21. Plant cells have the cell walls, which:
Help protect the cells
Maintain their shape
Keep the cells from absorbing too much water.
Animal cells have an extracellular matrix, which:
Helps hold cells together in tissues
Protects cells
Supports cells.

22. Structure and Function of the Nucleus
Is bordered by a double membrane (nuclear envelope) containing communication pores
Contains chromatin fibers (DNA molecule & proteins; each fiber is a chromosome).
Chromosomes are visible during cell division
Contains a nucleolus (mass of fibers & granules)

23. Structure and Function of the Nucleus
The nucleus is the manager of the cell.
Genes are stretches of DNA
Genes store information for protein production
Nucleolus make ribosome components
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

24. Figure 4.8

25. How DNA Controls the Cell
DNA transfers its coded information into mRNA
mRNA moves to cytoplasm
mRNA information is used to make protein
Ribosomes are responsible for protein synthesis

26. Figure 4.9

27. Many of the membranous organelles in the cell belong to:
The Endomembrane System: Manufacturing and Distributing Cellular Products
Many of the membranous organelles in the cell belong to:
The endomembrane system, which includes:
Endoplasmic reticulum
Golgi appraatus
Lysosomes
Vacuoles
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

28. The Endoplasmic Reticulum
The endoplasmic reticulum (ER)
Produces an enormous variety of molecules.
Is composed of smooth and rough ER.

29. Figure 4.10

30. The “roughness” of the rough ER is due to:
Ribosomes studding the outside membrane.
The functions of the rough ER include:
Producing two types of proteins
Membrane protein (new membrane)
Secretory protein (salivary glands)
Packages synthesized molecules into transport vesicles

31. Figure 4.11