1. Copyright © 2009 Pearson Education, Inc..
The
World
of the
Cell
Wayne M. Becker
Lewis J. Kleinsmith
Jeff Hardin
Gregory Paul Bertoni
Seventh Edition
Chapter 1
A Preview
of the Cell
Copyright © 2009 Pearson Education, Inc..

2. Overview: The Fundamental Units of Life
Cell is the basic unit of life.All organisms are made of cells
The cell is the simplest collection of matter that can live
Cell structure is correlated to cellular function
All cells are related by their descent from earlier cells
Cell biology is the science that deals with the form and functions of cells
For the Discovery Video Cells, go to Animation and Video Files.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. Figure 1-1

4. Figure 1-2

5. The emergence of modern Cell Biology
An interweaving of three different branches
Cytology, the study of cells,deals with cellular structures use microscopes (300 hundred years ago)
Biochemistry led to understanding of cellular functions,by development of various techniques, ultracentrifugation, chromatography, electrophoresis & mass spectrometry to identify and separate cellular components
Genetics, deals with the heredity
Though usually too small to be seen by the unaided can be complex
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. Main features of three strands
The cytology deals with cellular structures by microscopes, Lm & EM, led to formulation of cell theory
All organisms consist of one or more cells
The cell is the basic unit of structure(Schwann 1839)
All cells arise from preexisting cells(Virchow)
Biochemistry covers the chemistry of biological structures and function, it has led to a new field of Proteomics (function and interaction of all proteins present in a cell).
Genetics focuses on flow of hereditary information, contributed the knowledge of genes, chromosome theory,sructure of DNA. DNA sequencing has led to a new discipline called bioformatics, that merges computer science & biology to understand sequencing data

7. THE PROCESS OF SCIENCE
Scientists use two main approaches to learn about nature
Science
Is a way of knowing
Seeks natural causes for natural phenomena

8. Facts and Scientific Method
Facts and Scientific Method
Science is not a collection of facts but a process of discovering answers to questions about our natural world. Two approaches used
Discovery Science
In discovery science
Scientists describe some aspect of the world and use inductive reasoning to draw general conclusions

9. Hypothesis-Based Science
Hypothesis-Based Science
In hypothesis-based science
Scientists attempt to explain obser vations by testing hypotheses

10. With hypothesis-based science, we pose and test hypotheses
With hypothesis-based science, we pose and test hypotheses
Hypothesis-based science involves
Obser vations, questions, hypotheses as tentative statement based on the previous observation or experiment as answers to questions
Deductions leading to predictions, and then tests of predictions to see if a hypothesis is falsifiable
Hypothesis must be testable, scientist can design a controlled experiment to determine whether the hypothesis will be supported by data or observation
When a hypothesis have been tested many times, and by different scientist with the same results, it becomes a THEORY e.g theory of natural selection

11. A Case Study from Ever yday Life
A Case Study from Ever yday Life
Deductive reasoning is used in testing hypotheses as follows
If a hypothesis is correct, and we test it, then we can expect a par ticular outcome
Observations
Question
Hypothesis # 1:
Dead batteries
Hypothesis # 2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Replacing bulb
Test prediction
Test falsifies hypothesis
Test does not falsify hypothesis
Figure 1.8A

12. Percent of total attacks
A Case Study of Hypothesis-Based Science
In experiments designed to test hypotheses
The use of control groups and experimental groups helps to control variables
Percent of total attacks
on artificial snakes
100 80 60 40 20
83%
17%
16%
84%
Artificial king snakes
Artificial brown snakes
Coral snakes
absent
present
Figure 1.8B
Figure 1.8C
Figure 1.8D
Figure 1.8E

13. Figure 1B-1

14. Microscopy
Scientists use microscopes to visualize cells too small to see with the naked eye
In a light microscope (LM), visible light passes through a specimen and then through glass lenses, which magnify the image
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. Figure A-5

16. The quality of an image depends on
Magnification, the ratio of an object’s image size to its real size
Resolution, the measure of the clarity of the image, or the minimum distance of two distinguishable points
Contrast, visible differences in parts of the sample
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

17. Different types of microscopes
Can be used to visualize different sized cellular structures
Unaided eye
1 m
0.1 nm
10 m
0.1 m
1 cm
1 mm
100 µm
10 µ m
1 µ m
100 nm
10 nm
1 nm
Length of some
nerve and
muscle cells
Chicken egg
Frog egg
Most plant and Animal cells
Smallest bacteria
Viruses
Ribosomes
Proteins
Lipids
Small molecules
Atoms
Nucleus Most bacteria Mitochondrion
Light microscope
Electron microscope
Figure 6.2
Human height
Measurements
1 centimeter (cm) = 102 meter (m) = 0.4 inch
1 millimeter (mm) = 10–3 m
1 micrometer (µm) = 10–3 mm = 10–6 m
1 nanometer (nm) = 10–3 mm = 10–9 m

18. Units of Measurements Micrometer(um), 1/1ooooo of a meter
Micrometer most useful unit for expressing the cells and large organelles.
Plant and animal cells are ums; in diameter ,bacterial cell much smaller only 1x2 ums can be seen by LM.
Nanometer(nm) is one billionth of a meter, it is used to measure organelles fig1A-2 , ribosomes,
Membranes, microtubules & microfilaments seen by Em.

19. Figure 1A-1

20. Figure 1A-2

21. LMs can magnify effectively to about 1,000 times the size of the actual specimen
Various techniques enhance contrast and enable cell components to be stained or labeled
Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by an LM
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

22. Use different methods for enhancing visualization of cellular structures
TECHNIQUE
RESULT
Brightfield (unstained specimen).
Passes light directly through specimen.
Unless cell is naturally pigmented or
artificially stained, image has little
contrast. [Parts (a)–(d) show a
human cheek epithelial cell.]
(a)
Brightfield (stained specimen). Staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved).
(b)
Phase-contrast. Enhances contrast
in unstained cells by amplifying
variations in density within specimen;
especially useful for examining living,
unpigmented cells.
(c)
50 µm
Figure 6.3

23. Fluorescence. Shows the locations of specific
molecules in the cell by tagging the molecules
with fluorescent dyes or antibodies. These
fluorescent substances absorb ultraviolet
radiation and emit visible light, as shown
here in a cell from an artery.
Confocal. Uses lasers and special optics for
“optical sectioning” of fluorescently-stained
specimens. Only a single plane of focus is
illuminated; out-of-focus fluorescence above
and below the plane is subtracted by a computer.
A sharp image results, as seen in stained nervous
tissue (top), where nerve cells are green, support
cells are red, and regions of overlap are yellow. A
standard fluorescence micrograph (bottom) of this
relatively thick tissue is blurry.
50 µm
(d)
(e)
(f)
Differential-interference-contrast (Nomarski).
Like phase-contrast microscopy, it uses optical
modifications to exaggerate differences in
density, making the image appear almost 3D.

24. Figure A-1

25. Electron microscopes (EMs)
Focus a beam of electrons through a specimen (TEM) or onto its surface (SEM)

26. The scanning electron microscope (SEM)
Provides for detailed study of the surface of a specimen
TECHNIQUE
RESULTS
Scanning electron micro-
scopy (SEM). Micrographs taken
with a scanning electron micro-
scope show a 3D image of the
surface of a specimen. This SEM
shows the surface of a cell from a
rabbit trachea (windpipe) covered
with motile organelles called cilia.
Beating of the cilia helps move
inhaled debris upward toward
the throat.
(a)
Cilia
1 µm
Figure 6.4 (a)

27. The transmission electron microscope (TEM)
Provides for detailed study of the internal ultrastructure of cells
Transmission electron micro-
scopy (TEM). A transmission electron
microscope profiles a thin section of a
specimen. Here we see a section through
a tracheal cell, revealing its ultrastructure.
In preparing the TEM, some cilia were cut
along their lengths, creating longitudinal
sections, while other cilia were cut straight
across, creating cross sections.
(b)
Longitudinal
section of
cilium
Cross section
of cilium
1 µm
Figure 6.4 (b)

28. 10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm
Fig. 6-2
10 m
Human height
1 m
Length of some nerve and muscle cells
0.1 m
Unaided eye
Chicken egg
1 cm
Frog egg
1 mm
100 µm
Most plant and animal cells
Light microscope
10 µm
Nucleus
Most bacteria
1 µm
Mitochondrion
Figure 6.2 The size range of cells
Smallest bacteria
Electron microscope
100 nm
Viruses
Ribosomes
10 nm
Proteins
Lipids
1 nm
Small molecules
0.1 nm
Atoms

29. Table 1-1

30. Figure 1-4

31. Figure A-2

32. Figure A-3

33. Figure A-4

34. Figure A-6

35. Figure A-7

36. Figure A-8

37. Figure A-9

38. Figure A-25

39. Figure A-26 Comparison of TEM & SEM Electron Micrograph
TEM,Rough Endoplasmic reticulum membranes in the cytoplasm of rat pancreas cell.
The same structure prepared by SEM, just shows 3D appearance of RER.
Figure A-26

41. Figure A-27

42. Figure A-28

43. Figure A-33