Download Chapter 7 – A Tour of the Cell

Chapter 6 – A Tour of the Cell
Review Metric System
What is a μm?
10-6 m
What is a mm?
10-3 m
How many μm is 22 mm?
2,200 μm or
2.2 x 103 μm
Size Range of Cells
• Most cells are in the
range of 1 to 100 μm
– Not visible with
unaided eyes
• Light microscopes are
capable of resolving
most plant, animal,
and bacterial cells
• Electron microscopes
are used for smaller
cells and molecules
Figure 6.2
1. Light Microscope
- First used by Renaissance scientists (Remember
Hooke and Von Leeuwenhoek).
- Visible light is passed through a specimen and then
through multiple lenses to enlarge the apparent object.
- Object is usually stained so that some light is
absorbed or induced to fluoresce.
2. Electron microscopes
- Invented in the 1950s
- Beam of electrons is focused through or onto the surface
of a specimen
- Transmission electron microscope (TEM): internal cell
structure
- Scanning electron microscope (SEM): surface of
specimen
Figure 6.4 (p. 96) – Electron micrographs. Views are of
cilia in the windpipe of a rabbit.
TEM vs. SEM
Figure 6.4
• Transmission electron
microscopes (TEM)
are used mainly to
study the internal
structure of cells
• Scanning electron
microscopes (SEM)
are used to study the
surface of cells
As noted in Chapter 1, one of the Eleven Unifying Themes of
Biology is that the Cell is the basic Unit of Life.
Remember that there are two types of Cells:
Prokaryotic and Eukaryotic
Prokaryotic cells do not have a membrane enclosed nucleus
or organelles. What are the two types of Prokaryotes?
Bacteria and Archae
Figure 6.6 (p. 98) – A prokaryotic cell. From Fig. 6.6,
remember these different components:
a. Nucleoid: location of DNA, not enclosed by a
membrane in contrast to eukaryotic cells.
b. Pili: Structures most often used for attachment to
soil, tissue, etc., can be toxic to higher organisms.
c. Ribosomes: “Organelles” that synthesize protein.
d. Cell Wall: Rigid structure that maintains cell’s
shape; protects it from rupture.
e. Capsule: Slime-like layer used for protection and
attachment.
f. Flagellum (-a, pl.): Used for locomotion by a corkscrew motion.
g. Plasma Membrane: Controls what comes in and out
of cell; site of most energy production.
Prokaryotic Cell
Figure 6.6
2. Eukaryotic cells contain a nucleus and organelles that are
sub-cellular structures that perform specialized functions
within the cell. Know the following from:
Figure 6.9 (p. 100) – Overview of an animal cell.
Figure 6.9 (p. 101) – Overview of a plant cell.
a. Nucleus: contains majority of the genes in the
eukaryotic cell present in the cells’ chromosomes.
b. Cytoplasm: region between the nucleus and plasma
membrane; organelles are suspended in this region
c. Plasma Membrane: barrier that allows exchange of
oxygen, nutrients, and waste into and out of the cell
d. Cell Wall: maintains shape and structure of cell
(found only in plant cells)
Animal Cell
Figure 6.9
e. Ribosomes: carry out protein synthesis
f. Endoplasmic Reticulum (ER): site of membrane
synthesis and some metabolic processes. There are two
types of ER:
- Rough ER: covered with ribosomes (synthesis
of proteins)
- Smooth ER: surface lacks ribosomes
g. Golgi Apparatus: modifies, stores, and secretes
products of ER
h. Lysosomes: bodies of enzymes that are used to
digest macromolecules (found only in animal cells) and
harmful compounds
i. Vacuoles: membrane-bounded sacs within cells
- Food vacuoles: store and digest food
- Contractile vacuoles: excrete excess water
- Central vacuole: storage of excess organic and
inorganic compounds; isolation
j. Mitochondria: cellular respiration occurs and ATP is
generated
k. Chloroplasts: photosynthesis  convert light
energy to chemical energy (found only in plant cells)
Animal Cell
Figure 6.9
Plant Cell
Figure 7.8
Further details and Figures:
1. The Nucleus (pp. 102 and 103) Note the double membrane
and the chromatin (cellular DNA plus protein coat) in Fig.
6.10.
2. Endomembrane System (pp 104 - 109). Functions to
compartmentalize cellular activities. Includes the nuclear
envelope, endoplasmic reticulum, Golgi apparatus,
lysosomes, vacuoles, and the plasma membrane.
In the film accompanying this section, note where a secretory protein is produced
(endoplasmic reticulum, rough), how the protein moves to the Golgi apparatus
(transported in a vesicle), that the protein is modified by the Golgi apparatus, and
then transported to the plasma membrane where it is released to the outside of
the cell.
Note: secretory proteins are “secreted” to the outside of the cell so that they can
perform functions outside the cell. Can you think of any?
Fig. 6.12
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
3. Mitochondria and Chloroplasts
Mitochondrion - site of respiration (production of
energy from fats, sugars and other organic
molecules resulting in carbon dioxide, water and
waste
Chloroplasts - Site of photosynthesis (production
of sugars and energy from carbon dioxide, water
and light
4. Cytoskeleton – Network of fibers that extend throughout
the cytoplasm. Aids the cell in maintaining its shape.
Especially true for animal cells that do not have cell walls,
as plants cells do. Note Fig. 6.20 and Table 6.1.
Remember the following two cytoskeleton components and
their functions:
Microtublues: subset of these responsible for the beating of
cilia and flagella in eukarytoic cells. Note Figs. 6.23 and
6.24.
Microfilaments: subset of these is responsible for the
contraction of muscle cells. Note Fig. 6.27.