Download The Art of Looking at Cells

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 4
A Tour of the Cell
Modules 4.1 – 4.5
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Art of Looking at Cells
• Artists are often
inspired by biology and
biology depends on art
• The paintings of
Wassily Kandinsky
(1866-1944) show the
influence of cellular
forms
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Illustration is an
important way to
represent what scientists
see through microscopes
• The anatomist Santiago
Ramón y Cajal (18521934) was trained as an
artist
– He drew these retina
nerve cells
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Scanning
electron
microscope
(SEM)
• Scanning
electron
micrograph of
cilia
Figure 4.1B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Transmission
electron
microscope
(TEM)
• Transmission
electron
micrograph of
cilia
Figure 4.1C
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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
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cell size and
shape relate to
function
• 250 bacteria
would stretch
across the high
power field of
your
microscopes.
• 50 animal cells
would stretch
across that same
field.
Figure 4.2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Is there a limit to cell size? Can you have a giant man eating mouse?
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• A small cell has a greater ratio of surface area
to volume than a large cell of the same shape
30 µm
Figure 4.3
Surface area
of one large cube
= 5,400 µm2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
10 µm
Total surface area
of 27 small cubes
= 16,200 µm2
4.4 Prokaryotic cells are small and structurally
simple
• There are two kinds of cells: prokaryotic and eukaryotic.
Most cells are 70% water by weight, 18% protein, 3% lipids,
2% polysaccharides, 1.1% RNA and .25% DNA.
• Prokaryotic cells are small, relatively simple cells.
• The smallest prokaryotes are bacteria called mycoplasmas
which are 2 micrometers in diameter.
• Prokaryotes do not have a nucleus or membrane bound
organelles.
• Prokaryote means “before the kernel”
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• 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-for
movement
Ribosomes-site of protein synthesis
Capsule-protection
Cell wall-protection
– Inside the cell
are its DNA
and other parts
Plasma
membrane
Pili-for attachement
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Nucleoid region
(DNA)
Figure 4.4
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 averaging 10-100 micrometers.
• The largest cells include the nerve cell in the leg
of a giraffe which is 2 meters long.
• Eukaryotes are distinguished by the presence of
a true nucleus
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• An animal cell
Smooth
endoplasmic
reticulum
Nucleus
Rough
endoplasmic
reticulum
Flagellum
Not in most
plant cells
Lysosome
Centriole
Ribosomes
Peroxisome
Microtubule
Cytoskeleton
Intermediate
filament
Microfilament
Figure 4.5A
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Golgi
apparatus
Plasma membrane
Mitochondrion
• 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. ie. Poisonous H2O2 made in the peroxisomes
while hormones are being folded in the endoplasmic reticulum.
– Many organelles have fluid filled spaces-this allows for
activities termed cellular metabolism
– Membranes allow for surfaces for metabolic processes to
occur.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• A plant cell has some structures that an animal
cell lacks:
– Chloroplasts – site of photosynthesis
– A rigid cell wall with cellulose
– Central vacuole for storage of water and
chemicals
– Lack centrioles seen during cell division
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Nucleus
Rough
endoplasmic
reticulum
Ribosomes
Smooth
endoplasmic
reticulum
Golgi
apparatus
Microtubule
Not in
animal
cells
Central
vacuole
Intermediate
filament
Chloroplast
Microfilament
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
Figure 4.5B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Cytoskeleton