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Chapter 1.
Introduction
to cell biology
2nd Edition
11
Contents
1.1. What is cell biology?
1.2. The cell theory
1.3. Cell is the basic unit of life
1.4. Diversity of cells
1.5. The prokaryotic cell
1.6. The eukaryotic cell
1.7. Modern cell biology
1.8. The technology of cell biology
1.9. Training the scientists of tomorrow
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1.1. What is cell biology?
The application of molecular biological
approaches to an understanding of life at
the cellular level.
The molecular basis
of cell structure, cell
function and cell
interactions
Understanding of whole
organisms composed
with cells
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The Basis of Modern Biology
Study the molecules within cells
 macromolecules and
reactions, investigated
by biochemists
 the functional processes
described by cell
biologists
 the gene control
pathways identified by
molecular biologists and
geneticists.
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Cell Biology Is in Progress
Two gathering forces will
reshape cell biology:
The genomics, the complete
DNA sequence of many
organisms,
DNA
mRNA Protein
The proteomics, the knowledge
of all the possible shapes and
functions that proteins employ.
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The Study the molecular similarities
and differences between cell types
the
molecular composition
of cells
how cells work due to
molecular similarities and
differences
closely related to genetics,
biochemistry, molecular
biology and developmental
biology.
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1.2. The cell theory
Three indispensable theories
upon which the science of
biology is built.
 The theory of evolution
 The cell theory
 The theory of equilibrium
thermodynamics
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He gave the first complete descriptions of the bacteria,
the protozoans原生动物 (which he called animalcules),
spermatozoa, and striped muscle. He also observed
the red blood cells in his detailed study of capillary
circulation.
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Matthias Jakob, Schleiden, (1804-1881)
He worked under Johannes Müller and
studied primarily cells in plants. He
observed that all plants seemed to be
composed of cells, and is thus considered
the co-founder of cell theory together with
Schwann.
Theodor Schwann (1810-1882), German physiologist
and histologist
He identified the cell as the basic
structure of plant and animal tissue in
1938-1839. Together with Matthias
Schleiden he formulated the cell theory
of life.
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The Cell Theory (1938)
Schleiden and Schwann proposed the cell
theory in 1838. The cell theory states that:
The cell is the unit of structure, physiology, and
organization in living things.
 The cell retains a dual existence as a distinct entity
and a building block in the construction of organisms.
 Cells form by free-cell formation, similar to the
formation of crystals (spontaneous generation).

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The modern tenets of the Cell Theory






All known living things are made up of cells.
The cell is structural & functional unit of all living
things.
All cells come from pre-existing cells by division.
(Spontaneous Generation does not occur).
Cells contains hereditary information which is
passed from cell to cell during cell division.
All cells are basically the same in chemical
composition.
All energy flow (metabolism & biochemistry) of
life occurs within cells.
The cell theory also provides us with an
operational definition of "life".
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1.3. Cell is the basic unit of life
All cells have some
recognizable similarities
• Plasma membrane
• Nucleus
• Organelles
Ribosomes
mitochondrion
lysosomes
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 All
living things are composed of one or more cells.
 Cell has the special features of living thing.
Movement
Respiration
Sensitivity to
environment
Growth
Reproduction
Metabolism
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Even plants move, such as opening and closing petals,
and turning to face the sun.
Breathing. Animals breathe in oxygen, and breathe out
carbon dioxide. Plants breathe in carbon dioxide, and
breathe out oxygen.
Plants are sensitive to light and gravity (stems grow up
and roots grow down). Animals are sensitive to many
things such as noise and light.
Do I need to explain this?
Babies! Plants and animals can make more of
themselves with similarly inherited features.
All living things need to eat food and give off waste,
such as moisture (eg. sweat) or going to the toilet!
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Differences between
Plant Cell and Animal Cell
Plant Cell
Prokaryotic cells and
plant cells both have a
rigid cell wall made up of
polysaccharides.
Animal Cell
Plant cells have the
chloroplast which is the
site of photosynthesis.
While animal cells have
the mitochondrion which
is the site of aerobic
respiration.
The vacuoles, large empty
appearing areas in the
cytoplasm, are usually
found in plant cells where
they store waste. Vesicles
are much smaller than
vacuoles in animal cells.
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Origin of the Cell
The earliest cells might be as much as 3.8 billion years old.
Where did life originate and how ?
Inorganic
Extra-terrestrial or Organic Chemical Evolution
Organic
Amino acids
Pre-cellular
Single cell
Multicellular
organisms
Stanley Miller (b. 1930) was a doctoral student working with Urey at the University of
Chicago, researching possible environments of early Earth. In 1953 he combined the
ideas of Urey and Oparin in a short, simple experiment.
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The interactions of these molecules would
have increased as their concentrations
increased. Reactions would have led to the
building of larger, more complex molecules. A
pre-cellular life would have began with the
formation of nucleic acids. Chemicals made
by these nucleic acids would have remained
in proximity to the nucleic acids. Eventually
the pre-cells would have been enclosed in a
lipid-protein membrane, which would have
resulted in the first cells.
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Origins of Life and the RNA World
Which came first in the origin of life, DNA, RNA or protein?
RNA has the ability to act as both genes and
enzymes. This property could offer a way around
the "chicken-and-egg" problem. (Genes require
enzymes; enzymes require genes.) RNA can be
transcribed into DNA.
From RNA to life and the RNA world could be the
original pathway to cells.
Sidney Altman and Thomas Cech were awarded
the Nobel Prize for Biochemistry in 1989
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DNA
RNA
Protein
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Three Things Make Cell Different
from Non-cell system
1. The presence of enzymes and other complex molecules
essential to the processes needed by living systems. Miller's
experiment showed how these could possibly form.
2. The capacity for replication from one generation to another.
Most organisms today use DNA as the hereditary material,
although recent evidence (ribozymes) suggests that
RNA may have been the first nucleic acid system to have
formed,referred to the RNA world.
3. A membrane that separates the internal chemicals from the
external chemical environment. This also delimits the cell
from not-cell areas. The work of Sidney W. Fox has
produced proteinoid spheres , which while not
cells, suggest a possible route from chemical to cellular life.
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Microscope Is Needed to Visualize Cells
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1.4. Diversity of cells
Prokaryotes have no nucleus
or other membrane-bounded
compartments. They lack
distinct organelles, although
some do have invaginated
membrane structures.
Eukaryotes have a
membrane-bounded nucleus
and usually have other
membrane-bounded
compartments or organelles as
well.
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Differences between Prokaryotes and Eukaryotes
Prokaryotes
Eukaryotes
Size
1-10 microns
10-100 microns
Complexity
Nucleus
Unicellular, rarely small clusters or
filaments
None
(mesosome is infolding of
cytoplasmic membrane)
no
Sometimes unicellular more often
multicellular
nuclei, mitochondria, chloroplasts,
lysosomes,endoplasmic reticulum,
golgi, vacuoles
yes
Chromosome
Single and circular
Usually several and linear
Introns & Exons
occasionally
frequent
Histones
no
yes
Ploidy
haploid
Diploid
Mitosis & meiosis
absent
present
Membrane bound
organelles
(To be continued)
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Sexual reproduction
Ribosomes
None or unidirectional from
donor to recipient
70s(50s + 30s subunits)
Cytoskeleton
absent
Cell wall
Usually present
Motility
Simple, prokaryotic flagella,
gliding motion
Usually absent
Usually, involves fusion of haploid
gametes
80s(60s + 40s) in cytoplasm
(mitochondria & chloroplasts have
prokaryotic ribosomes)
Microtubules and microfilamemts
Many divers pathways in
various bacteria
absent
Absent in animals, present in fungi
{chitin) and plants (cellulose)
Complex “9+2” flagella or cilia with
centrioles
Cells differentiae to form tissue &
organs
Glycolysis in cytoplasm, krebs cycle
and ETC in mitochondria
present
Oxygen
Aerobic and / or anaerobic
Usually aerobic
Sterols甾酮
Usually absent
Used as hormones and in plasma
membrane
Differentiation
Energy metabolism
Endocytosis &
cytoplasmic streaming
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Prokaryotes
Two kingdoms of prokaryotes –
Eubacteria 真细菌 (细菌)
Archaebacteria 原始细菌(古细菌)
Three different types of bacteria
Bacilli 杆菌
Cocci 球菌
Spiral 螺旋菌
Philip Hugenholtz : Exploring prokaryotic diversity in the genomic era,
Genome Biol. 2002; 3(2): reviews
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Bacteria Morphological Diversity
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From http://ag.arizona.edu/plp/courses/plp329/micdivintro.ppt
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Prokaryotic cell
structure
Scale Bacteria
vs. Eucaryotes
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Eukaryotes
Algae
Protista
Fungi
Plantae
Animalia
Jessica L. Green, et al: Spatial scaling of
microbial eukaryote diversity
Nature 432, 747–750 (2004);
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Plant cell structure
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Animal cell structure
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Genetic Control of Cell Diversity
The diversity derives from both variety in gene
expression and from the patterns of cellular control
for gene product behavior.
Cell diversity derives from both
evolution and development of living things,
Evolution
Development
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genome difference
same genome
with different
gene expression
Different
cells
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One cell,
one cell type
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Trillions of cells,
200+ cell types
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Metazoan Phenotypic Complexity
from selective gene expression
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1.7. Modern cell biology
Contemporary cell biology, often referred
to as Molecular Cell Biology
Genetic control in cells
● Three flows within cells
1) flow of information;
2) flow of mass
3) flow of energy.
● Systems Biology of the Cell
1) Molecular cytomics
2) Cellular genomics
3) Cellular proteomics
4) Cellular epigenomics
5) In silico cell
●
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Genetic control in cells
The molecular basis of genetic control in cells,
particularly in eukaryotic cells is one of the most
basic active areas of molecular cell biology.
▪Each cell has whole genetic
information
▪ Different cell has different
genes expression pattern
▪ There are interactions among
genes
▪ Phenotype is a result of the
interaction between genes and
environment.
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Three flows within cells
Flow of inherit information
Flow of energy
Material flows within cells
None of these three flows operates in isolation from
the other two. The flow of mass and flow of energy
are extremely closely linked, as biological molecules
are broken apart to make other biological molecules
or to harvest energy.
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Flow of inherit information
Genetic
information
Central dogma (中心法则)
Epigenetic
information
Chromatin based gene
regulation
Chromatin remodeling （染色质重塑）
Histone acetylation (组蛋白乙酰化)
Histone methylation (组蛋白的甲基化 )
Histon phosphorylation (组蛋白的磷酸化 )
DNA methylation (CpG岛甲基化)
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Flow of energy- metabolism
— Some processes (anabolic) are energy consuming. Other
processes are energy producing (catabolic).
— Energy intermediates are the molecules, adenosine triphosphate
(ATP) and adenosine diphosphate (ADP), which are used to allow
endergonic reactions to occur in cells.
— Energy transduction happens in mitochondria and chloroplasts .
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Material flows within cells
Simple molecules absorbed
by cells are incorporated into
larger molecules and/or used
to make other molecules,
called material transformation.
Metabolic pathway networks
in a cell include:
 Carbohydrate metabolism
 Amino acid metabolism
 Lipids metabolism
 Nucleotide metabolism
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Systems Biology of the Cell
Currently, biologists tend to study the cell
structure and behaviors as the ultimate objective
to systemically understand the effect of
— the molecules on the whole cell, and
— the effect of the individual cell on the whole
organism as well.
cytomics
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E-cell
The computational model of living cell, reflecting
the molecular networks within a cell.
E-Cell
A concept of constructing virtual cells on computers.
E-Cell Project
An international research project aiming at developing necessary
theoretical supports, technologies and software platforms to allow
precise whole cell simulation.
E-Cell System
An object-oriented software suite for modeling, simulation, and
analysis of large scale complex systems such as biological cells
http://www.e-cell.org/software/e-cell-system
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Cell Models for Research of Life Sciences
1. Cell is the basic unit of life
2. Cell has all the features of
living things
3. Cell has whole inherit material
4. Cell has whole regulation on
gene expression
5. The developments of modern
techniques in researches
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1.8. The technology of cell biology
Cell Culture
Flow Cytometry
Functional Bio-imaging
of Cell
Modern light microscopy
Confocal microscopy
Two-photon microscopy
Live cell Image analysis
RNA Interference Technology
Antisense Technique
Gene Microarray
Protein Chips
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Flow Cytometry
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Fluorescence Microscopy
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Tracing molecule in living cells
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Exogenous and Endogenous RNAi
Liposome-mediated
Transfection
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Gene Microarray (Biochips)
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1.9. Training the scientists of tomorrow
What we know about the cell
— The main content of the molecular cell biology
course includes:
• The structure and function of the cell
• The organelles of the cell;
• The mechanisms of important activities of the cell
• The regulation of the activities.
• The advance in cellular research.
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How we know what we know about the cell
It is critical to present to students the experimental
basis of our understanding to show them how we
know what we know. Hopefully this will demonstrate
the dynamic nature of science and prepare them not
only to engage actively in scientific research and
teaching but also to become educated members .
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Why we do what we do about the cell
Of course, we want students to learn not only
how we know what we know, but why we do
what we do. As in other cell biology books,
our coverage of basic cell biology, medical
topics, biotechnology, human biology is
integrated throughout. We know that these
topics may be of particular interest to
students.
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Who Is a Cell Biologist
What do they work on
All aspects of cells, from their interactions
with each other and their environments to
their cellular and atomic composition.
What are they interested in
Very concerned with investigating both the
processes and structures that occur and
exist within cells.
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Questions
1. What does cell biology concern?
2. Why we say the cell is a complex
system?
3. What is cell theory?
4. What are the contemporary views on
cell biology?
5. What cause cell diversity?
6. How many modern techniques are
employed in cell biology research?
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