Download The Cell, 5e

세포생물학
2015 학년도 1 학기
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■ 교재:
The Cell: A molecular approach 5th Edition. 2009.
저자: Geoffrey Cooper and Robert E. Hausman
출판사: Sinauer Associates
부교재: 필수세포생물학 (저자: Bruce Alberts 역자: 박상대)
■ 강의시간?
도서 세포학: 분자적 접근 제5판
GEOFFREY M.COOPER
저/전진석 역 | 월드사이언스
1
An Overview of Cells
and Cell Research
Definition and Objective
Cell biology is a scientific discipline that studies cells
– their physiological properties, their structure, the
organelles they contain, interactions with their
environment, their life cycle, division and death. This
is done both on a microscopic and molecular level.
The number of applications of cell and molecular
biology continues to grow in medicine, agriculture,
biotechnology, and biomedical engineering.
Why do we study this subject?
-It is important to understand the current state of
knowledge, and the experimental basis of cell
biology.
Introduction
There is unity and diversity among
present-day cells in terms of their
evolution from a common ancestor
(origin).
Some have properties that make them
valuable experimental models.
Progress in cell biology depends on the
availability of experimental tools.
The Origin and Evolution of Cells
Two types of cells:
 Prokaryotic (bacteria) lack a nuclear
envelope. No intracellular membrane.
 Eukaryotic have a nucleus that
separates genetic material from
cytoplasm.
 However,
same mechanism for
maintaining lives.
The Origin and Evolution of Cells
All present-day cells are
descended from a single
primordial ancestor.
The first cells emerged at least
3.8 billion years ago.
Spontaneous synthesis of
organic molecules probably
provided the basic materials
from which the first living cells
arose.
Spontaneous formation of organic molecules
no O2
mainly CO2, N2
Small H2,H2S, CO
By Stanley Miller
in 1950s
The Origin and Evolution of Cells
Macromolecules may have formed by
spontaneous polymerization under
plausible prebiotic conditions (kinetics).
The critical characteristic of the
macromolecule from which life evolved
must have been the ability to replicate
itself.
Figure 1.2 Self-replication of RNA
Nucleic acids are capable of self-replication.
Sid Altman and Tom Cech (1980s) first discovered that
RNA is capable of catalyzing chemical reactions
(ribozyme), including the polymerization of
nucleotides.
The Origin and Evolution of Cells
RNA is able to both serve as a
template for, and to catalyze
its own replication.
Consequently, RNA is generally
believed to have been the
initial genetic system in
evolution.
This period is known as the
RNA world.
1) acquire more DNA
2) intracellular membrane
3) endosymbiosis
O2 is the waste
no O2
The Origin and Evolution of Cells
The first cell probably arose by the enclosure of selfreplicating RNA in a membrane composed of
phospholipids.
Phospholipids are the basic components of all
present-day biological membranes.
Phospholipids are amphipathic: one end of the
molecule is soluble in water and the other is not.
Water-insoluble (hydrophobic) hydrocarbon chains
are joined to water-soluble (hydrophilic) head
groups that contain phosphate.
When placed in water, phospholipids spontaneously
aggregate into a bilayer.
Figure 1.3 Enclosure of self-replicating RNA in a phospholipid membrane
The Origin and Evolution of Cells
Cells needed to evolve mechanisms for generating
energy and synthesizing molecules.
The principal pathways of energy metabolism are
highly conserved in present-day cells.
All cells use adenosine 5′-triphosphate (ATP) as
their source of metabolic energy.
The mechanisms of generation of ATP are thought to
have evolved in three stages, corresponding to the
evolution of glycolysis, photosynthesis, and
oxidative metabolism.
Generation of metabolic energy
w/o O2
with O2
The Origin and Evolution of Cells
Glycolysis evolved when the Earth’s
atmosphere was anaerobic.
Glycolysis: breakdown of glucose to lactic
acid, with 2 ATP gained.
All present-day cells carry out glycolysis.
Photosynthesis evolved more than 3 billion
years ago.
It allowed some cells to harness energy from
sunlight; and they no longer required
preformed organic molecules.
The Origin and Evolution of Cells
The first photosynthetic bacteria probably used
H2S to convert CO2 to organic molecules: a
pathway of photosynthesis still used by some
bacteria.
The use of H2O evolved later; it changed Earth’s
atmosphere by making free O2 available.
O2 in the atmosphere may have allowed the
evolution of oxidative metabolism
(respiration).
It is much more efficient than glycolysis; the
complete oxidative breakdown of glucose
yields 36 to 38 ATP molecules (vs. 2ATP by
anaerobic glycolysis).
The Origin and Evolution of Cells
Present-day prokaryotes:
Archaebacteria: many live in extreme environments.
Unusual today (primitive earth).
thermoacidophiles: >80 ºC pH<2.
Eubacteria: a large group that live in a wide range of
environments.
Most bacterial cells are small. 1 to 10 m. DNA 0.6~5
million. 5000 proteins.
Cyanobacteria, the group in which photosynthesis
evolved, are the largest and most complex
prokaryotes.
The Origin and Evolution of Cells
Escherichia coli (E. coli) is a typical
prokaryotic cell.
It has a rigid cell wall of polysaccharides
and peptides.
Beneath the cell wall is the plasma
membrane, a phospholipid bilayer with
associated proteins: separation of inside
and outside of the cells.
No intracellular membrane.
The DNA of E. coli is a single circular
molecule in the nucleoid which is not
surrounded by a membrane
separating it from the cytoplasm.
The cytoplasm contains approximately
30,000 ribosomes (sites of protein
synthesis).
Harmless except some of it (O157:H1)
The Origin and Evolution of Cells
Eukaryotic cells also have a plasma
membrane and ribosomes.
But they are much larger and more
complex, with a nucleus, other
organelles, and cystoskeleton.
The nucleus (5um) is the largest
organelle; it contains the linear DNA
molecules: DNA replication and RNA
synthesis
Structures of animal cells
Structures of plant cells
The Origin and Evolution of Cells
Organelles
Mitochondria: site of oxidative
metabolism.
Chloroplasts: site of photosynthesis.
Lysosomes and peroxisomes:
specialized metabolic compartments for
the digestion of macromolecules and
for various oxidative reactions.
The Origin and Evolution of Cells
Vacuoles: in plant cells; perform a variety of
functions, including digestion of
macromolecules and storage of waste
products and nutrients.
The endoplasmic reticulum is a network of
intracellular membranes, extending from the
nuclear membrane throughout the cytoplasm.
Smooth ER and Rough ER
It functions in the processing and transport of
proteins and the synthesis of lipids.
The Origin and Evolution of Cells
In the Golgi apparatus, proteins are further
processed and sorted for transport to their final
destinations.
It also serves as a site of lipid synthesis, and (in plant
cells) the site of synthesis of some polysaccharides
that compose the cell wall. The cytoskeleton is a
network of protein filaments extending throughout
the cytoplasm.
It provides structural framework, determines cell
shape and organization, and is involved in
movement of whole cells, organelles, and
chromosomes during cell division.
The Origin and Evolution of Cells
Eukaryote organelles are thought to
have arisen by endosymbiosis:
prokaryotic cells living inside the
ancestors of eukaryotes.
Evidence is especially strong for
mitochondria (aerobic eubacteria)
and chloroplasts (cyanobacteria).
Size, binary replication, containing
their own DNA.
Endosymbiosis
The Origin and Evolution of Cells
Many eukaryotes are unicellular organisms.
The simplest eukaryotes are the yeasts.
Saccharomyces cerevisiae is about 6 µm in diameter and
contains 12 million base pairs of DNA.
The Origin and Evolution of Cells
Other unicellular eukaryotes are more complex.
Amoeba proteus: its volume is more than 100,000 times
that of E. coli, and it can exceed 1 mm in length.
Amoebas use cytoplasmic extensions, called
pseudopodia, to move and to engulf other organisms.
The Origin and Evolution of Cells
Multicellular organisms evolved more than 1 billion years ago.
Some unicellular eukaryotes (green alga, Volvox) form
aggregates that may represent an evolutionary transition from
single cells to multicellular organisms.
Plants
Plants have 3 main tissue types: ground, dermal,
vascular tissues
1. Ground tissue

Parenchyma cells: site of metabolic reactions,
including photosynthesis.

Collenchyma and sclerenchyma have thick
cell walls and provide structural support.
2. Dermal tissue covers the surface of the plant;
forms a protective coat and allows absorption of
nutrients.
3. Vascular tissue (xylem (water) and phloem
(nutrients)): elongated cells which transport water
and nutrients throughout the plant.
Figure 1.11 Light micrographs of representative plant cells
Parenchyma
cells
Epidermal
cells in leaf
Collenchyma
cells
Vessel
elements
and
tracheids
Cross-section of a flax plant stem:
1. Pith,
2. Protoxylem,
3. Xylem I,
4. Phloem I,
5. Sclerenchyma (bast fibre),
6. Cortex,
7. Epidermis
Animals
Animals have five main tissue types:
1. Epithelial cells form sheets that
cover the surface of the body and
line internal organs: skin, intestine,
salivary glands).
2. Connective tissues include bone,
cartilage, and adipose tissue. Loose
connective tissue is formed by
fibroblasts.
Figure 1.12 Light micrographs of representative animal cells (Part 1)
The Origin and Evolution of Cells
3. Blood contains several different types
of cells:
 Red blood cells (erythrocytes)
function in oxygen transport.
 White blood cells (granulocytes,
monocytes, macrophages, and
lymphocytes) function in
inflammatory reactions and the
immune response.
Figure 1.12 Light micrographs of representative animal cells (Part 2)
Fibroblasts
The Origin and Evolution of Cells
4. Nervous tissue is composed of
supporting cells and nerve cells, or
neurons, and various types of
sensory cells. transmitting signals
through the body (eye, ear).
5. Muscle cells are responsible for the
production of force and movement.
Cells as Experimental Models
Because the fundamental properties of
all cells have been conserved during
evolution, the basic principles learned
from experiments on one type of cell
are generally applicable to other cells.
Several kinds of cells and organisms are
used as experimental models.
Jacque Monod said “What is true of
E.coli is true of elephant.”
Cells as Experimental Models
E. coli
The most thoroughly studied species of bacteria.
Simple.
Our understanding of DNA replication, the genetic
code, gene expression, and protein synthesis derive
from studies of this humble bacterium.
E. coli is particularly useful because of its simplicity
and ease of culture in the laboratory.
The genome consists of approximately 4.6 million
base pairs and contains about 4300 genes.
The small size of the genome is an advantage in
genetic analysis.
Cells as Experimental Models
E. coli divide every 20 minutes. A clonal population can be
readily isolated as a colony grown on agar medium.
Bacterial colonies containing as many as 108 cells can develop
overnight. Selecting genetic variants of an E. coli strain is easy
and rapid.
E. coli can carry out biosynthetic reactions in simple defined
media; this made them extremely useful in elucidating
biochemical pathways.
Cells as Experimental Models
Yeasts
Yeasts are the simplest eukaryotes, and
have been a model for fundamental
studies of eukaryote biology.
The genome of Saccharomyces cerevisiae
consists of 12 million base pairs of DNA
and contains about 6000 genes.
Yeasts can easily be grown in the laboratory
as colonies from a single cell.
Yeasts can be used for genetic
manipulations similar to those performed
using bacteria.
The unity of molecular cell biology is made
clear by the fact that general principles of
cell structure and function revealed by
studies of yeasts apply to all eukaryotic
cells.
Cells as Experimental Models
Understanding the development of multicellular organisms requires the
experimental analysis of plants and animals.
The nematode Caenorhabditis elegans is one of the most widely used
models.
Cells as Experimental Models
The fruit fly Drosophila
melanogaster has been a
crucial model organism in
developmental biology.
Drosophila is easy to grow in the
laboratory, and the short
reproductive cycle (2 weeks)
makes it very useful for genetic
experiments.
Many fundamental genetic
concepts were derived from
studies of Drosophila early in the
20th century.
Studies of Drosophila have led to
advances in understanding the
molecular mechanisms that
govern animal development,
particularly with respect to
formation of the body plan of
complex multicellular organisms.
Cells as Experimental Models
A model for plant molecular
biology and development
is the small mouse-ear
cress, Arabidopsis
thaliana.
It has a small genome (125
million bp) and is easily
grown in the lab.
Studies of Arabidopsis
have led to the
identification of genes
involved in aspects of
plant development, such
as the development of
flowers.
Eggs of the frog Xenopus laevis
Cells as Experimental Models
Zebrafish are small and reproduce rapidly.
Embryos develop outside of the mother and are transparent;
early stages of development can be easily observed.
Zebrafish bridge the gap between humans and simpler
invertebrate systems, like C. elegans and Drosophila.
The mouse as a model for human development
Piebaldism
Tools of Cell Biology
The cell theory proposed by Matthias Schleiden and
Theodor Schwann in 1838 resulted from their
studies of plant and animal cells using microscopes.
It was soon recognized that cells are not formed de
novo but arise only from division of pre-existing cells.
Contemporary light microscopes can magnify
objects up to about 1000x.
Most cells are between 1–100 µm, so they can be
observed by light microscopy, as can some
organelles.
Figure 1.22 Numerical aperture
Tools of Cell Biology
Types of light microscopy:
Bright-field microscopy: light passes directly
through the cell. Cells are often preserved with
fixatives and stained with dyes to enhance the
contrast.
This technique can’t be used to study living cells.
Tools of Cell Biology
Phase-contrast microscopy and differential interferencecontrast microscopy both convert variations in density or
thickness to differences in contrast that can be seen in the final
image.
Bright-field
Differential interference-contrast microscopy
Phase-contrast
Tools of Cell Biology
Video cameras and computers for image analysis and processing
can substantially enhance the contrast of images.
Video-enhanced differential interference-contrast microscopy
allows visualization of the movement of organelles along
microtubules, cytoskeletal protein filaments with a diameter of
only 0.025 µm.
Tools of Cell Biology
Fluorescence microscopy is used for molecular analysis.
A fluorescent dye is used to label the molecule of interest in fixed or living cells.
The fluorescent dye molecules absorb light at one wavelength and emit light at a different
wavelength.
This fluorescence is detected by illuminating the specimen with a wavelength of light that
excites the fluorescent dye, then using filters to detect the specific wavelength of light that
the dye emits.
Tools of Cell Biology
The green fluorescent protein (GFP) of jellyfish can
be used to visualize proteins in living cells.
GFP can be fused to any protein of interest using
standard methods of recombinant DNA.
Tools of Cell Biology
The images of conventional
fluorescence microscopy can be
improved by image deconvolution; a
computer analyzes images obtained
from different depths of focus and
generates a sharper image from
them.
Confocal microscopy increases
contrast and detail by analyzing
fluorescence from a single point.
A small point of light from a laser is
focused on the specimen at a
particular depth. The emitted
fluorescent light is collected by
detector such as a video camera.
Tools of Cell Biology
The emitted light must pass through a pin-hole aperture (confocal aperture). Thus
only light emitted from the plane of focus is able to reach the detector.
Scanning across the specimen generates a two-dimensional image of the plane
of focus.
A series of images can be used to reconstruct a three-dimensional image.
Noguchi Hideyo
•
•
•
•
•
•
•
•
•
•
Bacteriologist.
The eldest son of a farm family.
Passed the government medical examinations
in 1897.
After working at the Institute of Infectious
Disease, he went to the United States in 1900
(U. Penn, snake venom).
In 1911, he succeeded in cultivating a pure
culture of syphilis spirochete at the
Rockefeller Institute for Medical Research.
Doctor of Medical Science in 1911
Imperial Prize from the Japan Academy in
1915.
A member of the Japan Imperial Academy in
1923.
He visited Central and South America and
Africa in an attempt to find the pathogen of
yellow fever, but he contracted the disease
himself and died in Ghana in 1928.
his last words was " I don't understand".
WHY?
Tools of Cell Biology
Electron microscopy can achieve much greater resolution (0.2
nm) than light microscopy because of the short wavelength of
electrons.
Resolution for biological samples is about 1 to 2 nm because of
their inherent lack of contrast.
Transmission electron microscopy (TEM)
Specimens are fixed and stained with salts of heavy metals, which
provide contrast by scattering electrons.
A beam of electrons is passed through the specimen and forms an
image on a fluorescent screen.
Specimens can be prepared by either positive or negative staining.
Positive staining
WBC
actin filaments
Tools of Cell Biology
Scanning electron microscopy provides a three-dimensional
image of cells.
The electron beam does not pass through the specimen.
Instead, the surface of the cell is coated with a heavy metal, and
a beam of electrons is used to scan across the specimen.
Tools of Cell Biology
Subcellular fractionation:
In order to determine the function of organelles, they must be isolated from the cell.
Differential centrifugation was developed in the 1940s and 1950s to separate cell
components on the basis of size and density.
The plasma membrane and ER is broken into small fragments by sonication, grinding, or
high-speed blending.
The suspension is fractionated in an ultracentrifuge, which spins at very high speeds.
Larger, more dense organelles sediment at lower speeds; small organelles at high speeds.
Figure 1.38 Subcellular fractionation (Part 2)
Figure 1.38 Subcellular fractionation (Part 3)
Tools of Cell Biology
Greater purification can be achieved by
density-gradient centrifugation, in
which organelles are separated by
sedimentation through a gradient of a
dense substance, such as sucrose.
In velocity centrifugation, the starting
material is layered on top of the sucrose
gradient. Particles of different sizes
sediment through the gradient at
different rates.
Figure 1.39 Velocity centrifugation in a density gradient
Tools of Cell Biology
Equilibrium centrifugation in density
gradients is used to separate
subcellular components on the basis of
their buoyant density.
The sample particles are centrifuged
until they reach an equilibrium position
at which their buoyant density is equal
to that of the surrounding sucrose or
cesium chloride solution.
Tools of Cell Biology
In vitro culture systems
of plant and animal cells
enable scientists to study
cell growth and
differentiation, and
perform genetic
manipulations.
Most animal cell types
attach and grow on the
plastic surface of dishes
used for cell culture.
Tools of Cell Biology
The culture media for animal cells are complex and
must include salts and glucose, and various amino
acids and vitamins that cells can’t make for
themselves.
Serum provides polypeptide growth factors. The
identification of individual growth factors makes it
possible to culture cells in serum-free media.
Harry Eagle was the first researcher to describe a
defined medium for animal cells, in 1955.
This has enabled scientists to grow a wide variety of
cells under defined experimental conditions, which is
critical to studies of animal cell growth and
differentiation.
Tools of Cell Biology
An initial cell culture from tissue is a primary culture.
They can be replated at a lower density to form secondary
cultures many times.
Most normal cells such as fibroblasts cannot be grown in culture
indefinitely.
Tools of Cell Biology
Embryonic stem cells and tumor cells
can proliferate indefinitely in culture
and are referred to as permanent or
immortal cell lines.
Permanent cell lines have been
particularly useful for many types of
experiments because they provide a
continuous and uniform source of cells.
Tools of Cell Biology
Viruses are intracellular parasites that cannot replicate on their
own. They reproduce by infecting host cells and usurping the
cellular machinery to produce more virus particles.
Viruses consist of DNA or RNA surrounded by a protein coat.
Tools of Cell Biology
Viruses are important in studies of animal cells.
There are many diverse animal viruses.
The retroviruses have RNA genomes but synthesize a DNA copy of
their genome in infected cells. These viruses first demonstrated the
synthesis of DNA from RNA templates.
Summary
Endosymbiosis
Microscopy
Experimental organisms
Centrifugation to separate the
organells
Cell lines (in vitro culture)