Transcript Cellular Biochemistry

Cellular Biochemistry:
Cell Structure & Function
A TOUR OF THE CELL
Section A: How We Study Cells
1. Microscopes provide windows to the world of the cell
2. Cell biologists can isolate organelles to study their function
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
1. Microscopes provide windows to the
world of the cell
The discovery and early study of cells progressed •
with the invention and improvement of microscopes
in the 17th century.
In a light microscope (LMs) visible light passes •
through the specimen and then through glass lenses.
The lenses refract light such that the image is magnified •
into the eye or a video screen.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Microscopes vary in magnification and resolving •
power.
Magnification is the ratio of an object’s image to •
its real size.
Resolving power is a measure of image clarity. •
It is the minimum distance two points can be separated •
and still viewed as two separate points.
Resolution is limited by the shortest wavelength of the •
source, in this case light.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The minimum resolution •
of a light microscope is
about 2 microns, the size
of a small bacterium
Light microscopes can •
magnify effectively to
about 1,000 times the
size of the actual
specimen.
At higher magnifications, •
the image blurs.
Fig. 7.1
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Techniques developed in the 20th century have •
enhanced contrast and enabled particular cell
components to be labeled so that they stand out.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
While a light microscope can resolve individual •
cells, it cannot resolve much of the internal
anatomy, especially the organelles.
To resolve smaller structures we use an electron •
microscope (EM), which focuses a beam of
electrons through the specimen or onto its surface.
Because resolution is inversely related to wavelength •
used, electron microscopes with shorter wavelengths
than visible light have finer resolution.
Theoretically, the resolution of a modern EM could •
reach 0.1 nanometer (nm), but the practical limit is
closer to about 2 nm.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Transmission electron microscopes (TEM) are •
used mainly to study the internal ultrastructure of
cells.
A TEM aims an electron beam through a thin section •
of the specimen.
The image is focused •
and magnified by
electromagnets.
To enhance contrast, •
the thin sections are
stained with atoms
of heavy metals.
Fig. 7.2a
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Scanning electron microscopes (SEM) are useful •
for studying surface structures.
The sample surface is covered with a thin film of gold. •
The beam excites electrons on the surface. •
These secondary electrons are collected and focused on •
a screen.
The SEM has great •
depth of field,
resulting in an
image that seems
three-dimensional.
Fig. 7.2b
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Electron microscopes reveal organelles, but they •
can only be used on dead cells and they may
introduce some artifacts.
Light microscopes do not have as high a •
resolution, but they can be used to study live cells.
Microscopes are a major tool in cytology, the study •
of cell structures.
Cytology coupled with biochemistry, the study of •
molecules and chemical processes in metabolism,
developed modern cell biology.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Isolating Organelles by Cell Fractionation
Cell fractionation •
Takes cells apart and separates the major –
organelles from one another
The centrifuge •
Is used to fractionate cells into their –
component parts
The principle of fractionation
Homogenization
Tissue
cells
1000 g
Homogenate
(1000 times the
force of gravity)
Differential centrifugation
10 min
Supernatant poured
into next tube
20,000 g
20 min
Pellet rich in
nuclei and
cellular debris
Figure 6.5
80,000 g
60 min
150,000 g
3 hr
Pellet rich in
mitochondria
(and chloroplasts if cells
are from a Pellet rich in
plant)
“microsomes”
(pieces of
plasma membranes and
Pellet rich in
cells’ internal ribosomes
membranes)
2. Cell biologists can isolate organelles to
study their functions
The goal of cell fractionation is to separate the •
major organelles of the cells so that their individual
functions can be studied.
Fig. 7.3
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
This process is driven by a ultracentrifuge, a •
machine that can spin at up to 130,000 revolutions
per minute and apply forces more than 1 million
times gravity (1,000,000 g).
Fractionation begins with homogenization, gently •
disrupting the cell.
Then, the homogenate is spun in a centrifuge to •
separate heavier pieces into the pellet while lighter
particles remain in the supernatant.
As the process is repeated at higher speeds and longer •
durations, smaller and smaller organelles can be
collected in subsequent pellets.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Cell fractionation prepares quantities of specific cell •
components.
This enables the functions of these organelles to be •
isolated, especially by the reactions or processes
catalyzed by their proteins.
For example, one cellular fraction is enriched in enzymes •
that function in cellular respiration.
Electron microscopy reveals that this fraction is rich in •
the organelles called mitochondria.
Cytology and biochemistry complement each other •
in connecting cellular structure and function.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell
A
cell is the smallest unit of
living matter.
 Don’t confuse this with: atom,
element, proton, etc.
Cell Theory

Who? Matthias Schleiden, Theodor Schwann,

Rudolf Virchow
When? 1800s

What does it say?




All organisms are made of cells.
A cell is the structural & function unit of organs.
All cells come from pre-existing cells.
Cells are capable of self-reproduction.
Cell Size
Types of Cells

Unicellular organisms


Bacteria, Protists, etc.
Multicellular organisms


Plants
Animals

Muscles, skin, nerves, liver, digestive, bones,
blood, immune system, lungs, etc.
How do we observe cells?

Light microscope



Visible light passes through object
Lens magnify image
Electron microscope



Scanning - surface of object
Transmission - sees through objects
100,000 X to Millions magnification power
How do we know what happens in
each part of the cell?



Radioisotopes are used to "trace"
different chemical reactions through a cell.
Separate cellular structures with a blender
Centrifuge material and analyze each
layer.
Two basic cell types
Eukaryotes (Eu = true) (kary = nucleus)
Organisms whose cells contain a membrane-bound
nucleus and other organelles.
Prokaryotes (Pro = before) Organisms without a
membrane-bound nucleus (bacteria).
* These cells have genetic information,
but not in a nucleus.
* Evolutionists chose the prefix “pro” because
they believe these evolved before others.
Prokaryotic Cells
Organisms with prokaryotic cells are called
“prokaryotes”
Prokaryotes have no true nucleus or organelles.
Have a single strand of “looped” DNA
Most prokaryotes are single-celled microscopic
organisms.

Eukaryotic Cells
Organisms composed of eukaryotic cells are
called “eukaryotes”
 Have a membrane bound nucleus which
contains the cell’s DNA
 Some eukaryotes are one-celled organisms
 All multicellular organisms are eukaryotes
 Have organelles, each of which is surrounded
by (or bound in) a “plasma membrane”

Some Example Prokaryotes
Coccusshaped
bacterium
Bacillusshaped
bacterium
Spirillumshaped
bacterium
Prokaryotes vs. Eukaryotes (1)

Size



Complexity



Prokaryotes – simple
Eukaryotes – complex
Location of chromosomes



Prokaryotes ≤ 10 µm example: Bacteria & Archea
Eukaryotes ≥ 10 µm example: Protista, Fungi, Plants, Animals
Prokaryotes – free in cytosol
Eukaryotes – within a membrane-bound nucleus
Flagellar mechanisms differ
Prokaryotes vs. Eukaryotes (2)





Very simple cells
Always singlecelled
No nucleus
DNA arranged in
one single loop
Found only in
kingdom Monera
(bacteria)





Complex cells
Can be singlecelled or
multicellular
Have a nucleus
DNA arranged in
many separate
strands
Found in Animal,
Plant, Protists, and
Fungi kingdoms
Prokaryotic Cells




Have no membrane-bound organelles
Include true bacteria
On earth 3.8 million years
Found nearly everywhere


Naturally in soil, air,
hot springs
nucleoid (DNA)
Prokaryotic Cells
ribosomes
food granule
prokaryotic
flagellum
plasma membrane
cytoplasm
cell wall
Viruses




Viruses contain DNA or RNA & a protein coat
Some are enclosed by an envelope
Most viruses infect only specific types of cells
in one host
Host range is determined by specific host
attachment sites and cellular factors
Comparison of Cells and Viruses
Bacterium
(prokaryote)
Animal
(eukaryote)
Plant
(eukaryote)
Prokaryotic bacteria cells
surrounding a eukaryotic cell
(possibly a white blood cell?)
Comparison between prokaryotes &
eukaryotes (1)
Prokaryotes
Eukaryotes
Typical organisms
Bacteria, archaea
Protists, fungi, plants,
animals
Typical size
1 - 10 mm
10 – 100 mm
Type of nucleus
Nucleoid, no real
membrane
Real nucleus w/ double
membrane
DNA
Circular (usually)
Linear molecules
(chromosomes) with
histone proteins
RNA/protein
synthesis
Coupled in cytoplasm
RNA synthesis inside
the nucleus, protein
synthesis in cytosol
Comparison between prokaryotes &
eukaryotes (2)
Prokaryotes
Eukaryotes
Ribosomes
50S + 30S
60S + 40S
Cytoplasmic
structure
Very few structures
Highly structured by
endomembraes and a
cytoskeleton
Cell movement
Flagella
Flagella & cilia made of
tubulin
Mitochondria
None
One to several dozen
Chloroplasts
None
Algae & plants
Comparison between prokaryotes &
eukaryotes (3)
Prokaryotes
Eukaryotes
Organization
Usually single cells
Single cells, colonies,
higher multicultural
organisms w/
specialized cells
Cell division
Binary fission (simple
division)
Mitosis & meiosis
Eukaryotic Cell
Cell Structure & Function (1)
Bacteria
Cell Structure & Function (2)
Typical Plant
Cell Structure & Function (3)
Generic Animal Cell
Eukaryotic Cells Structure (1)

Have numerous internal structures

Various types & forms


Plants, animals, fungi, protists
Multicellular organisms
Eukaryotic Cells Structure (2)



The cell consists of two main compartments:
 The nuclear
 The cytoplasmic
The nucleus contains the genetic information
that regulates the structure and function of
all eukaryotic cells
The cytoplasm contains numerous cellular
organelles, which perform specific functions
Plant & Animal Cells (1)

Similarities

Both constructed from eukaryotic cells

Both contain similar organelles

Both surrounded by cell membrane
Plant & Animal Cells (2)

Differences
Plants have
 Cell wall – provides strength & rigidity
 Have chloroplasts, photosynthetic site
 Large vacuoles
 Animals have
 Other organelle not found in plants
(lysosomes formed from Golgi)
 Centrioles, important in cell division

Cellular Organelles





Cytoplasm
Nucleus
 Chromosomes,
nuclear
envelope,
nuclear pores,
nucleolus
Ribosomes
Endoplasmic
reticulum (smooth
& rough)
Golgi Apparatus










Lysosomes
Vesicles
Peroxisomes
Vacuoles
Chloroplast
Mitochondria
Cytoskeleton
Centrioles
Cilia, Flagella
Plasma Membrane
Nucleus

The nucleus is separated from the
cytoplasm by the nuclear envelope
Nucleus Structure
Nucleus: DNA stored here.
Nuclear
The Control Center envelope:
membrane
surrounding the
nucleus
Nuclear pores:
open portals of
communication
between the
nucleus &
cytoplasm
Chromatin:
condensed DNA
Chromosome:
very tightly
packed DNA
Nucleolus:
dense region of
chromatin
DNA proteins




DNA is associated with two major types of proteins:
The histone and nonhistone chromosomal proteins
The histones are primarily structure molecules that
pack DNA into chromatin fibers
The nonhistones include proteins that carry out one
of the most important cellular functions, the
regulation of gene activity
Chromosomes







DNA molecule, with its associated histone and
nonhistone proteins, is a chromosome
There are five classes of histone proteins:
H1
H2A
H2B
H3
H4
Nucleosomes


H2A, H2B, H3, and H4 are called core histones
because they form a beadlike core structure
around which DNA wraps to form
nucleosomes.
H1 is called the linker
Human Chromosomes

The entire complement of 46
chromosomes in a human cell, has a total
length of about 1 meter
Nucleolus (Nucleoli)


The RNA of ribosomes is synthesized from
genes in the nucleolus
No membranes separate nucleoli from the
surrounding chromatin in the nucleus
Protein-encoding gene




Each DNA segment containing the information in a
protein constitutes a gene
The information in a Protein-encoding gene is copied
into a messenger RNA (mRNA) molecules that moves
to the cytoplasm through the pores of the nuclear
envelop
In the cytoplasm, mRNA molecules are used by
ribosomes as directions for the assembly of proteins
DNA -----------> mRNA -----------> Protein (enzymes)
RNA types



mRNA
rRNA
tRNA
Ribosomes: protein factories
Rough ER: make proteins (studded with ribosomes)
Smooth ER: make lipids, modify proteins made in RER
Mitochondria & Chloroplast:
Power Stations of the cell
Mitochondria (1)




The mitochondria major role is ATP
production in the eukaryotic cell
These are mobile and flexible organelles,
although in some cells they tend to stay in
a fixed position
Mitochondria are also self-reproducing,
they have their own circular DNA
Mitochondria (2)






Generate cellular energy in
the form of ATP molecules
ATP is generated by the
systematic breakdown of
glucose = cell respiration
Also, surrounded by 2
membrane layers
Contain their own DNA!
A typical liver cell may
have 1,700 mitoch.
All your mitoch. come from
your mother
Inner Membrane and matrix (3)

Electron transport system
Oxidative phosphorylation (4)
H+
H+
3H+
H+
ATP
synthase
IV
III
I
H+
H+
3
ATP
H+
2e-
NADH
3H+
3 ADP +
3 Pi
Inner
Membrane
Electron
transport system
Mitochondria
Chloroplasts
Compartments
2
3
pH
7–8
5-8
Metabolic Sites
Matrix: TCA cycle, ATP
synthesis
ETC: 3H+ pumps
Stroma: Calvin cycle &
ATP synthesis
ETC: 1H+ pump
Substrates
Oxidizes glucose, other
metabolites to make ATP
Light Rxn: use energy
from light to synthesize
NADPH & ATP
Dark Rxn: use CO2 &
H2O & NADPH & ATP to
synthesize glucose
Wastes
CO2 & H2O
O2
Chloroplast
Mitochondria
Endoplasmic reticulum (1)


Rough endoplasmic reticulum
smooth endoplasmic reticulum

are connected and are continuous with the
nuclear envelope
Rough endoplasmic reticulum (2)





It is rough because imbedded in the membrane are
ribosomes
the site of the synthesis of secretory proteins
The rough ER is also the site for the synthesis of
membrane
Enzymes synthesize phospholipid that forms all the
membranes of the cell
Ribosomes in the rough ER synthesize protein that
then are converted to glycoprotein and packaged in
transport vesicles for secretion
Smooth endoplasmic reticulum (3)




The smooth ER is the site for the synthesis of lipids,
phospholipids, and steriods
Note that the production of steriod hormones is
tissue specific
For example, it is the smooth ER of the cells of the
ovaries and testes that synthesize the sex hormones
The smooth ER of the liver has several additonal
functions
Smooth endoplasmic reticulum (4)





Enzymes in the smooth ER regulate the release of
sugar into the bloodstream
Other enzymes break down toxic chemicals
As the liver is exposed to additional doses of a drug
the liver increases the amount of smooth ER to handle
it
It then takes more drug to get past the detoxifiying
ability of the liver
Finally the smooth ER functions to store calcium ions
Golgi apparatus (1)






The Golgi apparatus, like the ER, is a series of
folded membranes
It functions in processing enzymes and other
products of the ER to a finished product
It is the source of the production of lysosomes
Receives proteins & lipids in membrane-bound
vesicles from ER
Modifies those proteins & lipids
Sorts and ships the proteins & lipids away in
membrane-bound vesicles
vesicles
from ER
vesicles
leaving
Golgi
complex
Golgi
complex
Lysosomes


These are membrane bound vesicles that
harbor digestive enzymes
The membrane of a lysosome will fuse
with the membrane of vacuoles releases
these digestive enzymes to the interior of
the vacuole to digest the material inside
the vacuole
Vacuoles




These are membrane-bound sacs that
have many different functions
The central vacuole of a plant cell serves
as a large lysosome
It may also function in absorbing water.
The central vacuoles of flower petal cells
may hold the pigments that give the
flower its color
Endomembrane system






This section reviews the endomembrane
system
which encludes the nuclear envelope,
the rough and smooth ER,
the Golgi apparatus,
lysosomes and
vacuoles
Ribosomes (1)
•
Ribosomes assemble amino acid monomers
into polypeptide chains
• Associated with the ER
• Composed of RNA and proteins
rough endoplasmic reticulum
ribosomes
0.5 micrometers
smooth endoplasmic reticulum
0.5 micrometers
vesicles
Ribosome Assembly/Structure (2)



If individual proteins and rRNAs are
mixed, functional ribosomes will assemble
Structures of large and small subunits
have been determined in 2000/2001
Growing peptide chain is thought to
thread through the tunnel during protein
synthesis
Eukaryotic ribosomes (3)


Mitochondrial and chloroplast ribosomes are
quite similar to prokaryotic ribosomes, reflecting
their supposed prokaryotic origin
Cytoplasmic ribosomes are larger and more
complex, but many of the structural and
functional properties are similar
Mechanics of protein synthesis




All protein synthesis involves three phases:
initiation, elongation, termination
Initiation involves binding of mRNA and
initiator aminoacyl-tRNA to a small subunit,
followed by binding of a large subunit
Elongation: synthesis of all peptide bonds with tRNAs bound to acceptor (A) and
peptidyl (P) sites
Termination occurs when "stop codon"
reached
Cytoskeleton
Eukaryotic cells has a meshwork of tiny fibers that
support the structure. This network is the cytoskeleton.
Three types of fibers exist. Microfilaments are solid
helical rods composed of the protein actin. There is a
twist double chain of actin molecules that make up
microfilaments. These are found in cells that must
contract such as muscle cells. Intermediate filaments
are variable but in general are ropelike structures made
of twisted filaments of fibrous proteins. These function
in bearing tension and anchoring organelles.
Microtubles are straight, hollow tubes composed of
proteins called tubulins. These anchor organelles and
provide tract along which organelles may move. They
also make up flagella and cilia.
Cilia and flagella
These are found on cells, such as protists, that are
motile. Cilia are short and numerous. Longer less
numerous appendages are flagella. These are
composed of a core of microtubules wrapped in an
extension of the plasma membrane. It is sufficient to
know that Energy is required to move the cilia or flagella
in a whiplike motion to propel the cell.
Cell surfaces
Cells are held tightly together is higher organisms. There
is also a considerble amount of cell communication for
lack of a better term. Cell junctions are structures that
hold cells together. There are three types. Tight
junctions bind cells together forming a leakproof sheet.
Anchoring junctions attach adjacent cells or cells to an
extracellular matrix (the substance in which tissues cells
are embedded. These are leaky compared to tight
junctions. Communicating junctions are channels
between similar cells. Plasmodesmata are passages
between adjacent plant cells that allow material to go
from one cell to the next. Communication junctions fulfill
the same role between animal cells.
Cytoskeleton: provides structure and Support for
the cell. Also provides a Scaffolding for vesicle
transportation
Rapid Review (1)
Organelle
Prokaryotes Eukaryotes
Functions
Prokaryotes Animal
cells
Plant
cells
+
_
+
Protects & shapes the
cell
+
Plasma
membrane
+
+
Selective barrier
consisting of bilayers
of phospholipids,
proteins, & CHO
+
+
+
Protein synthesis,
formed in nucleolus
Cell wall
Ribosome
Rapid Review (2)
Organelle
Prokaryotes Eukaryotes
Functions
Prokaryotes Animal
cells
Plant
cells
Sooth ER
_
+
+
Lipid synthesis,
detoxification, CHO
metabolism, no
ribosomes on
cytoplasmic surface
Rough ER
_
+
+
Synthesizes proteins
to secrete or send to
plasma membrane.
Contains ribosomes
on cytoplasmic
surface
Gogli
_
+
+
Modifies lipids,
proteins, etc & sends
them to other sites in
the cell
Rapid Review (3)
Organelle
Prokaryotes Eukaryotes
Prokaryotes Animal
cells
Functions
Plant
cells
Mitochondria _
+
+
Powerhouse of
cell; host major
energy-producing
steps of
respiration
Lysosome
_
+
+
Contains enzymes
that digest organic
compounds;
serves as cell’s
stomach
Nucleus
_
+
+
Control center of
cell. Host for
transcription,
replication & DNA
Rapid Review (4)
Organelle
Prokaryotes Eukaryotes
Functions
Prokaryotes Animal Plant
cells
cells
Peroxisome
_
+
+
Breakdown of FA,
detoxification of
alcohol
Chloroplast
_
_
+
Site of
photosynthesis
Vacuole
_
+ (small)
+
(large)
Storage vault of
cells
Rapid Review (5)
Organelle
Prokaryotes Eukaryotes
Functions
Prokaryotes Animal Plant
cells
cells
Cytoskeleton _
+
+
Consists of
microtubules (cell
division, cilia,
flagella),
microfilaments
(muscles), &
intermediate
filaments
(reinforcing
position of
organelles
_
+
_
Part of microtubule
separation
apparatus that
assists cell division
Centrioles
CELL MEMBRANES

The Fluid-Mosaic Model
1. Phospholipids
Phosphatidic acid
Phosphatidyl-choline
phosphate
Glycerol
Hydrocarbon chains
Phosphatidyl-ethanolamine
2. Cholesterol
Function of cell membranes



Compartmentalization of tissues
Regulation of cell contents
Provides surface for enzymes, receptors,
recognition, etc.
Phospholipids: the “backbone” of
the membrane
Cartoon of a phospholipid molecule
Glycerol
plus
polar side
group
Fatty acids
*both polar and non-polar regions
Water molecules are polar


Structure of water and the Cartoon version
Water is a dipole
d/2 +
H
d
+
O
d/2 +
H
Water is a good solvent for
polar molecules and ions
Hydration Shells
-
+
Phospholipids

Cartoon of a phospholipid molecule
Oil/water partition: the
“kitchen” experiment
MIX OIL WATER AND TEST SUBSTANCE
OIL
WAIT
WATER
Mixing phospholipids and water:
spontaneous self-organization
Mixing phospholipids and water:
spontaneous self-organization
Mixing phospholipids and water:
spontaneous self-organization
Click ahead
Mixing phospholipids and water:
spontaneous self-organization
Sheet
Micelle
The membrane is fluid
The membrane is fluid
The membrane is fluid
The membrane is fluid
Cholesterol sits between fatty tails
The fluid-mosaic model
Channels and carriers are needed to
get ions across the bilayer
Channels and carriers are needed to
get ions across the bilayer
Types eucaryotic cells (1)





Stem Cells
Hemopoietic cells
Monocytes
Macrophages
Phagocytes
Stem Cells (2)




Research on stem cells is advancing knowledge
about:
how an organism develops from a single cell
and how healthy cells replace damaged cells in
adult organisms
This promising area of science is also leading
scientists to investigate the possibility of cellbased therapies to treat disease, which is often
referred to as regenerative or reparative
medicine
What are stem cells and why are
they important? (3)





Stem cells have two important characteristics
that distinguish them from other types of cells:
First, they are unspecialized cells that renew
themselves for long periods through cell division
The second is that under certain physiologic or
experimental conditions, they can be induced to
become cells with special functions such as:
the beating cells of the heart muscle
or the insulin-producing cells of the pancreas
Stem Cells (4)
Kinds of stem cells (5)




Scientists primarily work with two kinds of
stem cells from animals and humans:
embryonic stem cells
and adult stem cells,
which have different functions and
characteristics
Stem cells are important for living
organisms (5)









Stem cells are important for living organisms for many
reasons.
In the 3 to 5 day old embryo, called a blastocyst,
a small group of about 30 cells called the inner cell mass
gives rise to the hundreds of highly specialized cells
needed to make up an adult organism.
In the developing fetus, stem cells in developing tissues
give rise to the multiple specialized cell types that make up
the heart,
lung,
skin,
and other tissues
In some adult tissues (6)








In some adult tissues, such as:
bone marrow,
muscle,
and brain,
discrete populations of adult stem cells
generate replacements for cells that are
lost:
through normal wear and tear,
injury,
or disease
Hemopoietic cells (7)




The basis of haemopoiesis is a small
population of self-replicating stem cells,
which ultimately can generate all types
of blood cells.
The process of haematopoiesis is
controlled by a group of at least 11
growth factors.
Three of these glycoproteins initiate
the differentiation of macrophages from
uni- and bipotential progenitor cells in
the bone marrow.
Macrophages and monocytes (8)


Their development takes in the bone marrow
and passes through the following steps:
stem cell






committed stem cell
monoblast
promonocyte
monocyte (bone marrow)
monocyte (peripheral blood)
macrophage (tissues)
Blood monocytes (9)





The blood monocytes are
young cells that already
possess migratory,
chemotactic,
pinocytic
and phagocytic activities,
as well as receptors for
IgG
Macrophages (10)







Macrophages can be divided into
normal macrophages
and inflammatory macrophages.
Normal macrophages includes macrophages in
connective tissue .
Inflammatory macrophages are present in various
exudates.
Phagocytes
and since they are derived exclusively from
monocytes they share similar properties.
Phagocytes (11)



Phagocytes are cells
which ingest particles.
The process of eating
particles is called
"phagocytosis,"
a process which is
one of the
distinguishing
features of eukaryotic
cells,
Phagocytes (12)
How cells divide: Cell cycle
Cell cycle
Cells must be able to
grow & divide
New cells must contain
complete copies of
the entire set of
chromosomes and all
their DNA
A Cell’s lifetime of
growth & division can
be referred to as a
Cell Cycle
Cell cycle
Includes not only cell
division, but also the
intervening time period
when cells are not
dividing...
Cell cycle phases


Interphase: cell growth & DNA
replication
Mitosis: nuclear & cell Division
Interphase
Composed of G1, S & G2 phases
Interphase includes everything
except Mitosis
Interphase
G1: gap phase between Mitosis & S
S phase: DNA replication
G2: gap phase between S & Mitosis
Mammalian cell cycle
G1: Highly variable, Absent in rapidly dividing
cells, long in slow-growing cells
S: 6-8 hours
G2: 3-6 hours
M: 1-2 hours
G1 arrested cells



An important control point in cell cycle holds
cells in G1
Cells can remain indefinitely in G1
Such cells are said to reside in a G0 state, a
cell cycle holding point

G0 Cells may re-enter the normal cell cycle if
given conditions suitable for growth
The S phase
Each Chromosome replicates to form
2 Chromatids.
Replicated chromatids are joined
together at their centromeres
Cell cycle phases:
M = mitosis
Prophase:
Metaphase:
Anaphase:
Telophase:
1. Prophase

Three things visibly occur



Chromosomes condense (shorten)
Centrosomes migrate to the poles while
producing spindle fibers
Nuclear membrane fragments
2. Metaphase


Chromosomes are moved by
growing spindle fibers to the
equator of the cell (metaphase
plate)
Centrosomes are at the poles,
nuclear membrane is gone
3. Anaphase

Anaphase movement in
two parts:



Chromosomes move
toward opposite poles
Poles themselves move
apart
Anaphase movement
uses ATP
4. Telophase




Chromosomes unfold and disperse
(no longer condensed)
Spindle dissassemble
Nuclear membrane Reforms
Gene activity resumes
Cytokinesis


Actual cell division
stage
Cytokinesis (division
of the cytoplasm)
may occur
SEXUAL(MEIOSIS)
Figure 14.32. Comparison of meiosis
and mitosis. Both meiosis and mitosis
initiate after DNA replication, so each
chromosome consists of two sister
chromatids. In meiosis I, homologous
chromosomes pair and then segregate to
different cells. Sister chromatids then
separate during meiosis II, which
resembles a normal mitosis. Meiosis thus
gives rise to four haploid daughter cells.
Fuente: Cooper, 2000
In Conclusion
 A parent cell provides each daughter cell
with hereditary instructions
 Eukaryotes divide by mitosis or meiosis
 Each chromosome is one DNA molecule
with proteins attached
 Cells with a diploid number (2n) contain
two of each kind of chromosome
In Conclusion
 Mitosis maintains the chromosome number
from one cell generation to the next
 Mitosis is the basis of growth and tissue
repair, and asexual reproduction in some
eukaryotes
 The cell cycle includes interphase and
mitosis
 The phases of mitosis are prophase,
metaphase, anaphase, and telophase

developed by M. Roig
ATTACHMENT
Click after each step to view process
PENETRATION
UNCOATING
HOST
FUNCTIONS
Transcription
Translation
VIRAL
LIFE
CYCLE
REPLICATION
ASSEMBLY
(MATURATION)
RELEASE
MULTIPLICATION