BIO 411 Chapter 3 – Bacterial Morphology and Cell Wall Structure and Synthesis.
Bio 11 - Cell Structure
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FORMULATION OF THE CELL THEORY
In 1839, Theodor Schwann published his book on
animal and plant cells
He summarized his observations into three
conclusions about cells:
1) The cell is the unit of structure, physiology, and
organization in living things.
2) The cell retains a dual existence as a distinct entity
and a building block in the construction of organisms.
The correct interpretation of cell formation by division
was finally promoted by others and formally enunciated
in Rudolph Virchow's powerful dictum, "Omnis cellula e
cellula"... "All cells only arise from pre-existing cells".
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THE MODERN TENETS OF CELL THEORY
6. all energy flow (metabolism & biochemistry) of life
occurs within cells.
1. all known living things are made up of cells.2. the cell is structural & functional unit of all living things.
3. all cells come from pre-existing cells by division.
(Spontaneous Generation does not occur).
4. cells contains hereditary information which is passed
from cell to cell during cell division.
5. All cells are basically the same in chemical
composition.
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THE CELL : basic unit ofstructure and function
Animal
cell
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Eukaryotic and prokaryotic cells
Eukaryotic cells
subdivided by internal
membranes into
membrane-enclosed
organelles.
nucleus - Largest
organelle
Other organelles incytoplasm
Prokaryotic cells
Simples, smaller,DNA not separated
from the rest of the
cell by membrane-
bounded organelles
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prokaryoticeukaryotic
mitochondrion
Chloroplast
lysosome
Golgi complex
Nucleus with
several linear
chromosomes
Endoplasmicreticulum
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Kingdom Monera
(Prokaryotic)
Protists, fungi ,
plants, animals
(Eukaryotic)
Distinguishingfeatures of cell type
Nucleoid. Nomembrane-
bounded
nucleus
-Circular strand
of DNA
- Few cell
organelles
Nucleusbounded by a
membrane
DNA in several
linear
chromosomes
Many specialized
membrane-
bound organelles
prokaryote
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The minimum
resolution of a light
microscope is about
2 microns, the sizeof a small bacterium
Light microscopes
can magnifyeffectively to about
1,000 times the size
of the actualspecimen.
At highermagnifications, theimage blurs.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.1
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2. THE CELL
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2. THE CELL
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Sugar-phosphate
backbone Nitrogen bases
DNA molecule: composed of 2 nucleotide chains, twisted in a double helix
Nucleotide= base, sugar,
phosphate
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Flow of genetic information
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Type of protein function examples
Structural
enzymatic
Support
Accelerate chemical
rx
Silk fibers for cocoons and
web.Keratin in hair, horns,
feathers
Digestive enzymes
Storage
Defensive
Storage of amino
acids
protection
of egg white for dev of embryo.
Casein, protein of milk for baby
mammals
Antibodies that combat bacteria
Transport proteins Transport of othersubs.
Hemoglobin, transports O2 fromlungs to other parts of the body.
Other proteins transport
molecules across cell
membranes
Hormonal proteins
Receptor proteins
Coordination ofactivities
Response of cell to
chemical stimuli
Insulin, secreted by pancreashelp regulate concentration of
sugar in the blood
Receptors built into the
membrane of a nerve cell
Contractile movement Actin and myosin for muscular
movement
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Every function in the living cell depends on
proteins
Motion and locomotion depends on proteins, ex.
Muscles
Enzymes for catalysis of biochemical reactions
Structure of cells and the extracellular matrix in
which they are embedded are made of proteins
Receptors of hormones are proteins
Hemoglobin is a protein Signalling molecules are proteins
Among essential nutrients are proteins
Transcription factors that turn genes on and
off are proteins Hemoglobin is a protein
Feathers, spider webs horns are made of
proteins
Seeds are rich in proteins
Proteins
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James WatsonFrancis Crick
(1953)
Rosalind Franklin- X-ray crystallographer
made the photo that
Watson and Crick used
in deducing the double
helical structure of DNA
Heritable information carried by DNA
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Nucleotides: Basic chemical units of DNA and RNA,consist of 4 nitrogenous bases linked to a sugar which is
in turn linked to a phosphate.
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Flow of genetic information
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Robert Hookes simple
microscope
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The Cell theory predates other great paradigms of
biology:
Darwin's theory of evolution (1859),
Mendel's laws of inheritance (1865),
Establishment of Comparative biochemistry
(1940)
Profound revelations, led to greater understanding of
the structures and processes that make up the living
state.
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All cells are surrounded by aplasma
membrane. The semifluid substance within the
membrane is the cytosol, containing the
organelles. All cells contain chromosomes which have
genes in the form of DNA.
All cells also have ribosomes, tiny organellesthat make proteins using the instructions
contained in genes.
Prokaryotic and eukaryotic cells
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Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.4 The prokaryotic cell is much simpler in structure, lacking a nucleus and the other
membrane-enclosed organelles of the eukaryotic cell.
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Cellulose- linear chain
of covalently linked
glucose
In primary cell wall, one
cellulose polymer
has ca 6000 glucose
unitsAbout 80 celulose
m,olecules associate to
form a microfibril
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The plasma membrane functions as a selective
barrier that allows passage of oxygen, nutrients,
and wastes for the whole volume of the cell.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.6
Internal membranes
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A eukaryotic cell has extensive and
elaborate internal membranes, which
partition the cell into compartments.
These membranes also participate in
metabolism as many enzymes are built
into membranes.
Internal membranescompartmentalize the functions
of a eukaryotic cell
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The nucleus contains a
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The nucleus contains most of the genes in aeukaryotic cell. Some genes are located in mitochondria and
chloroplasts.
The nucleus averages about 5 microns indiameter.
The nucleus is separated from the cytoplasmby a double membrane. These are separated by 20-40 nm.
Where the double membranes are fused, apore allows large macromolecules and
particles to pass through.
The nucleus contains aeukaryotic cells genetic library
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Sugar-phosphate
backbone Nitrogen bases
DNA molecule: composed of 2 nucleotide chains, twisted in a double helix
Nucleotide= base, sugar,
phosphate
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Flow of genetic information
Type of protein function examples
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Type of protein function examples
Structural
enzymatic
Support
Accelerate chemical
rx
Silk fibers for cocoons and
web.Keratin in hair, horns,
feathers
Digestive enzymes
Storage
Defensive
Storage of amino
acids
protection
of egg white for dev of embryo.
Casein, protein of milk for baby
mammals
Antibodies that combat bacteria
Transport proteins Transport of othersubs.
Hemoglobin, transports O2 fromlungs to other parts of the body.
Other proteins transport
molecules across cell
membranes
Hormonal proteins
Receptor proteins
Coordination ofactivities
Response of cell to
chemical stimuli
Insulin, secreted by pancreashelp regulate concentration of
sugar in the blood
Receptors built into the
membrane of a nerve cell
Contractile movement Actin and myosin for muscular
movement
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Every function in the living cell depends on
proteins
Motion and locomotion depends on proteins, ex.
Muscles
Enzymes for catalysis of biochemical reactions
Structure of cells and the extracellular matrix in
which they are embedded are made of proteins
Receptors of hormones are proteins
Hemoglobin is a protein Signalling molecules are proteins
Among essential nutrients are proteins
Transcription factors that turn genes on and
off are proteins Hemoglobin is a protein
Feathers, spider webs horns are made of
proteins
Seeds are rich in proteins
Proteins
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The DNA of genes controls protein production indirectly
using RNA as intermediary.
Sequence of nucleotide along a gene is transcribed into
RNA.
Then translated into a specific protein with a unique shape
and function.
The entire process in which the information in a gene directs
the production of a cellular product is called Gene
expression
In translating genes into proteins, all forms of life
employ essentially the same genetic code
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James Watson
Francis Crick
(1953)
Rosalind Franklin- X-ray crystallographer
made the photo that
Watson and Crick used
in deducing the double
helical structure of DNA
Heritable information carried by DNA
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Nucleotides: Basic chemical units of DNA and RNA,consist of 4 nitrogenous bases linked to a sugar which is
in turn linked to a phosphate.
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Flow of genetic information
Kingdom Monera Protists fungi
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Kingdom Monera
(Prokaryotic)
Protists, fungi ,
plants, animals
(Eukaryotic)
Distinguishingfeatures of cell type
Nucleoid. Nomembrane-
bounded
nucleus
-Circular strand
of DNA- Few cell
organelles
Nucleusbounded by a
membrane
DNA in several
linear
chromosomesMany specialized
membrane-
bound organelles
prokaryote
The minimum
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The minimum
resolution of a light
microscope is about
2 microns, the sizeof a small bacterium
Light microscopes
can magnifyeffectively to about
1,000 times the size
of the actualspecimen.
At highermagnifications, the
image blurs.Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.1
S h h t
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Sugar-phosphate
backbone Nitrogen bases
DNA molecule: composed of 2 nucleotide chains, twisted in a double helix
Nucleotide= base, sugar,
phosphate
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Flow of genetic information
Type of protein function examples
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Structural
enzymatic
Support
Accelerate chemical
rx
Silk fibers for cocoons and
web.Keratin in hair, horns,
feathers
Digestive enzymes
Storage
Defensive
Storage of amino
acids
protection
of egg white for dev of embryo.
Casein, protein of milk for baby
mammals
Antibodies that combat bacteria
Transport proteins Transport of othersubs.
Hemoglobin, transports O2 fromlungs to other parts of the body.
Other proteins transport
molecules across cell
membranes
Hormonal proteins
Receptor proteins
Coordination ofactivities
Response of cell to
chemical stimuli
Insulin, secreted by pancreashelp regulate concentration of
sugar in the blood
Receptors built into the
membrane of a nerve cell
Contractile movement Actin and myosin for muscular
movement
Every function in the living cell depends on P t i
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Every function in the living cell depends on
proteins
Motion and locomotion depends on proteins, ex.
Muscles
Enzymes for catalysis of biochemical reactions
Structure of cells and the extracellular matrix in
which they are embedded are made of proteins
Receptors of hormones are proteins
Hemoglobin is a protein Signalling molecules are proteins
Among essential nutrients are proteins
Transcription factors that turn genes on and
off are proteins Hemoglobin is a protein
Feathers, spider webs horns are made of
proteins
Seeds are rich in proteins
Proteins
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James Watson
Francis Crick
(1953)
Rosalind Franklin- X-ray crystallographer
made the photo that
Watson and Crick used
in deducing the double
helical structure of DNA
Heritable information carried by DNA
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Nucleotides: B i h i l it f DNA d RNA
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Nucleotides: Basic chemical units of DNA and RNA,consist of 4 nitrogenous bases linked to a sugar which is
in turn linked to a phosphate.
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Flow of genetic information
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Nucleus directs protein synthesis
by synthesizing mRNA
Then mRNA is transported to the
cytoplasm via the nuclear pores.
Ribosomes translate the mRNAS genetic message into the
primary structure of a specific polypeptide (polymer of linked
amino acids- which are building blocks of proteins).
DNA-RNA-PROTEIN
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DNA RNA PROTEIN
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Transcription and translation
Genes provideinstructions
for making
specific proteins
enzymes Accelerate chem rx Digestive enzymes
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structural support Insects, spiders
make web
storage Storage of amino
acid
Ovalbumin=protein
of egg white
transport Transport of other
substances
Hemoglobin-
transports oxygen
Hormonal Coordination of the
organisms activities
Insulin regulate
concentration of
sugar in the blood
Receptor Response of cell to
chemical stimuli
receptors built in
membranes
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Contractile
and motorprotein
Movement Actin and
myosin formovement
Defensive
protein
Protection
against
certainmicrooorga-
nisms
Antibodies,
combat
bacteria andviruses
Proteins Continued
n clear
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nuclear
lamina, a
network of
intermediate
filaments that
maintain the
shape of thenucleus by
mechanically
supporting thenuclear
membrane,
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.9
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DNA
DNA and associated proteins
organized into chromatin-
appear as diffuse mass When cell prepares to divide,
chromatin fibers coil up, seen as
separate structures (chromosomes)
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nucleolus
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nucleolus
Mass of densely-stained
fibers and granules
where Ribosomal RNA
(rRNA) is synthesized
rRNA combine with
proteins from
cytoplasm to form
ribosomal subunits
Ribosomes build a cells
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Ribosomes contain rRNA and protein.
A ribosome is composed of two subunits that
combine to carry out protein synthesis.
Ribosomes build a cell sproteins
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.10
rRNA from
nucleolus
Proteins from
cytoplasm
Combine to
form ribosomal
Subunits.
Subunits exitnuclear pores
to the cytoplasm
Cell types that synthesize large quantities of
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Cell types that synthesize large quantities of
proteins (e.g., pancreas) have large
numbers of ribosomes and prominent nuclei. free ribosomes, are suspended in the
cytosol and synthesize proteins that function
within the cytosol
bound ribosomes, are attached to the
outside of the endoplasmic reticulum. These synthesize proteins that are eitherincluded into membranes or forexport from
the cell.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Endomembrane system
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Many of the internal membranes in a eukaryotic cellare part of the endomembrane system.
are either in direct contact
or connected via transfer ofvesicles, sacs of membrane.
the membranes are even modified during life.
endomembrane system includes: the nuclear envelope,
endoplasmic reticulum,
Golgi apparatus, lysosomes,
vacuoles,
the plasma membrane.
Endomembrane system
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Endomembrane system
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The endomembrane
system plays a key
role in the synthesis(and hydrolysis) of
macromolecules in
the cell.
The variouscomponents
modify
macromolecules
for their various
functions.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.16
ER accounts for half the
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ER accounts for half the
membranes in a eukaryotic
cell.
membranous tubules andinternal, fluid-filled spaces,
the cisternae.
ER membrane is
continuous with the nuclearenvelope and the cisternal
space of the ER is
continuous with the space
between the two
membranes of the nuclear
envelope
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There are two, regions
of ER that differ in
structure and function. Smooth ER looks
smooth because it
lacks ribosomes.
Rough ER looks rough
because ribosomes
(bound ribosomes) are
attached to the outside,including the outside of
the nuclear envelope.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.11
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Smooth ER are important in synthesis of
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Smooth ER are important in synthesis of
lipids, oil, phospholipids and steroids (sex
hormones of vertebrates), metabolism ofcarbohydrates.
Other enzymes in the smooth ER of theliver help detoxify drugs and poisons.
These include alcohol.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Rough ER is especially abundant in those
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g p y
cells that secrete proteins, ex. pancreatic
cells synthesize protein insulin on the ER.
As a polypeptide is synthesized by theribosome, it is threaded into the cisternal space
through a pore formed by a protein in the ER
membrane.
Many of these polypeptides are
glycoproteins, a polypeptide to which an
oligosaccharide is attached.
These secretory proteins are packaged intransport vesicles that carry them to their
next stage.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Proteins on free ribosomes in cytosol
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Proteins on free ribosomes in cytosol
Nucleus
Mitochondria
Chloroplast or peroxisomes
Proteins synthesized in bound ribosomes are transferred
into the rough ER
Proteins destined for secretion or incorporation into ER
Golgi
Lysosome
Plasma membrane
Secretory pathway- ERGolgi
Secretory
vesicles
Cell
exterior
.
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Membrane bound proteins
are synthesized directly into
the membrane.As the ER membrane
expands, parts can be
transferred as transport
vesicles to othercomponents of the
endomembrane system.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Rough ER is also a membrane
factory
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Golgi akso manufactures
Some molecules.
Pectin and other noncellulosic
molecules which are incorporated with
cellulosecto cell walls.
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After leaving ERmany transport
vesicles travel to
Golgi where
products of ER
such are proteins
are modified and
stored
and then sent to
other destinations
Vesicles form
cnd leave Golgi
carry proteins
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Golgi-flattened membranous sac
Lysosomes-digestive
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Lysosomes digestive
compartment, carry out
intracellular digestion
Lysosome digest materials
taken into the cell
Hydrolytic enzymes
In the lysosome
Lysosome digesting food
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Lysosome breaking down damaged organelles
Repository of inorganic ionsContain pigmentsvacuoles
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Contain pigments
Hold reserves of proteins stock-
piled in vacuoles
Major role in growth of plant cells ,enlarge as their vacuoles absorb
water, cells become larger with
minimal investment in new
cytoplasm
vacuoles
Raphide encased in Raphide crystals
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p
carbohydratesp y
http://www.botany.hawaii.edu/faculty/webb/bot311/bot311-00/Cells&Tissues/images/cell/or-52mod.jpghttp://www.botany.hawaii.edu/faculty/webb/bot311/bot311-00/Cells&Tissues/images/cell/RaphVacuole.jpg -
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Prismatic crystal
druses
prismatic
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prismatic
raphide
druse
C t lith
http://www.botany.hawaii.edu/faculty/webb/bot311/bot311-00/Cells&Tissues/images/cell/or-52mod.jpghttp://www.google.com/imgres?imgurl=http://www.opinion250.com/images/Ficus_Elastica_new_leaf.jpg&imgrefurl=http://www.opinion250.com/blog/view/11242&h=300&w=400&sz=30&tbnid=MivPEStzzwgYQM:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dficus%2Belastica&zoom=1&q=ficus+elastica&usg=__pNuJ83ehwxT3kHqPauFc_GczH5w=&sa=X&ei=A0fjTPjAG4KKvQPPtYCTDQ&ved=0CB4Q9QEwAQ -
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Cystolith
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Review organelle relationships
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Review organelle relationships
Nuclear
membrane
Vesicles from ER flow
to Golgi carrying
proteinsGolgi
pinches off
vesicles give
rise to
lysosomes,
etc.
LysosomeTransport vesicle carries protein to plasma
Membrane for secretion
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Hydrolytic
enzymes and
lysosomal
membranes
made by
rough ER,
then to Golgi.
Lysosomesarise by
budding
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CHAPTER 7
A TOUR OF THE CELL
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Section E: Other Membranous Organelles
1. Mitochondria and chloroplasts are the main energy transformers of cells
2. Peroxisomes generate and degrade H2O2 in performing various metabolic
functions
1. Mitochondria and chloroplasts are the main
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Mitochondria and chloroplasts are theorganelles that convert energy to forms thatcells can use for work.
Mitochondria are the sites of cellularrespiration, generating ATP from thecatabolism of sugars, fats, and other fuels inthe presence of oxygen.
Chloroplasts, found in plants and eukaryoticalgae, are the site of photosynthesis.
They convert solar energy to chemical energyand synthesize new organic compounds from
CO and H O.
1. Mitochondria and chloroplasts are the main
energy transformers of cells
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Mitochondria and chloroplasts are not part
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p p
of the endomembrane system.
Their proteins come primarily from freeribosomes in the cytosol and a few from
their own ribosomes.
Both organelles have small quantities ofDNA that direct the synthesis of the
polypeptides produced by these internal
ribosomes.
Mitochondria and chloroplasts grow and
reproduce as semiautonomous organelles.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
2 THE CELL basic unit of
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2. THE CELL : basic unit ofstructure and function
Mitochondria and chloroplasts are not part
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p p
of the endomembrane system.
Their proteins come primarily from freeribosomes in the cytosol and a few from
their own ribosomes.
Both organelles have small quantities ofDNA that direct the synthesis of the
polypeptides produced by these internal
ribosomes.
Mitochondria and chloroplasts grow and
reproduce as semiautonomous organelles.
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Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.17
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Almost all eukaryotic cells have
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y
mitochondria.
There may be one very large mitochondrion or
hundreds to thousands in individual
mitochondria.
The number of mitochondria is correlated with
aerobic metabolic activity.A typical mitochondrion is 1-10 microns long.
Mitochondria are quite dynamic: moving,
changing shape, and dividing.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Mitochondria have a smooth outer
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membrane and a highly folded inner
membrane, the cristae.
This creates a fluid-filled space between them.
The cristae present ample surface area for the
enzymes that synthesize ATP.
The inner membrane encloses the
mitochondrialmatrix, a fluid-filled space
with DNA, ribosomes, and enzymes.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The chloroplast is one of several members of a
li d l f l t t t ll d
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generalized class of plant structures called
plastids.
Amyloplasts store starch in roots and tubers.
Chromoplasts store pigments for fruits and flowers.
The chloroplast produces sugar via
photosynthesis. Chloroplasts gain their color from high levels of the
green pigment chlorophyll.
Chloroplasts measure about 2 microns x 5microns and are found in leaves and other
green structures of plants and in eukaryotic
algae.Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The processes in the chloroplast are
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p p
separated from the cytosol by two
membranes.
Inside the innermost membrane is a fluid-
filled space, the stroma, in which float
membranous sacs, the thylakoids.
The stroma contains DNA, ribosomes, and
enzymes for part of photosynthesis.
The thylakoids, flattened sacs, are stacked into
grana and are critical for converting light tochemical energy.
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Thylakoid-flattened sacGrana-stacks of thylakoid
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Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 7.18
y
Stroma-fluid filled space
Like mitochondria, chloroplasts aredynamic structures
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dynamic structures.
reproduce themselves by pinching in two.
Mitochondria and chloroplasts are mobile and move
around the cell along tracks in the cytoskeleton.
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Mitochondria and chloroplast compared
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2. Peroxisomes generate and degrade H2O2 inperforming various metabolic functions
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Peroxisomes contain enzymes that transferhydrogen from various substrates to oxygen
An intermediate product of this process ishydrogen peroxide (H2O2), a poison, but theperoxisome has another enzyme that convertsH2O2 to water.
Some peroxisomes break fatty acids down tosmaller molecules that are transported tomitochondria for fuel.
Others detoxify alcohol and other harmfulcompounds.
Specialized peroxisomes, glyoxysomes,convert the fatty acids in seeds to sugars, an
easier energy and carbon source to transport.
p g
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Peroxisomes are bounded by a single
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membrane.
Formed by incorporation of proteins andlipids from the cytosol.
They split in two
when they reach
a certain size.
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Fig. 7.19
Peroxisomes- membrane-enclosed
(from rat liver )
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(from rat liver )Assembled from
proteins
synthesized infree ribosomes
like chloroplast
and mitochondria
Contain various
enzymes
Carry out oxid.
that produce
H2O2 hydrogen
peroxide H2O2 decomposed by Catalase to water.
In seeds: fatty acids sugars during germination
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Formed by incorporation of proteins from free ribosomes
and lipids from cytosol
1. Peroxisomes
2. Mitochondrion
3. Chloroplast Also from their own proteins synthesized in
their own ribosomes
: The cytoskeleton is a network ofCytoskeleton
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Microtubule
Microfilaments
0.25 m
y
protein filaments/ extending throughout
the cytoplasm of all eukaryotes
Structural framework for the cell
Serves as a scaffold determining shape
Resp for movement
: The cytoskeleton is a network of protein
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filaments/ fibers that organizes structures and
activities
Less rigid
Less permanent
Dynamic,continually reorganized eg. In celldivision
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Roles of the Cytoskeleton:
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Support, Motility, and Regulation
The cytoskeleton helps to support the cell and
maintain its shape
It interacts with motor proteins to produce motility
Inside the cell, vesicles can travel along
monorails provided by the cytoskeleton
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Table 6-1
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10 m 10 m 10 m
Column of tubulin dimers
Tubulin dimer
Actin subunit
25 nm
7 nm
Keratin proteins
Fibrous subunit (keratins
coiled together)
812 nm
Table 6-1a
10 m
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Column of tubulin dimers
Tubulin dimer
25 nm
Fig. 6-21
VesicleATP
Motor proteins
tt h t th
Transport membranevesicles
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Receptor for
motor protein
Microtubule
of cytoskeleton
Motor protein
(ATP powered)(a)
Microtubule Vesicles
(b)
0.25 m
attach to the
receptors on
vesicles alongmicrotubules
Motor proteins can
walk the vesicles .
Involves interaction ofmotor proteins with
cytoskeleton
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Fig. 6-23
Direction of swimming
Undulates, drives
Flagella and cilia are locomotory organelles,they are microtubules extensions that project
from cells
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5 m(a) Motion of flagella
Direction of organisms movement
Power stroke Recovery stroke
(b) Motion of cilia15 m
,
cell in same
direction
Back andforth
motion
Bending of flagella and cilia by gripping & sliding microt. Pasteach other.
Table 6-1b
10 m
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Actin subunit
7 nm
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Microfilaments that function in cellular
motility contain the protein myosin in
addition to actin
In muscle cells, thousands of actin filaments
are arranged parallel to one another
Thicker filaments composed of myosin
interdigitate with the thinner actin fibers
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Cytoplasmic streaming is a circular flow of
cytoplasm within cells
This streaming speeds distribution of
materials within the cell
In plant cells, actin-myosin interactions and
sol-gel transformations drive cytoplasmic
streaming
Video: Cytoplasmic Streaming
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Table 6-1c
5 m
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Keratin proteinsFibrous subunit (keratinscoiled together)
812 nm
Extracellular components and
ti b t ll h l
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connections between cells help
coordinate cellular activities
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Cell Walls of Plants
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The cell wall is an extracellular structure that
distinguishes plant cells from animal cells
Prokaryotes, fungi, and some protists also
have cell walls
The cell wall protects the plant cell, maintains
its shape, and prevents excessive uptake of
water Plant cell walls are made of cellulose fibers
embedded in other polysaccharides and
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Plant cell walls may have multiple layers:
Primary cell wall: relatively thin and flexible
Middle lamella: thin layer between primary
walls of adjacent cells
Secondary cell wall (in some cells): addedbetween the plasma membrane and the
primary cell wall
Plasmodesmata are channels betweenadjacent plant cells
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Ca 80 Cellulose,molecules associate
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,
to form a microfibril
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Fig. 6-28
Secondary
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Seco da y
cell wall
Primary
cell wall
Middle
lamella
Central vacuoleCytosol
Plasma membrane
Plant cell walls
Plasmodesmata
1 m
The Extracellular Matrix (ECM) of
Animal Cells
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Animal Cells
Animal cells lack cell walls but are coveredby an elaborate extracellular matrix (ECM)
The ECM is made up of glycoproteins suchas collagen, proteoglycans, andfibronectin
ECM proteins bind to receptor proteins in
the plasma membrane called integrins
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Fig. 6-30a
Collagen ProteoglycanEXTRACELLULAR FLUID
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Co age
Fibronectin
Plasmamembrane
g ycomplex
Integrins
CYTOPLASMMicro-filaments
EXTRACELLULAR FLUID
(attaches ECM
to integrins)
(embedded in
a web of
proteoglycan
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Functions of the ECM: Support Adhesion Movement Regulation
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Intercellular Junctions
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Neighboring cells in tissues, organs, or organ
systems often adhere, interact, and
communicate through direct physical contact
Intercellular junctions facilitate this contact
There are several types of intercellular
junctions
Plasmodesmata
Tight junctions Desmosomes
Gap junctions
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Fig. 6-28
Secondary
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y
cell wall
Primary
cell wall
Middle
lamella
Central vacuoleCytosol
Plasma membrane
Plant cell walls
Plasmodesmata
1 m
Plasmodesmata in Plant Cells
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Plasmodesmata are channels that
perforate plant cell walls
Through plasmodesmata, water and small
solutes (and sometimes proteins and RNA)
can pass from cell to cell
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Cells walls are perforated with channels
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Gap junctions
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Proteinaceous tubes that connect adjacent cells.
These tubes allow material to pass from one cell to the next withouthaving to pass through
the plasma membranes of the cells.