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Sylvia S. Mader
Immagini e
concetti
della biologia
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
A4 - Observing
the Cell
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cells are the basic units of life
CELL THEORY
• The cell is the basic unit of life
• All living things are made up of cells
• New cells evolve only from preexisting cells
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cells are the basic units of life
Unicellular Organisms
Older organisms,
consist of a single cell.
Multicellular Organisms
More evolved,
have multiple cells organized
in tissues, organs and
systems.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cells have small dimensions
Cell are small in size in order to maintain a correct
surface/volume ratio.
Smaller volumes
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Higher surfaces
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Cells have small dimensions
In order to observe cells smaller than 0,1 mm a
microscope is necessary
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Optical Light Microscope (LM)
LM uses visible light and a system of lenses to magnify
images. The power of a light microscope is about 0,2μm.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Transmission Electron Microscope
A TEM uses a beam of electrons to illuminate a specimen
and produce a magnified image. The most powerful TEM
have a resolution of about 0,1 nm.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Scanning Electron Microscope
A SEM collects and focuses beams of electrons on a
specimen’s surface and produce a tree-dimensional image.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
All organisms may be classified as
prokaryotes or eukaryotes
Prokaryotes and eukaryotes posses two basic
features:
a plasma membrane and a cytoplasm.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Prokaryotic cell
(pro = before, karyon = nucleus)
•Evolved first
•Lack a membrane-bounded nucleus
•Simpler structure than Eukaryotic cells
•Archaea and Bacteria
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Eukaryotic cell
(eu = well, karyon = nucleus)
•Membrane-bounded nucleus
•Well organized organelles
•Animal cell and plant cell
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Animal cell
Nucleus:
it contains chromatin and is enclosed in a
nuclear envelop with double membrane and nuclear pores
Endoplasmic reticulum: is divided into:
•Rough E.R., studded with ribosomes and
Plasma membrane:
composed of
phospholipids and proteins, protects the cell
and regulates the transport of substances
involved in the synthesis of proteins
•Smooth E.R., lack in ribosome and involved in
the synthesis of lipids
Ribosomes:
small particles that
carry out protein synthesis
Cytoskeleton:
maintains cell shape and
assists movements of cell products
Peroxisome:
Cytoplasms:
vesicles
with various functions
semifluid
matrix
containing and supporting organelles
Mitochondrion:
Responsible
respiration
production
Vesicles:
membrane-bounded sac
that store and transport cell material
for nuclear
and
ATP
Polyribosomes:
string
of
ribosomes
simultaneously
synthesizing same protein
Lysosomes:
type of vesicles that
digest macromolecules and cell parts
Golgi
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
apparatus: packages
proteins and secrets macromolecules
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Plant cell
Central Vacuole:
store metabolites
and help maintain cell turgor
Nucleus
Chloroplast:
carries
out
photosynthesis, producing sugar
E.R.
Mitochondrion
Golgi apparatus
Plasma membrane
Granum:
a stack of chlorophyllcontaining thylakoids in chloroplast
Cell wall:
outer membrane
that shapes, supports and
protects the cell
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Protein Synthesis starts from DNA
The genetic information needed for the protein synthesis is
contained inside the nucleus.
Here genes, composed of DNA, are located on
chromosomes.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Protein Synthesis starts from DNA
mRNA transports the genetic information to the
cytoplasm where it joins with ribosomal subunits
and the protein synthesis starts.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Protein Synthesis starts from DNA
Ribosomes in the cytoplasms and embedded
on the E.R. carry out the protein synthesis.
The new forming protein enters the Endoplasmic
Reticulum lumen and folds into its final shape.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Protein synthesis is the cell major
Function
Proteins (produced in the rough ER) and lipids
(produced by the smooth ER) are secreted out to
the Golgi apparatus through vesicles.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The Golgi apparatus packages the
proteins into macromolecules
Macromolecules
Transport
vesicles
Golgi
apparatus
Vesicles, as lysosomes, leave
the Golgi apparatus and travel
to the plasma membrane where
secretion occurs.
ER
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Vesicles and vacuoles
• Lysosomes: contain enzymes that digest macromolecules.
• Peroxisomes: similar to lysosomes, break down fatty acids.
• Vacuoles: usually are use as cell store (water, sugar, sap)
and maintain turgor.
Animal cell
Plant cell
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Exocytosis
(eso = out, cyto = cell)
ER, Golgi apparatus and vesicles work in synergy in order to
direct the contents of secretory vesicles out of the cell
membrane.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Energy Transformations
Mitochondria and Chloroplast are the “power stations” of
the cell as control the energy production through
respiration and photosynthesis.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Chloroplasts
In plants, algae and some bacteria solar energy is used
through photosynthesis to produce carbohydrates
(glucose) and oxygen from carbon dioxide and water.
6CO2 + 6H2O
Carbon dioxide
Water
C6H12O6 + 6O2
Glucose
Oxygen
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Chloroplasts
Stroma: protein-rich fluid where carbohydrates synthesis occur.
Thylakoid membranes: contain chlorophyll and capture solar energy.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Mitochondria
Eukaryotic organisms generates energy (ATP) through the
respiration, using oxygen to release the energy stored in
glucose.
C6H12O6 + 6O2
Glucose
Oxygen
6CO2 + 6H2O
Carbon dioxide
Water
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Mitochondria
Mitochondria are divided into compartments: the outer
membrane, the intermembrane space, the inner
membrane, the cristae and matrix.
Matrix breaks down glucose while cristae produces ATP.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Mitochondrial Diseases
Mutations on Mitochondrial DNA (mtDNA) have been
linked to various diseases such as Alzheimer's disease and
Parkinson's disease.
Mitochondria in a muscular tissue
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cytoskeleton
The
cytoskeleton
microtubules.
consists
of
filaments
and
It maintains the cell's shape and is involved in the transport
of parts of the cell.
The eukaryotic cytoskeleton is composed of actin filaments,
intermediate filaments and microtubules.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Actin filaments
Organized in bundles and networks and play a key
structural role in the cell. As they are flexible and relatively
strong, actin filaments function in cell amoeboid movement
and crawling.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Intermediate filaments
Rope like assemblies of polypeptides having structural
function in the cell nucleus. Intermediate filaments have an
average diameter of 10 nm.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Microtubules
Made of a globular protein called tubulin. They can be
considered as the “motorway of the cell”. Motor proteins
move along them and carry materials inside vesicles
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cilia and flagella
Whiplike
appendages
that
protrude from the cell body of
certain
prokaryotic
and
eukaryotic cells. They typically
serve as sensory organelles or
for locomotion.
Cilia (sing. cilium) are shorter
(2-10μm).
Flagella (sing. flagellum) are
longer (200 μm).
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Communication through cells
Plant cells are joined to one another through microscopic
channels called plasmodesmata, enabling transport and
communication between them.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Communication through cells
Animal cells are joined by anchoring junctions (or
desmosoma), tight junctions and gap junctions.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012