good for medical

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Cell organelles and
functions
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learning outcomes
Draw and label a plant and an animal cell
Compare and contrast prokaryotic and eukaryotic cellular organelles
Review the structure of membranes and explain the significance of
different creating intracellular membranous compartments where
different cellular functions can take place.
Learn the structure and functions of each of the following,and
where applicable relate to specific problems / diseases (Nucleus,
Endoplasmic reticulum (smooth and rough), Golgi apparatus &
vesicles, Lysosomes, Peroxisomes, Mitochondria)
Explain the coordination of functions of several organelles that
bring about cellular functions such as secretion and flow of
genetic information from DNA to protein
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Cell Organelle
• An organelle is a membrane-bound
structure that carries out specific
activities for the cell.
• “Little Organs”
• Found in the cytosol (liquid part of cell)
• Compartments (ORGANELLES) provide different
local environments (pH, etc.)
Cell Organelles
 Nucleus
 Nucleoli
 Mitochondria
 Ribosomes
 Endoplasmic Reticulum
 Smooth Endoplasmic Reticulum
 Rough Endoplasmic Reticulum
 Golgi Apparatus (Golgi body or Golgi Complex)
 Lysosomes
 Peroxisomes
 Secretory Vesicles
 Cell Cytoskeleton
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THE NUCLEUS: genetic control of the cell
• The nucleus is the “chief executive” of the
cell.
• Genes in the nucleus store information
necessary to produce proteins.
• Proteins do most of the work of the cell.
• Cells with more than one nucleus include
muscle cells and liver cells
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Functions (general)
• Manufacturing, processing, and shipping of molecules
to appropriate destination: DNA, proteins, carbohydrates,
lipids
• Breakdown of molecules: large structures, lipids,
detoxification of certain substances
• Energy processing: forming cellular energy form
• Structural support, movement, and communication
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Structure and Function of the Nucleus
• The nucleus is bordered by a double membrane
called the nuclear envelope.
• Pores in the envelope allow materials to move
between the nucleus and cytoplasm.
• The nucleus contains a nucleolus where ribosomes
are made.
Ribosomes Chromatin Nucleolus Pore
Nuclear
envelope
Surface of nuclear envelope Nuclear pores
TEM
TEM
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• Stored in the nucleus are long DNA
molecules and associated proteins that form
fibers called chromatin.
• Each long chromatin fiber constitutes one
chromosome.
• The number of chromosomes in a cell
depends on the species.
DNA molecule
Chromosome
Proteins
Chromatin
fiber
Figure 4.9
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Ribosomes
• Ribosomes are responsible for protein synthesis
• Ribosome components are made in the nucleolus
but assembled in the cytoplasm.
• Ribosomes are small particles of RNA and protein
found throughout the cytoplasm in all cells.
• Ribosomes produce proteins by following coded
instructions that come from DNA - like a small
machine in a factory, turning out proteins on orders
that come from its DNA “boss.”
Ribosome
Protein
mRNA
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• Ribosomes may assemble proteins, while:
 Suspended in the fluid of the cytoplasm
or
 Attached to the outside of an organelle
called the endoplasmic reticulum
Ribosomes in
cytoplasm
Ribosomes attached
to endoplasmic
reticulum
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• Free: float through cytoplasm (make
proteins for use inside that cell)
• Bound: attached to Rough ER (make
proteins to be transported out of the
cell)
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How DNA Directs Protein Production
• DNA directs protein production by transferring its
coded information into messenger RNA (mRNA).
• Messenger RNA exits the nucleus through pores in
the nuclear envelope.
• A ribosome moves along the mRNA translating the
genetic message into a protein with a specific
amino acid sequence.
Synthesis of
mRNA in the
nucleus
Nucleus
DNA
mRNA
Cytoplasm
Figure 4.12-1
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Synthesis of
mRNA in the
nucleus
Nucleus
DNA
mRNA
Cytoplasm
mRNA
Movement of
mRNA into
cytoplasm
via
nuclear pore
Figure 4.12-2
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Synthesis of
mRNA in the
nucleus
Nucleus
DNA
mRNA
Cytoplasm
mRNA
Movement of
mRNA into
cytoplasm
via
nuclear pore
Ribosome
Protein
Synthesis of
protein in the
cytoplasm
Figure 4.12-3
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The Endoplasmic Reticulum
• Made up of membranous tubules and cisternae
(sacs)
• The “highway” of the cell that moves materials
around to other parts
• Is composed of smooth and rough ER
• The endoplasmic reticulum is where lipid
components of the cell membrane are
assembled, along with proteins and other
materials that are exported from the cell.
Nuclear
envelope
Smooth ER
Rough ER
Ribosomes
Ribosomes
TEM
Figure 4.13
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Rough ER
• The “rough” in the rough ER is due to
ribosomes that stud the outside of the ER
membrane.
• These ribosomes produce membrane
proteins and secretory proteins.
• After the rough ER synthesizes a molecule,
it packages the molecule into transport
vesicles.
Proteins are
often modified in
the ER.
Secretory
proteins depart in
transport vesicles.
Vesicles bud off
from the ER.
A ribosome
links amino acids
into a
polypeptide.
Ribosome
Transport
vesicle
Polypeptide
Protein
Rough ER
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The smooth ER
• Lacks surface ribosomes
• Produces lipids
• Helps liver cells detoxify circulating drugs
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The Golgi apparatus / complex
• Golgi apppartaus is made up of approx 4- 8 cisternae .
• Usually equally spaced in stark separated from each other
by thin layer of intercisternal cytoplasm.
• Golgi complex has a distinct polarity ,the two poles are cis
and transface responsible for receiving and shipping
departments.
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• Works in partnership with the
ER
• Receives, refines, stores, and
distributes chemical products
of the cell
• The Golgi apparatus modifies,
sorts, and packages proteins
and other materials from the
endoplasmic reticulum for
storage in the cell or
release outside the cell.
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• Two networks: the Cis Golgi Network( CGN) and Trans Golgi
Network (TGN) are made up of outermost cisternae at the cis and
trans face.
• Vesicles containing proteins from the endoplasmic reticulum
(ER) merge with the CGN and allowing protein to enter Golgi
complex
• As CGN receives protein from the ER it begins modification moving
along membrane to membrane towards the TGN .
• At Other end of Golgi complex, newly modified protein arrives at the
TGN where it is send off to different parts of the cell via transport
vesicles
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Lysosomes
• Lysosomes contain about 40 varieties of digestive enzymes called
with hydrolases. The lysosomal enzymes are classified into six
main types namely
 Proteases, which digest proteins.
 Lipase, which digests lipids.
 Amylase, which digest carbohydrates (e.g., sugars).
 Nucleases, which digest nucleic acids.
 phosphoric acid monoesters.
• They are most abundant in cells eg liver cells pancreatic cells,
kidney cells, macrophages etc
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Secretory vesicle
• In secretory cells, the bulk of newly synthesized membrane
and membrane-associated proteins may be devoted to
generation of the secretory vesicles, sometimes referred to
as secretory or dense core granules.
• Secretory vesicles mediate the vesicular transport of cargo -
proteins, peptides or neurotransmitters - from an organelle to
specific sites at the cell membrane, where it docks and fuses
to release its content .
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Secretory vesicle
• Actively transported to selected subcellular domains for
extracellular delivery in response to a specific extracellular
signal.
• Neurons in particular devote a large fraction of their
biosynthetic activity to the synthesis and assembly of
secretory vesicles.
• The extensive nissl substance (mostly RER) and large
Golgi complexes seen in neurons reflect this biosynthetic
activity, and both structures were first described in neurons.
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Plasma membrane Digestive enzymes
Lysosome
Digestion
Food vacuole
(a) Lysosome digesting food
Figure 4.16a
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Lysosome
Digestion
(b) Lysosome breaking down the molecules of damaged organelles
Vesicle containing
damaged organelle
Figure 4.16b
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• Lysosomes can also
 Destroy harmful bacteria
 Break down damaged organelles
• the cell’s “cleanup crew” or "suicide bags" or "suicide
sacs“..
• Tay Sachs may result if there is defective gene
affecting one of the enzymes
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Peroxisomes
• Occur in all eukaryotic cells
• Contain enzymes that transfer hydrogen from
various substances to oxygen, producing H2O2 as a
byproduct:
Rh2+O2 R + H2O2
• Various functions:
 Break fatty acids down into smaller
molecules for cellular respiration
 Detoxify alcohol in liver
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Mitochondria
• Produces energy ATP chemical reactions –
cellular respiration
• Converts glucose into ATP
• Cristae – inner membrane
Matrix – inner membrane space
• contains oxidative enzymes
and dissolved enzymes in matrix that work
in association with each other to produce
ATP
Contains DNA and are self-replicating
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