Download CELL ORGANNELS 1. Nucleus a. Nucleus Pores Large protein

CELL
ORGANNELS
1. Nucleus
a. Nucleus Pores
 Large protein complexes that cross the nuclear envelope
 Proteins that make up the nuclear pore complex are known as nucleoporins
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About on average 2000 nuclear pore complexes in the nuclear envelope of a vertebrate
cell, but it varies depending on cell type and throughout the life cycle
Nuclear pores allow the transport of water-soluble molecules across the nuclear
envelopeus
The entire nuclear pore complex (NPC) has a diameter of about 120 nm
The diameter of the opening (functional diameter) is about 9 nm wide and its "depth" is
about 200 nm
b. Nucleus Membrane (Nucleus Envelope)
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Encloses the genetic material in eukaryotic cells and serves as the physical barrier,
separating the contents of the nucleus (DNA) from the cystol (cytoplasm)
The nuclear envelope has two membranes, each with the typical unit membrane structure
Each of the two membranes is made up of a lipid bilayer. The outer membrane is
continuous with the rough endoplasmic reticulum (ER) and has ribosomes attached
The inner nuclear membrane is connected to the nuclear lamina, a network of
intermediate filaments composed of various lamin
Lamina acts as a site of attachment for chromosomes and provides structural stability to
the nucleus
Numerous nuclear pores are inserted in the nuclear envelope and facilitate and regulate
the exchange of materials (proteins such as transcription factors, and RNA) between the
nucleus and the cytoplasm
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The outer and inner nuclear membrane are fused at the site of nuclear pore complex
insertion
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2. Cell Membrane
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also called plasma membrane or phospholipid bilayer
contains a wide variety of biological molecules, primarily proteins and
lipids, that are involved in a lot of cellular processes such as cell
adhesion, ion channel conductance and cell signaling
also serves as the attachment point for both the intracellular
cytoskeleton and, if present, the extracellular cell wall
Function
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Surrounds the cytoplasm of a cell and separates the intracellular
components from the extracellular environment
Plays a role in anchoring the cytoskeleton to provide shape to the
cell, and in attaching to the extracellular matrix to help group cells
together in the formation of tissues
Movement of substances across the membrane can either be
passive, occurring without the input of cellular energy, or active,
requiring the cell to expend energy in moving it
Structure
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Is made up mainly of ampthipathic phospholipids which
spontaneously arrange so that the hydrophobic "tail" regions are
shielded from the surrounding polar fluid, causing the more
hydrophilic "head" regions to associate with the cytosolic and
extracellular faces of the resulting bilayer. This forms a continuous,
spherical lipid bilayer
Arrangement of hydrophilic heads and hydrophobic tails of the lipid
bilayer prevent polar solutes (e.g. amino acids, nucleic acids,
carbohydrates, proteins, and ions) from diffusing across the
membrane, but generally allows for the passive diffusion of
hydrophobic molecules
3. Cell Walls
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Located outside the cell membrane and provides these cells with
structural support and protection, and also acts as a filtering
mechanism
Major function of the cell wall is to act as a pressure vessel,
preventing over-expansion when water enters the cell
They are found in plants, bacteria, fungi, algae, and some archaea.
Animals and protozoa do not have cell walls
In plants, the strongest component of the complex cell wall is
cellulose, which is a polymer of glucose. In bacteria, peptidoglycan
forms the cell wall.
In this diagram, the cell wall is the outer green lining.
4. Ribosomes
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are complexes of RNA and protein that are found in all cells
Function
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Protein biosythesis, which is the process of decoding RNA into
protein
5. Endoplasmic Reticulum
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an eukaryotic organelle that forms an interconnected network of
tubules, vesicles (small ball of liquid in a cell), and cisternae within
cells
Function
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protein translation (process in which cells build proteins)
folding and transport of proteins to be used in the cell membrane
(e.g. transmembrane receptors and other integral membrane
proteins)
production and storage of glycogen, steroids, and other
macromolecules
Structure
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an extensive membrane network of cisternae (sac-like structures)
held together by the cytoskeleton
Rough Endoplasmic Reticulum
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studded with ribosome giving it a "rough" appearance
is known as RER
membrane of the RER is continuous with the outer layer of the
nuclear envelope
Smoth Endoplasmic Reticulum
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synthesis of lipids and steroids, metabolism of carbohydrates,
regulation of calcium concentration, drug detoxification, attachment of
receptors on cell membrane proteins, and steroid metabolism
6. Golgi Body (Golgi Apparatus)
Structure
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composed of membrane-bound stacks known as cisternae
cisternae stack contains five functional regions which are the cisGolgi network, cis-Golgi, medial-Golgi, trans-Golgi, and trans-Golgi
network
each region contains different enzymes which carefully go over the
contents depending on where they are supposed to be
Function
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main function is to process and package the marcomolecules such as
proteins and lipids that are synthesized by the cell
it is a major site of carbohydrate synthesis
7. Lysosomes
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organelles that contain digestive enzymes
some biologists say that they are only found in animal cells
sometimes call "suicide-bags" or "suicide-sacs" because of what they
do with autolysis which is destruction of a cell through the action of its
own enzymes
Functions
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the digestion of marcromolecules from phagoctosis (ingestion of
other dying cells or larger extracellular material, like foreign invading
microbes), endocytosis (where receptor proteins are recycled from
the cell surface), and autophagy (wherein old organelles or proteins,
or microbes that have invaded the cytoplasm are delivered to the
lysosome)
digesting foreign bacteria
8. Mitochondria
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are membrane-enclosed organelles found in most eukaryotic cells
ange from 0.5–10 micrometers in diameter
described as "cellular power plants" because they generate most of
the cell's supply of ATP, used as a source of chemical energy
Structure
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contains outer and inner membranes composed of phospholipid
bilayers and proteins
o Outer Membrane
 encloses the organelles
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has a protein-to - phospholipid ratio similar to that of the
eukaryotic plasma membrane (about 1:1 by weight)
 contains large numbers of integral proteins called porins
o Inner Membrane contains four types of proteins:
 (1) Those that perform the redox reactions of oxidative
phosphorylation
 (2) ATP synthase, which generates ATP in the matrix
 (3) Specific transport proteins that regulate metabolite
passage into and out of the matrix
 (4) Protein import machinery.
9. Chloroplast
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are organells found in plant cells and other eukaryotic organisms that
conduct photosynthesis
capture light energy to conserve free energy in the form of ATP
Structure
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contained by an envelope that consists of an inner and an outer
phospholipid membrane
between these two layers is the intermembrane space
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material within the chloroplast is called the stroma
also contains ribosomes, although most of its proteins are encoded
by genes contained in the host cell nucleus, with the protein products
transported to the chloroplast
10. Amyloplast
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are non - pigmented organelles found in plant cells
responsible for the storage of amylopectin, a form of starch, through
the polymerization of glucose
also convert this starch into sugar, for when the plant needs energy
found in underground storage tissues of some plants
11. Vacuole
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membrane-bound organelle which is present in all eukaryotic cells
enclosed compartments which are filled with fluid such as water or
different enzymes, though sometimes they may contain solids
majority of vacuoles are formed through the fusion of multiple
membrane vesicles
Functions
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"Isolating materials that might be harmful or a threat to the cell
Containing waste products
Maintaining internal hydrostatic pressure or turgor within the cell
Maintaining an acidic internal pH
Containing small molecules
Exporting unwanted substances from the cell"
The vacuole is located in the center.
12. Transport Vesicle
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could be any vesicle that transports material around the cell
transport vesicles are usually refered to those vesicles that transport
material from the Endoplasmic Reticulum to the Golgi apparatus or
from one part of the Golgi to another
13. Plasmodesmata
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are microscopic channels which traverse the cells walls of plant cells
and enable transport and communication between them
Structure
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typical plant cell may have between 103 and 105 plasmodesmata
connecting it with adjacent cells
are approximately 50-60nm in diameter at the mid-point and are
constructed of three main layers, the plasma membrane, the
cytoplasmic sleeve, and the desmotubule
similar in structure to the cellular phospholipid bilayers
14. Tight Junction
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are the closely associated areas of two cells whose membranes join
together forming a virtually impermeable barrier to fluid
Structure
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made up of a branching network of sealing strands, each strand
acting independently from the others
Functions
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they hold cells together
they block the movement of intergral membrane proteins between the
apical and basolateral surfaces of the cell which allows the
specialized functions of each surface to be preserved
they prevent the passage of molecules and ions through the space
between cells
15. Peptoglycans
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polymer consisting to sugars and amino acids that make up the cell
wall
peptide chain can be cross-linked to the peptide chain of another
strand forming the 3D mesh-like layer
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common mistake people make is that peptidoglycan gives the cell its
shape; however, the peptidoglycan helps maintain the structure of the
cell, it is actually the MreB protein (protein found in bacteria that has
been identified as a homologue of actin) that directs cell shape
Function
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"main purpose of peptidoglycan is to maintain bacterial shape and to
counteract the internal pressure of the bacterial cell"
Structure
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peptidoglycan layer in the bacterial cell wall is a crystal lattice
structure formed from linear chains of two alternating amino sugars
16. Glycoproteins
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proteins that contain oligosaccharide chains covalently attached to
their polypeptide side-chains
process is known as glycosylation
17. Cytoskeleton
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cellular "skeleton" contained in the cytoplasm in eukaryotic cells
(animal and plant)
Function
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maintains cell shape, protects the cell, enables cellular motion (using
structures such as flagella, cilia, and lamellipodia), and plays
important roles in both intracellular transport (the movement of
vesicles and organelles, for example) and cellular division
o Microtubules
 hollow cylinders about 25 nm in diameter, usually made
up of 13 protofilaments
18. Cilia and Flagella
Function
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to move a cell or group of cells or to help transport fluid or materials
past them
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respiratory tract in humans is lined with cilia that keep inhaled dust,
smog, and potentially harmful microorganisms from entering the
lungs
generate water currents to carry food and oxygen past the gills of
clams and transport food through the digestive systems of snails