Download Cell organelles

Cell organelles
Nucleus
• Largest organelle in eukaryotic cells
• Control center of the cell
• Contains DNA scattered throughout as
Chromatin
• Consists of:
• 1. 2 membranes surrounding the nucleus: each
a phospholipid bilayer
– Outer bilayer continues into the endoplasmic
reticulum
– Inner bilayer defines the nucleus
• NUCLEAR PORES are found on the membrane
– regulates movements of material between nucleus and
cytosol
• 2. Nucleolus
• Condensed area of chromatin in the nucleus
• Synthesizes:
– Ribosomal RNA (rRNA)
– Ribosomal Protein/subunits
• **These travel through the nuclear pores into the
cytosol.
Chromosomes:
• Linear structures
composed of DNA
molecules
• Found in nuclei of
eukaryotic cells
• Total DNA in the
chromosomes of an
organism is referred
to as its genome
• DNA is wound
around Proteins called
histones. Histones
help keep the DNA
organized.
• A series of histones
and DNA is called a
nucleosomes.
• A Chromosome is
composed of many
nucleosomes.
• Each chromosome
consists of 2 identical
sister Chromatids
(Each consisting of
one double-stranded
DNA molecule)
• Chromatids are
attached at a specific
region called a
centromere.
• Note: When cell division is not happening,
chromosomes are uncoiled and may be
called chromatin.
Cytoplasm:
• Gel-like material
• Found between the nucleus and cell membrane
• Consists:
–
–
–
–
Mostly of water
Many organelles
Protein-rich
Enzymes
• Creates the chemical environment in which the
other cell structures function
Ribosomes:
• Location:
• Free ribosomes in the cytoplasm are
attached to cytoskeletal filaments
• Ribosomes can also be attached to the
endoplasmic reticulum making it ‘Rough’
Endoplasmic reticulum.
• Structure:
• 2 Subunits
– 1 large subunit (50S)
– 1 small subunit (30S)
Total of 80S
**In prokaryotes, ribosomes contain 2 subunits but only
add up to 70S
• Both composed of
– Ribosomal RNA and
– Protein
• Function:
• Translate RNA (coming from the nucleus)
into protein. (Protein synthesis)
• Ribosomes attached to the Endoplasmic
Reticulum (ER) produce proteins that
move into the ER.
Endoplasmic Reticulum (ER)
• Membrane bound network of interconnected vesicles
• Enzymes are found embedded on the surface of the ER.
• Materials synthesized here include:
– Membrane phospholipids and cellular lipids
- Sex hormones (testosterone and estrogen) (In Specialized cells
ex. testicular cells produce testosterone)
- Production of Insulin (ex. liver)
Other functions at this site include:
- Storage of calcium ions until they are needed in muscle
contractions.
- Transporation of lipids to different parts of the cell.
• The ER keeps these materials from the rest of the cell. If
not, they may have harmful effects to the cell.
• There are 2 types:
• 1. Rough Endoplasmic Reticulum (RER)
• Ribosomes are attached to the ER – ‘Rough’
These ribosomes synthesize:
– Proteins
– Digestive Enzymes
• As they are synthesized they move into the ER to
become modified
• 2. Smooth ER
• Synthesis of :
– Membrane lipids (fatty acids and
phospholilpids)
– Membrane Proteins
• Once synthesized and modified in the ER,
the materials are carried to the golgi
complex through vesicles
• Vesicles are formed from portions of
membrane from the ER budding off to
form a small membrane bound transport
‘vehicle’.
Golgi Apparatus or Golgi
Complex
• Location and structure:
• Series of flattened saucer shaped sacs
• Located near the nucleus
Function:
• Vesicles transfers
macromolecules from the
ER to one golgi complex
sac. (The Cis side)
• Golgi complex completes
the processing of these
molecules making them
‘functional’.
• They also get sorted,
packaged and transported
out of the complex by a
second set of transport
vesicles. (On the opposite
side called the Trans side)
• Vesicles then travel to the
cell membrane and
secrete their contents into
the extracellular fluid
Lysosomes:
• Structure:
– Special vesicle formed from the golgi complex
Function:
• Transports cellular digestive enzymes safely
through the cytoplasm
• Degrades:
– Worn out cellular components
– Foreign molecules
• I.e.
• Contains enzymes such as:
• 1. Nuclease: Degrades RNA & DNA into
nucleotides
• 2. Proteases: Degrades Proteins and
peptides
• 3. Phosphatases: Remove phosphate
groups from nucleotides, phospholipids
Tay-Sachs Disease
• Commonly found in the Jewish Population
• Non-Jewish people are 100 times less likely to
have the Tay-Sachs gene
• Children Born with Tay-sachs:
–
–
–
–
Appear normal at birth
Central nervous system begins to deteriorate rapidly
Motor development slows down
Most children that have Tay Sachs die by the age of 2
or 3 years.
How does it occur?
• A recessive gene is inherited from both parents
• Lacks the gene to produce a lysosomal enzyme
that breaks down a certain glycolipid called
gangliosides found in nerve cells
• Nerve cells are therefore, greatly enlarged with
swollen lipid-filled lysosomes
• Nerve cells are eventually destroyed
Cell Organelles Continued
Mitochondria
FYI:
• Evidence shows, mitochondria evolved from
bacteria that were endocytosed into ancestral
cells containing a eukaryotic nucleus.
• Over time,
• Some Genetic Material transferred to the nucleus
and some stayed in the mitochondria
***Ribosomes found here are of the 70S
• Function:
• Responsible for producing energy for the cell
• Transforming energy from macromolecules into
ATP (Adenosine triphosphate)
• ‘Power Plant’ of the cell
• They replicate themselves by dividing down the
middle to create 2 daughter mitochondria
• Structure:
• Contains:
• 1. Two membranes:
– Outer Membrane
•
•
•
Composed of lipid and protein
Permeable, allowing molecules to pass
through
Separates the chemical reactions occurring
here from the rest of the cytoplasm
– Inner membrane
•
•
•
Composed of lipid and protein
Less permeable
The inner membrane folds many times to
create CRISTAE
– Cristae increases the surface area for enzymes to
produce ATP THEREFORE,
– Larger surface area = more chemical Reaction (ATP
production)
• 2. Their own set of Ribosomes
• 3. Circular DNA
• DID YOU KNOW?
• White Fat Tissue
•
Stores fat
•
Few mitochondria
•
More commonly found in adult humans
• Brown Fat Tissue
•
Colour is due to presence of many
mitochondria
•
Specialized for the generation of heat
(Thermogenesis)
• The inner-membrane protein thermogenin
is responsible for converting energy into
heat
• Seen commonly in :
– Cold adapted animals (ie. Rats, snakes)
– Hibernating mammals (i.e. Bear)
– Human infants (Thermogenesis is vital for
newborns to survive)
Chloroplast:
• Has the same evolutionary line as
mitochondria
• Location:
• Characteristic organelles in plants and
green algae
• Structure and Function:
• Contains its own ribosomes and DNA
• Surrounded by 2 membranes: (outer and inner
membrane)
• Internal system of membrane bound sacs called
Thylakoids
– Thylakoids are flattened to form disks
– Contains the pigment chlorophyll (gives green colour
and absorbs solar energy to carry out photosynthesis)
•
– Thylakoids are:
– Grouped in stacks called Grana
– These stacks (or Grana) are embedded in the
matrix called the Stroma
Intermediate Filaments
Cytoskeleton
• Internal movements are essential to the
growth and differentiation of cells
• All cell movements
•
1. Require fuel – ATP and
•
2. Proteins that convert the energy
stored in ATP in to motion
• Structure and Function:
•
•
•
•
System of fibers found in the cystoplasm
Extending from the nucleus to the cell membrane
Supports the cell membrane
Forms tracks on which organelles and other
elements move throughout the cytosol
• Can Disassemble and Reassemble in seconds or
minutes
• Consists of 3 types of cytosolic fibers:
• 1. Actin Filaments
– Supports the cell membrane
– Determines shape of cell
– Ability to contract (I.e. found in muscle cells)
• 2. Intermediate filaments
– Anchor organelles in different areas of the cell
– Supports nuclear envelope and cell membrane
•
3. Microtubules
– Act like ‘tracks’ where organelles can move
along
Cilia and Flagella
• Structure:
• Flexible membrane extensions of the cell
• Both consist of a bundle of microtubules
• Cells either possess
• 1 or 2 single flagellum or
• Many short cilia
• Function:
1. Used to move certain cells by propelling them
with a beating action
– (Speed of about 1mm/s)
2. Also used to bring in Food Particles
• I.e. Respiratory Passages are lined with many
short cilia that move out particles that collect in
the mucus secretions of the tissues.
Cell Wall
• Found in
•
Plants
•
Fungal Cells
•
Some single celled eukaryotes
• Structure:
• Consists of Celulose fibres
• Found outside the plasma membrane
• Function:
• Adds strength and rigidity to the cell
• Prevents cells from bursting in hypotonic
environments
• Prevents cells from Shrinking in
hypertonic solutions
• Other chemicals are found in cell walls…..
•
Lignin – Strength and rigidity (I.e.
Woody trees)
•
Waxes – Prevents plant tissues and
proteins from dying out (I.e. Pine needles)