Cell Organelles
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Nucleus
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Function
Nucleus- Carries the DNA
code for amino acid
sequences (which forms
proteins)
Nuclear envelopeSeparates the genetic
material from the
cytoplasm
Nuclear pore- Allows
transport of mRNA
Nucleolus- Synthesis of
ribosomes
Ribosomes
Structure
• Consists of 2 subunits
made from ribosomal
RNA (rRNA) and protein
– Large subunit
– Small subunit
• Can be free or attached to
rough endoplasmic
reticulum (RER)
Function
Protein synthesis
Rough Endoplasmic reticulum
Structure
• Forms a system of flattened
sacs (cisternae) which are
continuous with the nuclear
membrane and may link to
the Golgi apparatus
• RER has ribosomes attached
Function
• Transports proteins which are
synthesised by the ribosomes
attached.
Fact
Cells which secrete large
amounts of enzymes
have a larger amount of
RER
Smooth Endoplasmic reticulum
Structure
• Forms a system of
flattened sacs (cisternae)
which are continuous
with the nuclear
membrane and may link
to the Golgi apparatus
• Has NO ribosomes
attached
Function
• The synthesis and
transport of lipids
Golgi Body/ apparatus
Structure
• Is a similar structure to ER
however is more compact.
• Surrounded by vesicles.
Functions
• Vesicles transport proteins to the
Golgi body to be modified and
packaged
• The modified proteins are then
packaged into vesicles to be
transport around the cell or out of
the cell (exocytosis)
Other functions
• Transporting and storing lipids
• Forming lysosomes
Mitochondria
Structure
• Rod shaped and 1-10μm diameter
• Has a double membrane, the inner and
outer membranes
• The membranes are separated by a narrow
fluid filled inter membrane space.
• The inner membrane is folded to form
structures called cristae
• The interior of the mitochondrion is called
the matrix and contains enzymes
• Contains DNA and ribosomes
Function
• The site of aerobic respiration to release
energy in the form of ATP
• The cristae increase the surface area on
which part of the respiratory process takes
place
Fact
Cells with high metabolic
activity contain many
mitochondria
Animals
Vacuoles (vesicles)
Structure
• Small membrane bound
organelle
Function
• Act as a contractile vacuole to
maintain osmotic pressure.
Plants
Structure
• Large membrane bound organelle
surrounded by a tonoplast
Function
• Storage of ions and organic
molecules e.g. proteins and
maintaining osmotic pressure
Centrioles
Structure
• Consists of two hollow cylinders
positioned at right angles to one
another
Function
• Are used in spindle formation
(microtubles) in cell division.
Fact
Found in all animal cells
and most protoctists BUT
are NOT found in the
cells of higher plants
Lysosomes
Structure
• 1.0 um in diameter
• Small vacuoles formed when small
portions of the Golgi body are
pinched off.
Function
• They contain and isolate digestive
enzymes
• They can release these enzymes
and destroy organelles
• Digestion of material which has
been taken into the cell
• e.g white blood cells engulf
bacteria by phagocytosis and the
lysosomes are used in the
digestion of the bacterium.
Chloroplast
Structure
•2-10um in diameter and 1 um thick
•Have a double membrane
•The interior is made up of a fluid called
stroma, ribosomes, lipids , circular DNA
and starch granules.
•In addition there are thylakoidsflattened sacs, these form stacks which
are called granum. Each granum consists
of between 2-100 thylakoids. Between
the grana the thylaskoids form lamellae
Function
•Site of photosynthesis
•The thylakoids contain photosynthetic
pigments such as chlorophyll
Cellulose Cell Wall
Structure
• Made of cellulose
microfibrils in a
polysaccharide matrix
Function
• To provide strength and
support
• Freely permeable to
water
Plasmodesmata
Structure
• A narrow thread of
cytoplasm that passes
through the cell walls of
adjacent plant cells
Function
• Exchange of large organic
materials via cytoplasmic
streaming
• Allows communication
between adjacent cells