Download The Cell PPT File

THE CELL
STRUCTURE
AND
FUNCTION
MISS PANZICH
2A/B Human Bio
Cells  tissues  organs  systems
Our cells are found everywhere! Imagine the cell like a
factory containing many parts that have different functions.
These parts are:
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Nucleus
Cell membrane
Cytoplasm
Mitochondria
Endoplasmic Reticulum
Golgi Apparatus
Ribosomes
Vacuole
Lysosome
Cytoskeleton
YOU WILL NEED TO KNOW AND LABEL
ALL OF THESE ORGANELLES AND KNOW
THEIR FUNTIONS (WHAT THEY DO)!
Organelles
• Organelles = the cell structures that are
specialised for particular functions.
Cell membrane
• double layer made up of lipid
molecules (phospholipids and
cholesterol) + various proteins
• A semi-permeable membrane that
allows materials to pass
– It is selective as to what
materials will go through it (it will
depend on the material)
– and by what process.
• Materials pass through the
membrane in a number of different
ways:
– Passive transport (diffusion,
osmosis),
– Active transport (phagocytosis,
pinocytosis)
Cytoplasm
• The material in which the cell
contents are suspended
• fills the space between the nucleus
and the cell membrane
• 75 –90% water
• Substances are either
– Dissolved: sugars and inorganic
materials;
– Suspended: proteins and lipids.
• Protoplasm refer to the whole
contents of the cell(cytoplasm and
nucleus).
Nucleus
• Separated from the cytoplasm
by nuclear membrane (double
layer membrane with numerous
gaps - nuclear pores).
• contains DNA - which controls
the type of protein a cell can
make and the chemical
reactions that occur in the cell
(controls the cell activity)
• When DNA is not duplicating, it
is found as chromatin. In a
dividing cell it found as
chromosomes.
Nucleolus
• Within the nucleus is an
area called the nucleolus.
• Nucleolus mainly
composed of RNA
(ribonucleic acid) which
plays a vital role in protein
synthesis.
• Both chromatin and
nucleolus are suspended in
the nucleoplasm.
Ribosomes
• small spherical
organelles.
• They could occur free in
the cytoplasm or bound
to endoplasmic
reticulum membrane.
• Make proteins via
protein synthesis:
amino acids are joined
together to form
proteins in a sequence
determined by DNA.
(i.e. take information
from the DNA and use it
to make proteins)
Mitochondria:
• spherical or elongated in
shape.
• Each has a double
membrane (outer-smooth
and inner-folded)
• Known as the
‘powerhouse’ of the cell
• Chemical reactions take
place on the inner
surface of the
mitochondrion = site of
cellular respiration
whereby it produces
energy (ATP) for the
cell
Endoplasmic Reticulum
• Pair of parallel membranes
form a network of
channels.
• endoplasmic reticulum
provide a surface for
chemical reactions,
while the inner channels
are for storing or
transporting molecules.
ROUGH ER (granular): ribosome's
attached
SMOOTH ER (agranular): no
ribosome's
STORE, TRANSPORT
SA for REACTIONS
Golgi Apparatus
• flattened membranous bags
stacked one upon the other. Ends
are often expanded.
• It modifies proteins and
packages them for
secretion from the cell.
• It may add sugar, phosphate,
sulphate, fatty acid etc… to the
protein made at the ribosome.
• At the edge of the Golgi apparatus
the membrane pinches off to form
a vesicle carrying the modified
protein for transport outside the
cell.
Centrioles
• pair of cylindrical structures
close to the nucleus.
• made up of a ring of
microtubules triplets that
are perpendicular to each
other.
• The pair of centrioles are
also perpendicular to each
other.
• They play a vital role in
cell division (mitosis)
Lysosome
• They contain digestive
enzymes capable of
breaking down lipids,
proteins, nucleic acids,
and some
carbohydrates.
• They also digest wornout organelles.
• When particles enter the
cell in a vesicle, a
lysosome fuses with the
vesicle and digests all
the contents.
Cytoskeleton
• framework of protein
fibres that gives the cell
its shape.
• Microtubules - hollow
rods that fix organelles
or move them
• Microfilaments - move
materials around
cytoplasm/move whole
cell.
Cilia and flagella
• some cells have fine
projections that move
materials past the cell
or move the whole cell
itself.
• If projections are very fine
and small they are called
cilia (tiny hairs).
• If projections are longer
and only one or two are
found they’re called
flagella. (e.g. Sperm)
Inclusions - extras
• Are not part of the cell structure (e.g. melanin in
skin / haemoglobin in RBC)
• If the inclusion is a liquid that is capable of mixing
with the cytoplasm, then it is surrounded by a
membrane and known as a vacuole. Vacuoles are
like a storage compartment. Rare in animal cells,
more common in plant cells