Transcript Cell Structure and Function

CELLS…..
Size
Structure
Organisation
Bacteria prokaryotes ( no nucleus or membrane-bound organelles
Protists - eukaryotes
- true nucleus, membrane bound
organelles
Amoeba
Protists
Euglena (note the
light- sensitive eye spot)
Protists
Paramecium (note the anal
pore)and contractile vacuole
Animal Cell Structure
Animal cells are typical of the eukaryotic
cell, enclosed by a plasma membrane and
containing a membrane-bound nucleus and
organelles.
Unlike the cells of the two other eukaryotic
kingdoms, plants and fungi, animal cells
don't have a cell wall. This feature was lost in
the distant past by the single-celled
organisms that gave rise to Animalia.
Plasma Membrane - All living cells have
a plasma membrane that encloses their
contents. In prokaryotes, the membrane is
the inner layer of protection surrounded
by a rigid cell wall. Eukaryotic animal
cells have only the membrane to contain
and protect their contents. These
membranes also regulate the passage of
molecules in and out of the cells.
Mitochondria - Mitochondria are oblong shaped
organelles that are found in the cytoplasm of every
eukaryotic cell. In the animal cell, they are the
main power generators, converting oxygen and
nutrients into energy.
Ribosomes - All living cells contain ribosomes, tiny
organelles composed of approximately 60 percent RNA
and 40 percent protein.
Ribosomes are
scattered throughout
the cytoplasm and
are the protein
production sites for
the cell.
Endoplasmic Reticulum - The endoplasmic reticulum is
a network of sacs that manufactures, processes, and
transports chemical compounds for use inside and outside
of the cell. It is connected to the double-layered nuclear
envelope, providing a connection between the nucleus and
the cytoplasm
Golgi Apparatus - The Golgi apparatus is the
distribution and shipping department for the cell's
chemical products. It modifies proteins and fats built in
the endoplasmic reticulum and prepares them for export
to the outside of the cell.
Lysosomes - The main function of lysosomes is digestion.
They break down cellular waste products and debris from
outside the cell into simple compounds, which are
transferred to the cytoplasm as new cell-building materials.
Peroxisomes - are found in the cytoplasm, roughly
spherical and bound by a single membrane. Peroxisomes
function to rid the cell of toxic substances, in particular,
hydrogen peroxide -- a common byproduct of cellular
metabolism.
Microfilaments - Microfilaments are solid rods made
of globular proteins called actin. These filaments are
primarily structural in function and are an important
component of the cytoskeleton.
With myosin, they help in cellular contraction and basic
cell movements. They enable a dividing cell to pinch off
into two cells and are involved in amoeboid movements
and in contractions of muscle cells.
Microtubules - These straight, hollow cylinders,
composed of tubulin protein, are found throughout the
cytoplasm of all eukaryotic cells and perform a number
of functions.
They give structure and shape
to a cell, serve as conveyor
belts moving other organelles
through the cytoplasm, are the
major components of cilia and
flagella, and participate in the
formation of spindle fibers
during cell division (mitosis).
Centrioles - Centrioles are self-replicating organelles
made up of nine bundles of microtubules and are found
only in animal cells. They appear to help in organizing
cell division, but aren't essential to the process.
Cilia and Flagella - For single-celled eukaryotes, cilia
and flagella are essential for the locomotion of
individual organisms. In multicellular organisms, cilia
function to move fluid or materials past an immobile
cell as well as moving a cell or group of cells.
Nucleus - The nucleus is a highly specialized
organelle that serves as the information and
administrative center of the cell.
Plant cells
Plant cells have similar cell features
to animal cells except that they
•have cell walls
•have plastids e.g. chloroplasts
•a large vacuole
•lack centrioles
Cell wall Rigid, strong, porous
made of cellulose and other
substances such as
pectin or lignin for strength,
subarin or wax for waterproofing
Plastids - These are organelles responsible for
•starch storage (amyloplasts)
•pigment storage (chromoplasts)
•photosynthesis (chloroplasts).
Chloroplasts - can take in carbon dioxide
and water, and, with the suns energy
and chlorophyll convert these into sugar.
Note the discs ( thylakoids) stacked into
piles (grana) joined by lamellae and
found in the stroma.
Plant vacuoles
-Large, take up the whole centre of a mature plant cell.
•Acts as a fluid skeleton by inflating when full of water
and becoming flaccid when water is low - provides turgor
•Used to store organic compounds and ions
•stores enzymes that recycle “old” molecules
•stores wastes of metabolism
•stores poisons for herbivore defence