Download The Cell and Organelles

The Cell and Organelles
‚
‚
‚
A living thing capable of a separate existence is called an organism.
Organisms are made up of small sub-units called cells.
Some organisms consist of only one cell ( unicellular), while others consist of many cells
(multi-cellular)
A cell is like a complex machine that must perform a number of activities on a constant basis.
These activities include:
‚
Take in raw materials
‚
Use energy
‚
Grow and reproduce
‚
Respond and adapt to the environment
‚
Recycle and repair damaged parts
‚
Get rid of wastes
‚
Manufacture products
‚
Transport manufactured products
‚
Control all the above activities
A multi-cellular organism has specialized parts, called organs, to carry out these activities. A
one-celled organism may have specialized parts to carry them out. These parts are called
ORGANELLES.
Not all one-celled organisms have organelles. We can divide all cells up into two categories:
Prokaryotic (primitive cells)
Eukaryotic (true cells)
‚
Prokaryotic cells do not have a nucleus or any other organelles bound by a membrane.
Examples of prokaryotic cells include all types of bacteria
‚
Eukaryotic cells do have a nucleus and other membrane-bound organelles. Cells of
multi-cellular organisms are eukaryotic, as well as any one-celled organisms that are not
bacteria.
Eukaryotic cells may look very different but they are made up of mostly the same basic parts:
1.
Cell membrane - the outer boundary of the cell
2.
Nucleus - the control center of the cell
3.
Cytoplasm - the material in between the cell membrane and the nucleus;
other organelles are found here
1
FUNCTIONS OF CELL ORGANELLES:
1.
2.
3.
Cell membrane
‚
‚
‚
‚
‚
‚
‚
also called the plasma membrane
outer skin of the cell
semi-permeable ( only lets certain materials pass through its pores)
maintains homeostasis
made of phospholipids and proteins
thin and delicate
found in all cells
‚
‚
‚
‚
only found in plant cells, not in animal cells
thick rigid layer outside cell membrane
often made of cellulose
has large pores
‚
‚
‚
‚
jelly-like material inside cell membrane
where all other organelles are found
contains dissolved substances
where reactions take place
Cell wall
Cytoplasm
4.
Nucleus (plural nuclei)
‚
control center of the cell
‚
if removed the cell would die
‚
contains and protects the DNA (genetic material)
‚
surrounded by a nuclear membrane which is semi-permeable
‚
largest organelle, visible with light microscope
‚
may contain one or more nucleoli
5.
Nucleolus (plural nucleoli)
‚
found inside the nucleus
‚
made of genetic material
‚
ribosomes are produced here
‚
may be more than one present in the nucleus
6.
Endoplasmic Reticulum (ER)
‚
form a system of fluid-filled channels
‚
transports materials between cytoplasm and nucleus
‚
provides large surface area for reactions
‚
two types, rough ER (rough because ribosomes are located on the
surface) and smooth ER (has no ribosomes on the surface)
2
7.
Ribosomes
‚
‚
‚
‚
build proteins from amino acids using directions from the nucleus
(called protein synthesis)
can be found on ER, or scattered throughout the cytoplasm
cell may contain thousands
have no membrane envelope
8.
Golgi bodies ( also called Golgi apparatus)
‚
look like stacks of flattened sacs
‚
process, package, and store products to be released from the cell
‚
produce lysosomes
‚
act like a warehouse for the cell
‚
animal cells have one, plant cells have hundreds
9.
Lysosomes
‚
‚
‚
‚
‚
spherical, single membrane spheres
contain enzymes to break matter down into smaller bits
used for intracellular digestion
in white blood cells they defend against diseases by destroying
invaders
also used to break down worn out organelles (also tails of tadpoles)
10.
Mitochondria (singular- mitochondrion)
‚
round, slipper-shaped
‚
release energy in foods through cellular respiration
‚
called the powerhouse of the cell
‚
number would depend on function of cell ( usually 300-800)
‚
muscle cells would have many because of the need for more energy
‚
have a double membrane, provides greater surface area
‚
middle section is called cristae
‚
has its own genetic material ( DNA) and can duplicate itself
11.
Vacuoles
12.
‚
‚
‚
‚
‚
‚
fluid-filled
used for storage
plant cells have one large central vacuole filled with sap
helps to support in plant cells
other things stored may include toxins
animals may have specialized vacuoles to digest food or small ones
to pump out water
‚
‚
forms almost like a skeleton for the cell, to give it shape
used to make centrioles
Microtubules
3
13.
Centrioles
‚
‚
‚
‚
14.
15.
16.
17.
ring of 9 groups of 3 microtubules
found only in animal cells
a pair is located near the nucleus at 90o angles to each other
involved in cell division
Microfilaments
‚
‚
‚
thread-like strands
associated with intracellular movement
provides stabilization and a tract for organelle movement
‚
‚
hairlike organelles covering the cell surface
involved in movement of the entire cell
‚
‚
‚
longer than cilia
only a few or just one in cell
used for movement of entire cell, example the tail of a sperm cell
‚
‚
‚
found only in green plant cells and photosynthetic protists
the pigment chlorophyll gives it the green colour
photosynthesis occurs here
Cilia
Flagella
Chloroplasts
SUMMARY
All the cell organelles mentioned are found in both plant and animal cells
EXCEPT:
‚
‚
‚
‚
Only plant cells have cell walls
Only green plants have chloroplasts
Plant cells have one large central vacuole
Only animal cells have centrioles
4