cell_organelles

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Cell Organelles
Chapter 7, page 174
Modified from an
original PPT of
Beauchemin 2006
Introduction to Cells
Inside a Cell
What is a cell?
A cell is a collection of living matter
enclosed by a barrier that separates the
cell from its surroundings.
The cell is the basic unit of all forms of life.
Remember the three parts to cell theory:
1. All living organisms are composed of one
or more cells.
2. The cell is the basic unit of structure,
function in all organisms.
3. All cells come from preexisting, living cells.
(An organism is a living thing.)
There are two main categories
of cells:
Prokaryote (prokaryotic cells)
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



Bacteria
Have no membrane-bound nucleus
Nucleic acid is usually found in “loops” in the
cytoplasm
Usually smaller than eukaryotes
Have fewer organelles than eukaryotes
Eukaryotes (eukaryotic cells)



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Larger
Have a membrane-bound nucleus where DNA
is located
More organelles
All organisms except bacteria are eukaryotes
Homework



Read pages 174 to 181
Answer questions 1 to 4 on page 181
Be able to label both a plant and an animal cell
(use your handouts for practice)
Cell Organelles in
Eukaryotes
Organelle means
“little organ”
Cytoplasm is
everything inside the
cell membrane,
except the nucleus
Cytosol or the intracellular fluid is the
liquid found inside cells.
Cell Membrane
The boundary of the cell
Cell Membrane
Surrounds the cytoplasm and holds the
shape of the cell
Protects the cell
Allows certain material to pass through
(selectively permeable)
Phospholipid Bilayer
For more information on the cell membrane,
please refer to your handout.
Cell Wall
A tough, flexible but
sometimes fairly
rigid layer that
surrounds some
types of cells.
Located outside the
cell membrane
Provides structural support and protection,
sometimes preventing the cell from
bursting from water entering the cell.
Found in plants, some bacteria, fungi, and
algae.
Nucleus
Control center of the
cell
Contains DNA which
contains the coded
instructions for
making proteins which
are the molecules that
do “everything”.
Nucleus continued
Surrounded by a
double membrane
called the nuclear
membrane or
nuclear envelope.
Nuclear envelope
has thousands of
pores which allow
material to move into
and out of the
nucleus.
Usually one per cell
(red blood cells do not have nuclei.)
Usually the easiest organelle to see under a
microscope
Chromatin in the Nucleus
The thread-like material
in the nucleus is called
chromatin which is
DNA wrapped around
protein.
Usually looks like this
but as a cell prepares to
divide, chromatin
condenses to form
chromosomes.
Chromosomes
Nucleolus
Small dense region
within the nucleus
The assembly of
ribosomes begins here
Ribosome
Proteins are assembled
by ribosomes, following
instructions from DNA.
Ribosomes are found
attached to rough
endoplasmic reticulum
or floating free in
cytoplasm
Produced in a part of
the nucleus called the
nucleolus
Endoplasmic Reticulum
(ER)
The internal membrane
system of the cell
Connected to the nuclear
membrane
Assembles lipid
components of the cell
membrane, proteins and
other materials for export
from the cell.
Rough Endoplasmic Reticulum
Studded with
ribosomes
Proteins that are being
synthesized for export
from the cell and
proteins that are to be
used in the cell
membrane are made
on the these
ribosomes.
Proteins synthesized on the ribosomes
on the RER enter the RER where they
may be chemically modified.
Smooth Endoplasmic Reticulum
No ribosomes
Synthesizes lipids
Contains many
enzymes which
have specialized
jobs
Makes membrane
lipids; carries
proteins; detoxifies
drugs
Golgi Apparatus
Looks like a stack of
plates
Modifies, sorts, and
packages proteins
and other materials
made in the ER for
storage in the cell or
secretion from the
cell.
Golgi Apparatus (continued)
Vesicles which
contain the
materials modified
by the Golgi
Apparatus pinch
off the ends.
Lysosomes
Clean-up crew
(sometimes called
cannibals)
Membrane-bound
sacks filled with
enzymes that break
down lipids,
carbohydrates and
proteins from food
into smaller
molecules that the
cell can use.
Which organelles do lysosomes work
with?
Lysosomes (continued)
Also break down
organelles that
have outlived their
usefulness for
disposal.
Vacuoles
Storage container for
water, food, enzymes,
wastes, pigments, etc.
Large central vacuole
in plant cells
Many small vacuoles
in animal cells
What type of microscope may have
been used to take this picture?
Contractile
Vacuole
Mitochondria
mitochondrion)
“Powerhouse of the
cell”
Convert the chemical
energy from food into
energy that can be
used by the cell.
Enclosed by two
membranes---an outer
one and another that
is folded up inside the
mitochondrion
(singular =
Mitochondria (continued)
Cellular respiration occurs here to
release energy for the cell to use
Has its own strand of DNA
Our mitochondria are inherited from our
mothers via the eggs cell.
Chloroplast
Found in plant cells
Contains the green
pigment chlorophyll
which captures the
sun’s energy and
converts it into
chemical energy
(glucose) in a process
called
photosynthesis.
Cytoskeleton
A network of protein
filaments/tubes that
helps the cell maintain
its shape and which
helps move materials
around the cell.
Cytoskeleton (cont’d)
Acts as skeleton and muscle
Provides shape and structure
Microfilaments (1 type of
cytskeleton)
Thread-like structures
Made of a protein
called actin
Make a tough, flexible
framework that
supports the cell
May also help the cell
move by assembling
and disassembling
Microtubules (another type
ofmicroskeleton)
Hollow structures
made of proteins
known as tubulins
Perform different
functions in different
cells:

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Critical to maintaining
shape of some cells
Form spindles in
mitosis
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Form centrioles (animal cells only)
Build projections from cell’s surface such as
flagella and cilia that enable some cells to
“swim”
Some cells have them arranged so that they
can be used to produce controlled movements
of the cell.
Centrioles
Aid in cell division
Found in pairs in
animal cells
Made of microtubules
Cell Wall
Found in plant and
bacterial cells
Rigid, protective
barrier
Located outside of the
cell membran
Made of cellulose
(sugar/fiber)
Quick Review
Which organelle is the control center of the cell?
Nucleus
Which organelle holds the cell together?
Cell membrane
Which organelles are not found in animal cells?
Cell wall, central vacuole, chloroplasts
Which organelle helps plant cells make food?
Chloroplasts
What does E.R. stand for?
Endoplasmic reticulum
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