Transcript Cell Structure Ch.7

Cell Structure
Two Cell Types
1.
2.
Prokaryotic Cells- Simple cells made up of a
cell wall, cell membrane , cytoplasm, and DNA.
They do not have membrane bound
organelles. Ex. Bacteria
Eukaryotic Cells- are cells with specialized
organelles that are held together by a
membrane. They have a central organelle
called a nucleus that controls all the cell’s
activities and contains the DNA.
Plasma Membrane
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Is the flexible boundary of a cell that separates a cell
from its surroundings.
It allows nutrients to enter the cell and waste to be
removed.
– This healthy balance is called Homeostasis.
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To maintain this homeostasis the plasma membrane
allows some molecules into the cell and keeps others
out. This is called Selective Permeability. Pg 176
Some molecules are allowed in at any time and others
are only admitted at certain times and in limited
quantities. Others are not allowed in at all.
Structure of the Plasma Membrane
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The plasma membrane is made up of two layers of
phospholipids that are arranged back to back. This is
called the phospholipid bilayer. Pg 177
The phosphate group or the head is polar (which water
is also polar so they interact well together) which allows
the plasma membrane to interact with its watery
environment.
The fatty acid tail is nonpolar which avoids water and is
water insoluble.
So the outside of the plasma membrane is water soluble
and the inside of the membrane is water insoluble. This
means that water soluble molecules will not easily move
through the membrane b/c they are stopped by this
water insoluble layer.
Transport Proteins
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They regulate which molecules are
allowed to enter and which are allowed to
leave the cell. Called Selective
Permeability.
Eukaryotic Cell Structure
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Cellular Boundaries pg 180
– Cell wall is a rigid wall outside the plasma
membrane that dives extra support and
protection to the cell.
– Plasma Membrane is inside the cell wall and
acts as a flexible boundary of the cell.
Eukaryotic Cell Structure
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The Nucleus and Cell Control pg 181
– The nucleus directs the activity of a cell’s organelles
and contains directions to make proteins.
 The nucleus is surrounded by the nuclear envelope which is
the boundary in between the nucleus and the cytoplasm.
– It also contains the DNA that is in strands called
Chromatin. The chromatin tells the cell what kinds of
proteins to make. When the cell divides the
chromatin condenses and becomes chromosomes.
Eukaryotic Cell Structure
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The Nucleolus, which is inside the nucleus,
makes ribosomes.
– Ribosomes are where the cell makes protein,
which is made up of RNA.
 Ribosomes make the proteins in the cytoplasm.
– The Cytoplasm is a thick fluid in the cell.
Eukaryotic Cell Structure
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Assembly, Transport, and Storage pg 182
– Endoplasmic Reticulum (ER) is a series of tightly
folded membranes floating in the cytoplasm. It is the
site of cellular chemical reactions.
 Two types
– Rough ER is where ribosomes attach and make proteins. Other
ribosomes float freely in the cytoplasm. Each protein has a
specific job. Ex. Part of the plasma membrane.
– Smooth ER does not have ribosomes attached and also
performs chemical activities such as making and storing lipids.
Eukaryotic Cell Structure
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Other Organelles pg 183
– Golgi Apparatus) (or golgi body) sorts proteins and
then packs them into structures called vesicles. The
vesicles are then sent to where they are needed.
 When the golgi body packages digestive enzymes they form
a lysosome. A lysosome breaks down old cell parts and
removes waste.
– Vacuole is a sac inside a membrane where materials
needed by the cell are temporarily stored. Some
store food and enzymes and others store waste until
they can be removed or excreted.
Eukaryotic Cell Structure
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Energy Transformers pg 184 & 185
– Mitochondria is the cell’s powerhouse. It transforms
energy for the cells of plants and animals.
– Mitochondria stores the energy in bonds that the cells
can access easily when energy is needed.
 In green plants and some protists energy is received from
light energy by the chloroplasts.
 Chloroplasts are a type of plastid that re plant organelles that
store things.
 Chloroplasts contain chlorophyll (a green pigment) which
makes leaves and stems green.
Eukaryotic Cell Structure
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Support and Locomotion
– Cytoskeleton is inside the cell and supports the
organelles in the cytoplasm. It can be take apart in
on place and put back together in another, when this
happens the cell changes shape.
 It is made up of microtubules and microfilaments.
– Microtubules are tiny cylinders of protein.
– Microfilaments are even smaller solid protein fibers.
– They support the organelles and help materials move around
the cell.
 Centrioles are made of microtubules and are very important
in cell division.
Eukaryotic Cell Structure
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Two other organelles made from
Microtubules are
– Cilia which are short projections that look like
hairs. They move in a wave like motion and
cells have many of them.
– Flagella are longer projections that move in
a whip like motion. A cell usually has one or
two flagella.
– In a one celled organism the cilia and flagella
are the most important way of moving.