Cell Structure
{Chantel
Cell Theory
Fluids

The cell membrane (plasma membrane)
forms the outer boundary of the cell.
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Major components
 Phospholipids
 Proteins
 Glycolipids
 Cholesterol
Function
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Isolation
Protection
Sensitivity
Organization
Cell Membrane
Physical isolation
The cell membrane is a physical barrier that
separates
the inside of the of the cell from the
surrounding extracellular fluid.
Importance
The cell membrane is responsible for letting in
molecules or letting them out.
Structure
The cell membrane is extremely thin and
delicate. It ranges from 6 to 10nm in thickness. For
the most part it is a very complex structure.
Cell Membrane….
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Most of the communication involves the cell
membrane.
The cell membrane regulates the dynamic
exchange between intracellular and
extracellular fluids. These environments are
quite different and they must be maintained to
preserve homeostasis.
Communication Through
The Cells
Structure and Function
Doesn’t have a membrane
1.
2.
3.
4.
5.
Cytoskeleton- Strength,
movement of cellular structures
and materials
Microvilli- Absorption of
extracellular materials.
Centrioles- Movement of
chromosomes during cell
division
Cilia- Movement of materials
over surface
Ribosomes- Protein synthesis
Has a membrane
1.
2.
3.
4.
5.
6.
Mitochondria- Energy source
Nucleus- Control of metabolism;
storage and processing of genetic
information.
Endoplasmic Reticulum- Synthesis of
secretory products; in tracellular
storage and transport.
Golgi Apparatus- Storage, alteration,
and packaging or secretory products
and lysosomes.
Lysosomes- Intracellular removal of
damaged organelles or of pathogens.
Peroxisomes- Neutralization of toxic
compounds.
Energy

The Mitochondria is the main energy
source. They provide energy to cellular
functions from their metabolic enzymes.
Mitochondria contains DNA, RNA, and
the enzymes needed to synthesize
proteins. This synthetic capability enable
mitochondria to control their own
maintenance, growth, and reproduction.
The nucleus is the control center for the
whole cell.
It Controls
•
•
•
•
cellular operations through its regulation of protein
synthesis.
Metabolism
Storage
Processing of genetic information
Nucleus
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In order to have a cell cycle, a single cell must divide. Cellular
division occurs when one cell divides into two daughter cells.
Both of them are then half the size of the original cell. After a
cell divides, the two daughter cells may last from hours to
decades it just depends on the environment. Most cells don’t
last longer than a human being. Therefore, the life cycle repeats
itself by dividing again into two daughter cells.
Cells go into different phases which are broken up into
different parts.
Cell Life Cycle


Interphase
Stage One

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Stage Two

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Metaphase
Stage Three

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Prophase
Anaphase
Stage Four

Telophase
These are the most
common stages of
the life cycle.
Mitosis involves
Prophase,
Metaphase,
Anaphase, and
Telophase.
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The transmembrane potential is characteristic
of all living cells because it results from the
active and passive properties of their cell
membranes.
The transmembrane potential is just as
important as any structural characteristic or
organelle. Many cell functions that involve the
cell membrane, such as secretion or ciliary
movement, involve changes in the
transmembrane potential. But it has significant
functions.

Transmembrane Potential

Two factors, one passive and one active,
interact to create and maintain the
transmembrane potential .
The passive factor is that the
membrane permeabilities for
sodium and potassium are
quite different. Potassium ions
can diffuse out of the cell
through potassium channels
faster than sodium ions can
enter the cell through sodium
channels. The cell therefore
loses positive charges faster
than it gains them. The interior
of the cell develops excess of
negative charges.
The active factor is the presence of
the sodium potassium exchange
pump in the membrane surface.
At a transmembrane potential of 0
mV, potassium ions enter it, and
the exchange pump cannot
prevent the net loss of positive
charges.
Transmembrane Potential...
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Attachments occur at cell junctions that are
not involved in membrane flow. There are
four different types

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Gap junctions
Tight junctions
Intermediate junctions
desmosomes

Gap Junctions- two cells are held together by
an
interlocking of membrane proteins.

Tight Junctions- the strongest intercellular
connections.
Intermediate Junctions-held together by a
thick layer of proteoglycans.
Desmosomes- very thin proteoglycan layer
between the opposing cell membranes,
reinforced by a network of intermediate
filaments that lock the two cells together.
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Gap Junctions are
found mostly in the
muscle tissue, smooth
muscle tissue, and
sometimes nerve cells.
Desmosomes are very strong, and the
connection can resist stretching and twisting.
Cell Attachment