Cell Unit
Background picture:
Blood Cells
Cells
• The structural and functional building blocks
of all organisms.
• Robert Hooke: First scientist to describe the
cell (1665)
– Examined a thin slice of cork (plant), observed
the rectangular units that composed the
structure.
– Called the cell the “cell” because it resembled
the monk bedchamber.
• 1- Cells are the smallest structure that perform the
processes essential to life, including food
consumption, waste production, and the creation of
new cells through reproduction.
• 2- All cells arise form the division of existing cells
• 3- Every organisms is made up of one or more cells
• Four macromolecules: Lipids, carbohydrates,
proteins, and nucleic acid.
– Each macromolecule performs a specific task in
the cell function.
• Water molecules are essentials to many of the
cells function
Multicellular Organisms
• Have different types of cells must work
together to keep the organisms alive and
functioning.
• ALL cells carry the necessary hardware
contained in their DNA, for every other task
being performed inside the organism.
• We all started off as one cell: a zygote formed
fusion of sperm and egg.
Cell Differentiation
• The zygote will continue to divided with the
identical DNA.
• Each cell eventually takes on specific task– e.g.
brain cells, muscle cells, blood cells, & etc.
. Example: A stem cell is a cell that has not yet gone
through the process of cell differentiation. Many
scientist believe that stem cell research could hold the
key to curing spinal cord injuries, among other
disorders. In theory, if a stem cell can be manipulated,
it can be made to grow into new nerve tissue
Microscopes
• Most cells are too small to be seen with the
naked eye.
• Light Microscopes: Bend and magnify visible light
that passes through the specimen.
• Scanning Electron Microscopes: uses electrons to
scan the surface of a specimen that has been
coated with metal
• Transmission Electron Microscopes: uses
electrons to scan the internal structure of a thinly
structure of a thinly sliced specimen
Microscope Terms
• Light microscopes and electron microscopes
have different powers of magnification and
resolving powers.
• Magnification refers to the increase in the
visual size of an object.
• Resolution: refers to the clarity of the
magnified image.
• Electron microscopes have a higher resolution
and greater powers of magnification
Types of Cells
• Prokaryotic Cells: are
small, simple cells that
lack membrane bound
organelles and have
very little internal
division of labor
• Eukaryotic Cells: are
more complex cells with
membrane-bound
organelles units that
perform specific tasks.
Similarities in the two types of cells
• 1- Cell membrane: that surrounds the entire cell
and separates it from the environment.
• 2- Cytoplasm: the substance between the cell
membrane and the region of DNA. It is made up of
cytosol, which is the fluid-like material that fills the
celland can include cell components such as
organelles, macromolecules, ions, and filaments
• 3- DNA the genetic material of the organisms
Prokaryotic Cells
•
•
•
•
Smaller and simpler
No membrane bound organelles
No central nucleus containing DNA.
Instead of a nucleus, their DNA is concentrated in a
region called a nucleoid.
• Bacteria and archaea are the only two domains of
organisms composed of prokaryotic cells
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• Most primitive organisms and are always a
single cell organism.
• Some cells form colonies in which labor is
divided among specialized cells
• Earliest life forms on Earth and are highly
adaptable, found in the harshest
environments today.
Eukaryotic Cells
• Have membrane bound nucleus
– Contains chromosomes, pieces of DNA that are
tightly folded up by proteins.
• Membrane bound organelles
• The remaining substance of the cell consist of
cytoplasm, which includes cytosol, organelles
and materials suspended in it.
Organelles
• Perform functions in both prokaryotic and
eukaryotic cells.
• Prokaryotic are not membrane bound.
• Each has function very similar to a organ in
our body.
Organelles Functions:
Organelles and Function
Cells Walls: surround the cells membrane and gives
cells extra support and protection. Plants, fungi,
and bacterial cells are supported by cells walls.
Animal cells do not have a cell wall.
Nucleoid: region where prokaryotic cell’s DNA is
located. It is not enclosed by a membrane
Nucleus: is the command center for eukaryotic
cells. It houses the cell’s DNA and is differentiated
from the prokaryotic nucleoid by the presence of a
membrane
Ribosome: are structure that manufacture proteins
Prokaryotic cells are scattered.
Eukaryotic cells ribosomes are attached to the
endoplasmic reticulum
Found in Prokaryotic
Cells
Found in
Eukaryotic Cells
In plants and fungi
Organelles Continue…
Organelles and Their Function
Endoplasmic Reticulum (ER): system of
membranes that perform many functions, such
as the creations of different compartments
within the cell called vesicles
Two types of ER
Rough ER: has a rough appearance (ribosome
attached)
Manufactures new membranes and transports
proteins made by the attached ribosomes to
the cell’s Golgi bodies for further processing
Smooth ER: No ribosome attached
Makes lipids, stores calicum ions, and contains
enzymes that detoxify drugs and poisons.
Found in Prokaryotic Found in
Cells
Eukaryotic Cells
Organelles Functions Continue….
Organelles and Their Function
esicles are membranes within eukaryotic cells
sed for tasks such as transporting materials
etween the cell and the outside environment.
Golgi Bodies are stacks of flattened
membranous sacs that receive proteins and
pids from ER, process them, and send them to
heir final destination. Golgi bodies are typically
lustered together in a group known as a Golgi
omplex or Golgi apparatus
Mitochondria produce ATP, the energy currency
f the cell, in a process called cellular
espiration. Often times called the
powerhouse” of the cell. Each mitochondrion
as both inner and outer folded membrane
which creates a separate inner compartment
within the organelle called the matrix
Found in Prokaryotic
Cell
Found in Eukaryotic
Cell
Organelles Function Continue…
Organelles and Their Functions
Chloroplast convert light energy into ATP in a
process called photosynthesis. Like mitochondria,
chloroplast are surrounded by two membranes. A
third group of inner membranes form stacks called
grana. The grana are composed of disc-shaped
compartments called thylakoids, where
photosynthesis actually takes place.
Vacuoles store excess food , water, minerals, cellular
fluid, and other matter for future use. Animal cells
may contain several small vacuoles, where plant cells
have a single large central vacuole. The pressure of
the fluids in the central vacuole called turgor
pressure, helps maintain the shape of plant cells
Lysosomes contain digestive enzymes used to break
down food molecules or damaged parts of the cell.
Lysosome are made by the Golgi Apparatus
Found in
Prokaryotic Cells
Found in
Eukaryotic Cells
In plants and
some protists
Cell Organelles Function Continue…
Organelles and Their Function
Centrioles are barrel-shaped organelles that produce
microtubules, cylindrical protein fibers. These
microtubules fiber give the cell its shape and assist in
cell division. Centrioles exist in pairs. While
microtubules form part of the plant and fungi cells do
not contain centrioles
Microtubule fibers form a network, called the
cytoskeleton, which gives the cell its shape and
prevents the cell from collapsing. The also assist in
the movement of materials within the cell.
Flagella and cilia are appendages that protrude from
some cells and either provide motion or allow the
movement of substances across the cell or tissue
surface. Many unicellular organisms use flagella or
cilia for movement in water or other fluids
Found in
Prokaryotic Cells
Found in
Eukaryotic Cells
In all but plants
and fungi
Cell City Metaphor
Organelle
Nucleus
Function
The Mayor (The boss)
Ribosomes
Endoplasmic
Reticulum (ER)
Golgi
Apparatus
Lysosomes
Vacuoles
The protein factories
The highway (Transporter)
Mitochondria
The power plant
The post office (Packaging Plant)
The trash collectors (Lip-Smacking Good)
The storage warehouses (Vacuum)
Membrane Structure
• Cell membrane is responsible for maintaining
an internal environment for the cell by
regulating what enters and leaves the cell.
Membrane Proteins
In eukaryotic cells, selective entry and exit of other
molecules occurs through proteins embedded in the
phospholipids bilayer of the cell membrane.
Also Called the Fluid Mosaic Model
Phospholipids bilayer is composed of two layers of
phospholipids so that their nonpolar tails form the interior
of the membrane and the polar heads face outward.
The phospholipids bilayer forms an effective barrier to all
but the smallest nonpolar molecules, such as oxygen and
carbon dioxide.
Cell Membrane: Specialized Proteins
• Peripheral Proteins: Not implanted into the cell
– Transport or Channel Proteins: Transport molecules
into or out of the cell
– Receptor Proteins: receive or relay chemical messages
between cells
– Marker proteins: facilitate cell-to-cell recognition by
identifying a cell’s function or origin to other cell
• Are particularly crucial in sorting cells in an embryo into
tissues and organs and rejecting or accepting foreign cells in
transplanted organs
Continue…
• Integral Proteins: implanted within the lipid
bilayer.
– Membrane proteins: interact with the
cytoskeleton of the cell to stabilize the cell
membrane
• Form gap junctions and tight junctions that help
attach to cells to each other
Membrane Permeability
• Permeability: the degree to which substances can
pass through a cell’s membrane.
• Semipermeable: describe the cell membrane by only
allowing certain material in or out of the cell.
• Because of the semipermeable the cell membrane
then a concentration gradient exist.
– Concentration gradient: Some substances are present on
one side of the membrane in higher concentration than
on the other side.
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• All substances naturally move down their
concentration gradient from areas of high
concentration to areas of low concentration,
without the use of ENERGY.
• Movement up against a concentration
gradient is possible only with the expenditure
of energy
Passive Transport
• Is the movement down the concentration gradient.
NO ENERGY is expended in this activity.
• Four ways to move material through passive
transport:
– 1- Diffusion: Particles move spontaneously from an area
of higher concentration to an area of lower
concentration.
• Only small, unchanged particles, such as oxygen, carbon
dioxide, and some ions
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– 2-Facilitated diffusion: particles move spontaneously across
the cell membrane from an area of higher concentration to
an area of lower concentration with the help of special
transport proteins.
• Permits large molecules and charged molecules, such as glucose,
through the cell membrane.
– 3- Osmosis: allows water to diffuse across the cell
membrane from area of higher water concentration to an
area of lower water concentration.
Tonicity
• Tonicity or relative solute concentration of cell
determines the direction in which osmosis occurs.
• Water diffuses from an area of low tonciity (high
water, low solutes) to area of high tonicity (lower
water, higher solutes)
• Osmosis affects the turgidity of cells, different
solution can affect the cells internal water amounts
• Turgor pressure occurs in plants cells as their central
vacuoles fill with water.
Types of Osmotic Solutions
• Isotonic: equal amount solute inside and outside of the
cell.
– Cell will stay normal
– Plant cell- will become limp
• Hypertonic: More solute on the outside of the cell
– Water will move out of the cell
– Cell will shrivel up (animal)
– Plant cell plasmolyzed (wilt and death)
• Hypotonic: More solute inside the cell
– Water will move in the cell
– Cell will burst
– Plants will have turgid (exerts pressure) (Normal for plant
cells)
Osmosis without walls
No net
movement
Water
enters
the cell
Water
Leaves the
cell
Osmosis with walls
Active Transport
• Cells must actively transport substances being
up against the concentration gradient.
• This movement requires the cell to expend
energy and is enabled through the use of
carrier proteins, which bind to a substance
and shuttle it through pores in the cell
membrane.
Continue…
• Carrier Proteins can perform two methods of
active transport:
– Endocytosis: Occurs when proteins bring substances
into the cell through the vacuoles or vesicles.
• Phagocytosis: consumption of solid matter
• Pinocytosis: consumption of liquid
– Exocytosis: occurs when carrier proteins remove
substances from the cell through the vacuoles or
vesicles
• Insulin delievered from the cell to the blood stream
Cellular Connection and Communication
• The cells of multicellular organisms must stay
bound together to keep the organisms intact.
• These cells must also be able to communicate
and cooperate with each other to function as
a single organisms
• The cell membrane is extremely important in
the regulation of intracellular communication
and cooperation
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• The following structures connect different eukaryotic
cells to each other:
– Extracellular Matrices: are materials secreted by animals
cells that surround and bind them together.
• Thick and strong extracellular matrix surrounds bone cells.
– Tight Junctions or occluding junctions: Bind cells so tightly
together that molecules cannot pass between them.
• Small intestine: to prevent substances from leaking into other
parts of the body.
– Anchoring Junctions: Connect the cytoskeleton of two or
more cells.
• Cells for greater mobility than connective materials and are
common tissue that needs to be flexible, such as skin and
muscles.
Continue…
• Eukaryotic cells possess structures that
facilitate cell-to-cell communication.
• These structures differ in plant and animal
cells.
• Plasmodesmata: are molecular channels that
exist between adjacent plant cells.
• Gap Junctions: are molecular channels that
exist between animal cells