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The Cell
Cell Types
Cell Parts
Diffusion & Osmosis
Cell Types
Cell Types
Eukaryote
Have Nucleus
Plant
Animal
Prokaryote
No Nucleus
Fungi
Protista
Bacteria
Kindgom Monera
Prokaryotic Cells (Prokaryotes)
Bacteria
http://micro.magnet.fsu.edu/cells/bacteriacell.html
Capsule
• a protective covering
• made up of polysaccharides (complex carbohydrates).
• keep the bacterium from drying out and to protect it
from phagocytosis (engulfing) by larger
microorganisms.
• The capsule is a major virulence factor in the major
disease-causing bacteria, such as Escherichia coli
and Streptococcus pneumoniae. Nonencapsulated
mutants of these organisms are avirulent, i.e. they don't
cause disease.
Cell Wall
• composed of peptidoglycan, a protein-sugar.
• gives the cell its shape
• surrounds the cytoplasmic membrane, protecting it from
the environment.
• helps to anchor appendages like the pili and flagella,
which originate in the cytoplasm membrane and
protrude through the wall to the outside.
• responsible for keeping the cell from bursting when
there are large differences in osmotic pressure between
the cytoplasm and the environment.
Nucleoid
• A region of cytoplasm where the chromosomal
DNA is located.
• It is not a membrane bound nucleus
• Most bacteria have a single, circular
chromosome that is responsible for replication,
although a few species do have two or more.
• Smaller circular auxiliary DNA strands, called
plasmids, are also found in the cytoplasm.
Pili
• Small hairlike projections emerging from the
outside cell surface.
• Assist the bacteria in attaching to other cells and
surfaces, such as teeth, intestines, and rocks.
• Without pili, many disease-causing bacteria lose
their ability to infect because they're unable to
attach to host tissue.
Prokaryotic Ribosomes
• Site of protein synthesis
• Prokaryotic are smaller and have a slightly
different composition and molecular structure.
• Bacterial ribosomes are never bound to other
organelles as they sometimes are (bound to the
endoplasmic reticulum) in eukaryotes
• free-standing structures distributed throughout
the cytoplasm.
Eukaryotic Cells (Eukaryotes)
Nucleus &
Membrane Bound Organelles
Animal Cell
Cytoplasm
Centriole
Smooth
Endoplasmic Reticulum
Vacuole
Cell Membrane
Nucleolus
Nucleus
Mitochondria
Ribosome
Rough Endoplasmic
Reticulum
Nuclear Membrane
Golgi Apparatus
Lysosome
Plant
Cell
Smooth
Nucleus
Nucleolus
Chloroplast
Endoplasmic Reticulum
Nuclear Membrane
Golgi Apparatus
Cell Wall
Cell Membrane
Rough Endoplasmic
Reticulum
Vacuole
Mitochondria
Ribosome
Cytoplasm
Cell Membrane
•
•
•
•
Control what comes in and out
Protects and supports the cell
Phospholipid Bi-layer
Proteins – act as channels to pass molecules
into or out of the cell and others act as pumps to
“push” molecules from one side to the other.
• Cholesterol molecules prevent phospholipids
from sticking to each other
• Fluid Mosaic
Phospholipid Bilayer
Cell Membrane
Cell Membrane
• Carbohydrate chains
• Act like chemical ID cards – allows cells to
recognize each other.
Cell Wall
• Plants, algae, some bacteria
• Helps support and protect cell
• 2 or more layers thick
– Outer layer is where cells meet – gluey substance –
pectin
– Primary cell wall is next – made of cellulose
Nucleus
• large dark structure
• Not all cells have a nucleus
– Eukaryotes
– Prokaryotes
• Information center and holds DNA (genetic code)
• Chromosomes – DNA and Proteins – Genetic
code
Nucleolus
• Inside Nucleus
• Made of RNA
• Makes Ribosomes
– Ribosomes are the site of protein synthesis
Cytoplasm
• Jelly like substance
• Holds organelles
• Most reactions happen here
Mitochondria
• Powerhouse of the cell
• Break down sugars for energy
– Convert ADP to ATP
• 2 Membranes
– Outer surrounds mitochondria
– Inner increases surface area – more efficient
Mitochondria
Chloroplast
• Only in plant cells
• Have Chlorophyll
• Convert Sun energy into chemical energy
Chloroplast
Ribosome
• Composed of RNA and protein
• some attached to membranes, some free
• smallest organelles
 25 nanometers (1 billionth of a meter)
Endoplasmic Reticulum
• Network of channels – ER
• Transports materials through the inside of the
cell
• Smooth and rough ER – Rough has Ribosomes
all around it
• Synthesised proteins are moved to Golgi
Apparatus for modification
Golgi Apparatus
 Golgi for Italian scientist Camillo Golgi
• Looks like flattened stack of pancakes
• Modifies, collects, packages, and distributes
proteins
Lysosomes – The Cleanup Crew
• Lysosomes help digest particles – contain
enzymes and chemicals necessary for digestion
• Break down organelles that have outlived their
usefulness
• Formed by Golgi Apparatus
• Only in Animal Cells
CELL
• The basic unit of structure &
function in living organisms
Anton Van Leeuwenhoek
1632-1723
Was a merchant that ground up glass to
make lenses
•Invented microscope
•Made over 500 in his lifetime
•1st person to examine bacteria
Van Leeuwenhoek’s sketches of a nerve
Robert Hooke
• 1635-1702
• Used Van Leeuwenhoek’s microscopes
• Named cells after looking at cork
Robert Hooke’s Cork
Robert Brown
• 1773-1858
• Discovered the nucleus
in plant cells (1833)
Matthias Schleiden
• 1804-1881
• Discovered all plants
are made up of cells
(1838)
Theodor Schwann
• 1810-1882
• Discovered that all animals
are made up of cells (1839)
Rudolph Virchow
• 1821-1902
• Proposed that all cells come from preexisting cells (1855)
The Cell Theory
The cell theory states:
A.
All living things are composed of cells
B. Cells are the basic units of structure & function in
living things
C. All cells come from preexisting cells
Lynn Margoulis
• Proposed that
certain organelles
were once freeliving organisms
themselves (1970)
Movement of Materials Through
the Cell Membrane
• Cells are in a liquid environment
• Why is this important?
– Easier for materials to get into and out of the cells
Passive Transport
• Requires no energy
• Occurs due to natural concentration gradient
• Molecules move from high concentration to low
concentration (DOWN the gradient)
3 Types
 Diffusion
 Osmosis
 Faciliated Diffusion
Diffusion
Diffusion:
• Can’t have cell membrane too effective
– How would materials get into or out of the cell?
• What materials would we want to get into or out
of the cell?
– Oxygen, Carbon Dioxide, Food, Wastes
• Molecules are constantly moving. They spread
out as volume permits
Diffusion:
• Diffusion – the process by which
molecules of a substance move
from areas of higher concentration
to areas of lower concentration
Selectively Permeable:
• Molecules can pass through a solid if it contains
spaces large enough
• Window screen can keep out flies, but lets air in
and out it acts as a barrier
• If only certain substances can pass through, but
not others, it is said to be selectively permeable
Selectively Permeable:
• Substances present in unequal amounts on
either side
• Each substance moves toward area of lower
concentration
• Equilibrium – when concentration is equal
throughout, or on both sides of the membrane
Equilibrium:
• Does equilibrium mean the
molecules stoped moving?
• NO!
Osmosis:
• Molecules that can dissolve in the lipid bilayer of
the cell membrane can pass through easily. Most
other molecules do not.
• Water does
• The diffusion of water molecules through a
selectively permeable membrane is called
osmosis
Osmosis:
• What happens to raisins if you soak them in
water overnight?
• Moves water from more dilute to more
concentrated side
• Osmotic pressure – can be serious for cell – can
rupture cell
Cells in Isotonic Solution
Isotonic Solutions
• If the concentration of solute (salt) is equal on
both sides, the water will move back in forth but
it won't have any result on the overall amount of
water on either side.
• "ISO" means the same
Cells in Hypertonic Solution
Hypertonic Solutions
• The word "HYPER" means more, in this case there are
more solute (salt) molecules outside the cell, which
causes the water to be sucked in that direction.
• In plant cells, the central vacuole loses water and the
cells shrink, causing wilting.
• In animal cells, the cells also shrink.
• In both cases, the cell may die.
• This is why it is dangerous to drink sea water
Cells in Hypotonic Solution
Hypotonic Solutions
• The word "HYPO" means less, in this case there are less
solute (salt) molecules outside the cell, since salt sucks,
water will move into the cell.
• The cell will gain water and grow larger. In plant cells, the
central vacuoles will fill and the plant becomes stiff and
rigid, the cell wall keeps the plant from bursting
• In animal cells, the cell may be in danger of bursting,
organelles called CONTRACTILE VACUOLES will pump
water out of the cell to prevent this.
Osmosis Review
Plasmolysis
• When a plant cell is in a hypertonic solution and
the cell membrane pulls away from the cell wall
Plasmolysis
Water Potential
y is the symbol for water
potential
yp is pressure potential
Ys is solute potential
Water Potential
y =yp + ys
Facilitated Diffusion:
• Diffusion and osmosis – passive (no energy
required)
• materials carried across membrane by protein
molecules to speed up diffusion
• Fast, specific, and no energy required – still
diffusion
• Only occurs with concentration gradient
Facilitated Diffusion
Protein Channel or Pore
Facilitated Diffusion
Protein Carrier
Active Transport
• Requires cell energy (ATP) to move molecules
AGAINST the concentration gradient; from an area of
LOW concentration to an area of HIGH concentration
• Sodium–Potassium pump (Exchange 3 sodium ions for
2 potassium ions)
• Hydrogen ion, or proton pump (Pump hydrogen ion
against the concentration gradient)
Phosphorylation
The addition of a phosphate (PO4) group (From
ATP) to a protein or a small molecule
This changes the protein shape
Active Transport (Uniport)
Active Transport Na-K Pump
Na-K Pump Antiport
Glucose-Sodium Symport
Proton (Hydrogen Ion) Pump
Bulk Media Transport
• Endocytosis – Vesicle is created from the invagination of the
plasma membrane, which pinches off bringing large
molecules into the cell
• Pinocytosis – Cell drinking (endocytosis)
• Phagocytosis – Cell eating (endocytosis)
• Receptor Mediated Endocytosis – Substrate binds to
receptor found on the plasma membrance to be brought into
the cell
• Exocytosis – Vesicle binds to the plasma membrane
releasing the contents outside of the cell
Endocytosis
Pinocytosis
Phagocytosis
Receptor Mediated Endocytosis
Exocytosis