Cell Structure and
Function
The Cell Theory
All living things are
composed of cells.
Cells are the basic units of
structure and function in
living things.
All cells come from preexisting cells.

Cell Structure
Most
cells have three basic
structures.
–cell membrane (outer
boundary)
–cytoplasm (filling)
–nucleus (control center)
All
cells have a cell
membrane and
cytoplasm.
However
some do not have
a nucleus. These are called
Prokaryotes. (bacteria)
Cells
with a nucleus are
called eukaryotes. (plant,
animal, fungus and protists)
Nucleus
Cell Membrane
Separates and protects the
cell from its surroundings.
Regulates what enters and
leaves the cell.
Made of two lipid layers:
(Phospholipid bilayer)

The Cell Membrane
Phospholipid Bilayer
Hydrophobic
Hydrophyllic
(Fatty
acids)
(Phosphates)
Cytoplasm
The
area between the cell
membrane and nucleus.
Contains
structures called
organelles and each one
performs a specific job.
Cytoplasm
Nucleus (Control center)
Contains
DNA which are
the instructions for
making molecules the cell
needs.
Nucleus (Control center)
Directs
the activities of the
cell.
Surrounded by a
membrane called the
nuclear membrane or
nuclear envelope.
Nucleus
Nucleolus
A
small region of the
nucleus made up of RNA
and proteins.
The nucleolus makes
ribosomes.
Nucleus
Nucleolus
Ribosomes
Found
in prokaryotic and
eukaryotic cells
Protein factories.
Some ribosomes are
attached to the
endoplasmic reticulum.
Ribosomes
Others
are free in the
cytoplasm.
Smallest
organelle.
Ribosomes
Rough
ER
Endoplasmic Reticulum
Two
forms
Rough ER
Smooth ER
Endoplasmic Reticulum
Smooth ER: no ribosomes
are attached. Special
enzymes and chemicals are
stored here. Lipids (fats)
are produced
Endoplasmic Reticulum
Smooth ER: also resp. for
prod. of phospholipids for
cell membrane.
Endoplasmic Reticulum
Rough ER: has ribosomes
attached. After proteins are
made in the ribosomes they
are inserted in the rough ER
where they can be modified.
Endoplasmic Reticulum
Rough ER: from the ER,
proteins are sent to the
Golgi Apparatus
Golgi Apparatus (UPS)
modifies,
collects, and
packages molecules in the
cell.
Also distributes the
molecules to where they
need to be in the cell.
Golgi Apparatus
Lysosomes
Cleanup
crews for the
cell.
Lysosomes are formed in
the Golgi apparatus.
Lysosomes
Contain
chemicals and
enzymes that digest and
breakdown waste
particles.
Lysosome in action:
Vacuoles (Warehouse)
Storage
tanks in the cell.
Store materials like water,
salts, proteins, and
carbohydrates.
Plants have only one big
vacuole filled primarily
with water.
Vacuoles (Warehouse)
Cytoskeleton
The
framework of the cell.
Made of microfilaments
and microtubules
Provide support and are
often involved in cell
movement.
Mitochondria(Generator)
Generator
of the cell.
Changes chemical energy
stored in food (sugar) into
compounds easier for the cell
organelles to use (ATP).
Mitochondrion
Chloroplast (Solar Panel)
Where
photosynthesis
takes place
Found only in plant cells
and algae.
Chloroplast (Solar Panel)
Traps
energy from
sunlight and changes it
into chemical energy
(makes sugars).
Plant Cell
Chloroplast
Cell Wall
In
addition to the cell
membrane, plant (&
fungus) cells have a cell
wall.
Provides extra support.
Made up of cellulose and
lignin
Cell Wall
Found
outside the
cell
membrane
Movement of materials
through the cell membrane.
Cells must take in
materials, and release
waste products.
Molecules must be able to
move in and out of the
cell.
Movement of materials
through the cell membrane.
They
do this by diffusion.
Diffusion
The
process by which
molecules move from
areas of higher
concentration to areas of
lower concentration.
(spread out)
Diffusion
Driven
by the random
movement of molecules.
Diffusion
Two
factors determine
if diffusion takes place
equilibrium and
permeability.
Diffusion
membrane
higher conc.
lower conc.
Equilibrium
Equilibrium
is when the
concentrations on both
sides of the membrane are
equal.
Equilibrium
Semi-permeable
membrane
Permeability
If
a molecule can diffuse
across a membrane, the
membrane is permeable.
Permeability
If
a molecule cannot
diffuse across a
membrane, the membrane
is impermeable to that
membrane.
Selective Permeability
Membranes
are permeable
to some molecules and
impermeable to others.
These membranes are
described as selectively
permeable or semipermeable.
Osmosis
Osmosis
is a special type
of diffusion:
The diffusion of water
molecules through a
selectively permeable
membrane.
There
are three types of
transports across a
membrane.
–passive transport
(diffusion)
–facilitated diffusion
–active transport
Passive Transport
Energy
is not required for
movement across the
membrane to occur.
Diffusion and osmosis are
examples
Facilitated Diffusion
A
carrier protein “helps”
the molecule to enter or
leave the cell. (Passive)
Active Transport
Energy
is required for
movement across the
membrane to occur.
Molecules move from low
to high concentration.
Active Transport
Two types of active
transport:
–Protein pumps: Pumps
specific ions
–Endocytosis: cell engulfs
(eats) material.
Pumps
 Proteins stuck in the
membrane act as a
doorway into the cell.
Allows only specific things
through the doorway.
Energy is required to open
the door
Pumps
Endocytosis
Endocytosis
Type
of active transport
when the membrane
surrounds material and
pulls it into the cell
Endocytosis Types
Phagocytosis
Pinocytosis
Receptor Mediated
Endocytosis

Phagocytosis
“Cell
Eating”
Bringing large molecules
across the membrane.
Membrane becomes a
vacuole when entering the
cell
Pinocytosis
“Cell
Drinking”
Moving fluids and ions
across a membrane.
Usually going against
the concentration
gradient
Ion concentration outside
the membrane is less than
Membrane surrounding
ions and fluids
Vacuole
Receptor Mediated
Endocytosis
 Same process as
pinocytosis.
Specific ions are moved
across the membrane
Receptor Mediated
Endocytosis
Receptor
proteins trigger
when endocytosis should
begin
Exocytosis
Opposite
Process
of endocytosis
when cell removes
waste from cytoplasm
Vacuole
or lysosome fuses
with cell membrane and
releases materials outside
the cell