Cell Structure
Cell Boundaries
- Plasma Membrane
Cell Boundaries
- Plasma Membrane
Structure
• A bi-lipid envelope
around the cell that
contains proteins
and other markers
•
•
•
•
Function
Separates the cell from
its environment
Secretes materials out
of the cell
Recognizes friendly and
enemy objects
A selectively permeable
membrane that allows
some materials to enter
- Cell Wall
Structure
• A rigid covering of:
Function
• Gives the cell an
internal structure so it
– Cellulose in plants or
doesn’t collapse on
peptido-glycan in
bacteria or chitin in
itself
fungi
Cell Control
• Nucleus
– DNA
(Chromatin / chromosomes)
– Nucleolus
Nucleus
Structure
• Surrounded by a
double membrane
called the nuclear
envelope
– Has holes called
nuclear pores
Function
• Holds the DNA safe
inside the cell
• Controls what enters
and leaves the
nucleus
DNA as Chromatin
Structure
• A fine strand of DNA
coiled around
proteins
Function
• Contains all the
information for
making proteins
• Is the inherited
information that is
given to the
offspring during
reproduction
DNA as Chromosomes
Structure
• Chromatin that is
coiled up tightly
during cell division
Function
• Same as chromatid
except that it is coiled up
tightly so that it can be
separated cleanly into
the two daughter cells
Nucleolus
Structure
• A spherical body in
the nucleus
Function
• Makes the ribosomes
Protein Synthesis
- Ribosomes
Ribosomes
Structure
• Each cell has 1000’s
of ribosomes which
are little spheres
• A ribosome contains
a protein connected
to some RNA.
Ribosomes don’t
have membranes
Function
• Protein Synthesis
What is the function of
nucleic acids?
Assembly and Storage
Organelles
• Endoplasmic
reticulum
• Golgi Apparatus
• Vacuoles
• Lysosomes
Endoplasmic Reticulum ER
Structure
• A membrane system of
folded sacs and tunnels
• When it is covered with lots
of ribosomes= rough ER
• When it lacks ribosomes=
smooth ER
Endoplasmic Reticulum ER
Function
• The place where the
ribosomes assemble
their proteins
• Intercellular
highways (where
materials can move
from one part of the
cell to another.
Golgi Apparatus
Structure
• A system of
flattened sacs &
membranes that
emerge from the ER
Function
• Modifies the
proteins made in the
ER so they can be
put into packages
and exported from
the cell
Vesicles
Structure
• Little sacs that emerge
from the Golgi
apparatus
Function
• The transport
passage of
materials within the
cell
Vacuoles
Structure
• An empty sac is
usually large in
plants
Function
• Temporary storage
of water, enzymes,
food particles, or
waste
Lysosomes
Function
Structure
• A sac of very strong • Used to digest food
molecules and invaders of
digestive enzymes
the cell
in a double
• Sometime used to “self
membrane
destruct” cells suicide sacs
• Common in animal,
fungi and protist
cells, but are rare in
plant cells
Energy Transforming
Organelles
• Chloroplast
• Mitochondria
Chloroplasts
•
•
•
•
Structure
Have a double
membrane and their
own DNA
Contain the pigment
chlorophyll
Thylakoids look like
stacks of pancakes
Stroma fluid that
surrounds the
thylakoids ( sugary
syrup)
Function
• In the chloroplast,
thylakoids absorb
solar energy and
convert it into
chemical energy.
“makes food”
Mitochondria
Structure
• Large organelles that
contain their own DNA
• Has a bilayer: a smooth
outer membrane and
very folded inner
membrane (cristae)
Mitochondria
Function
• Releases energy in “food” into a form the cell
can use which is called ATP
– ATP is the currency of energy that cells use
• Parts of the body that use a lot of energy will
have a lot of mitochondria (muscle cells)
• Because the mitochondria has its own DNA, it
can reproduce itself.
Support and Locomotion
• Cytoskeleton: support structure/framework
for the cell
– Microtubules
– Microfillaments
• Centrioles
• Cillia
• Flagella
Microtubules
Structure
• Long, slender tubes
of protein
Function
• Gives structure to
the cell so it doesn’t
collapse on itself
• During cell division,
microtubules are
used to pull apart
the chromosomes
into the new
daughter cells
Microfilaments
Structure
• Long threads of
protein called actin
Function
• Used when the cell
moves and when a
muscle cell contracts
Centrioles
Structure
• Pair of small
cylindrical bodies
located near the
nucleus
Function
• Function in cell
division
Cilia
Cilia
Structure
Function
• The cilia beat in unison or
• Short, “hair-like”
in waves. Cilia are used to
structures that
move cells
emerge from the cell
– e.g. paramecium
membrane
• Cilia move mucus or fluids
• A cell may have
– e.g. over the cells of human
trachea and lungs
1000’s
Flagella
Structure
Function
• A long “whip-like” • Whip back and forth
structure that
to move a cell
emerges from the
through fluid (e.g.
cell membrane
Euglena)
• A cell has only 1-2
flagella