Cell Structure
& Function
http://koning.ecsu.ctstateu.edu/cell/cell.html
Cell Theory
1. All living things are made up
of cells.
2. Cells are the smallest working
units of all living things.
3. All cells come from preexisting
or other cells through cell
division.
Definition of Cell
A cell is the
smallest unit
that is
capable of
performing life
functions.
Examples of Cells
Amoeba Proteus
Plant Stem
Bacteria
Red Blood Cell
Nerve Cell
Two Types of Cells
1. Prokaryotic
2. Eukaryotic
Can you see what the difference between
them is?
http://www.biology4kids.com/files/cell_main.html
Prokaryotic
• DNA is not in a nucleus, it
sort of floats around the
cell. No organelles contain
membranes.
• Few internal structures.
No mitochondria, no
chloroplasts, no nucleus
• One-celled organisms,
Example: Bacteria, virus,
amoebas
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Examples of Cells that Move
Bacteria Cells
Notice the bacteria and paramecium have cilium & flagella.
Flagella is the tail-like structure and cilia are the hair-like structures.
Both help the cell with locomotion or movement of the cell.
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Eukaryotic Cells
1. Contain organelles surrounded by membranes
2. Have a true nucleus
3. Make up most living things.
Plant
http://library.thinkquest.org/C004535/eukaryotic_cells.html
Animal
Animal and Plant Cells
What’s the difference?
1.Animal cells do not have a cell wall, but
they both have a cell membrane.
2.Plant cells have a cell wall, chloroplasts,
and larger vacuoles
3.Animal cells are found in humans,
animals, insects, etc…
Cell Parts. . .
are called
Organelles
They are very small in size
They perform all the functions of the cell.
Can only be observed under a microscope
Have specific functions
Found throughout cytoplasm of the cell.
Surrounding the Cell
Cell Membrane
• Flexible outer
membrane of the animal
cell and found under the
cell wall in plants.
• Membrane controls
movement in and out of
the cell
• Must move oxygen,
wastes, water, and
nutrients in and out of
the cell.
http://www.biology4kids.com/files/cell_main.html
Cell Wall
• Most commonly found in
plant cells & bacteria
• Found to be more tough
and rigid than the cell
membrane
• Supports & protects cells
• Cell wall allows nutrients
and water through the
holes in the wall which are
called plasmodesmata.
http://www.biology4kids.com/files/cell_main.html
Inside the Cell
Nucleus
• Directs cell activities
• Separated from
cytoplasm by nuclear
membrane
• Contains genetic material
– DNA on chromosomes
• Inside the nucleolus is
RNA and protein, not
much DNA at all.
• Typically the largest
organelle in the cell.
When chromosomes are bundled
together they are called
chromatin.
http://www.biology4kids.com/files/cell_main.html
Nuclear Membrane
• Surrounds nucleus
• Made of two layers
• Openings allow
material to enter and
leave nucleus
• Only found in cells
with a nucleus.
(Eukaryotic)
http://library.thinkquest.org/12413/structures.html
Chromosomes
• Inside nucleus
• Made of DNA
• DNA contains
instructions for traits
& characteristics
• DNA is made up of 4
nitrogen bases:
http://library.thinkquest.org/12413/structures.html
1. Adenine
2.Guanine
3. Cytosine
4. Thymine
Nucleolus
• What’s inside the
nucleolus.
• Appears tightly
bundled within the
nucleus
• Contains DNA &
RNA.
• RNA is used to build
proteins that will carry
out many functions of
the cell.
http://library.thinkquest.org/12413/structures.html
Cytoplasm
• Thick gel-like mixture that fills the cell (light blue
below)
• Surrounded by cell membrane
• 80% water that is clear – fills the cell
Mitochondria
• Produces energy through
chemical reactions –
breaking down fats &
carbohydrates
• Controls level of water and
other materials in cell
• Recycles and decomposes
proteins, fats, and
carbohydrates
• Like the digestive system
of the cell.
http://library.thinkquest.org/12413/structures.html
Vacuoles
• Sac with a membrane used for storage of food,
water, and waste products.
• Vacuoles contain water solution
• Vacuoles are much larger in plant cells than animal
cells.
• A drooping plant would indicate empty vacuoles,
but a full plant shows the vacuoles are full of water.
http://www.biology4kids.com/files/cell_main.html
Chloroplast
• Usually found in plant cells,
not in animal cells –
photosynthesis takes place
here.
• Contains green fluid called
chlorophyll
• Chlorophyll uses the sun’s
energy to combine Carbon
Dioxide (CO2) & Water (H2O)
to create sugars. The plant
releases the O2 created and
uses the sugar to grow.
http://www.biology4kids.com/files/cell_main.html
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/chloroplast.html
Endoplasmic Reticulum
• Also called ER
• Looks like a maze
• Main function: helps
make proteins and
other substances
• Works with
Ribsomes
• Usually found
around the nucleus
Ribosomes
• Look like dots
• Main job: make
proteins needed by
the cell
• Is helped by the ER
• Can be found
attached to the ER
or floating in the cell
Golgi Apparatus
• Also called Golgi
Bodies
• Flattened sacs and
tubes
• Is like a warehouse
• Main job: packages
and sends out
proteins to other
organelles or to
other cells
Lysosomes
• Sac like structures
• They are like
recycling centers
• Main job: break
down old cell parts.
Break down large
food particles into
smaller ones