Cell Structure
& Function
http://koning.ecsu.ctstateu.edu/cell/cell.html
Definition of Cell
A cell is the smallest unit that is
capable of performing life
functions.
Examples of Cells
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
Two Types of Cells
•Prokaryotic
•Eukaryotic
Prokaryotic • Do not have
membrane bound organelles (structures surrounded by membranes)
• Few internal structures
• One-celled organisms
• Example: Bacteria
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Eukaryotic Cells • Contain organelles surrounded by membranes
• Includes most living organisms both single & multi-cellular
• Carry out more specialized functions than prokaryotic cells
b/c of their complex organization
Plant Animal
http://library.thinkquest.org/C004535/eukaryotic_cells.html
“Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
http://waynesword.palomar.edu/images/plant3.gif
“Typical” Plant Cell
Cell Parts
Organelles “little organs”
Surrounding the Cell
Cell Membrane
• Outer membrane of cell that controls movement
in and out of the cell
• Double layer called the phospholipid bilayer
http://library.thinkquest.org/12413/structures.html
• Also called the Plasma Membrane
Cell Wall
• Most commonly found
in plant cells, fungi
cells & bacteria
• Supports & protects
cells
• Double layer
http://library.thinkquest.org/12413/structures.html
Flagella & Cilia
Flagella- whip-like projections
Cilia- hair-like projections
Both are used for movement;
composed of cytoskeleton
filaments & protein; covered in an
extension of the cell membrane
Inside the Cell
Nucleus • Directs cell activities
• Separated from cytoplasm by nuclear
membrane
• Contains genetic material (DNA) inside the
nucleolus
Nuclear Membrane
• Surrounds nucleus
• Made of two layers
• Openings called
nuclear pores allow
material to enter and
leave nucleus
http://library.thinkquest.org/12413/structures.html
Chromatin/Chromosomes
• In nucleus
• Chromatin is DNA &
protein in a loose
network of bumpy
threads (condenses
to form chromosomes
during cell division)
• Contain instructions
for traits &
characteristics
http://library.thinkquest.org/12413/structures.html
Nucleolus
• Inside nucleus
• Contains RNA to build
proteins
• ribosome parts are
made here
http://library.thinkquest.org/12413/structures.html
Cytoplasm
• Gel-like mixture
• surrounded by cell membrane
• Organelles are supported by the
cytoplasm
• Site of most cellular activities (like the
factory area of the cell)
Endoplasmic Reticulum • System of canals that
coils & twists through the
cytoplasm
• Moves materials around
in cell
• Smooth ER: lacks
ribosomes, functions in
lipid metabolism (making
& breaking down
cholesterol and fats) and
detoxification of drugs
and pesticides http://library.thinkquest.org/12413/structures.html
Endoplasmic reticulum (cont.)
Rough ER:
•Has ribosomes on the surface
•Proteins made by the ribosomes
enter the rough ER then fold into
their functional 3-dimensional
shape. They are then transported
to other areas of the cell in
vesicles.
Ribosomes
• Each cell contains
thousands
• Makes proteins
• Floating free
throughout the cell
• Composed of 2
subunits
http://library.thinkquest.org/12413/structures.html
Mitochondria • Produces energy (ATP)
by breaking down food
(cellular respiration)
• Regulates cellular
metabolism
• Surrounded by 2
membranes
• Has its own DNA &
ribosomes!
• „busy‟ cells have
hundreds of mitochondria http://library.thinkquest.org/12413/structures.htl
Golgi Bodies or Golgi Apparatus • Stack of flattened
membrane bound
sacs
• Major function is to
modify & package
proteins
• Modifies, sorts, and
packages materials
for export from the
cell
http://library.thinkquest.org/12413/structures.html
Lysosome • Contains powerful
digestive enzymes
• Digestive „factory' for
proteins, fats, and
carbohydrates
• Abundant in cells that
dispose of bacteria &
cell debris
• Cell is digested if a
lysosome explodes
http://library.thinkquest.org/12413/structures.html
Peroxisomes
•Most important
function is to convert
free radicals into
hydrogen peroxide
(H2O2)
•If left to accumulate,
free radicals can have
devastating effects on
cells
Vacuoles/ Central Vacuole
• Membrane-bound
sacs for storage,
digestion, and waste
removal
• Contains water, ions,
nutrients, & wastes
• Very large in plants;
maintain plant shape
by holding lots of
water
http://library.thinkquest.org/12413/structures.html
Chloroplast
• A plastid found in
plant & algae cells
• Contains green
chlorophyll
• Where
photosynthesis takes
place
http://library.thinkquest.org/12413/structures.html
Cytoskeleton
•Elaborate network of protein structures that
extends throughout the cytoplasm
•Acts as the cells “bones & muscles” by providing
an internal framework that determines cell shape,
supports other organelles, and provides a route
for intracellular transport
•Made up of microfilaments,
micrtubules, & intermediate
filaments
Centrioles •Rod-shaped structures that direct
the formation of spindle fibers
during mitosis & meiosis
•Made of microtubles
Vesicles
These are not actually organelles.
This is a generic term for any
material that is enclosed in a
membrane. Vesicles are pinched
off from the golgi body, cell
membrane, and ER. They may
contain hormones, proteins,
nutrients, etc.