Cells
Some Random Cell Facts
• The average human being is composed of
around 100 Trillion individual cells!!!
• It would take as many as 50 cells to cover
the area of a dot on the letter “i”
Discovery of Cells
• 1665 Robert Hooke
– discovered cells while looking at a thin slice of cork.
– described the cells as tiny boxes or a honeycomb
– thought that cells only existed in plants and fungi
Anton van Leuwenhoek
• 1673- Used a handmade microscope to observe pond
scum & discovered single-celled organisms
• He called them “animalcules”
• He also observed blood cells from fish, birds, frogs,
dogs, and humans
• Therefore, it was known that cells are found in animals
as well as plants
• 1838 Matthias Schleiden
– concluded that all plant parts are made of
cells
• 1839 Theodor Schwann,
– stated that all animal tissues are composed of
cells.
• 1858- Rudolf Virchow
– concluded that cells must arise from preexisting cells.
The Cell Theory Complete
• The 3 Basic Components of the Cell Theory
were now complete:
1. All organisms are composed of one or more cells.
2. The cell is the basic unit of life in all living things.
3. All cells are produced by the division of preexisting
cells.
Can you design the “best cell”
shape?
• What do cells need?
• How could you measure if this need is
met?
• How could you compare different designs?
2 Basic Types of Cells
1) Prokaryotic examples ???
2) Eukaryotic examples????
Plasma membrane
• Structure
– Main component is
phospholipids that are
arranged in a double
layer (bilayer)
– Has scattered proteins
within the
phospholipids
Function of the Plasma
Membrane
• Regulate what gets
into or leaves the
cell
• Structure
Nucleus
– Surrounded by a
double membrane
– This “nuclear
membrane” has pores
• Function
– Holds the
chromosomes
(DNA) and the
nucleolus
Nuclear envelope
• Double layer of
membrane
• Has pores
• Surrounds the
nucleus
• Regulates what
goes into and out
of the nucleus
Chromosomes
• Structure
– String-like
structures in the
nucleus made of
DNA and protein
• Function
– Contain your genes
Nucleolus
• Structure
– Small dark
structure in the
nucleus
• Function
– Produce ribosomes
Ribosomes
• Small structures
(NOT made of
membrane)
• Make proteins
Central Vacuole
• Structure
– LARGE sac made
of membrane
– Found in center of
plant cells
• Function
– Stores chemicals
and water
Smooth Endoplasmic Reticulum
• Structure
– Canals and tubes
made of membrane
• Function
– Makes lipids (oils,
phospholipids,
steroids)
– Detoxifies poisons
Rough Endoplasmic Reticulum
• Structure
– Canals and tubes
made of membrane
– Have ribosomes
attached to the
outside
• Function
– Transport materials
in the cell
– Make proteins
(those exported
from the cell, those
found on the
plasma membrane,
those found in
lysosomes)
Golgi Apparatus
• Structure
• Function
– Stacks of membrane
– Chemically modifies
sacs
substances
– has a receiving end (from – Packages material for
ER) and a shipping end
transport out of the
cell or to other
locations within the
cell
Vesicles
• Structure
– Small membrane
“bubbles” that bud
off the ER or Golgi
• Functions
– Transport materials
to new locations
Lysosomes
• Structure
– Sacs of membrane
that contain
hydrolytic enzymes
– -found mostly in
animal cells
• Function
– Use enzymes to
break down old
organelles
– In white blood cells
are used to destroy
bacteria
Mitochondria
• Structure
– Surrounded by a
double membrane
• Folds found on the
inside
• Function
– Cellular Respiration
• Converts energy in
sugars into the
energy of ATP
molecule
Chloroplasts
• Structure
– Surrounded by a
double layer of
membrane
• Disks found inside
• Function
– Convert solar
energy into
chemical energy
(food)
– Site of
photosynthesis
Perioxisome
• Structure
– Small membranous
sac
• Function
– Some reactions
occurring here
produce H2O2 (toxic)
• So, it also contains an
enzyme (catalase) that
converts this to water
and oxygen gas
• Structure
Cell Wall
– Found outside the
plasma membrane
– Plant  made of
cellulose
• Function
– Give support to
certain cells (plant)
– Does NOT
determine what can
get into/out of the
cell
Cytoskeleton
• Structure
• Made of protein fibers
– Microtubules
• Hollow tube
– Microfilaments
• Small rods
– Intermediate filaments
• Function
– Give the cell shape
– Help to move
organelles around the
cell
Fig. 4-17
Nucleus
Nucleus
Actin subunit
Fibrous subunits
7 nm
Microfilament
Tubulin subunit
10 nm
25 nm
Intermediate filament
Microtubule
Centrioles
• Structure
– Made of rings of
microtubules
– Found in pairs that
lie at right angles
• Look similar to a
pair of barrels
• Function
– Found in animal
cells
– Help organize the
tubulin required for
cell division
Cilia
• Structure
– Microtubules that
extend from the cell
(still covered by the
plasma membrane)
– Short and many of
them
• Function
– In single-celled
organisms, they can
move the organism
from place to place
– If anchored in place,
can set up a current,
moving fluid across
the surface of a cell
Fig. 4-1c
Fig. 4-18a
Cilia
http://www.youtube.com/watch?v=YHb2Ja
ujIPo&feature=related&safety_mode=true&
persist_safety_mode=1
Flagella
Structure
• Same as cilia, but
are longer and there
are just a few of
them
• Prokaryotes also
have them
– Not made of
microtubules
Function
• Move the cell within its
environment
Fig. 4-20
Glycoprotein
complex with long
polysaccharide
EXTRACELLULAR FLUID
Collagen fiber
Connecting
glycoprotein
Integrin
Plasma
membrane
Microfilaments
CYTOPLASM
How large can cells get?
-depends on how efficiently they can get nutrients in
and wastes out
10 µm
30 µm
30 µm
Surface area
of one large cube
= 5,400 µm2
10 µm
Total surface area
of 27 small cubes
= 16,200 µm2
Fig. 4-21
Tight junctions
Anchoring junction
Gap junctions
Plasma membranes
of adjacent cells
Extracellular matrix
Fig. 4-22
Walls
of two
adjacent
plant cells
Vacuole
Plasmodesmata
cell wall
Cytoplasm
Plasma membrane
B
C
D
A
CD (CONTAINING
DIGESTIVE
ENZYMES)
E
BE
AB
BD
AC
BC
AE
AD
BE
A
BD
BC
B
AE
C
AD
AC
D
AB
E
D
B
C
A