Transcript 10 The Cell Theory

The Cell Theory – a timeline
• Late 1500’s:
• Early 1600’s:
-first lenses used in Europe
-used to determine cloth
quality (weave and
precision)
-combos of lenses gave better
view
Leeuwenhoek uses
microscope to study nature
Early
1600’s
Early 1600’s
• Leeuwenhoek
• first to view pond
water organisms
• First to see living
microscopic orgs
• Made careful
sketches
Robert Hooke ( 1665)
• Used light
microscope to look at
thin slices of plant
tissues -- cork
• Looked empty, like
monk’s chamber
• Called tiny chambers
“cells”
Matthias Schleiden 1838
• German Botanist
(plants)
• All plants looked at
were made of cells,
so concluded:
“All plants are
made of
cells.”
Theodore Schwann -- 1839
• German scientist
who studied animals
-- zoologist
• Saw that all animals
he studied were
cellular so
concluded:
“All animals are
made of cells.”
Rudolf Virchow -- 1855
• German physician
who studied cell
reproduction
• “Where a
cell exists,
there must
have been a
preexisting
cell…..”
The Cell Theory
• All living things are composed of
cells
• Cells are the basic units of structure
and function in living things
• New cells are produced from existing
cells
• Construct a timeline:
– Include years 1500s, early 1600s,
1665, 1838, 1839, and 1855 on your
timeline.
– Indicate the events and scientists
responsible for the events occurring
each year. (for 1500s, 1600s, and
late1600s you may not be able to
indicate a scientists)
• For each statement on your CELL
THEORY worksheet give the name
of the scientist(s) responsible for
the statement
– For statements three and four
multiple scientists are responsible.
Prokaryotes vs. Eukaryotes
• Prokaryotes:
• Eukaryotes:
*NO NUCLEUS
*Small and Simple – few
organelles
*Have cell membranes
and cytoplasm
Ex. Bacteria
*Contain nuclei
*Contains organelles that
perform specialized
functions
*Uni-or multicellular
Figure 7.4 A prokaryotic cell
Basic Cell Structures
• Cell membrane – thin, flexible
barrier around cell
• Nucleus – large, centralized structure
that contains genetic material and controls
cellular activities
• Cytoplasm – material inside membrane
(but not inside the nucleus) that supports the
internal cell shape and organelles
Basic cell parts: cell membrane and
cytoplasm
• Cell membrane –
*provides barrier between internal
and external environment of
cell
*is semi-permeable (some things
can go in, some cannot;
some things can exit, some
never can)
*made up of phospholipid bilayer with
proteins embedded that allow for
needed passage of large
molecules
• Major job of cell membrane is to maintain
the cell’s environment – establish
homeostasis
Fluid Mosaic Model
• Phospholipids and embedded proteins are
not locked into position – they flow against
one another as the cytoplasm and the
external liquid environment dictate (so, is
fluid)
• There are MANY different components of
the cell membrane – it is a mosaic of many
parts
Figure 8.6 The detailed structure of an animal cell’s plasma membrane, in cross section
Nucleus
• Largest organelle
• Enclosed by nuclear envelope or membrane,
which is a double membrane – each of which is a
lipid bilayer!!!
• Nuclear membrane has pores in it
• Contains inactive DNA – chromatin
• When gets ready to divide, chromatin condenses
into chromosomes
• Directs protein synthesis by synthesizing mRNA
and sending to ribosomes in the cytoplasm
Nucleus
• Contains the genetic information
that is the code for controlling ALL
of the cells activities
Cytoplasm
• Entire region between the nucleus
and the cell membrane
• The semifluid substance that fills this area is
called CYTOSOL, and this is what the
organelles are held in place with.
Cell Wall
• Found in plant cells (another barrier in
ADDITION to the cell membrane)
• Protects the cell
• Gives support to cell
• Made of polysaccharide called
cellulose
• Is very porous and allows molecules to pass
through, but is NOT SELECTIVELY
PERMEABLE
Organelles
• Control:
*Nucleus
(plant and animal)
• Assembly, Transport, and Storage:
*Endoplasmic reticulum
*Ribosomes
*Golgi apparatus
*Vacuoles
*Lysosomes
(plant and animal)
(plant and animal)
(plant and animal)
(plant and animal)
(plant and animal)
• Energy transformations:
*Chloroplasts
*Mitochondria
- Protection
- Cell Wall
- Cell Membrane
(plant only)
(plant and animal)
(Plant only)
(Plant and animal)
Endoplasmic reticulum –
“highway system”
• EXTENSIVE – accounts for more than half the
total membrane system in eukaryotic cells
• Name means “little net within the cytoplasm”
• Smooth and rough e.r. are actually connected, not
distinct, separate sections
• Job is to transport materials
quickly from one place to
another in cell
Figure 7.11 Endoplasmic reticulum (ER)
Smooth E.R.
NO ATTACHED RIBOSOMES
• Functions in making lipids,
metabolism of carbohydrates,
detoxification of drugs and poisons
Rough E.R.
ATTACHED RIBOSOMES
• Makes secretory proteins
(ex. Insulin made by pancreatic cells)
• Most are glycoproteins (proteins covalently bound
to carbs)
• Rough e.r. is also a membrane factory – grows by
adding proteins and phospholipids; parts can be
taken from here and added to other membrane
systems using the vesicles for transport
Ribosomes
“protein factories”
• Sites of protein synthesis
• Are made of rRNA and protein
• Cells with high rates of protein synthesis
have MANY ribosomes (human pancreas
cell has MILLIONS of ribosomes)
• Are “free” ribosomes in cytosol that make
proteins for the cell that they are INSIDE of
• Ribosomes that are attached to endoplasmic
reticulum (bound) are making proteins for
packaging and export OUTSIDE OF CELL
Figure 7.10 Ribosomes
Golgi apparatus
“Gift wrapper/UPS system”
• Finishes, sorts, ships cell products
• Golgi will modify products as needed –
gives more variety by removing some
monomers and substituting others
Figure 7.12 The Golgi apparatus
Vacuoles
“Bank Vaults” or “trash cans”
• Sites of storage in cells
*good things stored – water, minerals,
food etc.
*bad things stored – broken down cell
parts, waste
Lysosomes
• Membrane-bounded sac of digestive
enzymes
• Different lysosomes break down
each of the major classes of
macromolecules – proteins,
polysaccharides, fats, nucleic acids
• Work best at pH of 5
• Used in autophagy – recycle the cell’s own
organic material for use
Mitochondria and Chloroplasts
“powerhouses”
• Mitochondria – carry on cellular
respiration – sites of energy production in
cell (glucose broken down to produce ATP)
• Chloroplasts (only in plants) – carry
on photosynthesis
– sites where sunlight, CO2 and water are
converted into glucose
Figure 7.17 The mitochondrion, site of cellular respiration
Figure 7.18 The chloroplast, site of photosynthesis
Cytoskeleton
“hay in mud makes bricks”
• Network of fibers extending into
cytoplasm of cell
• Provides structural support, and aids in
cell motility and cell regulation
• Made up of microtubules (thickest),
microtubules (thinnest), and intermediate
filaments
Cilia and Flagella
“hairs and tails”
• Cilia are short projections from cell
body – hair-like
• flagella are much longer – whiplike
• Movement may not be for entire
organism; may be part of a larger unit – ex.
Cilia lining windpipe propel foreign
substances out…
Organelles do not work alone…
• Cell is a dynamic interaction of ALL of its
parts – literally, the basic unit of life….