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Cells
Structure, Function and other stuff
GETTIN’ THE JOB DONE:
A Blast from the Past
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REMEMBER OUR
CHARACTERISTICS
OF LIVING THINGS?
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The Toy Lab…
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Evolution
Reproduction
Reacting to
Environmment
Homeostasis
(Balance)
Movement
Organization
Energy (getting it,
using it)
CELL ORGANELLES
Each organelle performs specific functions
 The organelle’s function accomplishes one
or several of the necessary requirements
for life…
 e.g., NUCLEUS…
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a “Two-for-the-price-of-one” special
 REPRODUCTION
 Instructions for ORGANIZATION of cell
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A REAL Alien Invasion…
They come in peace
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Read Lewis Thomas’ essay
Answer the following as you read:
 What does Thomas mean when he says that “some
[organelles], and the most important ones at that, are
total strangers”?
 Which organelles does he suggest are the
“strangers”?
 What evidence does he provide for this suggestion?
 In the “master and slave” relationship that Thomas
alludes to in the reading, in what ways are we
“slaves” to our organelles?
 What is Thomas’s overall emotional reaction to the
idea of strangers living inside our cells? How can you
tell?
CELLULAR EVOLUTION
A tale of intrigue, suspense, and
neverending commitment to one another…
 Scene 1: A tale of two cell types
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Prokaryotes
(used to be Monera in the 5 kingdom classification)
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Archebacteria
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Harshest habitats
First life forms?
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Eubacteria
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Most modern bacteria
Cyanobacteria (sometimes
called blue-green algae)
Eukaryotes
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All complex cells that have membrane bound organelles.
10 – 100 X the size of prokaryotic cells
May be single cell organisms (still are complex and have
membrane bound organelles).
Cells making up all multicellular organisms.
In multicellular organisms, cells can group together to
form a various “levels of organization
Cell categories
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Prokaryotes
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Smaller than
eukaryotes
All bacteria
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Eukaryotes
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Archaebacteria
eubacteria
Much larger than
prokaryotes
Anything not bacteria
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No membrane covered
organelles
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Protista
Plantae
Fungi
Animalia
Membrane bound
organelles special
focus on nucleus
6 kingdoms connection
BUT…WHY DID THEY DIVERGE?
Remember their differences?
 Where did all of these cell parts come
from?
 Scene 2: Intrigue… “Having a friend for
dinner”…
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ECOLOGY: INTERACTION WITH
THE ENVIRONMENT
Living things interact with one another
 Lots of different kinds of interactions
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Predator-prey
 Mutualists
 Etc…more to come on these later
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Prokaryote vs Eukaryote sizes
Phagocytosis(food)/Pinocytosis (liquid)
same process
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Cell interior
Endocytosis/Exocytosis
SO…WHAT SHOULD HAPPEN?
A cell takes in “prey” using the cell
membrane
 Vesicles form and the food is digested by
the lysosomes, right?
 BUT NOT IN THIS CASE… SUSPENSE!
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REMEMBER:
Prokaryote vs Eukaryote sizes
What do we know about
mitochondria and chloroplasts?
Same size as prokaryotes (A.K.A.
Bacteria)
 Have their own DNA
 Have similar structure to prokaryotes
 Reproduce like prokaryotes
 Membrane structure is like prokaryotes
 Double membrane makes sense
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Enter…Lynn Margulis…Eukaryote
Lynn Margulis
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Her hypothesis originally proposed that:
mitochondria are the result of endocytosis of
aerobic bacteria
 chloroplasts are the result of endocytosis of
photosynthetic bacteria
 in both cases by large anaerobic bacteria who
would not otherwise be able to exist in an
aerobic environment.
 this arrangement became a mutually beneficial
relationship for both cells (symbiotic).
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HUH?
Instead of eating your roommate, you let
them live and pay rent…
 It’s win-win for both of you!
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Endosymbiotic theory
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Simply stated, the theory of
endosymbiosis is the concept that:
mitochondria and chloroplasts are the result
of years of evolution
 initiated by the endocytosis of bacteria and
blue-green algae
 instead of becoming digested, became
mutualistic.
 HENCE…A NEVERENDING COMMITMENT
TO EACH OTHER!
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Biological
levels
Of
organization
CELL ENERGY
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2 PROCESSES:
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Photosynthesis
(chloroplast)
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Builds sugar using the
energy from sunlight
and matter from the
atmosphere
Cell Respiration
(mitochondria &
cytoplasm)
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Releases energy from
sugar