Natural Science II – ERTH 1040
Cells
J. D. Price
From Nearing Zero (©Nick)
Cells: Robert Hooke's view
Advances in optical
physics permitted
scientists to view the
world between 1 E -3 m –
and 1 E -5 m
Robert Hooke used the
microscope to look at
thin preparations of plant
and animal tissue –
noticed common
compartment structure –
“cells” – like those found
in monasteries.
© McGraw-Hill, 2001
23-477a
What we know today about a cell
Advances in both optical
electron physics
permitted scientists to
view the world below 1 E4 m.
We have a good picture
of the components of a
cell. We are also
understanding what
those components do.
© McGraw-Hill, 2001
23-477b
Membranes:
Keeping “water” in/out
Q: What characteristic of the lipid molecule
makes it a good material to retain water?
Cell membranes are
made of two lipid
layers, bonded
together at their
hydrophobic ends.
Note: there are a
number of proteins
imbedded into the
membranes within
these diagrams (in
fact, about half the
membrane is
proteins).
Q: What function might the proteins serve?
If cell walls permitted no transport into/out of
cells, then respiration components not get in,
wastes could not be removed.
There are four principle ways in which
components are transferred through the cell
membranes:
•“Simple” diffusion
•Facilitated diffusion
•Active transport
•Phagocytosis
Q: What are the four means of
intermebranic transport?
Diffusion
In any matter over 0 K,
atoms migrate. The rate
of movement depends on
how well the atoms are
bonded.
In a gas, atoms may
dance around each other,
or switch places.
Q: what is chemical
diffusion?
Although diffusion
happens everywhere, we
can see diffusion in
places where atoms are
initially separated
The atoms will move in
random directions. As a
consequence, the atoms
are no longer in distinct
domains.
With time, the random
movements of the atoms
lead to complete random
dispersion of the atoms
Same thing here, except that
there is a clear boundary
between domains
The boundary we are
considering here is that of a
cell wall (phospholipid bilayer)
There may be a difference in
the rate of movement in the
areas on either side of the
boundary relative to that
through the boundary.
Note: atoms and lipids are not
to same scale
Not all
molecules are
able to cross
the boundary.
It depends on
size and
structure.
Small and
uncharged
permitted,
Large or
charged not.
The cell membrane is not entirely lipids, there are also
a number of enzymes (proteins) that transect the
membrane
© McGraw-Hill, 2001
23-478
The enzymes may permit faster
transport of molecules through the wall,
through diffusion (facilitated diffusion)
or by bonding with molecules and
moving them (active transport).
© McGraw-Hill, 2001
Facilitated
diffusion
Figure 23.9
Active transport
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Active transport
Q: what
molecules are
brought into the
cells through
active transport?
Phagocytosis
Transfer of really big
things through the cell
membrane. Membrane
completely encloses and
ingests the substance.
© McGraw-Hill, 2001
23-483
Mitochondria: oxidize
carbohydrate products
to release energy
(+H2O + CO2)
Cell energy transfer (in mitochondria)
Adenosine triphosphate (ATP)
Break here for 7.3 kcal/mole
energy release!
Q: what components are found
in both ATP and RNA?
kcal – energy required to
heat 1 kg of water 1oC
mole – 6.0221 E 23
molecules
The reaction can go backwards to
store energy.
All this is accomplished by the
enzyme ATPase (left)
This is one of the simple means of
energy transfer in cells (ATP goes
where energy is needed)
Q: For ATP formation, where is the
source of energy? What is it used for?
Recall combustion energy release
A bit more complicated than this. In simple terms the
carbohydrate (glucose) is split into several compounds
through glycolysis through the help of enzymes.
Glucose yields pyruvic acids and several ATP (though
two pathways)
In the absence of oxygen, cells may produce energy
through fermentation.
Yeast do this in bread, beer, and wine
Your muscles will do this if energy needs outpace
oxygen supply. They produce lactic acid through
glycolysis
Q: Can you draw a depiction of combustion of
ethanol? Why does it combust, producing heat?
Life in two parts
Prokaryotes: Kingdom Monera – simplest of
cells. Typically smaller. DNA is located
throughout the cell, not isolated
Eukaryotes: The rest of life – complex cells.
Typically larger. Lots of organelles. DNA is
isolated in the nucleus (not in the cytoplasm)
Q: What are the two types of cells, and
which do you have?
Figure 23.16a
Intermediate filament
Microfilament
Microtubules
Cytoskeltal components
Q: what type of molecule are these?
Parts of cytoskeleton
interconnect
Figure 23.17
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Two sets of short microtubules
Figure 23.18
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Eukaryotic cilia and flagella
Figure 23.19a
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Prokaryotic flagellum
Figure 23.19b
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Four structures in the cytoplasm
ER: contributes to
protein synthesis
Golgi bodies: process
proteins
Vacuoles: waste
storage (in plants)
Lysosome: contains
digestive proteins to
break down wastes.
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Illustration of a eukaryotic cell
Figure 23.13
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Chemical energy organelles
Chloroplast:
contains chlorophyll
which transfers
sun’s energy into
constructing
carbohydrates
Mitochondria:
oxidize
carbohydrate
products to release
that energy
Figure 23.14
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The Nucleus is
the organelle
that holds all of
the DNA within
a Eukaryote cell.
It contains
chromatin and
at least one
nucleoli, where
ribosomes are
constructed
(10K per minute)
Figure 23.20
Q: Why is there no DNA in the cytoplasm
of a Eukaryote?
Animal cell
Q: can
you
identify
and name
the
purpose
of each of
these
features?
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Plant cell
Q: what are the
differences
between plant and
animal cells?
The cell cycle
Q: what is the
cycle of a living
cell?
Figure 23.23
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Cell division in interphase stage
Figure 23.24
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Prophase, the first stage of mitosis
Figure 23.25
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Humans have 46 chromosomes. Shown are 1-22, plus X & Y
Women: double 1-22 and X
Men: double 1-22 and single X and Y
Each double (homologous pair) contains
similar, but not identical information
Each chromosome consists of DNA coiled
around and wrapped by proteins. Each
side of the chromosome contains the same
sequence (it’s a copy).
The late prophase
Figure 23.27
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Metaphase,
the second stage of mitosis
Figure 23.28
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Chromosomes
on the equatorial plane
Figure 23.29
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Anaphase,
the third stage of mitosis
Figure 23.30
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Telophase,
the last stage of mitosis
Figure 23.31
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Q: what are the stages of mitosis? What happens
during each stage?
Q: why is mitosis important for organisms?