Transcript Tour of the Cell

Tour of the Cell
AP Biology
2012-2013
I. Why do cells have organelles (little
organs)?
 Specialized structures

specialized functions
mitochondria
 cilia or flagella for locomotion
 Containers


partition cell into compartments
create different local environments
chloroplast
 separate pH, or concentration of materials

distinct & incompatible functions
 lysosome & its digestive enzymes
 Membranes as sites for chemical
Golgi
reactions


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unique combinations of lipids & proteins
embedded enzymes & reaction centers
 chloroplasts & mitochondria
ER
II. Isolation of organelles
A. Occurs by process of
cell fractionation.
B. Based on various densities
of organelles.
C. Begins with breaking open
cell membranes without
damaging organelles; Called
homogenization.
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D.Homogenate is spun in a centrifuge
to separate the pellet of
organelles from the liquid
(supernatant).
E. Pellet is removed, and the
supernatant is spun again at
higher speed to cause heaviest of
remaining organelles to settle out.
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F. Heaviest to lightest cell fractions
are nuclei,
mitochondria/chloroplasts,
parts of membranes, then
ribosomes.
G. Specific metabolic processes are
identified with certain cell
fractions, and then tied to
specific organelles.
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(Show “Cell Fractionation Animation”
from microbiology web site.)
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Types of cells
Eukaryote
animal cells
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Prokaryote
bacteria cells
Eukaryote
plant cells
II. General Types of cells
A.Basic cell structures
1. Plasma membrane
2. Cytosol (jelly-like substance)
3. Ribosomes
4. DNA
B. Prokaryotic cells have DNA in
nucleiod region; No membrane
around
DNA.
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C. Eukaryotic cells have DNA in
membrane-bound nucleus.
D. Eukaryotes also have membrane-bound
organelles floating in cytoplasm (region
between nucleus and cell membrane).
E. Eukaryotes are bigger than
prokaryotes.
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F. Eukaryotes have many internal
membranes that divide internal
space into compartments.
G. Compartmentalization allows for
multiple metabolic processes to
occur at the same time.
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Limits to cell size
 Lower limit

smallest bacteria
 mycoplasmas
 0.1 to 1.0 micron (µm = micrometer)

most bacteria
 1-10 microns
 Upper limit

eukaryotic cells
 10-100 microns
 micron = micrometer = 1/1,000,000 meter
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APdiameter
of human hair = ~20 microns
What limits cell size?
 Surface to volume ratio

as cell gets bigger its volume increases
faster than its surface area
 smaller objects have greater
ratio of surface area to volume
Why is a huge
single-celled
creature not
possible?
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s:v
6:1
~1:1
6:1
Limits to cell size
 Metabolic requirements set upper limit

in large cell, cannot move material in &
out of cell fast enough to support life
aa
aa
CH
NH3
aa
CHO
O2
CH
aa
CO2
CO2
CHO
CH
AP Biology
aa
aa
O2
CO2
CHO
O2
NH3
CHO
O2
NH3
O2
NH3
CO2
CH
aa
What’s the solution?
How to get bigger?
 Become multicellular (cell divides)
But what challenges do you have to solve now?
CO2
CO2
aa
aa
CO2
CHO
NH3
CH
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CO2
O2
NH3
aa
aa
CO2
NH3
CO2
CO2
NH3
NH3
CO2
CH
NH3
NH3
CO2
CHO
O2
NH3
CO2
O2
CH
aa
O2
NH3
CHO
CO2
aa
Cells gotta live!
 What jobs do cells have to do?

building proteins
 proteins control
every cell function

make energy
 for daily life
 for growth

build more cells
 growth
 reproduction
 repair
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Why study protein production?
proteins
cells
DNA
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Repeat after me…
organism
DNA gets the glory, but
Proteins do all the work!
Building Proteins
 Organelles involved
nucleus
 ribosomes
 endoplasmic reticulum
(ER)
 Golgi apparatus
 vesicles

The Protein Assembly Line
nucleus
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ribosome
ER
Golgi
apparatus
vesicles
Putting it together…
nucleus
nuclear pore
Making proteins
cell
membrane
protein secreted
rough ER
ribosome
vesicle
proteins
smooth ER
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transport
vesicle
cytoplasm
Golgi
apparatus
TO:
endoplasmic
reticulum
nucleus
protein
on its way!
DNA
RNA
TO:
vesicle
TO:
TO:
vesicle
TO:
ribosomes
finished
protein
protein
Golgi
apparatus
Making Proteins
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Cells gotta live!
 What jobs do cells have to do?

make proteins
 proteins control
every cell function

make energy
 for daily life
 for growth

build more cells
 growth
 reproduction
 repair
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ATP
Cells need power!
 Making energy
take in food & digest it
 take in oxygen (O2)
 make ATP
 remove waste

ATP
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1960 | 1974
Lysosomes
 Function

Christian de Duve
little “stomach” of the cell
 digests macromolecules

“clean up crew” of the cell
 cleans up broken down
organelles
 Structure

vesicles of digestive enzymes
Where
old organelles
go to die!
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only in animal cells
Lysosomal enzymes
 Lysosomal enzymes work best at pH 5


organelle creates custom pH
how?
 proteins in lysosomal membrane
pump H+ ions from the cytosol
into lysosome

why?
 enzymes are very sensitive
to pH

why?
 enzymes are proteins —
pH affects structure

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why is this an adaptation: digestive enzymes which
function at pH different from cytosol?
 digestive enzymes won’t function well if some leak
into cytosol = don’t want to digest yourself!
But sometimes cells need to die…
 Lysosomes can be used to kill cells when
they are supposed to be destroyed

some cells have to die for proper
development in an organism
 apoptosis
 “auto-destruct” process
 lysosomes break open & kill cell
 ex: tadpole tail gets re-absorbed
when it turns into a frog
 ex: loss of webbing between your
fingers during fetal development
 ex: self-destruct of cancerous cell
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syndactyly
Fetal development
6 weeks
15
weeks
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When things go wrong…
 Diseases of lysosomes are often fatal
digestive enzyme not working in lysosome
 picks up biomolecules, but can’t digest one

 lysosomes fill up with undigested material

grow larger & larger until disrupts cell &
organ function
 lysosomal storage diseases
 more than 40 known diseases
 example:
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Tay-Sachs disease
build up undigested fat
in brain cells
From food to making Energy
 Cells must convert incoming energy to
forms that they can use for work
mitochondria:
ATP
from glucose to ATP
 chloroplasts:
from sunlight to ATP & carbohydrates

 ATP = immediate energy
 carbohydrates = stored energy
ATP
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+
Mitochondria & Chloroplasts
 Important to see the similarities

transform energy
 generate ATP
double membranes = 2 membranes
 semi-autonomous organelles

 move, change shape, divide

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internal ribosomes, DNA & enzymes
Lynn Margulis
U of M, Amherst
Membrane-bound Enzymes
glucose + oxygen  carbon + water + energy
dioxide
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C6H12O6 +
6O2  6CO2 + 6H2O + ATP
Membrane-bound Enzymes
carbon + water + energy  glucose + oxygen
dioxide
light  C H O + 6O
6CO
+
6H
O
+
6 12 6
2
2
2
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energy
Mitochondria are everywhere!!
animal cells
plant cells
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Cells gotta live!
 What jobs do cells have to do?

building proteins
 proteins control
every cell function

make energy
 for daily life
 for growth

build more cells
 growth
 reproduction
 repair
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Cytoskeleton
 Function

structural support
 maintains shape of cell
 provides anchorage for organelles
 protein fibers


microfilaments, intermediate filaments, microtubules
motility
 cell locomotion
 cilia, flagella, etc.

regulation
 organizes structures
& activities of cell
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Cytoskeleton
 actin
 microtubule
 nuclei
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Centrioles
 Cell division
in animal cells, pair of centrioles
organize microtubules
 guide chromosomes in mitosis

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Cell Size
AP Biology
2012-2013
Limits to cell size
 Lower limit

smallest bacteria
 mycoplasmas
 0.1 to 1.0 micron (µm = micrometer)

most bacteria
 1-10 microns
 Upper limit

eukaryotic cells
 10-100 microns
 micron = micrometer = 1/1,000,000 meter
Biology
APdiameter
of human hair = ~20 microns
What limits cell size?
 Surface to volume ratio

as cell gets bigger its volume increases
faster than its surface area
 smaller objects have greater
ratio of surface area to volume
Why is a huge
single-celled
creature not
possible?
AP Biology
s:v
6:1
~1:1
6:1
Limits to cell size
 Metabolic requirements set upper limit
in large cell, cannot move material in &
out of cell fast enough to support life
aa
aa
What process is this?
CH
NH3
aa

CHO
O2
CH
aa
CO2
CO2
CHO
CH
AP Biology
aa
aa
O2
CO2
CHO
O2
NH3
CHO
O2
NH3
O2
NH3
CO2
CH
aa
What’s the solution?
How to get bigger?
 Become multicellular (cell divides)
But what challenges do you have to solve now?
CO2
CO2
aa
aa
CO2
CHO
NH3
CH
AP Biology
CO2
O2
NH3
aa
aa
CO2
NH3
CO2
CO2
NH3
NH3
CO2
CH
NH3
NH3
CO2
CHO
O2
NH3
CO2
O2
CH
aa
O2
NH3
CHO
CO2
aa
Cell membrane
 Exchange structure

plasma membrane functions as
selective barrier
 allows passage of O2 & nutrients IN
 allows passage of products & wastes OUT
Phospholipid
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Membrane
proteins
Cholesterol
Any Questions??
AP Biology
2012-2013