Cells
Cell Theory, Prokaryotes, and
Eukaryotes
Cell Theory
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Living organisms are composed of cells.
Cells are the smallest unit of life.
Cells come from pre-existing cells.
Cell Theory
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Discuss the evidence for the cell theory
Simple, get some broth, pour it in two
flasks, boil both, leave one uncovered,
and seal the other
What do you think will happen?
Cell Theory
Cell Theory
Unicellular organisms carry out all the
functions of life.
 Metabolism
 Response
 Homeostasis
 Growth
 Reproduction
Characteristics of Cells
Metabolism: the complete set of
chemical reactions in a living organism
Response: a change of internal or
external behavior based upon
environmental stimulus
Homeostasis: the ability to regulate the
internal environment of an organism
Characteristics of Cells
Growth: an organism captures and
stores energy from the environment
(food), at a faster rate than it uses the
captured energy (released as heat)
Reproduction: new individual
organisms are produced, can be
sexual or asexual
Give an example...
The human body is in homeostasis, name
three aspects of the body that must be
regulated and maintained at a constant
level.
1. Blood sugar levels
2. Temperature
3. Oxygen
4. Blood and extracellular fluid pH
Cell Theory
Compare the relative sizes of molecules, cell
membrane thickness, viruses, bacteria,
organelles and cells, using the appropriate
SI unit.
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What does SI stand for?
What types of units are considered SI?
Put the above structures in order from smallest
to largest, guess what size they might be, using
SI units.
Levels of Complexity
Appreciation of relative size is required, such as…
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molecules (1 nm)
thickness of membranes (10 nm)
viruses (100 nm),
bacteria (1 μm)
organelles (up to 10 μm)
most cells (up to 100 μm)
MTVBOC
Cell Theory
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Calculate the linear magnification of
drawings and the actual size of
specimens in images of known
magnification.
Magnification could be stated (for
example, ×250) or indicated by means of
a scale bar.
What is the Magnification of This Picture?
1 μm
10 cm
How Long are These Bacteria?
50 mm
50k X
Determination of Actual Size
Actual Size = Measured Size
Magnification
Actual Size = 50mm (50x10-3m or 0.05m)
50,000
(5x104)
Actual Size = 1μm (1x10-6m)
Cell Theory
Explain the importance of the surface area
to volume ratio as a factor limiting cell size.
 The rate of heat production/waste
production/resource consumption of a cell
is a function of its volume, whereas the
rate of exchange of materials and energy
(heat) is a function of its surface area.
Surface Area Limits Cell Size
The boundary of every cell acts as a barrier
that allows sufficient passage of oxygen,
nutrients, and waste to service the entire
volume of the cell.
Volume increase more rapidly than surface
area as cells grow
The rate of exchange with the environment is
inadequate in a cell with a very large
cytoplasm
Surface Area vs. Volume
radius of a cell is 1mm
surface area is about 13mm2
volume will be about 4mm3
radius is increased to 10mm
surface area is about 1300mm2
volume will be about 4000mm3
10x increase
100x increase
1000x increase
Cell Surface Area to Volume Ratio
Cell Theory
Multicellular organisms show emergent properties.
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Emergent properties arise from the interaction of
component parts: the whole is greater than the
sum of its parts.
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Can you think of something else with emergent
properties?
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Did you think of computers? Some other
technology?
Cell Theory
Cells in multicellular organisms differentiate
to carry out specialized functions by
expressing some of their genes but not
others.
Even though every cell has the same DNA
code, not every gene is being used at the
same time
Different cells use different genes
Cell
Differentiation
Cell Theory
Stem cells retain the capacity to divide and
have the ability to differentiate along
different pathways.
Stem cells have not yet decided what type of
specialized cells they will be.
Kind of like students before the find careers.
So how do cells decide?
How Stem Cells Decide
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All participants will begin seated at a table or lab bench
If you are within arms reach of a member of the opposite sex,
then stand up and put your stool under the table.
If you are standing and wearing pants, then take five steps in any
direction.
If you took a shower this morning, then switch places with the
nearest person to you.
If you are full IB, then put your right hand on top of your head.
If the person nearest you has their hand on their head, then put
your left hand on your stomach.
If you have a hand on your head on your stomach, then pat your
head and rub your stomach in a circular motion. Do not stop.
If you are still sitting, spin in a circle, click your heals together
three times, and say, ‘there’s no place like home’.
Cell Theory
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Outline one therapeutic use of stem cells.
This is an area of rapid development. In
2005, stem cells were used to restore the
insulation tissue of neurons in laboratory
rats, resulting in subsequent
improvements in their mobility.
Stem Cell Video
Prokaryotes
Simple, single celled organisms
Prokaryotic Structure
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Cell wall: rigid structure surrounding cell, made of
proteins
Plasma membrane: lipid bi-layer enclosing the
cytoplasm
Ribosomes: site of protein synthesis, type 70s
Pilli: used for attachment
Flagella: used for locomotion in some bacteria
Nucleoid: region containing DNA
Cytoplasm: interior of cell
Prokaryote Genome
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Prokaryotes do not have a nucleus
The DNA exists as a single circular
chromosome
It does not have histone proteins, and is
known as naked DNA
The region where the circular DNA strand
is found is called the nucleoid
Prokaryotes
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Draw and label a diagram of the
ultrastructure of Escherichia coli (E. coli)
as an example of a prokaryote.
The diagram should show the cell wall,
plasma membrane, cytoplasm, pili,
flagella, ribosomes and nucleoid (region
containing naked DNA).
See page 98 of your textbook.
Prokaryotes
Prokaryotes
You should be a
able to identify
structures in
electron
micrographs of
E. coli.
Review
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What a factor limits cell size?
Why?
Prokaryotes
Binary fission is used by most
prokaryotes for asexual
reproduction.
This process replicates the original,
or mother, cell, to produce two
identical daughter cells.
Binary Fission
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The fission process begins when the DNA of the mother
cell is replicated and joins into a circular structure, pair
by pair.
Each circular DNA strand then attaches to the plasma
membrane.
Near the site of attachment, the cell elongates and
causes the two duplicated chromosomes to separate.
At this point, the plasma membrane invaginates, or
pinches inward toward the middle of the cell.
When it reaches the middle, the cell splits into two
daughter cells.
Binary Fission
Binary Fission
Eukaryotes
Complex Cells with Organelles
Eukaryotes
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Draw and label a diagram of the
ultrastructure of a liver cell as an example
of an animal cell.
The diagram should show free ribosomes,
rough endoplasmic reticulum (rER),
lysosome, Golgi apparatus, mitochondrion
and nucleus.
See page 100 of your textbook
Eukaryotes – Cell Parts
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Plasma membrane
Nucleus
Nuclear envelope
Nucleolus
Ribosomes
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Endoplasmic Reticulum
Golgi Apparatus
Vesicles
Lysosomes
Mitochondria
Centrioles
Plasma Membrane
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Phospholipid bi-layer that surrounds cell
Functions to separate internal cell
environment (cytoplasm) from exterior
environment
Selectively Permeable: allows specific
substances to cross membranes but not
others
Contains various types of membrane proteins
Plasma Membrane
Nucleus
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Location of genetic material (DNA
chromosomes)
Consists of nuclear envelope, chromatin
(DNA), nucleolus, and nuclear pores
Functions to separate DNA from the rest of
the cell
Nuclear Envelope
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Double membrane
surrounding nucleus
Nuclear pores allow entry
and exit of molecules
between nucleus and
cytoplasm
Continuous with rough
endoplasmic reticulum
Nuclear Pores
Nucleolus
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Located within
nucleus
Site of ribosome
production and
assembly
Ribosomes
Composed of two
subunits
 Created in nucleolus
 Located in cytoplasm
or RER
 Functions in
synthesis of proteins
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Ribosomes
 Composed
of
multiple proteins
and ribosomal
RNA (rRNA)
 80s
Endomembrane System
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Membranous organelles function to
compartmentalize cellular reactions in
isolated locations
Includes RER, the Golgi, lysosomes,
vacuoles, vesicles, mitochondria, and
cholorplasts
Rough Endoplasmic Reticulum
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Studded with ribosomes on outer surface
Site of protein synthesis for…
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hydrolytic enzymes: destined for lysosomes
membrane proteins: channel and receptor proteins
secretory proteins: proteins going outside the cell
Continuous with nuclear envelope
Vast complex of channels
Inside is called the lumen
Vesicles
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Lipid bi-layer spheres
Used to transport
proteins throughout
the cell
Transported along
cytoskeleton
microtubules
Golgi Apparatus
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Receives vesicles
from ER
Modifies, packages,
and transports
molecules to final
destination
Cis face toward ER
Trans face toward
plasma membrane
Lysosomes
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Storage vesicles
containing hydrolytic
(digestive) enzymes
Enzymes used to
breakdown food or
damaged organelles
Protein Trafficking
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Proteins destined for specific cellular
locations such as the plasma membrane or
lysosomes are synthesized at the RER
Vesicles transport proteins to Golgi
apparatus
From Golgi apparatus proteins are sent, via
vesicles, to specified cellular location
Mitochondria
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Location of cellular
respiration (making
ATP from glucose)
Parts include:
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Double membrane
Intermembrane space
Cristae
Matrix
DNA
70s ribosomes
Cytoskeleton
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A series of protein
tubes and filaments
create an internal
skeleton within cells
Functions in cell
shape, cell division,
locomotion, and
vesicle transport
Extracellular
Matrix
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Animal cells secrete
glycoproteins that
form the extracellular
matrix
This functions in
support, adhesion
and movement.
Eukaryotes
Identify structures in
electron
micrographs of
liver cells.
Plant Cells
Plant cells are eukaryotes with additional
modifications
 Chloroplasts
 Cell walls
 Central vacuoles
 Plasmodesmata
 No centrioles
Generalized
Plant Cell
Chloroplasts
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Location of photosynthesis
Photosynthesis: the
transfer of light energy into
the chemical bonds of
glucose
Parts include:
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Thylakoid
Grana
Stroma
DNA
70s ribosomes
Cell wall
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maintains cell shape
prevents excessive water
uptake
holds the whole plant up
against the force of gravity
Composed of the
polysaccharide cellulose
Central Vacuole
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Used for storage
of starch
Filled with water,
functions in
maintaining cell
pressure
Plasmodesmata
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Pores connecting
adjacent plant cells
Allow free movement
of molecules between
cells
Eukaryotes
State four differences between plant and
animal cells.
1. Plants have chloroplasts, animals don’t
2. Plants have cell walls, animals don’t
3. Plants have large central vacuole,
animals don’t
4. Plants have plasmodesmata, animals
don’t
Animal and Plant Cell Comparison
Eukaryotes
Compare prokaryotic and eukaryotic cells.
3 Differences should include:
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naked DNA versus DNA associated with proteins
DNA in cytoplasm versus DNA enclosed in a nuclear
envelope
no mitochondria versus mitochondria
70S versus 80S ribosomes
eukaryotic cells have internal membranes that
compartmentalize their functions
Inner Life of the Cell
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No narration 3min
With narration 8min