Cell Theory
 Cell
theory has three main principles
 1. All organisms are composed of one
or more cells
 2. Cells are the smallest units of life
 3. All cells come from preexisting cells
Discrepancies: the cell
theory( explain)
 Striated muscle cells
 Algae
 fungi
Unicellular Organisms
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One cell only(move, drift, fixed)
Must carry on life functions.
Nutrition
Metabolism
Growth
Response
Excretion
Homeostasis
Reproduction
Limitations on cell size
 Metabolism=large number of chemical
reactions taking place within a living
organism.
 The rate of these reactions is proportional to
the cell.
 The rate and amount of materials absorbed
and removed depend on the surface to
volume ratio
 Small ratio: cell can’t absorb or excrete
materials quickly, the cell will also overheat
easily because heat produced can’t be
eliminated fast enough,
Limitations on cell size
 Metabolic rate is proportional to cell volume.
 Used materials (absorbed)
 Waste products(removed)
 Small cells overheat, slow entrance of
materials and wastes accumulate quickly
Multicellular organisms
 Organisms consisting of a single mass of cell
fused together.
 Cooperative groups
 No one group is leader, they organize
themselves and interact with other groups to
have one distinct purpose
Emergent properties
 These are characteristics of the whole
organism
 Interaction of component parts of a complex
structure
Cell differentiation
 Different cells=different functions (job or
role)
 Groups of cells that specialize in the same
way to perform the same function = tissue
 Tissues= more efficient job
 Differentiation: development of cells to carry
out specific functions.
Gene expression and
differentiation
 Every cell contains the same set of genes.
 Some genes are activated (switched on or
being used) = production of a certain cell
type.
 Differentiation: different sets of genes are
expressed and active. This is the key to
development
Stem cells
 Versatile and can differentiate along any
pathway to produce any type of cell or tissue
 1. divide many times = large quantities of new
cells. Used to grow tissues or replace lost or
damaged cells.
 2. not fully differentiated so they can produce
any cell type.
Embryonic stem cells
 1. regenerate tissues for burn victims
 2. type 1 diabetes treatment
 3. grow replacement organs
 Therapeutic use: therapies or treatments for
disease or health issues.
 Non therapeutic use:
 Production of meat without the cow.
 Stem cells: early stages are very versatile.
 Later stages they begin to commit to a
growth pattern or differentiate.
 They will still divide but all will develop in the
same way. No longer a stem cell
 Stem cells: found in adults
 Much repair: bone marrow, skin, liver
 Limited repair: brain, kidney, heart
Uses of stem cells
 Stargardt’s disease (genetic)
 Progressive loss of vision until blindness. Use
embryonic stem cells to treat.
 Leukemia:
 Cancer: several specific mutations occur in
one cell and that cell divides.
 Remove patients stem cells by needle
aspiration
 Chemotherapy
 Return stem cell to patients bone marrow
Ethical objections
 1. informed consent
 2. clear understanding by the patient of the
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treatment involved
P15 take your own notes in class regarding
the sources of stem cells
1. create an embryo( for that purpose only
IVF) (abortions)
2. cord blood
3. Adult tissue (e9 Bone marrow)
When does life begin
 1. sperm fertilizes the egg (IVF)
 2. early stage embryo has no human
characteristics, can’t feel pain so its ok
 3. heartbeat, bone tissue, brain activity.
Usually seen a few weeks into development.
 4. fetus stage = viable outside the uterus
(24 to 28 weeks)
 Positive= reduction of the suffering of
diseased individuals.
Ultrastructure of cells
resolution of microscopes
 Resolution: making an objects parts
distinguishable.
 Light microscope limited by the wavelength
of light
 Electron microscope ; higher resolution the
beams of electrons have shorter wavelengths
to provide more resolution.
 Used for viewing the ultrastructure of cells
 Ernst Ruska: 1939 developed the first electron
microscope. Used beams of electrons instead
of light.
Difference between prokaryotes
and eukaryotes
PROKARYOTES
EUKARYOTES
 No nucleus
 Nucleus: contains
 Simple cell structure
 Small in size
 Found everywhere even in
extreme conditions
 Have cell walls
 Filled with cytoplasm
 No organelles
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chromosomes
Nuclear membrane
Cytoplasm that contains
organelles (analogous to
organs) specialized
functions.
Multicolor
Ingest materials
(pinocytosis, phagocytosis)
prokaryotes
eukaryotes
 Do contain ribosomes
 Sexual reproduction (The
 Lack membrane bound
sperm is the only
eukaryotes with flagella)
 Compartments within the
cell where the organelles
are located
 Advantage to
compartments:
concentration of molecules
in one area
organelles
 DNA called a nucleoid
 Plasmid: an extra piece of
DNA, circular, contains
nonessential genes that may
be needed later
 Gene for antibody resistance
 Contain cilia and flagella
Prokaryotes
Eukaryotes
 Reproduction by binary
 Keep material separated
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fission (asexual
reproduction) (mitosis)
EXAMPLES bacteria
single celled organisms
Diffusion thru the cell wall
No compartments all
cytoplasm
Contain ribosomes
 Maintains pH easily
 Organelles can move
around
 See page 21 for a picture
and description of each
organelle
Activity
 Draw both a Eukaryotic and Prokaryotic cell.
 You will be given a whit piece of paper fold it
in half. One half for each cell.
 Draw the cell, Label the cell parts, annotate
the organelles or parts of each cell.
Phospholipid layers
 Hydrophilic: water attracting (phosphate)
(head)
 Hydrophobic: does not attract water
(hydrocarbon chain) (tails)
 Amphiphatic: has both properties.
 Proteins are dark in electron micrographs and
phospholipids appear light.
 Protein globules were also discovered so the
previous model was disproved (DavsonDanielli)
 Singer Nicolson : fluid mosaic model
Evidence that falsified the
Davson Danielle model
 P27,28
 Freeze etched electron micrographs
 Structure of membrane proteins
 Fluorescent antibody tagging
Membrane proteins
 Proteins in the membrane prevent and slow the
passage of materials
 Active cells with have a higher protein content in
the membrane
 1. Integral Protein: hydrophobic and found on
the hydrocarbon portion of the chain
 Transmembrane: extends across the membrane.
Hydrophilis part project thru the phosphate head
on either side.
 Channel protein
 Carrier protein
 Peripheral protein these are not embedded in
the membrane
 Hydrophilic
 (they are attached to the surface of an
integral protein or to the hydrocarbon chain.
 Internal cell communication
 Lipid bound proteins: found within the bilayer
of phospholipids
 Glycoproteins: found anywhere and it
consists of a sugar and protein together
allows for cell communication
Cholestrol in membranes
 Found only in anmial cell membranes
 Lipid = steroid category
 Hydrophobic = attracted to the hydrocarbon
chain
 Contain OH (hydroxyl group) so that portion
is hydrophilic and attracted to the phosphate
head portion
 Found between the phospholipids (p31)
FLUIDITY
Distance between
molecules
Temperature increases
increases
Increases (molecules
are lose
Temperature
decreases
decreases
Decreases (molecules
cluster crystalize)
Cholesterol/ low temp
Fluidity increases
Increases distance
between Phospholipids
Cholesterol/ high temp Fluidity decreases
molecules are drawn in
tighter
Saturated fats (single
bonds between the
carbon atoms)
Fluidity decreases
Stacked together and
closely
Unsaturated fats
(double bonds
between the carbon
atoms
Fluidity increases
The molecules don’t
stack up together
 The amount of cholesterol present varies
amongst cells
 Keeps the cells in a fluid state (from
becoming crystallized)
 Reduces permeability ( to other hydrophilic
particles)
 Allows(helps) the membrane to change shape
so vesicles can be formed for transport.
Endocytosis
 When a small region of the membrane is
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pulled in and pinched off.
Energy (ATP) is needed for the process
Vesicle formed contains materials from
outside the cell (large molecules)
Can contain food (amoeba)
Pathogens (WBC)
Vesicle
 Allows movement of material and the vesicle
itself within the cell membrane
 Contents are taken to the area of need.
 When you have an increased membrane size
then you will see an increased size in the
organelle
exocytosis
 The vesicle fuses with the cell membrane and
the contents are released outside the cell
 Secretion: useful substances only
 Expel waste products
 Contractile vacuole: expels excess water that
has accumulated within the cell
Movement across the membrane
by:
 Simple diffusion: materials move from an
area of high concentration to an area of lower
concentration.
 Down or with the concentration gradient
 Materials pass thru the lipid layers charges on
the molecule (atom) limits diffusion
 Concentration gradient ?
 Passive diffusion: no energy is needed.
 Polar molecules have little or no charge on
them so they diffuse easily.
2. Facilitated diffusion
 Channels or holes are present in the cell
membrane.
 Properties of the proteins that line the
channels decide which ions can pass and how
many.
Osmosis
 The movement of water freely in or out of the
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cell.
When an equal number of ions is reached
there will be no movement
High solute content = low water
Low solute content = high water
Passive: movement of water with the
gradient (low solute=high water) low water =
high solute
 Small materials pass thru the phospholipid
bilayer
 Aquaporin: water channel (slightly wider than
a water molecule so passage is easy)
Active Transport
 Taking in of substances even though there is a
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high concentration already.
Materials are moving against the gradient
Define concentration gradient?
This type of transport requires energy (ATP
which is a result of cellular respiration)
Sometimes material is pumped out inspite of
the concentration difference.
 Pump proteins carry out this type of transport
(p38 note how it works)
 P 39 and 40 Na K pump take notes.
Na/K pump Active transport
Neurons
 Nerve impulses involve the rapid movement
of Na and K ion exchange.
 3Na out and 2K in and this process uses 1 ATP
 3Na enter the pump from inside the cell
 The ATP causes the pump to change shape
and close with the Na inside
 The pump opens to the outside and the 3 Na
ions are released into the environment
 2K from the outside( enter and attach to the
binding site) ( release a phosphate from the
ATP)
 The pump changes shape and opens allowing the K ions to pass into the axon.
Potassium pump (facilitated
diffusion)
 4 proteins with a narrow passage (material
can pass either way)
 The potassium is bonded to water which is
too large to pass. The bonds must be broken
and the K attaches to an amino acid.
 K passes thru the membrane and reattaches
to water, the amino acid will then block the
opening
Voltage gated
 More + outside (more – inside) the channels
will be closed
 More + inside (more – outside) the channels
are open and rapidly close due to the
presence of the amino acid.
Estimation of Osmolarity
 = the total concentration of osmotically
active solutes (These solutes are osmotically
active: since they cannot pass through the
membrane water has to move in order to
equilibrate the osmotic pressures.)
 ISOTONIC: same osmolarity as a tissue
 HYPERTONIC : higher osmolarity Many
dissolved solutes
 HYPOTONIC : lower osmolarity fewer
dissolved solutes
Preventing osmosis
Hypertonic high osmolarity
Hypotonic low osmolarity
 High solutes concentration
 Low solutes concentration
low water. Water rushes
from the cell causing it to
shrink and crenellate
and high water. Water
rushes into the cell causing
it to swell and burst.
isotonic
Uses for normal saline
 Water enters and leaves
 1. iv
the cell at the same rate
and no cell damage is seen
 2. wound rinsing
 3. moisten skin
 4. eye drops
 5. frozen slush for organ
transplant
The origin of cells
 Cells are formed from pre existing cells the
genetic information was copied so that the
two new cells had a full set of DNA (genes)
 The zygote was the first cell of our life.
 Scientists claim to have created a cell,
however it was formed from the genes of a
bacterium and merely modified to create a
new species of bacterium
Spontaneous generation
 Formation of living organisms from nonliving
matter.
 Many experiments designed to test this
theory. Redi, Spallanzani, Pasteur.
 Cells are highly complex, no way has been
thought of to produce cells from simpler
subunits
 Cell division is the only way to increase the
number of cells in an organism
 Viruses are simpler subunits, they are not
made of cells, they can only be produced
inside a host cell that they have infected.
Origins of the first cell
 Cells must have arisen from nonliving
subunits.
 Four hypothesis for the production of cells
p48
Endosymbiosis and eukaryotic
cells
 Mutualistic relationship: both parties benefit
 Natural selection favors the organism that
can adapt and survive.
Endosymbiosis and eukaryotic
cells
 Cellular organelles (mitochondria and
chloroplasts) were taken into larger cells thru
endocytosis. (larger prokaryotes didn’t die)
 They replicated themselves along or at the
same rate as the larger cell (endosymbiosis)
 Evolution now makes them a part of the
cellular structure.
 Symbiotic relationship: both organisms
benefit from the contact.
 Symbiotic and mutualistic relationship are
the same thing.
 This same theory applies to the presence of
chloroplasts within a plant cell (the produce
photosynthetic energy for eukaryotes
 See page 50 for a diagram
 After much time these organelles are no
longer capable of independent living.
Features of mitochondria and chloroplasts that suggest they
were capable of independent living.
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Cell division
mitosis
Role of
 The cell divides into two daughter cells, each
with its own identical nuclei to the other.
 The DNA must be replicated (during
interphase) (before mitosis begins)
 Double DNA replicated called chromatids.
INTERPHASE
 The number of mitochondria and
chloroplasts (PLANT CELLS AND ALGAE)
increase. Synthesizing material to add to
the cell wall (protein synthesis)
 G1 phase: cellular contents other than
DNA are duplicated
 S phase: chromosomes are duplicated
 G2 phase: Growth and preparation
for cell division (lower SA to V so
the cell can become bigger)
 G0 phase: cells enter when they
are not going to divide
(temporary or permanent)
PROPHASE
 Chromosomes undergo supercoiling
(condensation) DNA becomes tighter and
shorter more compact.
 Nucleolus breaks down
 Microtubules form from MTOC (microtubule
organizing center) they will be linked to each
pole of the cell.
 End of phase nuclear membrane disappears.
No nucleus can be seen, chromosomes are
dispersed.)
METAPHASE
 Microtubules grow and attach to centromere.
Allows for the correct migration of the
chromatids to opposite poles (sides of the
cell)
 Microtubules will shorten and contract, at this
point if they are not attached the
chromosome will remain in the center
ANAPHASE
 Centromeres separate allowing for
chromatids to separate.
 Pulled rapidly by shortening of spindle fibers
TELOPHASE
 Chromatids reached the poles now called
chromosomes (uncoiled).
 Pulled into a tight group and the nuclear
membrane reforms around them.
 Nucleolus reforms
CYTOKINESIS
 Occurs when mitosis is complete. (starts a
little before)
 Animal cells plasma membrane pulls in
forming a cleavage furrow.
 Reaches the center pinches off and equal
amounts of cytoplasm goes to each cell.
 Plants cells the 2 plasma membranes are
formed across the equator of the cell
(cytoplasm has been divided)
 Cell plates form and build into new cell walls
for each of the daughter cell.
 Please go online and look for different
pictures of mitosis so you can begin to
distinguish one phase from the next
CYCLINS
 These are proteins that make sure everything
moves to the next stage when the prior stage
is complete
 Cyclin dependent kinase: an enzyme that will
bind to the cycline and become active
 This allows the cell to be specific to one stage
at a time.
 Threshold concentration of cyclins is needed
to proceed to the next level of mitosis
 List the 4 cyclins and define what they do on
the next slide
List the 4 cyclins and
define what they do
Tumor formation
 Tumor is any abnormal group od cells found
in any part of the body at any age.
 Benign tumor: the cells don’t spread and
invade other tissues
 Malignant when the tumor cells move to
other tissues else where in the body. These
are called secondary tumors.
 The first tumor site is called the primary site.
 Carcinogen: any chemical agent that causes
cancer.
 Mutagens are carcinogenic (chemicals, uv
light, high energy x rays) These cause
mutations which result in the formation of
cancer.
 Several mutations are needed to form a
tumor cell.
 The first tumor site is called the primary site (
first collection of tumor cells)
 Metastasis : the movement of tumor cells to
other tissues setting up a secondary site.
Smoking and cancer
 Correlation: relationship between two factors
 Positive correlation: one factor increases and
so does the other
 Negative correlation: one factor increases
and the other factor decreases.
 Correlation is a relationship
 Cause definite proved connection between
the two factors