Transcript CELLS: The Basic Units of Life

Cells
The Basic Unit of Life
Are all Cells Alike?
All living things are made up of cells.
organisms are made of only one cell.
organisms are made of many cells.
Some
Other
1. What are the advantages of a one-celled
organism?
2. What are the advantages of an organism that
is made of many cells?
Cell Theory – Life is Cellular
1.All living things are made of cells.
2.Cells are the basic unit of structure and
function in living things.
3.New cells come from pre-existing cells.
B. Exceptions to Cell Theory
Section 19-3
1. Viruses and Bacteriophage
T4
Bacteriophage
Tobacco Mosaic
Virus
(Plants)
(Bacteria)
Protein Coat
Head
Influenza
Virus
(Humans)
RNA
DNA
Nucleic Acid
Core
Capsid
RNA
Capsid
proteins
Tail
sheath
Tail
fiber
Surface
proteins
Can Change
Shape
Membrane
envelope
Virus Characteristics
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Not cellular
Made of protein coat (capsid) surrounding …
A nucleic acid (DNA or RNA) core
Classified by shape – can be very complex
Are PATHOGENIC – disease causing
Are all OBLIGATE PARASITES
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Must live off of a host
Host is harmed
Parasite benefits
Virus is specific to species of host
Virus is specific to cell type once in host
Viral Life Cycle
Bacteriophage
DNA
Bacterial
chromosome
Bacteriophage attaches to
host bacterium
Bacteriophage DNA
(prophage) can exit the
bacterial chromosome
Lytic
Cycle
Bacteriophage enzyme lyses the
bacterium’s cell wall, releasing
new bacteriophage particles that
can attack other cells
Lysogenic
or Latent
Cycle
Bacteriophage DNA
enters cell
Bacteriophage DNA (prophage)
may replicate with bacterium for
many generations
Prophage
New phage produced by cells.
Bacteriophage DNA inserts
itself into bacterial chromosome
Viral Diseases
AIDS
Conjunctivitis (Pink Eye)
Coxsackie Virus
Pneumonia
Croup
Polio
Dengue Virus
Rabies
Ebola Hemorrhagic Fever
SARS
Herpes Simplex (Genital Herpes,Cold Sores) Chicken Pox/Shingles (Varicella)
Hanta Hemorrhagic Fever
Yellow Fever
Hepatitis (A,B,C,D,E)
RSV
Influenza
Papilloma Virus
Measles
Small Pox
Mumps
Rubella (German Measles)
Meningitis
Mononucleosis/Epstein-Barr (Herpes)
Herpes Viruses
Shingles
Varicella Zoster
Chicken Pox
Herpes Simplex
Cold Sore
MMR
Measles
Mumps
Rubella
Polio
Dr. Jonas Salk (~1954)
First vaccination campaign
Small Pox
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Extremely contagious –
airborne particles (Variola)
Eradicated
by
massive
vaccination campaign.
The last naturally occurring
outbreak was in Somalia
on 26th October 1977.
Vaccinations halted about
25 years ago.
2 (???) samples remain,
one on Vector (lab in
Siberia,
one
in
CDC
(Georgia)
Bioterrorism???
Treatment of Viral Diseases
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Cannot be cured
Must be prevented
Vaccines given before virus exposure
Vaccines come in two varieties:
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weakened or “dead”
fragments
Cause the body to develop “immune memory”
Never get the same virus twice. Except when:
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Very young at time of first exposure (boosters)
Get a very mild infection the first time
Get very sick later in life (immunocompromised)
Edward Jenner
(~1798)
First vaccine
Used cow pox to vaccinate (vacca = cow in Latin) against small pox
Exception #2 to Cell Theory
2. Cell Organelles
Organelles are structures within cells that do the work of
the cell – “little organs”
a. Some carry out life functions independently of the cell
they are part of.
- Reproduction
- Heredity
- Metabolism (convert energy)
b. Their structure also suggests that they are/were
independent life forms.
Ex. Mitochondrion
Inner
Membrane
Christae
Matrix
Outer
Membrane
Ex. Chloroplast
Exception #3 to Cell Theory
3. The First Cell
Types of Cells
Prokaryotic Cells (Prokaryotes)
General Characteristics
- smallest type of cell , 1-5 μm in diameter
-
most common cell type
lack nucleus
cell wall present around the cell membrane
diverse: eubacteria, archaebacteria
archaebacteria ancestors of our cells???
classified by shape …
Shapes of Prokaryotes
Round
Oval
Spiral
Electron Micrographs of Bacteria
Structure of a Prokaryote
Ribosome
Peptidoglycan
Cell
Cell
wall membrane
Flagellum
DNA
Pili
Structure of a Prokaryote
1. Cell Wall: Provide support and shape
2. Cell Membrane: Control entry/exit of materials
to/from the cell
3. Ribosome:
Only
organelle
present
in
prokaryotes; site of protein synthesis
4. Flagellum/Cilia: Strands of protein used for
locomotion
5. DNA: One large central loop of genetic
information
6. Pili: Extensions of the cell membrane used for
cell attachment
Bacteria and Disease
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Pathogenic = disease causing; includes
some types of bacteria
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Species: Group of similar bacteria
Strain: Smaller sub-group of species; have
many similarities (same species) but
significant differences exist
May breakdown cells and tissues for food
 May release toxins (usually a protein) that
harm the body
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Bacterial Diseases
Strep Throat
Scarlet Fever
Rheumatic Fever
Dental Carries
Pneumonia
Pimples, Boils, Impetigo
Toxic Shock Syndrome
Gonorrhea
Meningitis
Pertussis
Acne
Diptheria
Tetanus
Gas Gangrene
Botulism
Trachoma
Chlamydia
Anthrax
Tuberculosis
Leprosy
Conjunctivitis
Traveler’s Diarrhea
Typhoid Fever
Salmonellosis
Shigella (Dysentery)
Bubonic Plague
Cholera
Syphillis
Thyphus Fever
Rocky Mountain Spotted Fever
Lyme Disease
Necrotizing Fasciiitis
Anthrax: A Bacillus Bacterium
Also Presents as Inhalation Anthrax
Streptococcus:
A Round Bacterium
Strep Throat
Scarlet Fever
Rheumatic Fever
Necrotizing Fasciitis
Staphylococcus
Impetigo
Boil
Clostridium tetani: A Bacillus Bacterium
B. burgdoferi: A Spiral Bacterium (Lyme Disease)
Looks bad, but …..
95% of all bacteria are either
helpful or just there!!!
Helpful Bacteria
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Lactobacillus: yogurt, cheese
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E. coli: lives in your large intestine
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Petroleum-eating bacteria help clean up oil
spills.
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Biotechnology research
Treatment of Bacterial Infections
Treat each exposure
 Re-infection always possible
 Some vaccines available
 Most infections treated with antibiotics
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“anti” = against
“biotic” = living
Are cell poisons that prevent prokaryotic cells
from functioning
Discovered by accident by Alexander Fleming
Resistance is a dangerous possibility
Controlling Bacterial Growth
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Sterilization
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Chemicals = disinfectants
Heat
Pasteurization
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Heat product to just below
boiling
Kills most bacteria
Increases shelf life
Bacteria in Nature
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Decomposers
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Recycle nutrients within organisms – return them
to the ecosystem
Sewage treatment; septic systems – purify water
Bacteria in Nature, Continued
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Nitrogen Fixation
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Process by which plants
convert N to a usable form
N2
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Requires the presence of
bacteria
Symbiosis
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Legume
Soy Beans
Peas
Clover
Bacteria
In Root Nodule
NH3
Two different organisms living
together
At least one must benefit from
relationship
 One benefits, other harmed =
parasitism
 One benefits, other not
effected = commensalism
 Both benefit = mutualism
Types of Cells
Eukaryotic Cells (Eukaryotes)
General Characteristics
- large cells, 100-300 μm
- have a well-defined nucleus
- organelles present
- more advanced than prokaryotes
Animal Cell
Nucleus: Contains DNA;
control center of cell
Cytoplasm: Watery
environment for chemical
reactions of the cell
Mitochondrion: Site of
cellular respiration;
energy production;
powerhouse of the cell
Cell Membrane: controls
entry/exit of materials
to/from cell; maintains
homeostasis
Animal Cell
Other Organelles and Structures
Endoplasmic Reticulum:
System of channels for
cell transport
DNA: Either as chromosomes
or chromatin
Nucleolus: site of RNA
production; temporary
Ribosomes: site of protein
production
Vacuoles: storage of waste,
water, food
Cytoskeleton: Protein fibers that provide
support and hold organelles in place
Lysosomes: Vacuole-shaped organelles
that contain digestive enzymes
Centrioles: Protein microtubules that
help during animal cell division
Golgi Apparatus: Stacks of membrane
that package cell secretions (products)
Plant Cell
Cell Wall: made of cellulose;
nonliving layer for structure
and support
Nucleus: contains DNA
Central Vacuole: single
large vacuole for water
storage and support
Chloroplasts: site of
photosynthesis; contains
the pigment chlorophyll
● Plant cells lack centrioles &
lysosomes
● They have all the other
organelles found in animal
cells
Comparison of Animal & Plant
Cells
Animal Cells
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Plant Cells
Have well-defined nucleus
with DNA
Cell membrane present
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Vacuoles small and
numerous
Centrioles aid in cell division
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Lysosomes for digestion
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Have well-defined nucleus with
DNA
Cell membrane present
AND
Cell wall surrounds membrane
One large central vacuole and
some small
No centrioles – cell wall takes
over function
Chloroplasts produce glucose
for the plant
No Lysosomes
The End …..
Cells