The Single Cell

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The Single Cell

• Viruses, Bacteria, Protists

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What do you notice as the levels go from atom to
organism?
Once at the organism level how do we organize?
Why are levels of organization important?
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Structure

• Viruses, Bacteria, Protists

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What is a Virus?
½ to 1/100 the size of the smallest bacteria
Classification on basis of nucleic acid

• DNA viruses - Herpes simplex virus (HSV)

• RNA viruses - influenza virus

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Structure of a Virus?

• Envelope additional layer
• surrounding the capsid

• Capsid - a shell of protein
• surrounding nucleic acid

Proteins determine the viruses shape
Polyhedral - papilloma virus
with projections - HIV
helical - tobacco mosaic virus
Polyhedral head w/cylindrical tail w/ leg fibers
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What are Bacteria?
Kingdom Archebacteria Prokaryote Extreme
environment No free O2 High salt or sulfur
concentration Some produce methane
The Extremists!
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What are Bacteria?
Kingdom Eubacteria Human pathogens Decomposers Sym
biotic living Prepare food Make antibiotics
Can be found just about anywhere
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Structure of Bacteria
Prokaryotic cells lack a nucleus and membrane
bound organelles
Common shapes among prokaryotes are spheres,
rods, spirals
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What are Protists?
Kingdom Protista All organisms that are neither
animals, plants, bacteria or fungi are called
'protists'
Unicellular, multicellular, colonial
Eukaryotic Aquatic environments
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What are Protists?

• Plant like Protists - Algae
• Live in fresh or salt water
• Reproduction metabolism similar to plants

• Animal like Protists - Protozoa
• Aquatic
• All are single celled
• Metabolism similar to animals
• Grouped according to how they move

Pseudopod
Ciliate
Sporazoan
Flagellate

• Fungus like Protists
• plasmodium, slime mold, downy mildew
• Behavior metabolism similar to fungus

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Reproduction

• Viruses, Bacteria, Protists

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Viral Reproduction
Lytic Cycle
The viruses attaches to a host cell and deposits
its DNA
The viral DNA instructs the host cell to use its
own enzyme raw material energy to only make new
viruses
The new viruses burst from the host cell
killing it are able to go infect other cells

• Attachment
• Entry
• Replication
• Assembly
• Release

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Viral Reproduction
Lysogenic Cycle
The viral DNA is integrated into the host cells
chromosome - provirus
Every time the host cell replicates it also
replicates the viral DNA
Once activated, the provirus enters the lytic
cycle replicates and kills the host cell

• Attachment
• Entry
• Provirus formation
• Replication
• Assembly
• Release

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Bacterial Reproduction
Most prokaryotes have a single, circular,
double-stranded DNA chromosome condensed in the
nucleoid region of the cytoplasm
Many bacteria have an additional small ring of
DNA The Plasmid prokaryotes can survive
without the plasmid the genes for essential
functions are on the chromosome. Plasmids
sometimes contain genes for resistance and other
special issues
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Bacterial Reproduction ASEXUAL
No cell cycle like seen in Eukaryotes
No mitosis or meiosis

• Prokaryotes reproduce mostly
• asexually via binary fission,
• making DNA almost continuously

Translation and transcription occur
simultaneously
Allows for rapid response to Environment
ADAPTATION
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Bacterial Reproduction SEXUAL
Conjugation, one cell directly transfers DNA to
another
Resulting in a bacterium with a new genetic
composition
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Fragmentation occurs when a filament breaks apart
and each piece develops into another organism.
Spirogyra
Conjugation occurs when two filaments form
conjugation tubes. The contents of one cell
passes through the tube an fuses with a cell from
the other filament. Fertilization occurs and a
zygote is formed.
Alternation of generations Sexual and asexual
reproduction occurs during alternating periods in
the life cycle of the plant like protist.
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Animal Like Protist Reproduction
Multiply asexually by fission. The cell divides
into two individuals.
Paramecium undergoing fission.
Fungus Like Protist Reproduction
Plasmodium - Reproduces by haploid spores Slim
molds are haploid their entire life reproduce
by cell division
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Metabolism

• Viruses, Bacteria, Protists

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Do viruses need energy?
Do viruses need to eat?
Do viruses produce waste?
Do viruses have a metabolism?
HOST CELL DOES IT ALL!
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Heterotrophic Bacteria
Use organic molecules as a food source
Parasites
Unable to produce organic molecules
Obtain nutrients from living organisms
Excretes waste thru cell wall
Saprophytes
Feed on dead organisms or organic waste
Break down nutrients locked in body tissues of
dead organisms
Excretes waste thru cell wall
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Autotrophic Bacteria
Use sunlight to make organic molecules
Make organic molecules from inorganic ones
Chemosynthetic autotrophs
Obtain energy needed to make food from Chemicals
like sulfur nitrogen Excretes waste thru cell
wall
NITROGEN FIXATION
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Protists
Animal like Heterotrophic feed on other
organisms or dead organic matter. Some are
parasitic Have specialized organelles used to
release waste

• Plant like
• Able to perform photosynthesis
• contain chlorophyll
• Not all are green. Diatoms dinoflagellates have
  yellow to brown chloroplasts. There are brown
  algae red algae
• Release waste thru cell wall

Fungus like

• Heterotrophic
• Plasmodium Eats as it moves
• Mildew Feed on dead organisms
• Releases waste thru cell membrane

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Gas Exchange

• Viruses, Bacteria, Protists

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Why is gas exchange important?
Do viruses need oxygen or carbon dioxide?
HOST CELL DOES IT ALL!
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Bacteria Metabolism
Obligate aerobes require oxygen
Mycobacterium tuberculosis the organism that
causes the lung disease tuberculosis
Obligate anaerobes require NO oxygen
Treponema pallidum the bacterium that causes
syphilis
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Bacteria Metabolism

• Prokaryotes used infolded regions of the plasma
  membrane to perform many metabolic functions,
  including cellular respiration and photosynthesis.

Respiratory membranes in aerobes
Thykaloid membranes in photosynthetic bacteria
Autotroph
Heterotroph
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Protists Metabolism
Protists are eukaryotic cells Have many
specialized organelles including mitochondria or
chloroplasts used in cellular respiration Protist
s are aerobic they require oxygen
Paramecium
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Homeostasis

• Viruses, Bacteria, Protists

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What is HOMEOSTASIS?
Why is it important?
How do VIRUSES maintain homeostasis?
They DONT! The Host Cell does it for them!!
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Bacteria Homeostasis
The cell wall maintains the shape of the cell,
protects the cell, and prevents the cell from
bursting in a hypotonic environment
When life gets rough some bacteria can form
resistant endospores
Endospores contain a bacteriums DNA and a small
amount of cytoplasm
Endospores are encased in a tough outer covering
that resists drying out and extreme temperatures
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Protist Homeostasis
Because the kingdom protista contains such a
variety, several homeostatic behaviors exist
If you would keep Euglenoids in the dark they
start feeding on organic matter and may loose
their chloroplast. Sometimes classified as animal
like other times classified as plantlike
Amoebas can grow to very large sizes. Some
species are 5 mm long! They can survive by having
many nuclei within their single cell.
Star-shaped contractile vacuoles are used to
balance the amount of water in the cell. Two
nuclei contain the genetic information.
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Are viruses alive?
What are the characteristics of life?
Reproduction
Genetic information
Maintain Homeostasis
How do characteristics of viruses compare to that
of living organisms?
Metabolism
Cellular organization
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Are viruses alive?
NO
How do characteristics of viruses compare to that
of living organisms?
No cell organization
Has genetic material
Unable to reproduce with out a host cell
Use host cells metabolism
Homeostasis?