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Cell Biology
Unit Eight
Viruses
Viruses are non-living structures that are obligatory
parasites of living cells
Viruses are cell specific, causing a variety of diseases
in almost all organsisms
Viruses
Viruses are considered non-living because of the
following:
* not made of cells
* no organelles
* cannot metabolize
* they replicate, not
reproduce
Viruses
All viruses are comprised of a nucleic acid
encapsulated by protein
The nucleic acid can be DNA or RNA and may be
single or double stranded
Viruses
The proteins form a coat around the nucleic acid
called a capsid
Some viruses will also have an envelope made of the
cell membrane stolen from a host cell
Viruses
Viruses are very small and come in a variety of shapes
* liver cell = 20µm
RBC = 8µm
E. coli = 2µm
typical virus = .02µm
Viruses
Viral Replication Cycles
Viral Replication Cycles
Viral Replication Cycles
Retroviruses
Prokaryotic Cells
Prokaryotic Cells
Coccus
Bacillus
Spirillus
Prokaryotic vs. Eukaryotic Cells
Prokaryotic vs. Eukaryotic Cells
Ecological Impact of Bacteria
Bacteria have three major
ecological impacts:
~ decomposers (vast majority)
~ nitrogen fixers
~ pathogens
Ecological Impact of Bacteria
Most bacteria are decomposers,
breaking down dead organisms,
lost or shed organismal parts &
organic wastes
Bacterial decomposers break down
organic compounds into their
elemental states
Ecological Impact of Bacteria
Decomposition is vital to all mineral
cycles in that nutrients and
minerals are returned to the soil for
use by other organisms
As a result of their decomposing
activities bacteria act as a natural
“maid”, cleaning up after everyone
else
Ecological Impact of Bacteria
Nitrogen makes up 78% of the
atmosphere in the form of N2
In this form nitrogen is unusable to
organisms due to its triple bonding
A large complex of bacteria fix
nitrogen by converting into a form
that can be used by organisms
Ecological Impact of Bacteria
Nitrogen fixing bacteria live in the
soil and in nodules on the roots of
certain types of plants (legumes)
The bacterial complex carries out a
series of reactions that break the
bonds of N2, converting it to nitrates
and nitrites
Ecological Impact of Bacteria
Ecological Impact of Bacteria
Some bacteria negatively impact
their environment by being
pathogenic parasites
Bacterial pathogens cause disease
by secreting toxins that can poison
or destroy cells
Ecological Impact of Bacteria
Bacterial pathogens impact fungi,
plants and animals
Human diseases caused by bacteria
are numerous – typhoid,
pneumonia, cholera, tetenus,
tuberculosis, diptheria, plague,
botulism, gonorrhea, syphilis, etc.
Bacterial Metabolism
Bacterial metabolism exhibits a number of different
strategies:
> photosynthesizing
> heterotrophic consumers
> aerobic & anaerobic respiration
Bacterial Metabolism
This versatility could create problems with
overproduction of synthesized materials
Bacteria conserve energy and materials by not
producing inductable enzymes if they are not needed
at the moment (induced synthesis)
Bacterial Metabolism
Feedback inhibition is used to block overproduction of
synthesized materials by constituative enzymes
Repression system blocks the production of the
enzymes needed to produce a product already
available
Prokaryotic Genetic Material
Prokaryotic DNA is composed of the same materials
that of eukaryotic cells
It is not found in a nucleus, but is localized in a region
called the nucleoid
The DNA molecule is circular is shape, being
supercoiled and bound to proteins, then folded into
an extensive series of loops
Prokaryotic Genetic Material
Plasmids are small circular molecules of DNA that
can replicate themselves and genes for other cell
functions (usually non-essential)
Bacterial cells may contain one or more plasmids
Prokaryotic Genetic Material
Plasmids are found in three forms:
+ F factors – used in conjugation
(fertility)
+ R factors – used in resistance to
harmful drugs, etc.
+ Col factors – used to produce
colicins (kill other
bacteria)
Recombinant DNA
DNA
Cloning
Genetic Engineering
Tissues
The next organizational level of life above
the cell is that of tissue
A tissue is a group of similar cells that
work in conjunction with each other to
perform a specific function
Plant Tissues
Plant tissues can be divided into five
main types:
+ growth tissue
+ surface tissue
+ ground tissue
+ vascular tissue
+ photosynthetic tissue
Plant Tissues
Growth tissues are the regions that enable
a plant to grow both in length and in
girth
Plants grow throughout their life span,
so these tissues are continually
producing new growth
Plant Tissues
Plant growth tissues are called meristems
Apical meristems produce growth in
length (primary growth) and are found
on the tips of stems and roots
Plant Tissues
Lateral meristems produce growth
around the sides (secondary growth)
As apical meristems increase length,
lateral meristems provide the necessary
support
Plant Tissues
Surface tissues make up the epidermis
and function to protect underlying tissues
and prevent water loss
These tissues produce a waxy cuticle that
functions to prevent water loss
Plant Tissues
Ground tissues are found throughout a
plant, making up much of the interior of
the plant
These tissues function in storage,
support and basic metabolism
Plant Tissues
Ground tissues consist of three cell types:
+ parenchyma – storage and
metabolism
+ collenchyma - support
+ sclerenchyma - support
Plant Tissues
Parenchyma is the most abundant tissue,
structurally unspecialized and acts as
storage cells
Parenchyma differentiates into
chlorenchyma which can photosynthesize
Plant Tissues
Parenchyma also differentiates into the
other two types of ground tissue cells –
collenchyma & sclerenchyma
Plant Tissues
Vascular tissues function to carry
materials throughout the plant
Xylem carries water and minerals up
from the roots
Phloem carries sugars and nutrients
down to the roots
Plant Tissues
Xylem is comprised of long, thin cells
stacked end to end that eventually die,
becoming hollow
Living, functional xylem makes up the
sapwood of a plant
Dead, filled in xylem makes up the core
heartwood of a plant
Plant Tissues
Phloem is comprised of wider cells in
which fluids are transported from cell to
cell
It is found in the cambium, the living
outer layer of a plant just beneath the
bark
Plant Tissues
Photosynthetic tissue is found mainly in
leaves (some in green stems) and
functions to carry out photosynthesis
The palisade and spongy layers are
loaded with chloroplasts, carrying out
most of the photosynthesis
Plant Tissues
Animal Tissues
Animals are comprised of four types of
tissue:
- epithelial
- connective
- muscle
- nervous
All animals will have all four tissues
represented
Animal Tissues
Epithelial tissues function to provide
coverings or linings to structures, as well
as secreting a variety of substances
Animal Tissues
Connective tissues provide support,
adhesion, insulation and attachment
Connective tissues function to “connect”
tissues to other tissues or one structure to
another
Animal Tissues
Muscle tissue functions to contract, which
in turn provides movement
Nervous tissue functions to send rapid
messages throughout the body, reacting to
stimuli and enacting responses to them
Epithelial
Tissues
Epithelial
Tissues
Epithelial
Tissues
Connective Tissues
Connective tissues are the most abundant and
variable in an animal body
They are comprised of living cells embedded in a nonliving matrix
Connective Tissues
These tissues function to fill spaces, attach epithelium
to other tissues, protect & cushion organs and provide
mechanical support
Connective tissues include blood, bone, cartilage,
adipose, loose connective (aerolar) and dense
connective
Connective Tissues
Connective Tissues
Nervous Tissue
Anatomy of a Neuron
Myelin Sheath Formation
Anatomy of a Neuron
Resting Membrane Potential
Resting Membrane Potential
Action Potential
Action Potential
Action Potential Propogation
Saltatory Conduction
Refractory Periods
Pre-Synaptic Action
Post-Synaptic Action
The Reflex Arc
Integrating
Center
Sensor
Stimulus
Effectors
Response
The Muscle Stretch Reflex
Muscle Characteristics
The ability to contract
Excitability
The property of extensibility
Elastic properties
Muscle Characteristics
Contraction results in movement
Contraction occurs due to
sliding filaments
Muscles contract due to nerve
activity
Muscles can be under
voluntary or involuntary
control
Skeletal Muscle Characteristics
Appear striated
Under voluntary control
Quick response time due to nerve
stimulation of independently
contracting muscle fibers
Results in body movement and
balance
Smooth Muscle Characteristics
Appear non-striated
Under involuntary control
Relatively slow response time
due to stimulation produced
by pacemaker potentials
Results in internal organ
movements and glandular
secretions
Cardiac Muscle Characteristics
Appear striated
Under involuntary control
Quick response time due to
pacemaker produced action
potentials
Cardiac Muscle Characteristics
Intercalated discs connecting
fibers produce simultaneous
contraction
Results in heart beats and the
movement of blood
Muscle
Anatomy
Muscle Anatomy
Filament
Arrangement
Actin Filament Composition
Myosin Action
The
Power
Stroke
Conduction
in the
Muscle Cell
Motor Unit