Test 3 Flashcards
Large bacteria picture
What did scientists initially think this organism?
Why?
How does this species overcome the challenges
of large cells?
Turns out it is a bacteria not a eukaryote. It was large.
the copy number increased as the cells grew. they produce thousands of copies of the chromosome ensuring that transcription and translation can occur at sufficient levels.
Viruses are diverse in form. What are the two
structures that all viruses share? What do only
some viruses have? Define them.
Where does the virus get the membrane
envelope from?
They all share protein coat (capisd) and some type of genetic material. Only some viruses have. some of them have membrane envelopes with enzymes such as reverse transcriptase.
capsids are from capsomeres.
viral membrane envelope is a phospholipid bilayer that the virus steals from a host.
protein encoding genes v genome size graph. What pattern does this figure highlight? What
makes it difficult to separate a free-living cell vs.
a symbiont vs an organelle?
symbionts and parasites are smaller. however, some free living bacteria can be smaller. once symbionts and organelles become acclimated to living inside of a cell, they become redundant.
Graph about bacteria with lines. Approximately how much distance would there be between two molecules if there were 100
inside E. coli?
200 nm, since that means the
concentration is ~10^2.5
pink cell engulfing another cell. What does this figure show? What is secondary endosymbiosis (see lecture)? How can you tell if a chloroplast came from secondary or primary endosymbiosis?
It shows the origin of diatoms, which are photosynthetic unicellular eukaryotes.
A non-photosynthetic eukaryote ate a photosynthetic algae. The algae eventually became the cholorplasts .
Why are cells so small? Explain the relationship
of surface area to volume. Also explain how
diffusion constrains the size of cells
Cells are small so that they can have a high surface area to volume ratio so that it can easily exchange material in itself and the environment. As the cell grows, the volume increases at a higher rate than the surface area.
High protein concentration reduce distance between two molecules, but the proteins diffuse slower because of the increased viscosity.
.
As the size of a cell increases, what happens to
the surface area to volume ratio?
How would this affect traffic into and out of the
cell?
If a cell grows, the surface area to volume ratio will decrease. The SA will grow proportionately slower than the volume. It would decrease traffic in and out of the cell.
What are the different types of viral genomes?
they can be linear or circular. They can have double DNA, single DNA, double RNA, or singel RNA.
What are prions? How are they
transmitted? What do they do?
prions are infectious proteins that cause degenerative brain diseases in animals. they are most likely transmitted through food. they cause proteins to misfold. leads to brain damage and death.
What are alarming characteristics of prions?
their incubation period is like 10 years. they do not get destroyed by heat.
they convert normal host proteins into misfolded prion protiens. lack nucleic acids.
Which virus is the only one we have eradicated
globally due to vaccinations?
smallpox
Expalin cell theory
all cells come from other cells
dendrites
receive signals from other neurons
axon
carries nerve impulses away from cell body towards target cells
synapse
the junction where a neruon communicates with another cell across a narrow gap via neurotransmitter or electric coupling
synaptic terminal
part of each axon branch that releases neurotransmitters
neurotransmitter
chemical messenger that passes information from transmitting neuron to receiving cell across synaptic cleft
cell body
part of the neuron that houses the nucleus and most other organelles
myelin sheath
composed of many lipid membranes. poor electrical conductors. good insulator.
nodes of ranvier
gaps in sheath where voltage gated channels occur.h
threshold of action potential
-50
resting voltage of neuron
-70
What does this figure highlight about voltage gated
ion channels?
they do not open and close in sync.
Figure with neuron with light specturm that turns red
What does this figure show? What were they
measuring and how does this relate to neuron
function?
When action potential reaches axon terminal, it becomes flooded with calcium ions because voltage gated calcium channels open in reaction to action potential, and the Ca ions rushed down their gradients. this triggers exocytosis of neurotransmitters to communicate with muscle or neuron.
Explain how an action potential is transmitted from
one cell to another across a synapse by summarizing
what is shown above in four steps. Use the example
of neuromusclar junction and acetylcholine.
- an action potential arrives and depolarizes membrane.
- depolarization opens Ca channels triggering an influx of Ca ions.
- The elevated Ca2+ concentration
causes synaptic vesicles to fuse
with the presynaptic membrane,
releasing neurotransmitter into
the synaptic cleft (exocytosis) - The neurotransmitter diffuses
across cleft and binds to ligandgated ion channels in the
postsynaptic membrane.
5.In muscles, acetylcholine is
release and binds to chemicallygated sodium channels. The
allows sodium to flow into the
muscle cells and triggers an
action potential to eventually
release Calcium ions to cause
muscle contraction.
Label the neuromuscular junction.
Here is a jumbled summary of steps involved in
muscle contraction. Put them into correct order in
the following chart, and then place the number for
each step in the correct location on the preceding
diagram.
- nerve impulse arrives at neuromuscular junction
2.acetylcholine is released from synaptic vesicles
3.acetylcholine binds to receptors on muscle fibers this allows Na ions to rush, causing depolarization. - depolarizaton
- Ca++ is released from cisterns of SR
- Ca binds to troponin on thin filaments.
- The troponin/tropomyosin is moved so that myosin binding site of actin is exposed.
- in presence of ca++ myosin acts as an enzyme. it catalyzes breakdown of ATP. energy is transferred from ATP to myosin head myosin is activated.
How does myosin use ATP to cause muscles to
contract? Describe why rigor mortis happens to
muscles after death?
In the presence of Ca++, myosin acts as an enzyme. it catalyzes the brreakdown of ATP. it goes and activates the myosin heads. myosin binds to the actin and pulls the actin fibers toward center of sarcomere. atp is necessary to release myosin from actin. when a cell is dead, it cannot produce atp, so myosin cannot release, and is stuck as contracted.
Use this figure to explain how Calcium ions modify
the thin filament
Ca++ is relased from cisterns in the SR. Ca++ binds to troponin, and causes the troponin and tropomyson to move so the active site is open for the myosin to bind.
Describe the function of the sarcoplasmic reticulum
and transvers (T) tubules in muscle cells
the t-tubles allow for the action potential to continue throughout the interior of a skeletal muscle.
the SR stores calcium and has voltage gated ca++ channels that allow Ca to flow into cytoplasm to trigger action potential once action potential reaches them.
Use this figure to explain two things
Why do action potentials only travel in one direction
down and axon?
What does myelenation do to the speed of an action
potential travelling down and axon?
action potentials only travel one way down the axon because there is a recovery phase where another action potential could not occur. (refractory period).
Action potentials can only be generated in the nodes of ranvier. The inward current produced during the rising phase of the action potential at a node
travels to the next node, where
it depolarizes the membrane and
regenerates the action potential.
This saves the time of opening
and closing many ion channels,
instead limiting it to a certain
number of positions along the
axon, a mechanism called
saltatory conduction which is
faster.
Why is an action potential an example of positive
feedback mechanism?
Once the threshold is reached, more Na channels open which leads to more depolarization which continues to open more channels etc. the system enhances the original stimulus.
initial depolarization oepns Na channels.
Na+influx leads to more depolarizaton.
More depolarization opens more Na channels and the loop repeats,
How does the sodium potassium pump work? What
is its function? Is is a part of the action potential?
it reestablishes a resting membrane potential. it uses one ATP to move 3 Na+ out of cell and 2 K+ into cell. Maintains a more negative charge inside cell.
