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Answers PhysioEx 8.0 Cell Transport Mechanisms and Permeability
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ACTIVITY 1: Simple Diffusion
What is the molecular weight of Na??  22.99 amu
What is the molecular weight of Cl?? 35.45 amu
Which MWCO dialysis membranes allowed both of these ions through?  50, 100, 200 MWCO
Which materials diffused from the left beaker to the right beaker?  Na/Cl, Urea, Glucose
Which did not? Albumin
Why? Because the molecular weight exceeded the highest MWCO membrane, thus being too large to pass through.

ACTIVITY 2: Simulating Dialysis
What happens to the urea concentration in the left beaker (the patient)? It is reduced to 50%. travels to the right beaker and reaches equilibrium at 17 minutes.

ACTIVITY 3: Facilitated Diffusion
At a given glucose concentration, how does the amount of time it takes to reach equilibrium change with the number of carriers used to “build” the membrane? The higher number of carriers the quicker it reaches equilibrium
Does the diffusion rate of Na?/Cl? change with the number of receptors? No
What is the mechanism of the Na?/Cl? transport? Plasma vesicles
If you put the same amount of glucose in the right beaker as in the left, would you be able to observe any diffusion? No
Does being unable to observe diffusion necessarily mean that diffusion is not taking place? No

ACTIVITY 4: Osmosis
Did you observe any pressure changes during this experiment? If so, in which beaker(s), and with which membranes? In the L beaker with the 20 MWCO Membrane, the pressure went up.
Why? Because no diffusion took place.
Did the Na?/Cl? diffuse from the left beaker to the right beaker? If so, with which membrane(s)? Yes, 50, 100, and 200 MWCO
Why? Because diffusion took place.
Explain the relationship between solute concentration and osmotic pressure.
They are directly proportional, if the solute concentration increases the osmotic pressure will increase.
Does diffusion allow osmotic pressure to be generated?
If? solutes ?are ?able ?to ?diffuse,?then ?equilibrium ?will? be ?established and osmotic ?pressure ?will ?not ?be? generated.
Would pressure be generated if solute concentrations were equal on both sides of the membrane?
Osmotic ?pressure ?would? be ?zero ?if? albumin ?concentration ?was ?the same? on ?both? sides ?of ?the? membrane.
Why or why not? If? you ?increased? (or ?doubled) ?the ?concentration ?of ?albumin,?osmotic? pressure ?will increase ?(or ?double).
Would pressure be generated if you had 9 mM glucose on one side of a 200 MWCO membrane and 9 mM NaCl on the other side? If so, which solution was generating the pressure? No, because both glucose and NaCl are diffusible with a 200 MWCO membrane.
Would pressure be generated if you had 9 mM albumin on one side of a 200 MWCO membrane and 9 mM NaCl on the other side? If so, which solution was generating the pressure? Yes, the albumin would generate the pressure, because it does not diffuse.
 
ACTIVITY 5: Filtration
What were the results of your initial membrane analysis? Solute Residue for all solutes (Na/Cl, Urea, Glucose, Powdered charcoal) were present.
Does the membrane MWCO affect filtration rate?  Yes, the larger the MWCO the faster the filtration
Does the amount of pressure applied affect the filtration rate?  Yes, the greater the pressure, the faster the filtration
Did all solutes pass through all the membranes? If not, which one(s) did not? No, powdered charcoal
Why? The size of the powdered charcoal was too large
How can the body selectively increase the filtration rate of a given organ or organ system? By increasing the pressure or using a larger sized porous membrane

ACTIVITY 6: Active Transport
At the end of this experimental run, did the Na/Cl move from the left vessel to the right vessel? No
Why? Because the ATP was used up in the first 3 min.
As the run progresses, the concentrations of the solutes will change in the windows next to the two beakers. The rate will slow down markedly, then stop before completed. Why? The rate of Active Transport decreases
Does the amount of NaCl/KCl transported change? Yes
Does the amount of solute transported across the membrane change with an increase in carriers or pumps? Yes
Is one solute more affected than the other? No, Both are equa.l
Does the membrane you “built” allow simple diffusion? No it does not
Does the amount of ATP added make any difference? Yes





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Answers PhysioEx 8.0 Cell Transport Mechanisms and Permeability
3 years ago
Activity 2: Determining the Latent Period


Questions:   ?answer each question; use full sentences; ask instructor if you need help
2-1: How long is the latent period?          2.78  msec

2-2: What occurs in the muscle during this apparent lack of activity?
The muscle cell is biochemically preparing for contraction, including events such as the release of calcium from the sarcoplasmic reticulum, and the movement of the chemicals of contraction within the cell; includes all biochemical events beginning with acetylcholine binding to the sarcolemma through the beginning of cross-bridge binding.

Activity 3: Investigating Graded Muscle Response to Increased Stimulus Intensity

Questions:  ?answer each question; use full sentences; ask instructor if you need help   
3-1: What is the minimal, or threshold, stimulus?      0.8  v

3-2: What is the maximal stimulus?                       8.0  v

3-3: How can you explain the increase in force that you observe?
As more voltage is delivered to the whole muscle, more muscle fibers are activated and total force produced by muscle is increased.

Activity 4: Investigating Treppe
Questions:  ?answer each question; use full sentences; ask instructor if you need help
4-1: What happens to force production with each subsequent stimulus?
As long as stimuli are delivered relatively close together, the active force produced by subsequent stimuli slightly increases for the first few stimuli.

Activity 5: Simulating Active Transport
Questions:  ?answer each question; use full sentences; ask instructor if you need help

5-1: Is the peak force produced in the second contraction greater than that produced by the first stimulus?
The peak force produced in the second contraction is greater than that produced by the first stimulus.
5-2: Is the total force production even greater?
The total force production is even greater when stimuli are delivered more rapidly.
5-3: In order to produce smooth, sustained muscle contraction at Active Force = 2 gms, do you think you will need to increase or decrease the voltage?
Decrease voltage
5-4: At what voltage were you able to achieve Active Force=2gms?
7-2.5 volts (depends on the rapidity of clicking).
5-5: How does the frequency of stimulation affect the amount of force generated by the muscle?
The greater frequency of stimulatin results in a greater force generated.
Activity 6: Investigating Fusion Frequency/Tetanus
Questions: 
6-1: Describe the appearance of the tracing.
The force rises and falls at 30 stimuli/sec.
6-2:  How do the tracings change as the stimulus rate is increased?
As the stimulus rate is increased, the active force produced by the muscle also increases.
6-3:  From your graph, estimate the stimulus rate above which there appears to be no significant increase in force.  120 Stimuli/sec
6-4:  What stimulus intensity produced smooth force at Force = 2 gms?   
Smooth, sustained force at 2 gms can be produced at approximately 1.2 v and 120 stimuli/sec.                   
6-5:  Which intensity produced smooth contraction at Force = 3 gms? 
Smooth, sustained force at 3 gms can be produced at approximately 1.6 v and 120 stimuli/sec.                         
6-6:  Explain what must happen to the intensity and frequency of the stimulus to achieve smooth contraction at different force levels.
Increasing the stimulation rate causes smoother force production.  Lowering the voltage decreases the total force produced.  Manipulating both allows the muscle to produce smooth force at any desired level.


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