Docstoc

ASTI Anatomy and Physiology Glucose

Document Sample
ASTI Anatomy and Physiology Glucose Powered By Docstoc
					ASTI Anatomy and Physiology
Example Laboratory Report

                                                                                                             Steven Fong
                                                                                                                 9-04-08
                                                Cell Transport Lab

Background:

Key Terms:
       Selective Permeability: allowing some solutes/substances to enter the cell while keeping others out.
       Concentration Gradient: difference in concentration
       Active Transport: Cell provides energy (often ATP) to power transport
       Passive Transport: process is driven by concentration or pressure differences
       Diffusion: movement of molecules from a region of high concentration to low
       Osmosis: diffusion of water
       Facilitated Diffusion: solutes that are transported down their gradient by carrier proteins because they are too big
       or too insoluble
       MWCO (Molecular Weight Cut Off): Term used to describe the pore size of a membrane
       Filtration: process where water and solutes pass through a membrane due to pressure

Concepts:
    The larger the MWCO, the larger the pores in the membrane, the more things can pass through.
    Facilitated diffusion relies on carrier proteins so the rate varies with the number of proteins.
    If a semipermeable membrane is used, some solutes will be unable to move and water will move instead. If the
       system is closed and volumes cannot increase, osmotic pressure will be generated.
    Filtration is not selective. The amount of fluid depends almost entirely on the pressure.
    Active transport pumps require energy to function as they move against a concentration gradient.



Activity 1: Simple Diffusion
        Purpose: To investigate the effects of membrane pore size on simple diffusion.
        Hypothesis: If pore size is increased, more solutes will be able to pass through the membrane.


Data Table 1: Dialysis Results (average diffusion rate in mM/min)
       Solute                                                  Membrane (MWCO)
                                   20                       50                 100                           200
        Na+                         0                     0.0150             0.0150                         0.0150
        Urea                        0                        0                  0                              0
      Albumin                       0                        0                  0                              0
      Glucose                       0                        0                  0                           0.0040

Notes/Questions:
   1. Both Na+ and glucose diffused from the left into the right
   2. Urea and Albumin did NOT diffuse
   3. To separate urea and albumin we would need membranes with larger MWCOs.
   4. To remove urea from a solution that also contained NaCl you would need an appropriate membrane MWCO (big
       enough for Urea) and a solution in the right beaker with an equal concentration of NaCl so that so net NaCl would
       leave. This would need to be repeated many times until as much urea was removed as possible.
Activity 2: Facilitated Diffusion
        Purpose: To investigate the affect of varying transport proteins on solute transport rate.
        Hypothesis: Increasing the number of transport proteins increases the rate of solute transport.

Data Table 2: Facilitated Diffusion Results (glucose transport rate, mM/min)
      Glucose
   Concentration                               Number of Glucose Carriers
                                  500                      700                       900
        2.00                     0.0008                   0.0010                    0.0012
        8.00                     0.0023                   0.0031                    0.0038

Notes/Questions:
   1. As the number of protein carriers increased the rate of facilitated diffusion increased.
   2. If you began at equilibrium there would be no net rate of transport.
   3. NaCl should have no effect if it can pass through the membrane.


Activity 3: Osmosis
        Purpose: To investigate the effect of solute concentration on osmotic pressure in a closed system.
        Hypothesis: The greater the concentration gradient in a closed system, the greater the osmotic pressure.

Data Table 3: Osmosis Results (pressure in mm Hg)
       Solute                                                     Membrane (MWCO)
                                  20                         50                       100                    200
        Na+                      272                          0                        0                      0
      Albumin                    153                        153                       153                    153
      Glucose                    170                        170                       170                     0

Notes/Questions:
   1. Yes. Osmotic pressure builds in all cases except for Na+ at 50 MWCO and above and Glucose at 200.
   2. Yes – all MWCO over 50.
   3. An increase in solute concentration leads to an increase in pressure.
   4. If solutes are able to diffuse osmotic pressure will NOT be generated as the solute will equilibrate.
   5. See answer 4. At equilibrium there will no net movement of water.
   6. The pressure would increase.
   7. The glucose would equilibrate and osmotic pressure should eventually reach the same level.
   8. The glucose would not be able to transport and there would be a higher solute concentration in the RIGHT beaker
       and thus osmotic pressure would build there.


Activity 4: Simulating Filtration
        Purpose: To investigate the effect of pressure and pore size on the rate of filtration.
        Hypothesis: The more you increase pressure and/or pore size, the faster the rate of filtration.

Data Table 4: Filtration Results
                      Solute                                                   Membrane (MWCO)
                                                            20                50            100                    200
                  Filtration Rate                            1                2.5            5
     NaCl                 In filtrate (mg/mL)                0               4.81           4.81                   4.81
                      Membrane Residue (+/-)                +                  +             +                      +
     Urea                 In filtrate (mg/mL)                0                 0            4.74                   4.74
                      Membrane Residue (+/-)                +                  +             +                      +
   Glucose                In filtrate (mg/mL)                0                 0             0                     4.39
                      Membrane Residue (+/-)                +                  +             +                      +
  Powdered                In filtrate (mg/mL)                0                 0             0                      0
  Charcoal            Membrane Residue (+/-)                +                  +             +                      +
Notes/Questions:
   1. As MWCO increased, filtration rate increased.
   2. Powdered charcoal did not appear in any filtrate.
   3. Increasing the driving pressure also increases filtration rate.
   4. In living membranes you could increase filtration rate by increasing pressure (constriction of vessels) or
       increasing the size of gaps (pores) within the membrane.
   5. The molecular weight of glucose must be greater than 100 but less than 200.


Activity 5: Active Transport
        Purpose: To investigate the effect of ATP on active transport.
        Hypothesis: Increasing the concentration of ATP will allow more active transport to occur.

Notes/Questions:
   1. Na+ transport stops before transport has completed because all ATP has been exhausted and the pumps can no
       longer function.
   2. Dispensing no ATP would result in no transport.
   3. Increasing ATP increases the amount of Na+ that is transported.
   4. Decreasing the number of pumps would reduce the amount of solute transported.
   5. If you set the concentration of Na+ to be equal on both sides of the membrane there will still be transport.
   6. The lack of K+ means transport cannot occur since the pump only works when it has both Na+ and K+ present.
   7. As long as there is sufficient ATP, increasing the number of pump proteins will increase transport.
   8. Adding glucose would not increase transport.


Conclusion/Discussion:
         In this lab we investigated the effect of several factors on the rate of transport across membranes. In the first
activity we found that as pore size increases, more types of solutes are able to diffuse across the membrane. However,
once pore size is large enough, increasing it further does not affect the rate of transport. In the second activity we found
that in facilitated diffusion increasing the number of carrier proteins increases the rate of transport as does increasing the
concentration of solute. However, it is expected that once solute concentration is high enough and all carriers are
allowing transport at their maximum rate no further increase in solute concentration would have an effect. In the osmosis
investigation we found that in a closed system, osmotic pressure is generated when there is a solute that cannot pass
through the membrane. This occurs because when solute cannot move, water attempts to move across the membrane to
balance. Since the system is closed and volume cannot increase, pressure builds. In the model of filtration, it was found
that increasing the pore size and/or pressure increases the filtration rate. In the final activity we found that increasing the
concentration of ATP provides more energy to protein pumps which results in more overall transport. The amount of
active transport is unaffected by the addition of solutes on either side of the membrane as it is not dependent on
concentration gradients.
         All hypotheses were supported in this lab and results were as expected. These results demonstrate several
fundamental concepts of membrane transport and help to explain many physiological functions. For example, blood
pressure can play a strong role in the rate of filtration in the kidney. This allows the body to maintain proper osmotic
balance. In transporting nutrients into the body from the digestive tract, facilitated diffusion and active transport are
employed. Cells maintain their osmotic pressure by regulating the solute concentrations in their cells and in some cases
solute concentrations can lead to dangerous pressures. This can happen with blood pressure due to disease such as
diabetes.

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:3010
posted:7/21/2010
language:English
pages:3
Description: ASTI Anatomy and Physiology Glucose