SEMMELWEIS UNIVERSITY MEDICAL BIOPHYSICS FINAL EXAM Questions and Answers
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Course
Semmelweis
Institution
Semmelweis
Coulter principle.
Ans- The ability to count and measure the size of particles using an electric
circuit. Particles are moved through a small aperture, their presence causes a
narrowing of the aperture, which leads to an increase in resistance.By using
constant I, According to Ohms law (U= I...
SEMMELWEIS
UNIVERSITY MEDICAL
BIOPHYSICS FINAL
EXAM Questions and
Answers
Coulter principle.
Ans- The ability to count and measure the size of particles using an electric
circuit. Particles are moved through a small aperture, their presence causes a
narrowing of the aperture, which leads to an increase in resistance.By using
constant I, According to Ohms law (U= I * R), when R increases, U increases and
pulse is generated.
Parts and functions of the Coulter-counter
,Ans- - Two spaces with a small aperture in between, capillary (contains the
electrolyte solution with the cells)
- Measuring electrode, one in each of the spaces (closing the circuit and
measuring voltage between the two spaces)
- Pump (draws the solution into the smaller space, and out
again, through the capillary)
- Auxiliary electrode (signals when certain volume is
reached, to initiate pumping out of the solution)
- Integral Discriminator (filter out noise)
- Differential Discriminator (mapped of the size distribution
of the particles)
How does the voltage pulse amplitude depend on particle size in the Coulter-
counter?
Ans- Its proportional, bigger particle will form higher resistance, higher
voltage pulse.
,How do you separate the red-blood-cell versus white-blood-cell signals in a
Coulter-counter?
Ans- when you want to measure RBC, it's not necessary to separate them
from the RBC b.c. the number of WBC is negligible (less than error of the
measurement)
By hemolyze RBC and measured them separately photochemically and subtracted
the result from the coulter-counting measurement
How do you separate the red-blood-cell versus platelet signals in a Coulter-
counter?
Ans- By integral discrimination (the size of the platelets is much
smaller)
What is the role of differential discriminator in Coulter-counting?
Ans- Mapping the size distribution of the particle
Why is dilution of blood is necessary in Coulter-counting?
, Ans- Because the cells themselves do not conduct well, and so we dilute them
with an electrolyte solution so changes in resistivity are noticed. Also, for
practical reasons (e.g. we don't want the solution to dry up.)
What solution is used for blood dilution in Coulter-counting?
Ans- Saline solution, for optimal osmotic pressure (keep the RBCs in their
natural size) and for good conduction (NaCl)
How does the matter flow density (flux) change if the concentration gradient is
doubled?
Ans- It doubles, due to flicks first law: Jv=-Dxdeltac/deltax
Name the parameters influencing the value of diffusion coefficient.
Ans- Size and shape of the particle as well as the temperature and viscosity
of the medium. Can be calculated for spherical particles: D=kT/6 pi n r
What diffuses faster: a potassium ion or a virus particle?
Ans- K+ ion due to smaller diffusion coefficient (smaller size)
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