Flow cytometry, illustrated in Figure P20.750, is a technique used to sort cells by type. The cells are placed in a conducting saline solution which is then forced from a nozzle. The stream breaks up into small droplets, each containing one cell. A metal collar surrounds the stream right at the point where the droplets separate from the stream. Charging the collar polarizes the conducting liquid, causing the droplets to become charged as they break off from the stream. A laser beam probes the solution just upstream from the charging collar, looking for the presence of certain types of cells. All droplets containing one particular type of cell are given the same charge by the charging collar. Droplets with other desired types of cells receive a different charge, and droplets with no desired cell receive no charge. The charged droplets then pass between two parallel charged electrodes where they receive a horizontal force that directs them into different collection tubes, depending on their charge. Figure P20.75 Nozzle Liquid Cells stream Laser probe Charging collar Deflection- plates Collection tubes Screenshot Question #1 (Flow Cytometry): I If the charging collar has a positive charge, the net charge on a droplet separating from the stream will be A. Positive. B. Negative. C. Neutral. D. The charge will depend on the type of cell. Question #2 (Flow Cytometry): | Which of the following describes the charges on the droplets that end up in the five tubes, moving from left to right? A. +2q, + q, 0, – q, – 29 В. +9, + 2q, 0, — 2q, — 9 С. -q, — 2q, 0, + 2q, +9 D. -2q, - q, 0, + q, + 2g
Flow cytometry, illustrated in Figure P20.750, is a technique used to sort cells by type. The cells are placed in a conducting saline solution which is then forced from a nozzle. The stream breaks up into small droplets, each containing one cell. A metal collar surrounds the stream right at the point where the droplets separate from the stream. Charging the collar polarizes the conducting liquid, causing the droplets to become charged as they break off from the stream. A laser beam probes the solution just upstream from the charging collar, looking for the presence of certain types of cells. All droplets containing one particular type of cell are given the same charge by the charging collar. Droplets with other desired types of cells receive a different charge, and droplets with no desired cell receive no charge. The charged droplets then pass between two parallel charged electrodes where they receive a horizontal force that directs them into different collection tubes, depending on their charge. Figure P20.75 Nozzle Liquid Cells stream Laser probe Charging collar Deflection- plates Collection tubes Screenshot Question #1 (Flow Cytometry): I If the charging collar has a positive charge, the net charge on a droplet separating from the stream will be A. Positive. B. Negative. C. Neutral. D. The charge will depend on the type of cell. Question #2 (Flow Cytometry): | Which of the following describes the charges on the droplets that end up in the five tubes, moving from left to right? A. +2q, + q, 0, – q, – 29 В. +9, + 2q, 0, — 2q, — 9 С. -q, — 2q, 0, + 2q, +9 D. -2q, - q, 0, + q, + 2g
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Transcribed Image Text:Question #3 (Flow Cytometry):
| Because the droplets are conductors, a dropletť's positive and negative charges will
separate while the droplet is in the region between the deflection plates. Suppose a neutral
droplet passes between the plates. The droplet's dipole moment will point
A. Up.
B. Down.
C. Left.
D. Right.
Question #4:
|| BIO A protein molecule in an electrophoresis gel has a negative charge. The exact
charge depends on the pH of the solution, but 30 excess electrons is typical. What is the
magnitude of the electric force on a protein with this charge in a 1500 N/C electric field?
Question #5:
II| A small metal bead, labeled A, has a charge of 25 nC. It is touched to metal bead B,
initially neutral, so that the two beads share the 25 nC charge, but not necessarily equally.
When the two beads are then placed 5.0 cm apart, the force between them is 5.4 x 10-4 N.
What are the charges qa and qB on the beads?
Transcribed Image Text:Flow cytometry, illustrated in Figure P20.750, is a technique used to sort cells by type. The cells
are placed in a conducting saline solution which is then forced from a nozzle. The stream breaks
up into small droplets, each containing one cell. A metal collar surrounds the stream right at the
point where the droplets separate from the stream. Charging the collar polarizes the conducting
liquid, causing the droplets to become charged as they break off from the stream. A laser beam
probes the solution just upstream from the charging collar, looking for the presence of certain
types of cells. All droplets containing one particular type of cell are given the same charge by the
charging collar. Droplets with other desired types of cells receive a different charge, and droplets
with no desired cell receive no charge. The charged droplets then pass between two parallel
charged electrodes where they receive a horizontal force that directs them into different collection
tubes, depending on their charge.
Figure P20.75
Nozzle
Liquid
stream
Cells
Laser
probe
Charging
collar
Deflection
plates
Collection
tubes
Screenshot
Question #1 (Flow Cytometry):
| If the charging collar has a positive charge, the net charge on a droplet separating from
the stream will be
A. Positive.
B. Negative.
C. Neutral.
D. The charge will depend on the type of cell.
Question #2 (Flow Cytometry):
| Which of the following describes the charges on the droplets that end up in the five
tubes, moving from left to right?
А. +2q, + q, 0, — 9. — 2q
В. +9, + 2q, 0, — 2q, — 9
С. -q, — 2q, 0, + 2q, + q
D. -24, – q, 0, + q, + 2q
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