Questions 1. How does the patch-clamp technique help researchers study ion transport across cell membranes? 2. In general, about 107-108 ions/s pass through an open ion channel. In contrast, only 10² ions/s pass through an ion pump. How would you expect the strength of an electric current across an ion channel to compare with the strength across an ion pump? 3. What does Observation 1 suggest about ion flow through the sodium-potassium pump when palytoxin is added?
Questions 1. How does the patch-clamp technique help researchers study ion transport across cell membranes? 2. In general, about 107-108 ions/s pass through an open ion channel. In contrast, only 10² ions/s pass through an ion pump. How would you expect the strength of an electric current across an ion channel to compare with the strength across an ion pump? 3. What does Observation 1 suggest about ion flow through the sodium-potassium pump when palytoxin is added?
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
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Transcribed Image Text:Palytoxin is a deadly compound found in certain marine
animals. When scientists first isolated palytoxin from sea
corals in the 1970s, they did not know how it affected
people exposed to it. In time, they began to suspect that
the toxin was interfering with the sodium-potassium pump.
Researchers have measured the effect of palytoxin on ion
transport through the sodium-potassium pump using the
patch-clamp technique. This involves using a fine-tipped
microelectrode to measure the electric current across pumps
in the cell membrane. In this activity, you will examine some
of the researchers' results and conclusions.
Procedure
1. Read the following observations that researchers made
after adding palytoxin to a membrane, and then answer
the questions.
• Observation 1: The current across a single pump
jumped from 0 picoamperes to 1 picoamperes.
• Observation 2: When ATP was added to the
cytoplasm-facing side of the membrane, the current
across a group of pumps increased by a factor of 8
times.
Observation 3: A molecule 0.75 nm in diameter was
able to pass through the pump. (For comparison
purposes, a hydrogen atom measures 0.1 nm in
diameter.)
Questions
1. How does the patch-clamp technique help researchers
study ion transport across cell membranes?
2. In general, about 107-108 ions/s pass through an open
ion channel. In contrast, only 10² ions/s pass through
an ion pump. How would you expect the strength of an
electric current across an ion channel to compare with
the strength across an ion pump?
3. What does Observation 1 suggest about ion flow
through the sodium-potassium pump when palytoxin
is added?
4. Given that the sodium-potassium pump is a form
of active transport, suggest an explanation for
Observation 2.
5. What does Observation 3 suggest about the size of the
passage through the sodium-potassium pump?
Expert Solution
Step 1
NOTE: according to the answering guidelines, I am going to answer only first three parts of the given question. Please post the remaining question as a separate question. Thank you.
The glass micropipette used in the patch-clamp technique creates a tight gigaohm seal with the cell membrane. A wire used to conduct ions in the micropipette is submerged in an electrolytic solution. A "patch" of membrane is taken away from the cell after creating a gigaohm seal in order to measure individual ion channels.
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