Question
TOPIC – 4.2 Introduction to Signal Transduction
(a) – TOPIC – 4.2 Introduction to Signal Transduction
(b) – TOPIC – 4.2 Introduction to Signal Transduction
Acetylcholine receptor (AChR) proteins are found at the synapse between neurons and skeletal muscle cells. Acetylcholine released from neurons binds to a specifi c site on the receptor proteins, which causes an ion channel in the receptors to open and allow sodium ions (Na+) to enter muscle cells. The resulting depolarization of muscle cells initiates muscle contractions. Another molecule, nicotine, can also bind to certain types of AChR proteins and activate the receptors.
A researcher is investigating two different types of AChR proteins: type 1 and type 2. To determine which stimuli activate the receptors, the researcher exposes muscle cells expressing the different types of receptor proteins to stimuli and observes the results indicated in Table 1.
(a) Describe the difference in the structure AND function between AChR type 1 and AChR type 2.
(b) Acetylcholinesterase is an enzyme that breaks down acetylcholine in the synapse. Describe the effect of inhibiting acetylcholinesterase on the muscle cells with AChR type 2.
Answer/Explanation
Ans:
(a) Describe the difference in the structure AND function between AChR type 1 and AChR type 2.
Description (2 points)
Points may be earned from only one row.
(b) Acetylcholinesterase is an enzyme that breaks down acetylcholine in the synapse. Describe the effect of inhibiting acetylcholinesterase on the muscle cells with AChR type 2.
Description (1 point)
• Continued activation
• Repeated opening of sodium channels OR repeated depolarization OR muscle spasms
(a) AChR Type I work has two binding sites, and can be activated by both Acetylcholine and nicotinic – AChR Type 2 only has one binding site and can only be activated be Acetylcholine.
(b) If acetylcholinesterase is inhibited in muscle alls with type 2, the cells will be unable to break down the Acetylcholine molecule. This will cause the receptor proteins to be constantly stimulated, forcing the nation channels to star open. Since the opening of the Not channels cause muscle contractions, the inhibition of acetylcholinesterase would force repeated muscle contractions without end, chin to a seizure.