AP Biology. Sample Student Responses and Scoring Commentary. Inside: Free Response Question 8. Scoring Guideline. Student Samples. Scoring Commentary

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1 2018 AP Biology Sample Student Responses and Scoring Commentary Inside: Free Response Question 8 RR Scoring Guideline RR Student Samples RR Scoring Commentary College Board, Advanced Placement Program, AP, AP Central, and the acorn logo are registered trademarks of the College Board. AP Central is the official online home for the AP Program: apcentral.collegeboard.org

2 AP BIOLOGY 2018 SCORING GUIDELINES Question 8 Acetylcholine receptor (AChR) proteins are found at the synapse between neurons and skeletal muscle cells. Acetylcholine released from neurons binds to a specific 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. TABLE 1. RESPONSE OF AChR PROTEINS TO DIFFERENT STIMULI AChR Protein Type Acetylcholine Nicotine Type Type indicates activation indicates no activation (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. Structure (1 point maximum) Binding sites differ in shape/ specificity/number Differential binding of molecules to type 1 and type 2 receptors Receptors activated by one (ACh) or both (ACh and nicotine) molecules Function (1 point maximum) Differential binding of molecules to type 1 and type 2 receptors Activated by one (ACh) molecule or both (ACh and nicotine) molecules No difference in response (both open channels OR both result in depolarization OR both cause muscle contraction) Activated by one (ACh) or both (ACh and nicotine) molecules No difference in response (both open channels OR both result in depolarization OR both cause muscle contraction) No difference in response (both open channels OR both result in depolarization OR both cause muscle contraction) (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.

3 AP BIOLOGY 2018 SCORING GUIDELINES Question 8 (continued) Description (1 point) Continued activation Repeated opening of sodium channels OR repeated depolarization OR muscle spasms

4 8. Acetylcholine receptor (AChR) proteins are found al the synapse between neurons and skeletal muscle cells. Acetylcholine released from neurons binds 10 a specific site on the receptor proteins, which causes an ion channel in the receptors lo 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: ty))l: I 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 I. (a) (b) TABLE 1. RESPONSE OF AChR PROTEINS TO DIFFERENT STIMULI AChR Protein Type Acetylcholine Nicotine Type Type indicates activation - indicates no activation Describe the difference ii'! the structure AND function between AChR type 1 and AChR type 2. Acctylcholinesterase is an enzyme that breaks down acetylcholine in the synapse. Describe the effect of inhibiting acetylcholinesterase on the muscle cells with AC:::hR type 2. BA: PAGE FOR ANSWERING QUESTION 8 t-\ ALlrL7; I 'lu..s 11. 0:5 s 3 Ja1 o.1\.1 ut1 k<k.vkwkil b1 fb tj'-ol,'nl '"" J. U:c:ohnL - AU Yl 1 pl 1 MI L( h,$ 1,.,'lll J S 1'kl-1 f.;j L tbcfl a11 l 1. t h-t- c..j v-c,! b-t Au, l l, (t'nl,. Unauthorized copying or reuse of any part of this page Is Illegal GO ON TO THE NEXT PAGE.

5 8. Acetylcholine receptor (AChR) proteins are found at the synapse between neurons and skeletal muscle cells. BB Acetylcholine released f r om neurons binds to a specific site on the receptor proteins, which causes an ion channel in the receptors 10 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 I 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) (b) TABLE l. RESPONSE OF AChR PROTEINS TO DIFFERENT STIMULI AChR Protein Type Acetylcholine Nicotine Type I + + Type md1cates activation - indicates no activation Describe the difference in the structure AND function between AChR type I and AChR type 2. Acetylcholinesterase is an enzyme that breaks down acetylcholine in the synapse. Describe the effect of inhibiting acetylcholinesterase on the muscle cells with ACl1R type 2. PAGE FOR ANSWERJNG QUESTION 8 \jqy'\.\ l, o'i((, \ ( 1, (,,+' \1,'\ I'.._ ' "' I v,rxa,& 'M½l.c1¼ b 4-1,1>0 \ Unauthorized copytng or rouse of any part of this page Is lllogal GO ON TO THE NEXT PAGE.

6 8. Acety!cho!ine receptor (AChR) proteins are found at the synapse between neurons and skeletal muscle cells. Acetylcholine released from neurons binds to a specific 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 l 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 I. TABLE l. RESPONSE OF AChR PROTEINS TO DIFFERENT STIMULI ACliR Protein Type Acetylcholine Nicotine Type Type indicates activation - indicates no activation /ca) Describe the difference in the structure AND function between AChR type l and AChR type 2. J ( b) Acetylcholinesterase is an enzyme that breaks down acetylcholiae in th synapse. Describe the effect of inhibiting acetylcholinesterase on the muscle cells with ChR type 2. PAGE FOR ANSWERING QUESTION 8 ACh\\. 1Vj\?t 1- Y\):\:t\ tx\11 L\t-tl.\lfA\:fLi.\\'l :t\ \?Y'S,k(\'.\I.Q 0 h)i\:½ lj..ll\: \ t\\ul\, (U'\n \l\\ll}:\l\\r,,bl\)\\l A t\1 1\,}?( '2. ITz\{.\ '{\) c,\"i C\uh\luJ:fd t;v) in :\Na \'t>ut)lj 0 JlHtyitht\\\\P J \'\ } \'\\L -r\\. by U\\u)., v:s\'\ of L\ vt\ \ t\) c \,\\'\ 1\') -\ \r\i s \\O,.\)'><, ""',u, '"i 1,, m \ 1 1\ 0-.uw n.iin cf AC\,'i:- J½! i- \'\-.HiY\S ) v\\y\\v\1 v.,\\\\ i,,\t\,'1\\: t\\j: J.Mn f Nt\. '" \bth \f\\,j(_\..l vt\ \N\ \).AC\"R e i, \i\l\ \u1 \;'I!\\\,\l\vu\i\\ Unouthorlzod copying or rouso ot any part of this page Is Illegal GO ON TO THE NEXT PAGE.

7 AP BIOLOGY 2018 SCORING COMMENTARY Question 8 Overview This question focused on molecular interactions at a neuromuscular junction. Students were provided with information on acetylcholine receptor (AChR) proteins and the series of events that occurs upon the binding of acetylcholine to an AChR. A data table showed the results of an investigation that exposed two types of AChR proteins (type 1 and type 2) to two different stimuli. Students analyzed the data to describe a structural and functional difference between the two AChR proteins. Information was given about the action of acetylcholinesterase, and the students were asked to describe the effect of inhibiting the enzyme on muscle cells with type 2 AChR proteins. The key understandings and skills students were expected to demonstrate included the following: The relationship between structure and function was used to describe the activation of a specific signaling system and transmission of a signal in the nervous system. Data analysis was used to describe molecular interactions. Reasoning skills were needed to predict how inhibition of a pathway will alter the propagation of a signal. Sample 8A Score: 3 The response earned 1 point in part (a) for describing that a difference in structure between AChR type 1 and AChR type 2 is AChR type 1 has two binding sites, but AChR Type 2 has one binding site. The response earned 1 point in part (a) for describing that a difference in function between AChR type 1 and AChR type 2 is AChR type 1 can be activated by both acetylcholine and nicotine, but AChR type 2 can only be activated by acetylcholine. The response earned 1 point in part (b) for describing the effect of inhibiting acetylcholinesterase as repeated muscle contractions. Sample: 8B Score: 2 The response earned 1 point in part (a) for describing that a difference in structure between AChR type 1 and AChR type 2 is AChR type 1 has both receptors for acetylcholine and nicotine, but AChR type 2 has only the Acetylcholine receptor. The response earned 1 point in part (b) for describing the effect of inhibiting acetylcholinesterase as making the muscles spasm. Sample: 8C Score: 1 The response earned 1 point in part (a) for describing that a difference in function between AChR type 1 and AChR type 2 is AChR type 1 proteins are activated in the presence of both acetylcholine and nicotine, while AChR type 2 proteins are activated only in the presence of acetylcholine, not nicotine.