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It specifies exam structure: 100 multiple-choice questions, 150 total points, to be completed in 90 minutes, with scoring rules for different numbers of correct options. It also includes proctor instructions and the question prompts covering ovarian hormone changes, voltage-clamp channel properties, current-voltage matching, gastric drug effects, and developmental fate mapping.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":20,"@type":76,"position":81},"https://docshare.wps.com/document/exam/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/usabo-semifinal-exam-answer-key-2020/447312/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/usabo-semifinal-exam-answer-key-2020/447312.png","ImageObject",300,407,{"name":92,"@type":93},"Alexandar","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-25","2026-09-29",true,{"@type":102,"interactionType":103,"userInteractionCount":29},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"How many questions and points are in the exam, and how long is it?","Question",{"text":112,"@type":113},"The exam has 100 multiple-choice questions totaling 150 points and must be completed in 90 minutes.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"What do “Select ONE” and “Select ALL that apply” mean for answering?",{"text":117,"@type":113},"“Select ONE” requires choosing a single answer, while questions with multiple correct options use “Select ALL that apply” to indicate more than one correct choice.",{"name":119,"@type":110,"acceptedAnswer":120},"How is scoring determined when a question allows multiple answers?",{"text":121,"@type":113},"For multi-answer questions, partial credit uses a scheme based on the number of correctly selected options relative to the total point value.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},447312,1790818209,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":19,"category_name":20,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":29,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":139,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":144,"read_time":145},962090768658,"https://ap-avatar.wpscdn.com/davatar_6f874abed73319feea01a86fa6f0fab8","USABO Semifinal Exam-Answer Key  \nJune 24, 2020  \n100 questions, 150 points  \n90 minutes  \nAnimal Anatomy and Physiology (25 questions, 37.5 points)  \nCell Biology (20 questions, 30 points)  \nGenetics and Evolution (20 questions, 30 points)  \nPlant Anatomy and Physiology (15 questions, 22.5 points)  \nEcology (10 questions, 15 points)  \nEthology (5 questions, 7.5 points)  \nBiosystematics (5 questions, 7.5 points)  \nInstructions:  \nDo not start until instructed to do so by your proctor. Please put away your books and other materials. Clear your desk of all but the following items: photo ID, number 2 pencil, scratch paper, non-programmable calculator (optional) .  \nThe exam consists of 100 multiple choice questions, totaling 150 points, to be completed in 90 minutes. Questions are worth either 1 point, 1.5 points, or 2 points; the point value of each question is indicated next to the question number. Questions asking for a single answer state “Select ONE” while questions which may have more than one answer state“Select ALL that apply”. Questions which may have more than one answer will receive 1.0/0.7/0.2/0/0/0, relative to the question’s total point value, for 5/4/3/2/1/0 options correctly selected, respectively.  \nAnimal Anatomy and Physiology  \n25 questions, 37.5 points  \n1. [1.5 pts] With the onset of menopause, ovarian follicles gradually stop releasing eggs. A corresponding change in reproductive hormone levels occurs. The figure shows the changes in estradiol, FSH, hormone X, and LH during this pre-to post-menopausal transition. Hormone X is a marker for developing follicles. Which choice correctly labels the four hormones? Select ONE.  \na. I-Estradiol; II-Hormone X; III-FSH; IV-LH  \nb. I-FSH; II-LH; III-Estradiol; IV-Hormone X  \nc. I-FSH; II-Estradiol; III-LH; IV-Hormone X  \nd. I-Hormone X; II-LH; III-Estradiol; IV-FSH  \ne. I-Estradiol; II-Hormone X; III-LH; IV-FSH  \n2. [2 pts] You use voltage clamp to measure the current (I) at different voltages (V) of two membrane ion channels, channels 1 and 2, plotted in the figures below.  \nIn addition to current and voltage, you define two more characteristics:  \nEquilibrium point: Voltage at which no ions flow  \nConductance: Change in current per change in voltage  \nWhich of the following statements about the two channels is accurate? Select ONE.  \na. Both channels have one equilibrium point when the voltage is 0  \nb. The maximal current of channel 1 is smaller than the maximal current of channel 2  \nc. The voltage of channel 1 changes faster than the voltage in channel 2  \nd. The conductance of channel 1 does not change with voltage while that of channel 2 does  \ne. Channel 1 is monomeric while channel 2 is dimeric  \n3. [2 pts] Below are current-voltage graphs of three different ion channels, plotting ion  \ncurrent (I) as a function of membrane potential (V) . Note that outward current is measured.  \nWhich of the following choices best matches the current-voltage graphs to the  \ncorresponding ion channel? Select ONE.  \na. 1: voltage-gated potassium channel; 2: voltage-gated sodium channel; 3: sodium pore channel (not gated)  \nb. 1: voltage-gated sodium channel; 2: voltage-gated potassium channel; 3: chloride pore channel (not gated)  \nc. 1: voltage-gated potassium channel; 2: potassium pore channel (not gated); 3: chloride pore channel (not gated)  \nd. 1: voltage-gated sodium channel; 2: voltage-gated potassium channel; 3: sodium pore channel (not gated)  \ne. 1: sodium pore channel (not gated); 2: potassium pore channel (not gated); 3: voltage-gated sodium channel  \n4. [1.5 pts] You discover a new drug affecting the digestive system. Upon characterization, you discover that it inhibits H+/K+ ATPase and increases mucin secretion in the stomach. Its half life is 75 minutes and is easily absorbed by the body. Which of the following is true after taking the drug? Select ONE.  \na. The blood after passing through the stomach will have a higher pH than before  \nb. The change in K+ conce","cbCair9wqWJAtzeJ","https://ap.wps.com/l/cbCair9wqWJAtzeJ","pdf",4978631,75,"English","# USABO Semifinal Exam - Answer Key\n## Exam details and scoring rules\n## Instructions for examinees\n## Animal Anatomy and Physiology questions","[{\"question\":\"How many questions and points are in the exam, and how long is it?\",\"answer\":\"The exam has 100 multiple-choice questions totaling 150 points and must be completed in 90 minutes.\"},{\"question\":\"What do “Select ONE” and “Select ALL that apply” mean for answering?\",\"answer\":\"“Select ONE” requires choosing a single answer, while questions with multiple correct options use “Select ALL that apply” to indicate more than one correct choice.\"},{\"question\":\"How is scoring determined when a question allows multiple answers?\",\"answer\":\"For multi-answer questions, partial credit uses a scheme based on the number of correctly selected options relative to the total point value.\"}]","USABO Semifinal Exam-Answer Key - 2020 | PDF",1790719717,189]