
Concept explainers
Active sites on actin become available for binding when
(a) calcium binds to troponin.
(b) troponin binds to tropomyosin.
(c) calcium binds to tropomyosin.
(d) actin binds to troponin.

Introduction:
Muscles are made up of two main protein filaments namely, a thick filament that is made up of a protein called myosin and a thin filament that is composed of a protein known as actin. When these two filaments crossover one another in a row of repetitive events then muscle contraction takes place.
Answer to Problem 1RFT
Correct answer:
Thin filament consists of regulatory proteins called tropomyosin and troponin and the calcium ions binds with the troponin.
Explanation of Solution
Explanation for the correct answer:
Option (a) is given as calcium binds to troponin. The muscle contraction takes place in a series of steps. The cycle starts with electrical events in the sarcolemma. This accelerates the generation of calcium ions from the cisternae of the sarcoplasmic reticulum. The calcium ions then enter the zone of overlap. The next step involves binding of these calcium ions to troponin in the complex of troponin-tropomyosin. This alters the position and rolls the tropomyosin molecule away from the active sites present on the actin. This makes the active sites exposed for the formation of cross-bridges. Hence option (a) is correct.
Explanation for the incorrect answers:
Option (b) is given as troponin binds to tropomyosin. Troponin binds to the troponin-tropomyosin complex and rolls away from the tropomyosin complex. So, it is a wrong answer.
Option (c) is given as calcium binds to tropomyosin. Calcium binds to the troponin molecule instead of tropomyosin molecule. So, it is a wrong answer.
Option (d) is given as actin binds to troponin. Troponin binds to the calcium and makes actin sites exposed. So, it is a wrong answer.
Hence, option (b), (c) and (d) are incorrect.
Therefore, it can be concluded that calcium ions bind to the troponin and this troponin then binds to the troponin-tropomyosin complex, making active sites exposed during muscle contractions.
Want to see more full solutions like this?
Chapter 9 Solutions
HUMAN ANATOMY-ACCESS
- can you help? I think its B but not surearrow_forwardSkip to main content close Homework Help is Here – Start Your Trial Now! arrow_forward search SEARCH ASK Human Anatomy & Physiology (11th Edition)BUY Human Anatomy & Physiology (11th Edition) 11th Edition ISBN: 9780134580999 Author: Elaine N. Marieb, Katja N. Hoehn Publisher: PEARSON 1 The Human Body: An Orientation expand_moreChapter 1 : The Human Body: An Orientation Chapter Questions expand_moreSection: Chapter Questions Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,... format_list_bulletedProblem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,... See similar textbooks Bartleby Related Questions Icon Related questions Bartleby Expand Icon bartleby Concept explainers bartleby Question Draw a replication bubble with two replication forks.blue lines are DNA single strands and red lines are RNA single strands.indicate all 3' and 5’ ends on all DNA single…arrow_forwardProvide an answerarrow_forward
- Question 4 1 pts Which of the following would be most helpful for demonstrating alternative splicing for a new organism? ○ its proteome and its transcriptome only its transcriptome only its genome its proteome and its genomearrow_forwardIf the metabolic scenario stated with 100 mM of a sucrose solution, how much ATP would be made then during fermentation?arrow_forwardWhat is agricuarrow_forward
- When using the concept of "a calorie in is equal to a calorie out" how important is the quality of the calories?arrow_forwardWhat did the Cre-lox system used in the Kikuchi et al. 2010 heart regeneration experiment allow researchers to investigate? What was the purpose of the cmlc2 promoter? What is CreER and why was it used in this experiment? If constitutively active Cre was driven by the cmlc2 promoter, rather than an inducible CreER system, what color would you expect new cardiomyocytes in the regenerated area to be no matter what? Why?arrow_forwardWhat kind of organ size regulation is occurring when you graft multiple organs into a mouse and the graft weight stays the same?arrow_forward
- What is the concept "calories consumed must equal calories burned" in regrads to nutrition?arrow_forwardYou intend to insert patched dominant negative DNA into the left half of the neural tube of a chick. 1) Which side of the neural tube would you put the positive electrode to ensure that the DNA ends up on the left side? 2) What would be the internal (within the embryo) control for this experiment? 3) How can you be sure that the electroporation method itself is not impacting the embryo? 4) What would you do to ensure that the electroporation is working? How can you tell?arrow_forwardDescribe a method to document the diffusion path and gradient of Sonic Hedgehog through the chicken embryo. If modifying the protein, what is one thing you have to consider in regards to maintaining the protein’s function?arrow_forward
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage LearningAnatomy & PhysiologyBiologyISBN:9781938168130Author:Kelly A. Young, James A. Wise, Peter DeSaix, Dean H. Kruse, Brandon Poe, Eddie Johnson, Jody E. Johnson, Oksana Korol, J. Gordon Betts, Mark WomblePublisher:OpenStax CollegeHuman Physiology: From Cells to Systems (MindTap ...BiologyISBN:9781285866932Author:Lauralee SherwoodPublisher:Cengage Learning
- Biology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStaxBiology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage Learning





