Home / IB DP Biology-B3.3 Muscle and motility -FA 2025- IB Style Questions For HL Paper 1

IB DP Biology-B3.3 Muscle and motility -FA 2025- IB Style Questions For HL Paper 1

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Question 

8. How do human muscle cells respond to intense exercise?
 
A. They stop using oxygen and replace glycolysis with lactic fermentation.
 
B. They produce smaller amounts of ATP in order to reduce the need for oxygen.
 
C. They produce lactate in order to quickly supply the energy for muscle contraction.
 
D. They produce ethanol and carbon dioxide as waste products.
▶️Answer/Explanatio
Ans: C

Question

The electron micrograph displays a transverse section of a skeletal muscle fiber. Where is the specialized endoplasmic reticulum (sarcoplasmic reticulum) likely located?

▶️Answer/Explanation

Ans. C

The sarcoplasmic reticulum (SR) is a specialized form of the endoplasmic reticulum (ER) that surrounds the myofibrils in muscle fibers:
  • Location
    The SR is a network of tubules that surrounds each myofibril, a contractile unit of the muscle cell. The SR is located in the sarcoplasm of striated muscle.
  • Structure

    The SR is made up of two parts:

    • Terminal cisternae: Sacs that make contact with the T-tubules.
    • Longitudinal SR: Thin tubes that connect the terminal cisternae from one side of the sarcomere to the other.
  • Function

    The SR stores calcium ions, which are released to cause muscular contraction. The SR also contains calcium pumps and ryanodine receptors. 

Question

Movement of insects requires muscles in antagonistic pairs. The diagram shows an insect leg with muscles labelled $\mathrm{X}$ and $\mathrm{Y}$.

What actions in the human arm are equivalent to muscle X contracting and muscle Y relaxing?
A. triceps contracts, biceps relaxes, arm extends

B. biceps contracts, triceps relaxes, arm flexes

C. triceps contracts, biceps relaxes, arm flexes

D. biceps contracts, triceps relaxes, arm extends

Answer/Explanation

Ans:A

Question

The electron micrograph shows sarcomeres in myofibrils of striated muscle during muscle contraction. The lines P–Q and R–S show two regions of one sarcomere.

How would regions P–Q and R–S change when the muscle relaxes?

Answer/Explanation

Ans: D

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