GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Muscle Specialization
Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology
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Example Questions
Example Question #261 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
Which of the following is true regarding muscle cell specialization?
I. Contraction is controlled by the presence or absence of calcium ions
II. Actin filaments are known as the "thick" filaments
III. Contraction is an ATP-independent process
IV. The basic functional unit of muscle contraction is called the sarcoplasmic reticulum
I only
II and III
II, III, and IV
I, III, and IV
I only
The only statement that is true of those presented is that muscle contraction is controlled by the release of calcium ions. Calcium ions expose the myosin binding sites on actin filaments by causing the protein troponin to move out of the way. Static interaction between troponin, tropomyosin, and the actin binding sites prevents involuntary contraction of skeletal muscle, only allowing contraction during stimulation and subsequent calcium release.
Actin is known as the "thin" filament and myosin is known as the "thick" filament. The contraction process is highly dependent on ATP, and without it contraction will not occur. The basic unit of contraction is the sarcomere; the sarcoplasmic reticulum houses the calcium ions that will be released when stimulated by the appropriate neural pathways.
Example Question #262 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
Which of the following statements about cardiac muscle is not true?
Cardiac contractions are involuntary
There are significantly more T-tubules in cardiac muscle as compared to skeletal muscle
Cardiac muscle has sarcomeres which contribute to its striated appearance.
The primary structural components of cardiac muscle are actin and myosin
Cardiac muscle contraction requires extracellular calcium ions
There are significantly more T-tubules in cardiac muscle as compared to skeletal muscle
Skeletal muscle has more t-tubules than cardiac muscle. Cardiac muscle does have larger T-tubules than skeletal, but not as many. All the other statements regarding cardiac muscle are true.
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