GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Specialized Structures
Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology
All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #1 : Specialized Structures
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 #2 : Help With Muscle Specialization
Which of the following statements about cardiac muscle is not true?
There are significantly more T-tubules in cardiac muscle as compared to skeletal muscle
The primary structural components of cardiac muscle are actin and myosin
Cardiac muscle contraction requires extracellular calcium ions
Cardiac muscle has sarcomeres which contribute to its striated appearance.
Cardiac contractions are involuntary
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.
Example Question #2 : Specialized Structures
Neurons transmit signals via transmission of an electrical signal called an action potential. Which integral membrane protein is crucial for the rising phase of an action potential?
Voltage-gated potassium channels
Metabotropic glutamate receptors
Voltage-gated sodium channels
Ligand gated sodium channels
Ligand gated calcium channels
Voltage-gated sodium channels
Voltage gated sodium channels allow the influx of sodium to quickly depolarize the neuron and generate the action potential. They are voltage gated, meaning they open in response to changes in membrane potential, thus providing the positive feedback required to get such a dramatic change in membrane potential once threshold has been reached. The other channels listed are not involved with the rising phase of the action potential.
Example Question #2 : Help With Neural Specialization
In synaptic transmission, the __________ of the pre-synaptic cell can make either a chemical or electrical synapse with a __________ of the post-synaptic cell.
axon . . . dendrite
spine . . . dendrite
soma . . . dendrite
dendrite . . . axon
axon . . . nucleus
axon . . . dendrite
Of all the choices, axon and dendrite are the best answers to fill in the blanks because the axon is typically the pre-synaptic structure and the dendrite is the post-synaptic structure. In each of the other selections at least one of the choices does not make sense as a post/pre synaptic structure, or has nothing to do with synaptic transmission.
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