GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Cellular Signals and Communication
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 : Help With Signal Transduction
Which of the following best describes proteins that facilitate signal transduction by binding many proteins of a signal transduction pathway into a complex?
Transcription factors
Adaptor proteins
Scaffold proteins
Ligases
Kinases
Scaffold proteins
The correct answer is scaffold proteins. By bringing signaling transduction pathway proteins into complex, scaffolds rapid promote activation (often by phosphorylation) of the pathway proteins to effect a biological output. Kinases phosphorylate substrates, ligases bind substrates, and transcription factors regulate transcription, however, these proteins do not complex signaling pathway intermediates to amplify a signal. Adaptor proteins are involved in signal transduction, however, their role is mainly in cross-talk between different pathways upon a certain stimulus or activation of a given signaling pathway.
Example Question #11 : Cellular Processes
Individual cell death can occur via an energy-dependent mechanism that involves the highly coordinated induction of caspases to induce death signaling cascades. What is this process referred to as?
Apoptosis
None of these
Paraptosis
Necrosis
Autophagy
Apoptosis
The correct answer is apoptosis. Apoptosis, commonly referred to as "programmed cell death", is an energy dependent mechanism that produces apoptotic bodies that are engulfed by the immune system. Mitochondrial leakage of cytochrome c can activate caspase pathways to proteolytically cleave host intracellular proteins. While necrosis is a mechanism for cell death, it is energy-independent and much less controlled and is characterized by organelle swelling and disintegration. Autophagy is a mechanism of cell death in which autophagosomes and autolysosomes are formed and degrade intracellular proteins. Paraptosis is a specific form of cell death that occurs by cell-surface receptors initiating cell death signals in the absence of normal ligands.
Example Question #81 : Cell Biology
Which of the following hormones will elicit a response in cells by attaching to a membrane bound receptor?
Insulin
Testosterone
Estrogen
Cortisol
Insulin
Before answering this question, consider what types of hormones would not attach to a membrane bound receptor. Steroid hormones can simply diffuse through the plasma membrane, so they do not need to attach to a receptor there. Cortisol, testosterone, and estrogen are all steroid hormones. This leaves insulin as the only acceptable answer. In fact, insulin attaches to a receptor tyrosine kinase on the outside of cells.
All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
