Cell and Communication Test
A cell is treated with a drug that prevents the formation of new lysosomes. The cell continues to transcribe the genes that code for the hydrolytic enzymes that are normally found in lysosomes and continues to translate the mRNAs for those proteins on membrane-bound ribosomes. The hydrolytic enzymes are most likely to accumulate in which of the following cellular structures?
Golgi complex
Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must _____.
Have receptors that recognize and bind the hormone molecule
The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway?
In involves enzymes activating other enzymes
Put the steps of the process of signal transduction in the order they occur: 1.A conformational change in the signal-receptor complex activates an enzyme.2. Protein kinases are activated.3. A signal molecule binds to a receptor.4. Target proteins are phosphorylated.5. Second messenger molecules are released.
3, 1, 2, 4, 5
The diagram below shows a developing worm embryo at the four-cell stage. Experiments have shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and the posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are separated from one another early during the four-cell stage, no intestine will form. Other experiments have shown that if cell 3 and cell 4 are recombined after the initial separation, the posterior daughter cell of cell 3 will once again give rise to normal intestine. Which of the following is the most plausible explanation for these findings?
A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine.
Illustration below depicts a neuromuscular junction of a patient with an autoimmune disorder. Acetylcholine is a stimulatory neurotransmitter. Which of the following would be the most likely result of the continued presence of the antibody?
A decrease in action potential in the muscle, causing muscle weakness and fatigue
Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell?
A ligand binds to a receptor
For following group of questions first study the description of the situation or data and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.In the first step of an experiment, rat liver cells were exposed for 5 minutes to amino acids labeled with a radioactive isotope. The cells were then washed to stop any further incorporation of radioactive amino acids. The cells were sampled periodically thereafter, and the radioactivity of a certain protein (protein X) was measured in various cell components, as shown below.
An enzyme that participates in the degradation and recycling of cell components.
The vertebrate immune system consists of multiple types of cells that work together to protect the body from infections as well as from damaged cells. In the immune response represented above, antibodies are synthesized and secreted into the blood and the lymph. The diagram shows the interaction of macrophages, B cells, and helper T cells.Which of the following correctly labels the cells depicted in the diagram?
Cell X= macrophages; Cell Y= Helper T cells; Cell Z= B cells
During a fight-or-flight response, epinephrine is released into the body's circulatory system and transported throughout the body. Some cells exhibit a response to the epinephrine while other cells do not.Which of the following justifies the claim that differences in components of cell signaling pathways explain the different responses to epinephrine? *
Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors for epinephrine. Only cells with such receptors are capable of responding.
An antigen can induce an immune response in a host organism. Antigens are targeted by antibodies that are produced by the organism's immune system in response to contact with the antigen. Antibodies are specific to antigens. Many different cell types are involved in immune responses.Which of the following best describes the role of cell-to-cell communication during a response to an invasion of antigens?
Chemicals that are secreted from antigen-presenting cells then activate helper T cells
Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the presynaptic membrane.To test their model, the researchers used a modified version of green fluorescent protein (GFP*). In slightly alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence. Using standard techniques, the gene encoding GFP* is easily introduced into living cells. By engineering the expression of GFP* in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus.Based on the model, which of the following best explains how regulation of neurotransmitter release might increase the range of responses to a stimulus in the nervous system?
Different neurons in the same neural network can release different amounts of neurotransmitter
Signal transduction may result in changes in gene expression and cell function, which may alter phenotype in an embryo. An example is the expression of the SRY gene, which triggers the male sexual development pathway in mammals. This gene is found on the Y chromosome
If the SRY gene is absent or nonfunctional, the embryo will exhibit female sexual development.
Prokaryotic and eukaryotic cells generally have which of the following features in common?
Ribosomes
When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?
Signal molecule
The operation of the sodium-potassium "pump" moves
Sodium ions out of the cell and potassium ions into the cell
Which of the following statements best supports the claim that certain organelles within eukaryotic cells evolved from free-living prokaryotic cells?
Some organelles contain their own DNA that is more similar to prokaryotic DNA in structure and function than to the eukaryotic DNA found in the cell's nucleus.
Which of the following types of signaling is represented in the figure?
Synaptic
Type 1 diabetes results from the destruction of insulin-producing cells in the pancreas. Individuals with type 1 diabetes produce insufficient amounts of insulin, a hormone that regulates the concentration of glucose in the blood.Which of the following best explains how treatment with a drug that stimulates the production of insulin receptors on target cells will affect the insulin signaling pathway in an individual with type 1 diabetes?
The drug will have little or no effect on the signaling pathway because the receptors will not be activated in the absence of insulin
A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of the brain. The hormone targets specific cells in many parts of the body.Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the target cells in the body?
The hormone is released into the bloodstream where it can be transported to all cells with the correct receptors
Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances?
The proteins interact directly with proteins on the surfaces of other cells
Organelles such as mitochondria and the endoplasmic reticulum have membranes that compartmentalize reactions and other metabolic processes. To function properly, the organelles must move substances across their membranes.Which of the following statements describes a feature shared by mitochondria and the endoplasmic reticulum that increases the efficiency of their basic functions?
They have highly folded membranes.
The figure below illustrates a eukaryotic cell. Which of the following best describes how the three structures indicated by the arrows work together?
To synthesize and isolate proteins for secretion or for use in the cell
The Hedgehog protein (Hh) plays a critical role during a certain period of embryo development, but it normally has no role in adults except for the maintenance of adult stem cells. However, the Hedgehog protein has been detected in 70 percent of pancreatic cancer cell samples. As illustrated in the figures below, the Hedgehog protein binds to an integral embrane protein receptor known as Patched (Ptc), thus initiating a pathway of gene expression. When Hedgehog is absent, Ptc inhibits another protein known as Smoothened (Smo), which, in turn, blocks the activation of a group of proteins collectively known as the Hedgehog signaling complex (HSC). The inactivation is the result of proteolytic cleavage of one component of the HSC complex, a transcription factor known as Cubitus interruptus (Ci). When Hedgehog is present, it binds to Ptc, which prevents the inhibition of Smo by Ptc. The result is that Ci remains intact and can enter the nucleus, where it binds to and activates certain genes. One approach to treating patients with pancreatic cancer and other cancers in which the Hedgehog protein is detected is to modify the Hedgehog signaling pathway. Which of the following is the most useful approach?
Treating patients with a membrane-soluble compound that can bind to Smo and block its activity.
A certain cell type has existed in the blood and tissue of its vertebrate host's immune system for over twenty years. One day, it recognizes a newly arrived antigen and binds to it, subsequently triggering a secondary immune response in the body. Which of the following cell types most accurately describes this cell?
macrophage
