Biology 1401 Chapter 9 Cell Communication
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Questions and Answers
- 1.
Located on or within the cell are _________ proteins, each of which has a three dimensional shape complementary to that of a specific signal molecule.
- A.
Amplification
- B.
Monoclonal
- C.
Transmembranal
- D.
Receptor
- E.
Messenger
Correct Answer
D. ReceptorExplanation
Receptor proteins are located on or within the cell and have a three-dimensional shape that matches a specific signal molecule. These receptors bind to the signal molecule, allowing the cell to receive and respond to the signal. Receptors are essential for cellular communication and play a crucial role in various physiological processes.Rate this question:
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- 2.
The space into which neurotransmitters are released is called a chemical
- A.
Synapse.
- B.
Junction.
- C.
Channel.
- D.
Desmosome.
- E.
Vesicle.
Correct Answer
A. Synapse.Explanation
A synapse is the space where neurotransmitters are released. It is a specialized junction between two nerve cells, allowing for the transmission of signals. A synapse is responsible for the communication between neurons in the nervous system. A chemical synapse involves the release of neurotransmitters into the synaptic cleft, which then bind to receptors on the postsynaptic neuron, transmitting the signal.Rate this question:
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- 3.
Which of the following is not a second messenger?
- A.
CAMP
- B.
Ca++ions
- C.
Diacyl glycerol (DAG)
- D.
Inositol-1,4,5-triphosphate (IP3)
- E.
Phospholipase C
Correct Answer
E. Phospholipase CExplanation
Phospholipase C is not a second messenger. Second messengers are small molecules that transmit signals from the cell surface to the interior of the cell, amplifying the signal and initiating a cellular response. cAMP, Ca++ ions, diacyl glycerol (DAG), and inositol-1,4,5-triphosphate (IP3) are all examples of second messengers. Phospholipase C, on the other hand, is an enzyme that cleaves phospholipids to generate DAG and IP3, which then act as second messengers.Rate this question:
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- 4.
Specific protein receptors are present for all of the following except
- A.
Signal amplification.
- B.
Signal transduction.
- C.
Intracellular receptors binding to DNA.
- D.
Signaling to other cells.
- E.
Cell junctions.
Correct Answer
A. Signal amplification.Explanation
Protein receptors are involved in various cellular processes, including signal transduction, intracellular receptors binding to DNA, and signaling to other cells. These receptors are responsible for receiving signals and transmitting them within the cell or to other cells. However, signal amplification is not a specific function of protein receptors. It refers to the process of increasing the strength or magnitude of a signal, which can occur through various mechanisms but does not involve specific protein receptors. Therefore, signal amplification is the correct answer.Rate this question:
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- 5.
Communication between cells can occur by all of the following basic mechanisms except
- A.
Direct contact.
- B.
Intracellular signaling.
- C.
Paracrine signaling.
- D.
Endocrine signaling.
- E.
Synaptic signaling.
Correct Answer
B. Intracellular signaling.Explanation
The question is asking for the basic mechanisms of communication between cells, and the answer is "intracellular signaling." Intracellular signaling refers to communication that occurs within a single cell, rather than between different cells. The other options listed - direct contact, paracrine signaling, endocrine signaling, and synaptic signaling - all involve communication between different cells.Rate this question:
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- 6.
Signals with short-lived, local effects are called
- A.
Direct contact.
- B.
Endocrine signals.
- C.
Paracrine signals.
- D.
Synaptic signals.
Correct Answer
C. Paracrine signals.Explanation
Paracrine signals refer to signals that are released by cells and act on nearby cells in the immediate vicinity. These signals have short-lived and local effects, meaning they only affect cells in close proximity to the releasing cell. This is in contrast to endocrine signals, which are released into the bloodstream and can have widespread effects throughout the body, and synaptic signals, which are transmitted across synapses between neurons. Therefore, the correct answer is paracrine signals.Rate this question:
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- 7.
Synaptic signaling requires which of the following to be released into the synaptic gap?
- A.
Hormones
- B.
Internal receptors
- C.
Genes
- D.
Neurotransmitters
- E.
Lipids
Correct Answer
D. NeurotransmittersExplanation
Synaptic signaling involves the transmission of signals between neurons at the synapse. Neurotransmitters are the chemical messengers that are released into the synaptic gap to transmit these signals from one neuron to another. They are stored in vesicles within the presynaptic neuron and are released upon the arrival of an action potential. Once released, neurotransmitters bind to receptors on the postsynaptic neuron, initiating a response. Therefore, neurotransmitters are essential for synaptic signaling to occur.Rate this question:
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- 8.
Signal molecules activate intracellular receptors in
- A.
Chromosomes.
- B.
Vesicles.
- C.
Target cells.
- D.
Skin cells.
- E.
Surface cells.
Correct Answer
C. Target cells.Explanation
Signal molecules are molecules that are released by cells to communicate with other cells. These molecules bind to specific receptors on the surface of target cells, triggering a response within the target cell. Activation of intracellular receptors occurs within the target cells, not on chromosomes, vesicles, skin cells, or surface cells. Therefore, the correct answer is target cells.Rate this question:
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- 9.
The molecules that convert extracellular signals into intracellular ones are
- A.
Neurotransmitters.
- B.
Peptide hormones.
- C.
Cell surface receptors.
- D.
Growth factor proteins.
- E.
Genes.
Correct Answer
C. Cell surface receptors.Explanation
Cell surface receptors are molecules that convert extracellular signals, such as neurotransmitters, peptide hormones, and growth factor proteins, into intracellular signals. These receptors are located on the surface of cells and play a crucial role in signal transduction, transmitting signals from outside the cell to the inside. Genes, on the other hand, are segments of DNA that contain instructions for building proteins and are not directly involved in the conversion of extracellular signals. Therefore, the correct answer is cell surface receptors.Rate this question:
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- 10.
All of the following statements about chemically-gated ion channels are true except
- A.
Their amino acid chains wind back and forth across the membrane.
- B.
They close in response to binding of the signal molecule.
- C.
A pore exists in the center of the protein.
- D.
The pore connects the extracellular fluid with the cytoplasm.
- E.
The pore is big enough for ions to pass through it.
Correct Answer
B. They close in response to binding of the signal molecule.Explanation
Chemically-gated ion channels are protein channels that open or close in response to the binding of a specific signal molecule, allowing ions to pass through the pore. The amino acid chains of these channels do wind back and forth across the membrane, and a pore exists in the center of the protein that connects the extracellular fluid with the cytoplasm. Additionally, the pore is big enough for ions to pass through it. However, the statement that they close in response to binding of the signal molecule is incorrect. These channels actually open in response to the binding of the signal molecule, allowing ions to flow through.Rate this question:
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- 11.
The class of cell surface receptors that acts indirectly on plasma membrane-bound enzymes or ion channels is called
- A.
G-protein-coupled receptors.
- B.
Gated ion channels.
- C.
Enzymatic receptors.
- D.
Second messenger receptors.
Correct Answer
A. G-protein-coupled receptors.Explanation
G-protein-coupled receptors (GPCRs) are a class of cell surface receptors that indirectly activate plasma membrane-bound enzymes or ion channels. When a ligand binds to a GPCR, it triggers a conformational change in the receptor, which in turn activates a G-protein inside the cell. The activated G-protein then interacts with enzymes or ion channels in the plasma membrane, leading to the production of second messengers or the opening/closing of ion channels. Therefore, GPCRs act indirectly on plasma membrane-bound enzymes or ion channels, making them the correct answer.Rate this question:
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- 12.
Which of following statements about G proteins associated with G-protein-coupled receptors is false?
- A.
G proteins provide a link between the receptor and effector protein.
- B.
G proteins can propagate the signal by either the G~ or the G(by) components.
- C.
G proteins are heterotrimeric.
- D.
Associated G proteins become active by exchanging GTP and GDP.
- E.
Activated G protein diffuses away from the receptor.
Correct Answer
D. Associated G proteins become active by exchanging GTP and GDP.Explanation
G proteins become active by exchanging GTP and GDP. This is a true statement, not a false one. When a G protein is inactive, it is bound to GDP. Upon activation by a G-protein-coupled receptor, the G protein exchanges GDP for GTP, which leads to a conformational change and dissociation of the G protein into its alpha and beta-gamma subunits. The alpha subunit then interacts with effector proteins to propagate the signal. Therefore, the correct answer is that this statement is false.Rate this question:
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- 13.
Which pair are examples of second messengers?
- A.
Sodium, potassium ions
- B.
Amino acids, proteins
- C.
Steroids, lipids
- D.
Sugars, starches
- E.
CAMP, calcium ions
Correct Answer
E. CAMP, calcium ionsExplanation
cAMP (cyclic adenosine monophosphate) and calcium ions are examples of second messengers. Second messengers are molecules that relay signals from the cell surface to the inside of the cell, amplifying and transmitting the signal. cAMP is involved in many cellular processes, such as regulating metabolism and gene expression. Calcium ions play a crucial role in intracellular signaling, controlling processes like muscle contraction, neurotransmitter release, and cell division. Both cAMP and calcium ions act as secondary messengers, mediating the effects of primary messengers like hormones or neurotransmitters.Rate this question:
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- 14.
A small number of surface receptors can ultimately generate a large intracellular response, as each step of the pathway is often expanded by
- A.
Enzymatic receptors.
- B.
Gated ion channels.
- C.
Signal amplification.
- D.
G-protein-coupled receptors.
Correct Answer
C. Signal amplification.Explanation
Signal amplification is the correct answer because it explains how a small number of surface receptors can generate a large intracellular response. Signal amplification refers to the process in which a signal is amplified or increased at each step of a signaling pathway. This can occur through various mechanisms, such as the activation of multiple downstream molecules or the recruitment of additional signaling molecules. By amplifying the signal, the initial input from a few surface receptors can lead to a significant response within the cell.Rate this question:
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- 15.
Most cells are in physical contact with other cells at all times by forming permanent connections called
- A.
Cell junctions.
- B.
Gated ion channels.
- C.
Enzymatic receptors.
- D.
G-protein-coupled receptors.
- E.
Cell surface markers.
Correct Answer
A. Cell junctions.Explanation
Cell junctions are the correct answer because they are structures that allow cells to physically connect with each other. These connections are permanent and help to maintain the integrity and cohesion of tissues and organs. Cell junctions come in different types, such as tight junctions, adherens junctions, and gap junctions, and they play important roles in cell communication, signaling, and tissue function.Rate this question:
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- 16.
Small molecules or ions can pass from one cell to another through
- A.
Tight junctions.
- B.
Gap junctions.
- C.
Diffusion spheres.
- D.
Desmosomes.
- E.
Adherens junctions.
Correct Answer
B. Gap junctions.Explanation
Gap junctions are specialized protein channels that allow small molecules or ions to pass directly from one cell to another. These junctions create a direct connection between the cytoplasm of adjacent cells, enabling the rapid and coordinated communication between cells. Tight junctions, desmosomes, and adherens junctions are involved in cell adhesion and maintaining the integrity of tissues, but they do not allow for direct passage of molecules between cells. Diffusion spheres is not a recognized term in cell biology.Rate this question:
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- 17.
In plants, cell-cell junctions can only occur at gaps in the cell walls through cytoplasmic connections that form across the plasma membranes of the touching cells. These junctions are called
- A.
Desmosomes.
- B.
Tight junctions.
- C.
Plasmodesmata.
- D.
The cellulose matrix.
- E.
Adhering junctions.
Correct Answer
C. Plasmodesmata.Explanation
Plasmodesmata are cell-cell junctions in plants that occur at gaps in the cell walls. They are formed through cytoplasmic connections that extend across the plasma membranes of adjacent cells. Plasmodesmata allow for the exchange of various molecules and substances between plant cells, including nutrients, signaling molecules, and hormones. Therefore, plasmodesmata are the correct answer as they are the specific type of junctions that occur in plants for intercellular communication.Rate this question:
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- 18.
Chemically-gated ion channels are receptor proteins through which ions pass. A cell biologist has blocked these channels in a lab rat's liver tissue by using a chemical that
- A.
Prohibits binding of a signal molecule.
- B.
Prohibits ions from entering the cell via active transport.
- C.
Causes ions to move in the opposite direction of the ion gradient.
- D.
Prohibits second messenger signaling.
Correct Answer
A. Prohibits binding of a signal molecule.Explanation
The correct answer is "prohibits binding of a signal molecule." Chemically-gated ion channels are receptor proteins that open or close in response to the binding of specific signal molecules. By blocking these channels, the chemical prevents the signal molecule from binding to the receptor, thereby inhibiting the passage of ions through the channels. This disruption in the binding process would prevent the normal cellular response that occurs when the signal molecule binds to the receptor.Rate this question:
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- 19.
What characteristics do all cell surface receptors share?
- A.
They are composed of hydrophilic proteins.
- B.
They all must bind to a molecule to be activated.
- C.
They all result in creation of an ion channel.
- D.
They include the activation of a G protein.
Correct Answer
B. They all must bind to a molecule to be activated.Explanation
All cell surface receptors share the characteristic of needing to bind to a molecule in order to be activated. This is because cell surface receptors are proteins that are located on the surface of cells and are responsible for receiving signals from the external environment. In order for these receptors to transmit the signal into the cell, they must first bind to a specific molecule, such as a hormone or neurotransmitter. This binding triggers a series of intracellular events that ultimately lead to a cellular response. Therefore, the requirement of binding to a molecule is a common characteristic shared by all cell surface receptors.Rate this question:
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- 20.
Why is phosphorylation-dephosphorylation commonly used to regulate signal transduction pathways?
- A.
Phosphate groups are efficient second messengers.
- B.
Protein kinase and phosphatases are abundant in most cells.
- C.
The hydolysis of bound GTP results in GDP and Pi.
- D.
The addition or removal of a phosphate group can expose or hide potential binding sites in proteins.
Correct Answer
D. The addition or removal of a phosphate group can expose or hide potential binding sites in proteins.Explanation
Phosphorylation-dephosphorylation is commonly used to regulate signal transduction pathways because the addition or removal of a phosphate group can expose or hide potential binding sites in proteins. This allows for the activation or inactivation of specific proteins, thereby controlling the flow of signals within the pathway. Protein kinase and phosphatases are abundant in most cells, making phosphorylation-dephosphorylation a readily available and efficient mechanism for regulating signal transduction. Phosphate groups themselves can also act as efficient second messengers, further enhancing the effectiveness of this regulatory process. The hydrolysis of bound GTP resulting in GDP and Pi is not directly related to phosphorylation-dephosphorylation and does not explain its common usage in signal transduction regulation.Rate this question:
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- 21.
Which of the following proteins phosphorylates MAP kinase kinase?
- A.
MAP kinase
- B.
MAP kinase kinase
- C.
MAP kinase kinase kinase
- D.
MAP phosphatase
Correct Answer
C. MAP kinase kinase kinaseExplanation
MAP kinase kinase kinase is the protein that phosphorylates MAP kinase kinase. This is because the name "MAP kinase kinase kinase" indicates that it is a kinase that acts on MAP kinase kinase, which in turn phosphorylates MAP kinase. Therefore, MAP kinase kinase kinase is the correct answer.Rate this question:
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- 22.
Long-lived; affects cells very distant from the releasing cell.
- A.
Paracrine signaling
- B.
Direct contact
- C.
Endoctine signaling
- D.
Synaptic signaling
Correct Answer
C. Endoctine signalingExplanation
Endocrine signaling is the correct answer because it involves the release of hormones into the bloodstream, which can then travel throughout the body to affect cells that are located far away from the releasing cell. This type of signaling is long-lived and can have widespread effects on various target cells and tissues. In contrast, paracrine signaling affects nearby cells, direct contact signaling occurs when cells physically touch each other, and synaptic signaling occurs between neurons at synapses.Rate this question:
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- 23.
Signal molecules on a cell membrane interact with molecules on a neighboring cell membrane.
- A.
Paracrine signaling
- B.
Direct contact
- C.
Endoctine signaling
- D.
Synaptic signaling
Correct Answer
B. Direct contactExplanation
Direct contact is the correct answer because it refers to the interaction between signal molecules on a cell membrane and molecules on a neighboring cell membrane. In this type of signaling, the cells are physically in contact with each other, allowing for direct communication and the transfer of signals between the two cells. This can occur through gap junctions, tight junctions, or other physical connections that allow for the exchange of molecules and signaling between adjacent cells.Rate this question:
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- 24.
Short lived; used by nerve cells.
- A.
Paracrine signaling
- B.
Direct contact
- C.
Endoctine signaling
- D.
Synaptic signaling
Correct Answer
D. Synaptic signalingExplanation
Synaptic signaling is the correct answer because it involves communication between nerve cells through the release and reception of neurotransmitters at synapses. This type of signaling is short-lived as the neurotransmitters quickly diffuse across the synaptic cleft and bind to receptors on the target cell, allowing for rapid and precise transmission of signals. Other options such as paracrine signaling, direct contact, and endocrine signaling do not specifically involve the use of neurotransmitters by nerve cells.Rate this question:
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- 25.
Short-lived, causing local effects.
- A.
Paracrine signaling
- B.
Direct contact
- C.
Endoctine signaling
- D.
Synaptic signaling
Correct Answer
A. Paracrine signalingExplanation
Paracrine signaling involves the release of signaling molecules that act on nearby cells, causing local effects. This type of signaling is short-lived because the molecules are quickly degraded or taken up by neighboring cells. In contrast to endocrine signaling, which involves the release of hormones into the bloodstream to act on distant target cells, paracrine signaling is more localized. Direct contact and synaptic signaling also involve communication between neighboring cells, but they differ in the mechanism of signal transmission.Rate this question:
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