Biological Membranes, Membrane Transport,And Cell Signaling Ch. 4 & 5
Biological transport for zoo 235 cal poly pomona winter 2012. Voss instructor.
- 1.
Which of the following describes intracellular fluid?
- A.
Rich in sodium, potassium, and chloride
- B.
Rich in sodium and chloride
- C.
Rich in proteins and chloride
- D.
Rich in proteins and potassium
- E.
Rich in potassium and chloride
Correct Answer
D. Rich in proteins and potassiumExplanation
The intracellular fluid is described as being rich in proteins and potassium. This means that within the cells of the body, the fluid contains a high concentration of proteins and potassium ions. This is important for maintaining cell function and regulating various cellular processes.Rate this question:
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- 2.
Which of the following pairs of characteristics is more likely to make a substance diffuse through the cell membrane?
- A.
Large, polar molecule
- B.
Large, non polar molecule
- C.
Small, polar molecule
- D.
Small, non polar molecule
- E.
Large, amphipathic molecule
Correct Answer
D. Small, non polar moleculeExplanation
A small, non polar molecule is more likely to diffuse through the cell membrane because non polar molecules can easily pass through the hydrophobic lipid bilayer of the membrane. The small size of the molecule allows it to fit between the lipid molecules, while the non polar nature ensures compatibility with the hydrophobic interior of the membrane. In contrast, large molecules are hindered by their size, and polar molecules are hindered by their inability to interact with the hydrophobic interior of the membrane. Amphipathic molecules have both polar and non polar regions, but their large size still limits their ability to diffuse efficiently through the membrane.Rate this question:
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- 3.
The affinity of a receptor for its ligand is a measure of
- A.
The strength of binding between ligand and receptor
- B.
The number of binding sites available for the ligand
- C.
The ability of the ligand to permeate the plasma membrane and reach its receptor
- D.
The response produced in the targe cell when the ligand binds to the receptor
- E.
The percent of receptors on a specific target cell with cell bound ligand.
Correct Answer
A. The strength of binding between ligand and receptorExplanation
The affinity of a receptor for its ligand refers to the strength of the binding between the ligand and receptor. It indicates how likely the ligand is to bind to the receptor and form a stable complex. A higher affinity means a stronger binding interaction, while a lower affinity indicates a weaker binding. Therefore, the correct answer is "the strength of binding between ligand and receptor."Rate this question:
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- 4.
Direct communication between cells in contact with one another is accomplished through
- A.
Ligands
- B.
Receptors
- C.
Gap junctions
- D.
Paracrine chemical messengers
- E.
Endocrine hormones
Correct Answer
C. Gap junctionsExplanation
Gap junctions are specialized channels that directly connect the cytoplasm of adjacent cells, allowing for direct communication and exchange of small molecules and ions. These junctions play a crucial role in coordinating the activities of cells in tissues and organs. Unlike ligands, receptors, paracrine chemical messengers, and endocrine hormones, which involve signaling molecules that need to be released and received by target cells, gap junctions provide a direct pathway for electrical and chemical signals to pass between cells.Rate this question:
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- 5.
Referring to a membrane as "selectively permeable" describes its ability to
- A.
Restrict movement of particular molecules across a membrane
- B.
Restrict only the movement of sodium across a membrane
- C.
Provide a barrier that restricts the movement of all molecules across a membrane
- D.
Restrict only the movement of potassium across
Correct Answer
A. Restrict movement of particular molecules across a membraneExplanation
The term "selectively permeable" refers to the membrane's ability to control the movement of certain molecules while allowing others to pass through. This means that the membrane restricts the movement of specific molecules across it, while still allowing other molecules to freely move. This term does not imply that only sodium or potassium movement is restricted, but rather that the membrane can selectively control the passage of different types of molecules.Rate this question:
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- 6.
Which type of chemical messenger is released from the axon terminal of a neuron and directly communicates with other cells?
- A.
Paracrine
- B.
Autocrine
- C.
Hormone
- D.
Cytokine
- E.
Neurotransmitter
Correct Answer
E. NeurotransmitterExplanation
Neurotransmitters are chemical messengers released from the axon terminal of a neuron that directly communicate with other cells. They are responsible for transmitting signals across the synapse, the junction between two neurons or between a neuron and a target cell. Neurotransmitters play a crucial role in the functioning of the nervous system by facilitating the transmission of electrical impulses and regulating various physiological processes such as cognition, movement, and emotions.Rate this question:
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- 7.
When alpha subunit of the G protein is activated, it can stimulate ion channels to
- A.
Either open or close
- B.
Open only
- C.
Close only
- D.
Alter the ion that travels through the channel
- E.
Degrade
Correct Answer
A. Either open or closeExplanation
When the alpha subunit of the G protein is activated, it can stimulate ion channels to either open or close. This is because the alpha subunit can interact with the ion channels and trigger a conformational change that either allows the channel to open and allow ions to pass through or closes the channel and prevents ions from passing through. This activation of ion channels by the alpha subunit of the G protein is an important mechanism for regulating ion flow and cellular signaling.Rate this question:
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- 8.
Which of the following transport mechanisms is passive?
- A.
Cotransport of glucose with sodium
- B.
Transport of sodium and potassium across the membrane by the Na+/K+ pump
- C.
Movement of sodium through ion channels
- D.
Movement of sodium out of the cytosol
- E.
Movement of calcium out of the cytosol
Correct Answer
C. Movement of sodium through ion channelsExplanation
Passive transport refers to the movement of molecules or ions across a membrane without the need for energy. The movement of sodium through ion channels is a passive transport mechanism because it occurs down its concentration gradient, without the need for ATP or any other energy source. In contrast, cotransport of glucose with sodium, transport of sodium and potassium across the membrane by the Na+/K+ pump, and movement of calcium out of the cytosol all require energy in the form of ATP. Movement of sodium out of the cytosol can also be an active process, depending on the specific mechanism involved.Rate this question:
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- 9.
Lipophilic hormones transported blood ___ and bind to receptors located _____ .
- A.
Dissolved in the plasma : on the plasma membrane of the target cell
- B.
Dissolved in the plasma : inside the target cell
- C.
Bound to carrier proteins : on the plasma membrane of the target cell
- D.
Bound to the carrier proteins : inside the target cell
- E.
Inside red blood cells: inside the target cell
Correct Answer
D. Bound to the carrier proteins : inside the target cellExplanation
Lipophilic hormones are hydrophobic and cannot dissolve in the aqueous plasma. Therefore, they bind to carrier proteins in the blood to be transported to their target cells. Once inside the target cell, the lipophilic hormones dissociate from the carrier proteins and bind to receptors located inside the cell. This allows the hormones to exert their effects on the target cell.Rate this question:
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- 10.
Which of the following describes the signal transduction mechanism for estrogen, a steroid horomone?
- A.
Opening of fast ligand-gated channels
- B.
Activation of enzyme-linked receptor
- C.
Activation of cAMP second messenger system
- D.
Opening or closing of fast ligand-gated channels
- E.
Altering transcription of mRNA
Correct Answer
E. Altering transcription of mRNAExplanation
Estrogen, being a steroid hormone, acts by altering transcription of mRNA. Steroid hormones, including estrogen, bind to intracellular receptors located in the cytoplasm or nucleus. Once bound, the hormone-receptor complex enters the nucleus and binds to specific DNA sequences called hormone response elements (HREs) located in the promoter region of target genes. This binding leads to the recruitment of transcription factors and other co-regulators, ultimately resulting in the transcription of specific mRNA molecules. These mRNA molecules are then translated into proteins, which mediate the physiological effects of estrogen in the cell.Rate this question:
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- 11.
Which of the following correctly describes phagocytosis?
- A.
A cell synthesizes a product and packages it into vesicles. The product is released by phagocytosis
- B.
Cells engulf large particles, such as bacteria, by phagocytosis
- C.
A substance in the extracellular fluid binds to specific receptors for it on the cell membrane inducing the formation of a coated pit. the coated pit invaginates and enters the cell by phagocytosis.
- D.
Cells non-specifically engulf extracellular fluid
- E.
Carrier proteins in the cell membrane transport a specific substance into the cell.
Correct Answer
B. Cells engulf large particles, such as bacteria, by phagocytosisExplanation
Phagocytosis is a process in which cells engulf large particles, such as bacteria. This process involves the cell membrane forming a coated pit in response to a substance in the extracellular fluid binding to specific receptors on the cell membrane. The coated pit then invaginates and enters the cell, allowing the engulfment of the large particles. This explanation accurately describes the process of phagocytosis.Rate this question:
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- 12.
The fluid compartment with high sodium concentration contains only trace amounts of protein is called
- A.
Interstitial fluid
- B.
Plasma
- C.
Intracellular fluid
- D.
Extracellular fluid
- E.
Intracellular and extracellular fluids
Correct Answer
A. Interstitial fluidExplanation
The fluid compartment with high sodium concentration contains only trace amounts of protein is called interstitial fluid. This fluid is found between the cells and tissues of the body and plays a crucial role in maintaining the balance of electrolytes and nutrients. It allows for the exchange of substances between the cells and blood vessels, providing them with necessary nutrients and removing waste products. Unlike plasma, which is the liquid component of blood and contains proteins, interstitial fluid has very low protein content.Rate this question:
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- 13.
Molecules with a relatively high lipophilicity are capable of crossing membrane ___
- A.
Directly across the lipid bilayer
- B.
Only through specific protein channels
- C.
Only with the addition of energy
- D.
Indirectly by moving across a carrier protein
- E.
Through specific lipid channels
Correct Answer
A. Directly across the lipid bilayerExplanation
Molecules with a relatively high lipophilicity are capable of crossing the lipid bilayer directly. Lipophilicity refers to the ability of a molecule to dissolve in lipids or fats. Since the lipid bilayer is composed of phospholipids, which have a hydrophobic (water-repelling) tail, lipophilic molecules can easily pass through this hydrophobic region without the need for any additional energy or assistance from proteins or carrier molecules. Therefore, they can cross the membrane directly by moving through the lipid bilayer.Rate this question:
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- 14.
Primary active transporters are unique in their ability to couple the movement of ions directly to ____
- A.
Another ion's electrochemical gradient
- B.
ATP
- C.
A carrier protein
- D.
Its electrochemical gradient
- E.
A channel
Correct Answer
B. ATPExplanation
Primary active transporters are unique in their ability to couple the movement of ions directly to ATP. This means that these transporters use the energy from ATP hydrolysis to actively transport ions across a membrane against their electrochemical gradient. This process is essential for maintaining ion concentration gradients and is crucial for various cellular processes such as nerve conduction, muscle contraction, and nutrient uptake.Rate this question:
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- 15.
Which type of chemcical messenger is released into the bloodstream by an endocrine gland where it can affect target cells throughout the body?
- A.
Paracrine
- B.
Autocrine
- C.
Hormone
- D.
Cytokine
- E.
Neurotransmitter
Correct Answer
C. HormoneExplanation
Hormones are chemical messengers that are released into the bloodstream by endocrine glands. Once in the bloodstream, hormones can travel throughout the body and affect target cells in various organs and tissues. They play a crucial role in regulating numerous physiological processes, such as growth, metabolism, reproduction, and mood. Therefore, the correct answer is hormone.Rate this question:
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- 16.
Which of the following statements best describes the function of a receptor protein-tyrosine kinase?
- A.
It catalyzes the formation of dopamine from L-dopa
- B.
It catalyzes the formation of norepinephrine from dopamine
- C.
It catalyzes the phosphorylation of a protein inside the cell
- D.
It catalyzes the phosphorylation of a protein in the extracellular fluid
- E.
It sequesters calcium in the cytosol
Correct Answer
C. It catalyzes the phosphorylation of a protein inside the cellExplanation
A receptor protein-tyrosine kinase catalyzes the phosphorylation of a protein inside the cell. This means that it adds a phosphate group to a protein molecule, which can have various effects on the protein's structure and function. Phosphorylation is an important mechanism in cell signaling, as it can activate or deactivate proteins, regulate enzyme activity, and control cellular processes such as growth, division, and differentiation. Therefore, a receptor protein-tyrosine kinase plays a crucial role in intracellular signaling pathways.Rate this question:
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- 17.
Which of the following molecules is least likely to cross the plasma membrane?
- A.
Fatty acid
- B.
Water
- C.
Disaccharide
- D.
Oxygen
- E.
Steroids
Correct Answer
C. DisaccharideExplanation
A disaccharide is least likely to cross the plasma membrane because it is a larger molecule composed of two sugar units joined together. The plasma membrane is selectively permeable and allows only small, non-polar molecules to pass through. Disaccharides are larger and more polar than other options such as fatty acids, oxygen, and steroids, making it difficult for them to pass through the membrane. Water, although polar, is a small molecule and can easily cross the plasma membrane through specialized channels called aquaporins.Rate this question:
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- 18.
Oxygen diffuses from the blood cells down its concentration gradient. As cells become more active and oxidative phosphorylation increases in the cell, which of the following occurs?
- A.
The concentration gradient for oxygen decreases and oxygen movement into the cell decreases.
- B.
The concentration gradient for oxygen increases and oxygen movement into the cell decreases.
- C.
The concentration gradient for oxygen decreases and oxygen movement into the cell increases.
- D.
The concentration gradient for oxygen increases and oxygen movement into the cell increases.
- E.
The concentration gradient for oxygen and its rate of movement into the cell do not change
Correct Answer
D. The concentration gradient for oxygen increases and oxygen movement into the cell increases.Explanation
As cells become more active and oxidative phosphorylation increases, the demand for oxygen also increases. This leads to a decrease in the concentration of oxygen in the blood cells, creating a concentration gradient between the blood cells and the cell. According to Fick's law of diffusion, substances move from an area of higher concentration to an area of lower concentration. Therefore, the concentration gradient for oxygen increases, and oxygen movement into the cell also increases.Rate this question:
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- 19.
Which of the following is NOT true for all 3 transport mechanisms : facilitated diffusion, primary active transport, and secondary active transport?
- A.
The transport mechanism is specific for a particular solute(s)
- B.
The transport mechanism requires a protein.
- C.
The transport mechanism has a limit to the total number of molecules that can be transported per unit of time.
- D.
The transport mechanism requires energy
- E.
Transport can be increased by increasing the number of transport molecules in the plasma membrane.
Correct Answer
D. The transport mechanism requires energyExplanation
All three transport mechanisms - facilitated diffusion, primary active transport, and secondary active transport - require a protein for the transportation process. They are all specific for particular solutes and have a limit to the total number of molecules that can be transported per unit of time. Additionally, transport can be increased by increasing the number of transport molecules in the plasma membrane. However, the one statement that is NOT true for all three transport mechanisms is that they require energy. Facilitated diffusion does not require energy, while primary and secondary active transport both require energy in the form of ATP.Rate this question:
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- 20.
Which of the following substances crosses a pure lipid bilayer most easily by passive diffusion?
- A.
Water
- B.
Glucose
- C.
Ca+2
- D.
Ethanol
- E.
CO2
Correct Answer
E. CO2Explanation
CO2 is the correct answer because it is a small, nonpolar molecule that can easily dissolve in the lipid bilayer of the cell membrane. Being nonpolar, CO2 does not interact strongly with the polar head groups of the lipid molecules, allowing it to pass through the membrane without the need for a transport protein. In contrast, water, glucose, Ca+2, and ethanol are all polar or charged molecules that cannot easily pass through the nonpolar lipid bilayer without the assistance of specific transport proteins.Rate this question:
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- 21.
Which of the following will NOT affect the magnitude of a cell's response to a specific hydrophilic ligand?
- A.
Ligand concentration
- B.
Number of receptors
- C.
Receptor upregulation
- D.
Affinity of the receptor for the ligand
- E.
Lipid solubility of the ligand
Correct Answer
E. Lipid solubility of the ligandExplanation
The magnitude of a cell's response to a specific hydrophilic ligand is not affected by the lipid solubility of the ligand. Hydrophilic ligands are not able to cross the cell membrane easily due to their hydrophilic nature. Therefore, the lipid solubility of the ligand does not play a role in determining the magnitude of the cell's response. The other factors listed, such as ligand concentration, number of receptors, receptor upregulation, and affinity of the receptor for the ligand, can all influence the cell's response to the ligand.Rate this question:
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