BIO 361 Biology Practice Exam: Trivia Quiz

The equilibrium potential and the reversal potential are indeed interchangeable terms when considering only one ion. Both terms refer to the same concept, which is the membrane potential at which there is no net movement of ions across the cell membrane. This occurs when the electrical gradient and the concentration gradient for the ion are balanced. Therefore, it is correct to say that the equilibrium potential and the reversal potential are interchangeable terms in this context.

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The equilibrium potential for Na+ can be calculated using the Nernst equation, which is given by:

E = (RT/zF) * ln([Na+]out/[Na+]in)

Where:
E = equilibrium potential
R = gas constant
T = temperature in Kelvin
z = charge of the ion (in this case, +1 for Na+)
F = Faraday's constant
[Na+]out = extracellular concentration of Na+
[Na+]in = intracellular concentration of Na+

Plugging in the given values and solving the equation, we get a positive value of +60.6mV as the equilibrium potential for Na+.

The Goldman equation is a mathematical formula used to calculate the resting membrane potential of a cell. It takes into account the permeability of the cell membrane to different ions, such as sodium, potassium, and chloride, as well as their concentration gradients. By considering these factors, the Goldman equation can determine the electrical potential difference across the cell membrane when the cell is at rest. This resting membrane potential is important for various cellular processes, including the transmission of nerve impulses and the maintenance of cellular homeostasis.

The correct answer is that the Antarctic fish is expected to have more unsaturated membrane fatty acids. This is because unsaturated fatty acids have lower melting points and can help maintain fluidity in the cell membranes of organisms living in cold environments. Since the fish in Antarctica has a body temperature of only 1 degree Celsius, it would need more unsaturated fatty acids to adapt to the extreme cold and maintain proper membrane function.

The inside of the resting cell membrane is typically negatively charged. This is because there is a higher concentration of negatively charged ions, such as proteins and organic molecules, inside the cell compared to the outside. Additionally, there is an uneven distribution of ions across the cell membrane, with more positive ions, such as sodium, on the outside and more negative ions, such as potassium, on the inside. This creates an electrical potential difference across the membrane, resulting in a negative charge on the inside.

Passive diffusion is the process by which lipid-soluble molecules cross membranes without the need for energy or assistance from transport proteins. This occurs because the lipid bilayer of the membrane is composed of hydrophobic tails that allow lipid-soluble molecules to easily dissolve and pass through. Active transport requires energy and transport proteins, while facilitated diffusion uses transport proteins but does not require energy. Therefore, the correct answer is passive diffusion as it is the most suitable mechanism for lipid-soluble molecules to cross membranes.

Permease is the correct answer because it is a type of protein that facilitates the diffusion of molecules across the membrane by binding to the substrate and undergoing a conformational change. This conformational change allows the substrate to be transported across the membrane. Permeases are commonly found in biological systems and play a crucial role in the transport of various substances across cell membranes.

Action potentials are self-propagating, meaning that once initiated, they can regenerate themselves along the length of the neuron without any loss of strength. This is due to the positive feedback mechanism that occurs during the depolarization phase of an action potential. In contrast, graded potentials are not self-propagating and their strength diminishes as they travel along the neuron. This is because graded potentials are generated by the passive spread of ions through the neuron's membrane, and as they spread, they experience leakage and dissipation, resulting in a decrease in strength. Therefore, action potentials can be transmitted over long distances while graded potentials are limited to relatively short distances.

Depolarization is the process in which the membrane potential of a neuron becomes less negative than its resting potential. This occurs when there is an influx of positively charged ions into the cell, causing the inside of the cell to become more positive. As a result, the membrane potential becomes less negative, bringing the neuron closer to its threshold and increasing the likelihood of generating an action potential.

When two subthreshold excitatory graded potentials arrive at the axon hillock at exactly the same time, they can summate and reach the threshold for an action potential. This is because the combination of the two subthreshold potentials can generate enough depolarization to surpass the threshold and trigger the firing of an action potential.

The relative fluidity of the bilayers would depend on the temperature of measurement. This is because temperature affects the movement of molecules in the bilayer. At higher temperatures, the molecules have more kinetic energy and move more rapidly, resulting in increased fluidity. On the other hand, at lower temperatures, the molecules have less kinetic energy and move more slowly, leading to decreased fluidity. Therefore, the fluidity of the bilayers, including the cholesterol-containing one, would be influenced by the temperature at which the measurement is taken.

Glucose exhibits an electrochemical gradient across the cell membrane. This means that there is a combination of both electrical and chemical forces that drive the movement of glucose molecules across the membrane. The electrical component is due to the difference in charge between the inside and outside of the cell, while the chemical component is due to the difference in concentration of glucose on either side of the membrane. Together, these forces create an electrochemical gradient that allows glucose to move into or out of the cell.

As the strength of the signal increases, the frequency of the action potential (AP) also increases. This means that the neurons fire more frequently to convey the information about the stronger signal.

Closing of the inactivation gates of the voltage-gated Na+ channel in a squid giant axon ends the depolarization phase of an action potential. During the depolarization phase, the voltage-gated Na+ channels open, allowing the influx of Na+ ions into the axon, which leads to the rapid depolarization of the membrane. Once the inactivation gates close, the Na+ channels become inactive, preventing further influx of Na+ ions and ending the depolarization phase. This is followed by the repolarization phase, where the voltage-gated K+ channels open, allowing the efflux of K+ ions and restoring the membrane potential to its resting state.

Energy is the ability to do work. It is a fundamental concept in physics that describes the capacity of a system to perform tasks or cause changes. Energy exists in various forms such as kinetic, potential, thermal, and electrical. It can be transferred or transformed from one form to another, but it cannot be created or destroyed. In the context of this question, energy is the most appropriate choice as it directly relates to the ability to do work.

Electrogenic carriers generate a charge difference across the membrane. This means that these secondary active transporters transport charged particles across the membrane, resulting in the establishment of an electrical gradient. This electrical gradient can have important physiological implications, such as influencing the movement of other ions or molecules across the membrane.

The correct answer is that all available transporters are working at their maximal rate. This means that once all the Glut-1 transporters are fully occupied, increasing the external glucose concentration will not result in any further increase in the rate of glucose transport. At this point, the transporters have reached their maximum capacity and cannot transport glucose any faster, leading to a stabilization of the rate of glucose transport.

When a subthreshold excitatory stimulus reaches the axon hillock, it means that the stimulus is not strong enough to reach the threshold required to generate an action potential. In this case, no voltage-gated sodium channels will open, preventing the depolarization of the cell membrane. Instead, the greater potential will continue to travel into the axon, but it will decrease in magnitude until it eventually dissipates completely. This process is known as decremental conduction and is characteristic of graded potentials, which do not result in the generation of an action potential.

When the neurotransmitter molecules bind to the ligand-gated K+ channels on the dendrite of a motor neuron, it stimulates these channels to open. As a result, K+ ions will leave the cell, causing an efflux of positive charge. This efflux of positive charge will result in hyperpolarization of the cell membrane, making it more negative than its resting potential. This hyperpolarization will prevent the generation of a graded potential, inhibiting the generation of an action potential. Therefore, the correct answer is that K+ ions will leave the cell, hyperpolarizing the cell membrane.

During the absolute refractory period, the axon hillock is unable to generate an action potential because it is still in the process of repolarizing after a previous action potential. This period is characterized by the inactivation of voltage-gated sodium channels, which prevents the generation of another action potential until the membrane potential returns to its resting state. Therefore, the axon hillock cannot generate an action potential during this period, regardless of the strength of the stimulus.

The correct answer is that the membrane is more permeable to K+ than to any other ion. This is because the cell membrane contains a higher number of potassium channels compared to other ion channels. As a result, potassium ions can easily move in and out of the cell, leading to a higher concentration of K+ inside the cell. This creates an electrochemical gradient that makes the interior of the cell electronegative at rest.

Increasing the temperature and increasing membrane unsaturation both result in an increase in membrane fluidity. Higher temperatures cause the lipids in the membrane to move more rapidly, making the membrane more fluid. Increasing membrane unsaturation refers to increasing the proportion of unsaturated fatty acids in the membrane phospholipids. Unsaturated fatty acids have double bonds in their carbon chains, which introduce kinks and prevent tight packing of the lipids. This increases the fluidity of the membrane. Therefore, both a and b will lead to an increase in membrane fluidity.

Both increasing the temperature and increasing membrane unsaturation will result in an increase in membrane fluidity. When the temperature is increased, the molecules in the membrane gain more kinetic energy, causing them to move more freely and increasing fluidity. Increasing membrane unsaturation refers to increasing the proportion of unsaturated fatty acids in the membrane. Unsaturated fatty acids have double bonds in their carbon chains, which introduces kinks and prevents tight packing of the lipid molecules. This also increases fluidity as the lipid molecules can move more easily past each other.

The length of time that the voltage gated potassium channel remains open determines the length of the relative refractory period in a squid giant axon. During the relative refractory period, the membrane potential is hyperpolarized due to the efflux of potassium ions through these channels. This hyperpolarization makes it more difficult for the neuron to reach the threshold for generating another action potential. Therefore, the longer the potassium channels remain open, the longer the relative refractory period will be.

Increasing the total number of Glut-1 transporters would allow more glucose molecules to be transported into the cell at a given time. This would increase the rate of glucose transport as more transporters would be available to facilitate the movement of glucose across the cell membrane.

Desaturase enzymes are responsible for catalyzing the desaturation of fatty acids. In general, enzyme activity tends to increase with temperature up to an optimal point, after which it starts to decrease. Therefore, it is expected that the desaturase enzyme activity in the goldfish living at 30 degrees Celsius (warm fish) would be higher compared to the goldfish living at 10 degrees Celsius (cold fish). This is because the higher temperature provides more energy for the enzyme reaction to occur, resulting in increased enzyme activity.