BMS 595 Exam 1 Practice Questions
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Describe the fluid mosaic model of the cell membrane. - correct answer ✔✔ The fluid mosaic
model describes the cell membrane as a fluid structure where phospholipids form a bilayer with
embedded proteins, creating a mosaic of components, including cholesterol in animal cell
membranes. The fluid nature of the bilayer allows for movement of phospholipids.
What is the difference between passive and active transport and give two examples of each? -
correct answer ✔✔ Passive transport does not require energy (ATP) and moves substances
down their concentration gradient, including diffusion and osmosis. Active transport requires
energy from ATP to move substances against their concentration gradient, including the sodium-
potassium pump and bulk transport.
What are the two main components of extracellular fluid (ECF), and how do they differ? -
correct answer ✔✔ The two main components of ECF are interstitial fluid (IF), which surrounds
the cells, and plasma, the liquid matrix of blood. IF makes up 75% of ECF, while plasma makes
up 25% of ECF.
Explain the role of the sodium-potassium pump in maintaining membrane potential. - correct
answer ✔✔ The sodium-potassium pump uses ATP to actively transport three sodium ions out
of the cell and two potassium ions into the cell, both against their concentration gradients. This
action helps establish and maintain the negative resting membrane potential.
What are the three stages of an action potential and how are they achieved? - correct answer
✔✔ The three stages of an action potential are depolarization, caused by sodium ion influx;
repolarization, caused by sodium channels closing and potassium ion efflux, and
hyperpolarization, caused by excess potassium leaving the cell.
, Distinguish between graded potentials and action potentials. - correct answer ✔✔ Graded
potentials are changes in membrane potential of varying size and decrease over distance,
arising from ligand-gated ion channels, while action potentials are large, all-or-none changes in
membrane potential that follow a fixed time course, arising from voltage-gated ion channels.
How does the concentration gradient and the electrical gradient affect the movement of ions
across the cell membrane? - correct answer ✔✔ The concentration gradient causes ions to
move from areas of high concentration to low concentration, while the electrical gradient
causes ions to move towards areas with the opposite electrical charge. These gradients both
contribute to the net movement of ions across the membrane.
Define equilibrium potential and explain its significance. - correct answer ✔✔ Equilibrium
potential is the membrane potential at which the electrical and chemical forces are equal and
opposite for a specific ion, resulting in no net movement of that ion across the membrane. It is
crucial for understanding resting membrane potential and nerve impulses.
Define homeostasis in your own words. - correct answer ✔✔ Homeostasis is the process by
which an organism maintains a stable internal environment, despite external changes or
internal activities. This is achieved through a dynamic and active regulatory system rather than
fixed values.
How do negative feedback loops work to maintain homeostasis? - correct answer ✔✔ Negative
feedback loops work to maintain homeostasis by detecting a deviation from a set point and
triggering responses that counteract the change, bringing the variable back to its normal range.
This process is vital for regulating physiological parameters.
Explain what a feedforward (adaptive) mechanism is and give an example. - correct answer ✔✔
Feedforward mechanisms are anticipatory controls that allow the body to predict changes in its
internal environment and initiate a response to minimize disturbances. An example would be
the anticipatory increase in breathing frequency before exercise, which helps prevent a large
decrease in blood oxygen levels.
(LRQ) correctly answered already
passed
Describe the fluid mosaic model of the cell membrane. - correct answer ✔✔ The fluid mosaic
model describes the cell membrane as a fluid structure where phospholipids form a bilayer with
embedded proteins, creating a mosaic of components, including cholesterol in animal cell
membranes. The fluid nature of the bilayer allows for movement of phospholipids.
What is the difference between passive and active transport and give two examples of each? -
correct answer ✔✔ Passive transport does not require energy (ATP) and moves substances
down their concentration gradient, including diffusion and osmosis. Active transport requires
energy from ATP to move substances against their concentration gradient, including the sodium-
potassium pump and bulk transport.
What are the two main components of extracellular fluid (ECF), and how do they differ? -
correct answer ✔✔ The two main components of ECF are interstitial fluid (IF), which surrounds
the cells, and plasma, the liquid matrix of blood. IF makes up 75% of ECF, while plasma makes
up 25% of ECF.
Explain the role of the sodium-potassium pump in maintaining membrane potential. - correct
answer ✔✔ The sodium-potassium pump uses ATP to actively transport three sodium ions out
of the cell and two potassium ions into the cell, both against their concentration gradients. This
action helps establish and maintain the negative resting membrane potential.
What are the three stages of an action potential and how are they achieved? - correct answer
✔✔ The three stages of an action potential are depolarization, caused by sodium ion influx;
repolarization, caused by sodium channels closing and potassium ion efflux, and
hyperpolarization, caused by excess potassium leaving the cell.
, Distinguish between graded potentials and action potentials. - correct answer ✔✔ Graded
potentials are changes in membrane potential of varying size and decrease over distance,
arising from ligand-gated ion channels, while action potentials are large, all-or-none changes in
membrane potential that follow a fixed time course, arising from voltage-gated ion channels.
How does the concentration gradient and the electrical gradient affect the movement of ions
across the cell membrane? - correct answer ✔✔ The concentration gradient causes ions to
move from areas of high concentration to low concentration, while the electrical gradient
causes ions to move towards areas with the opposite electrical charge. These gradients both
contribute to the net movement of ions across the membrane.
Define equilibrium potential and explain its significance. - correct answer ✔✔ Equilibrium
potential is the membrane potential at which the electrical and chemical forces are equal and
opposite for a specific ion, resulting in no net movement of that ion across the membrane. It is
crucial for understanding resting membrane potential and nerve impulses.
Define homeostasis in your own words. - correct answer ✔✔ Homeostasis is the process by
which an organism maintains a stable internal environment, despite external changes or
internal activities. This is achieved through a dynamic and active regulatory system rather than
fixed values.
How do negative feedback loops work to maintain homeostasis? - correct answer ✔✔ Negative
feedback loops work to maintain homeostasis by detecting a deviation from a set point and
triggering responses that counteract the change, bringing the variable back to its normal range.
This process is vital for regulating physiological parameters.
Explain what a feedforward (adaptive) mechanism is and give an example. - correct answer ✔✔
Feedforward mechanisms are anticipatory controls that allow the body to predict changes in its
internal environment and initiate a response to minimize disturbances. An example would be
the anticipatory increase in breathing frequency before exercise, which helps prevent a large
decrease in blood oxygen levels.
