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BIOL 253 EXAM 1 2025 QUESTIONS AND
CORRECT ANSWERS
Which of the following transport mechanisms may be utilized to move glucose across cell membranes?
Secondary active transport and facilitated diffusion
Which of the following statements about the Na-K pump is(are) true?
The location of the binding sites on the Na-K pump dictates the direction of solute movement.
Examples of active transport may include __________.
the movement of Na+ ions out of cells and the movement of glucose molecules into intestinal epithelial cells
Which of the following statements about epithelial transport in the intestines is (are) true?
The Na+/K+ ATPase is found only in the basolateral membrane of intestinal epithelial cells and the movement of Na+ ions across the apical membrane of intestinal epithelial cells is dependent on the electrochemical gradient created by the Na+/K+ ATPase.
Which of the following statements is false with regard to primary/secondary active transport?
Substances will always move down their concentration gradient.
If a cell were to become depleted of its ATP, which type of membrane transport would be most directly and immediately affected?
Primary active transport
Energy released by the hydrolysis of ATP is used to move K+ and Na+ across cell membranes. This process is called __________.
primary active transport
Substances that are going to move against their concentration gradient (from low concentration to high concentration) will use which type(s) of membrane transport?
Primary or secondary active transport
Transport processes that can be saturated include __________.
Primary active transport, Secondary active transport, Facilitated diffusion, ion channel proteins
Which of the following will always be true of primary and secondary active transport?
At least one substance will move against its concentration gradient.
Which of the following statements makes an accurate comparison between primary and secondary active transport?
In primary active transport ATP is directly utilized, while in secondary active transport the potential energy of a concentration gradient is utilized.
Transport processes that require an energy source include __________.
primary active transport and secondary active transport
Which of the following molecules would not simply diffuse through cell membranes easily?
Na+ ions and glucose
As the solute concentration of a solution increases, __________.
the water concentration decreases and the osmotic pressure increases
Which of the following types of molecules would be most likely to pass through the plasma membrane by means of simple diffusion?
Oxygen - nonpolar
In order for water to be absorbed by epithelial cells, __________.
aquaporins must be present in the cell membranes and the concentration of impermeable solutes must be higher on the inside of the cell
Which of the following does not require the use of ATP?
Osmosis
In comparing a solution to a fluid in a cell, a hypertonic solution always has __________.
a higher concentration of non-penetrating solutes than that in the cell
extracellular fluids become hypotonic, causing brain cells to swell
In people with diabetes mellitus, glucose is not being transported into cells at the normal rate. This buildup of glucose in the plasma causes the extracellular fluid to become __________.
hypertonic and hyperosmotic
The term simple diffusion can be used to describe the movement of molecules from an area of __________.
higher concentration to areas of lower concentration
An increase in which of the following increases the rate of diffusion of oxygen molecules across pulmonary cell membranes?
Membrane surface area, the oxygen concentration inside the lung, and temperature
Which of the following conditions would lead to the fastest rate of oxygen diffusion into a cell?
a large concentration gradient and a thin membrane
The difference between carrier and channel proteins is that __________.
channel proteins create a continuous passage between intra- and extracellular compartments
The second messenger DAG.
is membrane bound
In contrast to fast ligand-gated channels, slow ligand-gated channels.
are regulated by G proteins
The cellular response to the second messenger cAMP can be inhibited by activating ________.
phosphodiesterase
The interaction between chemical messengers and their receptors is similar to the interaction between.
substrates and enzymes
second messenger
Put the following events of the PIP2 second messenger system in the correct order:
a. G protein activates phospholipase C.
b. Ligand-bound receptor activates a G protein.
c. PIP2 DAG + IP3.
d. IP3 triggers calcium release from endoplasmic reticulum.
b, a, c, d
Which of the organ systems below produces more focused and direct—and the fastest—responses from target cells?
nervous system
The signal transuction mechanism of steroid hormones can lead to.
transcription of a particular gene
are ligands that bind to target cell receptors but do not initiate a response by the target cell.
Antagonists
Up regulation allows a target cell to.
increase the sensitivity of a target cell to a ligand
Which muscle fiber type experiences slow-wave potentials?
Smooth muscle
Contraction in smooth muscle is initated when ________.
calcium binds to calmodulin
Which of these statements best characterize single-unit smooth muscle?
Single-unit smooth muscle has gap junctions and light innervation by the autonomic nervous system.
An overlap of cardiac action potential and contraction prevents summation of muscle contractions so that the heart has time to relax and fill with blood before the next contraction.
Which of these statements best characterize multi-unit smooth muscle?
Multi-unit smooth muscle lacks gap junctions but has dense innervation by the autonomic nervous system.
In what way(s) is cardiac muscle similar to smooth muscle?
It contains gap junctions, possesses pacemaker cells, and is innervated by autonomic neurons.
In which type of muscle is the function of gap junctions of the greatest importance in maintaining life?
Cardiac
Which of the following statements about smooth muscle is true?
Actin and myosin generate force through the crossbridge cycle.
In which types of muscle does myosin have ATPase activity?
Smooth, cardiac, and skeletal
Which of the following statements comparing smooth muscles to skeletal muscles is false?
Smooth muscles have more sarcoplasmic reticulum than skeletal muscles.
Calcium is removed from the cytosol of cardiac muscle cells by each of the following mechanisms except for ________.
Ca2+ leak channels in the plamsa membrane
Place the following structures involved in cardiac impulse conduction in the correct order:
a. bundle of His
b. AV node
Which of the following statements is false?
Only the SA node can initiate an action potential.
How do pacemaker cells differ from contractile cells?
Pacemaker cells are autorhythmic and do not contract.
Which type of membrane junctions are located at intercalated disks?
Gap junctions and desmosomes
In contrast to most other types of excitable cells, cardiac contractile cells ________.
have a plateau phase in the action potential
Blood is ejected from the left ventricle once pressure within the
ventricle is greater than pressure within the aorta.
During isovolumetric relaxation, __________.
the atria are receiving blood from the vena cavae
During which phase of the cardiac cycle are all four heart valves open?
none
During isovolumetric relaxation,
the AV and semilunar valves are closed and ventricular pressure is decreasing.
The increase in ventricular volume early in diastole reflects the
passive movement of blood through the atrium and into the ventricle.
What phase of the cardiac cycle is the heart in when all four valves of the heart are closed and ventricular pressure is building, but is not yet great enough to open a valve?
isovolumetric contraction
Which of the following events occurs during systole?
maximal arterial pressure
epinephrine
Parasympathetic activity decreases nodal rate of depolarization by ________.
decreasing the flow of calcium into the cytosol
Where on the heart do the sympathetic nerves terminate?
At the SA node, AV node, and myocardium
Which of the following may increase heart rate?
Norepinephrine
Regarding ventricular volumes ________.
the larger the end diastolic volume, the larger the stroke volume becomes
Which nerve provides parasympathetic supply to the heart?
The vagus nerve
Cardiac output is increased by ________.
increasing stroke volume and increasing heart rate
When someone begins to exercise, the working tissue needs an increased delivery of blood to obtain the oxygen and nutrients necessary for the maintenance of the increased metabolism. Which of the following occurs to help enhance the blood flow to the working tissue?
Increased heart rate and stroke volume
All of the following increase stroke volume except ________.
the inspiratory phase of respiration
Which of the following is (are) the same for the left and right ventricles?
Cardiac output, heart rate, and stroke volume
End diastolic volume is influenced (directly or indirectly) by ________.
heart rate, preload, afterload, and sympathetic nerve activity
