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Physiology Final study guide

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7. _______ autocrine 8. _______ neurohormone 9. _______ neurotransmitter 10. ______ paracrine a. chemical released by axon terminals into a synaptic cleft b. chemical released by axon terminals into the bloodstream c. regulators of cellular activity by messengers from nearby cells. d. regulators of cellular activity by chemical mediators produced by that same cell

7. d 8. b 9. a 10. c

Which is true about mediated transport across cell membranes? a. It refers to the movement of ions through protein channels. b. It refers both to simple diffusion and to the active transport of molecules. c. It is characterized by saturation of the carriers and a maximum velocity of transport. d. As the concentration gradient across a membrane increases, the transport rate always increases. e. It is nonspecific, any transporter can transport any molecule across the cell membrane.

During the concentric contractions of skeletal muscle, the I band approximate, H zone narrows and the A band stays the same width. a. true b. false

Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP. a. true b. false

If a biopsy of the quadriceps (thigh extensor) muscles were taken from gold medal-winning speed skaters in the 4 events below, which would most likely have the greatest percentage of type i muscle fibers? a. 10,000 meters b. 5,000 meters c. 1,000 meters d. 500 meters

In the first few seconds of skeletal muscle contraction, what is the main mechanism by which ATP is replenished? a. Energy and phosphate are transferred from creatin phosphate to ADP b. Oxidative phosphorylation rapidly generates ATP from glucose. c. Glycolysis produces ATP from glycogen d. Oxidation of fatty acids into ATP occurs in the mitochondria. e. Myoglobin catalysis produces ATP

Jennifer is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Amy is a marathon runner who specializes in long, steady runs. Compared to Amy, Jennifer is likely to have: a. legs with a larger diameter. b. legs with a smaller diameter. c. hypertrophy of type I muscle fibers. d. a higher density of capillaries in his legs. e. lower concentrations of glycolytic enzymes in his leg muscles.

Skeletal muscles are made up of bundles of muscle fibers attached to bone by connective tissue called tendons. a. true b. false

Smooth muscle cells may contract in the absence of neuronal stimulation. a. true b. false

Sustained contraction and tension in a skeletal muscle is called tetanus. a. true b. false

The binding of ATP to myosin causes an allosteric change in myosin's actin-binding site such that the affinity of myosin for actin is decreased. a. true b. false

The condition of shock is an example of failure of homeostatic mechanisms to compensate when one or more parts of the reflex control system are damaged. a. true b. false

The left ventricle has a thicker wall than the right ventricle because the left ventricle has to pump blood against a higher pressure. a. true b. false

The myosin in smooth muscle cells differs from that in skeletal muscle in that smooth muscle myosin requires phosphorylation before it can bind to actin. a. true b. false

The pacemaker of the heart is normally what structure? A. sinoatrial node B. atrioventricular node C. mitral valve D. bundle of His E. left ventricle

The sarcomere is the repeating functional unit that causes the stirated apperance in skeletal muscle myofibrils. a. true b. false

What is the definition of a motor unit? a. a single motor neuron plus all the muscle fibers it innervates b. a single muscle fiber plus all of the motor neurons that innervate it c. all of the motor neurons supplying a single muscle d. a pair of antagonistic muscles e. all of the muscles that affect the movement of any given joint

What protein is the prinicipal component of skeletal muscle thin filaments? a. actin b. mysoin c. troponin d. calmodulin e. tropomyosin

When the load on a skeletal muscle is less than the tension the muscle generates, a concentric isotonic contraction results. a. true b. false

Which of the following is false regarding single-unit smooth muscle cells? a. They have an individual neuron innervating of each individual smooth-muscle cell. b. They have many gap junctions between cells. c. They may have pacemaker activity. d. They may respond to stretch by contracting. e. They exhibit tone.

Which of the following statements concerning the capillaries is FALSE? A. Increasing capillary hydrostatic pressure decreases the likelihood that filtration will occur. B. Velocity of blood flow is slower in the capillaries than in the arteries. C. It is possible for a capillary to filter fluid at its arterial end and absorb fluid at its venous end. D. Large capillary pores are more likely to be found in liver capillaries than in brain capillaries. E. Large proteins that escape capillaries and enter the interstitial fluid are returned to the circulation via the lymphatic system.

. Free radicals a. rapidly oxidize other atoms by removing an electron. b. are inert molecules that don't interact readily with other molecules. c. contain two electrons in the outermost orbital. d. have extra neutrons in their nuclei. e. are found in high quantities in most sports drinks.

4. Which of the following is not a product of glycolysis? a. carbon dioxide b. ATP c. pyruvate d. NADH + H+ e. Two of the above are not products of glycolysis.

A major product of metabolism is H2O. a. true b. false

A portion of cells plasma membrane is removed during endocytosis. a. true b. false

ATP is a(n) a. nucleotide. b. lipid. c. amino acid. d. carbohydrate. e. steroid.

Activated calmodulin functions to activate or inactivate cytosolic enzymes. a. true b. false

Aerobic respiration may be characterized by following final electron acceptor. a. oxygen b. NAD+ c. FAD d. nitrite ion e. Two of the above are correc

All other factors being equal, the rate of diffusion across a permeable surface will be greater for small molecules than for larger ones. a. true b. false

Allosteric modulation of a protein involves noncovalent binding of a ligand to a regulatory binding site. a. true b. false

An antagonis blocks the action of a chemical messenger by binding to its receptor. a. true b. false

An atom is electrically neutral a. true b. false

Because of the active transport of Na+ and K+, the intracellular concentration of Na+ is lower than the extracellular concentration, whereas the reverse is true for K+. a. true b. false

Cells can increase or decrease their responsiveness to an external chemical regulators by up-regulation or down regulation of genes coding for protein receptors. a. true b. false

Cells can increase their responsiveness to an external chemical regulator by a. increasing the number of their transmembrane receptors by exocytosis b. decreasing the number of their transmembrane receptors by endocytosis c. uncoupling their receptors from the second message generator. d. increasing the number of their transmembrane receptors by endocytosis. e. mutating their extracellular receptors so that the affinity for the chemical regulator is reduced

Chromatin is a composition of DNA and protein a. true b. false

During anaerobic glycolysis, the net ATP generated in the production of lactic acid (lactate) is significantly less than that which is generated during aerobic glycolysis and the production of pyruvic acid (pyruvate). a. true b. false

During oxidative phosphorylation, electrons are passed serially from a coenzyme through a chain of molecules called cytochromes. a. true b. false

Eicosanoids are a family of ubiquitous, fatty-acid-derived, local chemical messengers. a. true b. false

Electrons transferred along the electron transport chain can be used to form a. water. b. glucose. c. ATP. d. NADH + H+. e. acetyl coenzyme A.

Enzymes a. are catalysts in chemical reactions. b. can be carbohydrate molecules. c. are broken down during chemical reactions they catalyze. d. have names generally ending in the suffix "-ose." e. are polymers of ATP that store large amounts of energy.

Feedforward regulatory processes a. work in anticipation of changes in regulated variables. b. are identical to negative feedback processes. c. lead to instability of the regulated variable. d. maximize fluctuations in the regulated variable. e. tend to force physiological variables away from their set points.

First messengers may bind to a membrane receptor that is an ion channel, which promotes a change in membrane potential. a. true b. false

Glucose cannot be synthesized from fatty acids because the reaction converting pyruvic acid to acetyl coenzyme A is not reversible. a. true b. false

Heart rate is increased by the release of epinephrine by the adrenal medulla into the bloodstream. This is an example of a. endocrine control b. exocrine control c. paracrine control d. direct neural control e. positive feedback

How does the synthesis of secretory protein differ from proteins with functions inside the cell? a. Proteins destined to be secreted have a signal sequence. b. Proteins destined to be secreted are synthesized on free ribosomes c. proteins destined to be secreted are packaged into secretory vesicles in the granular endoplamsic reticulum d. Only proteins destined for secretion need transfer RNA to be synthesized. e. Genes for proteins with functions inside the cell are located in the cytoplasm.

If a normal cell is placed into an unknown solution and it shrinks, what can be concluded about the unknown solution? a. Its non-pentrating solute concentration is greater than that of a normal cell. b. Its non-pentrating solute conecntration is less than that of a normal cell. c. Its non-pentrating solute concentration is equal to that of a normal cell. d. Its penetrating solute concentration is less than that of a normal e. its pentrating solute concentration is greater than that of a normal cell.

If the ATP-generating mechanisms in a cell are poisoned and the cell depletes its ATP reserves, which would occur first? a. Primary active transport of molecules would cease. b. Secondary active transport of molecules would cease. d. Facilitated diffusion of molecules would cease. d. Ion concentration gradients would reach equilibrium across the cell membrane. e. All transport processes would cease immediately when the ATP was depleted.

In eukaryotic cells, substrate-level phosphorylation may occur in a number of cellular locations, whereas oxidative phosphorylation must occur in mitochondria. a. true b. false

In general, polar molecules will dissolve in polar solvents, while nonpolar molecules cannot. a. true b. false

In most of the cells in the body there is an electrical difference such that the inside of cells is negative with respect to the outside. a. true b. false

Integral membrane proteins can form channels through which ions such as Na+ and K+ can diffuse. a. true b. false

Living cells cannot be viewed under an high-voltage electron microscope (HVEM). a. true b. false

Methadone is a drug given to treat heroin addicts. It works by binding to the same receptors as heroin but with greater affinity, thereby preventing heroin from binding. This is an example of a. competition b. down-regulation c. signal transduction d. agonistic behavior e. up-regulation

Molecules increase their rate of diffusion as temperature increases. a. true b. false

Most of the body weight of an average young adult is what substance? a. water b. protein c. minerals d. lipids e. carbohydrates

Once protein synthesis is completed, the protein that was synthesized may undergo further changes prior to its secretion or use within the cell. a. true b. false

One fate of endocytotic vesicles is digestion of their contents by lysosomal enzymes. a. true b. false

One function of epithelial cells is to form selective barriers regulating exchange of materials across them. a. true b. false

One function of integral membrane proteins in the plasma membrane of cells is to form channels to allow passage of polar solutes into the cell. a. true b. false

Phosphorylation is a common component of many enzyme activations. a. true b. false

Second messengers may bind to a membrane receptor that is an ion channel, which promotes a change in the membrane potential. a. true b. false

The Na+ and K+ channels that open during an action potential are voltage-regulated, both opening in response to depolarization of the membrane. a. true b. false

The absolute refractory period of an excitable membrane roughly corresponds to the period when sodium channels are opening and inactivated. a. true b. false

The active site of an enzyme is a functional binding site. a. true b. false

The chemical group into which glucose best fits is a. monosaccharides. b. disaccharides. c. polysaccharides. d. glycoproteins. e. phospholipids.

The concentration of calcium in the cytosol of most resting cells is very much lower than the concentration of extracellular calcium. a. true b. false

The diffusion potential due to the concentration gradient for Na+ across a nerve cell membrane a. favors its movement into the cell at the resting membrane potential b. favors its movement out of the cell at the resting membrane potential c. is equal and opposite to the electrical potential acting on Na+ at the resting membrane potential. d. is in the same direction as the diffusion potential due to the concentration gradient for K+ e. favors movement of Na+ in the opposite direction as the electrical potential acting on Na+ at the resting membrane potential

The extracellular fluid compartment includes the interstitial fluid and blood plasma. a. true b. false

The first step in glycolysis is the phosphorylation of glucose. a. true b. false

The lipid portion of a cell's plasma membrane constitutes a barrier to a current. a. true b. false

The shape of a molecule may change as atoms rotate about their covalent bonds. a. true b. false

The total energy change in a system as it proceeds to equilibrium is called: a. free energy. b. activation energy. c. maximum energy. d. All of the above are correct.

Transcription factors activate or repress the transcription of specific genes by binding to regions of DNA that interact with the promoter region of a gene. a. true b. false

Two receptors, A and B, can bind the same chemical signaling molecules but the concentration of those molecules required to reach 50% saturation is twice as great for receptor B. Therefore, the receptors have the same _____, but different ______. a. specificity, affinity b. specificity, saturation c. affinity, specificity d. affinity, competition e. competition, affinity

What is a coenzyme? a. an organic molecule that directly participates in the modulation of an enzyme b. a metal, such as zinc, that participates in the modulation of an enzyme c. a term regarding enzymatic reactions that is synonymous with "cofactor" d. any ligand that binds to a specific site on a protein receptor e. an inorganic molecule that catalyzes enzymatic reactions

When a reversible chemical reaction is at equilibrium. a. the rate of the reaction in one direction is equal to the rate in the reverse direction. b. the concentration of the reactants is equal to the concentration of the products c. both the forward and reverse reactions stop occuring. d. the supply of reactants has become exhuasted, so the forward reaction ceases and the rate of the reverse reaction increases e. catalysts no longer influence either the forward or reverse reaction rates.

When multiple repeating simple sugar molecules combine to form a larger molecule, it is called a polysaccharide. a. true b. false

Which best describes a hydrolysis reaction? a. Molecules are broken down into smaller ones by breaking covalent bonds within water molecules and transferring hydrogen atoms and hydroxyl groups to the smaller ones. b. Electrically charged molecules separate into ions when they dissolve in water, and then hydrogen ions and hydroxyl groups covalently attach themselves to the oppositely charged ions. c. Large molecules are assembled from smaller ones by breaking water into hydrogen and hydroxyl ions. d. Dissolving a large molecule in water reduces it to its individual atoms. e. The breaking of hydrogen bonds between any two molecules.

Which best describes rigor mortis? a. Lack of ATP following death causes cross-bridges to remain tightly bound to actin b. Lack of ATP following death causes calcium to remain in the cytosol, continuously stimulating cross-bridge cycling c. Repeated, high-frequency action potentials to a skeletal muscle fiber causes sustained contraction following death. d. Following death, calcium-activated proteases degrade all proteins in skeletal muscle fibers, making muscles limp. e. Build-up of K+ in T-tubules causes constant, tetanic contractions of skeletal muscles that last for about 12 hours following death.

Which best describes temporal summation? a. A synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated. b. It only refers to addition of EPSPs. c. Two synapses on different regions of a cell are stimulated at the same time. d. It always brings a postsynaptic cell to threshold. e. The size of an EPSP depends on the size of the stimulus.

Which is true about mediated transport of substances across cell membranes? a. It involves a specific membrane protein that functions as a carrier molecule. b. It always involves the movement of substances against a concentration gradient. c. It is always directly coupled to the splitting of ATP molecules. d. There is no limit to how fast it can occur as the concentration gradient becomes larger. e. It is the main mechanism for transporting hydrophobic molecules across membranes.

Which is true about the Na+/K+ ATPase pump in neurons? a. It generates a small electrical potential such that the inside is made negative with respect to the outside. b. It maintains a concentration gradient for K+ such that diffusion forces favor movement of K+ into the cell. c. It maintains an electrical gradient at the equilibrium potential of K+. d. It transports equal numbers of sodium and potassium ions with each pump cycle. e. It pumps 3 Na+ ions into the cell for every 2 K+ ions it pumps out.

Which of the following is known to be a second messenger? a. diaclglycerol b. phospholipase c c. atp d. adenylyl cyclase e. epinephrine

Which of the following is not typically true about G-proteins? a. They act as second messengers b. They can be stimulatory for second messneger production. c. They can be inhibitory for second-messenger production. d. They can act as transducers for activated receptors by opening or closing ion channels

Which of the following metabolic pathways can proceed in the absence of oxygen? a. glycolysis b. oxidative phosphorylation c. Krebs cycle d. beta-oxidation e. oxidative deamination

Which of the following statements is true? a. diffusion depends upon the random motion of molecules b. diffusion results in net movement of molecules from regions of low concentration to regions of high concentration c. Diffusion is the principal mechanism by which molecules are moved over large distances in the body. d. Diffusion requires energy in the form of ATP e. Simple diffusion requires integral membrane proteins to occur.

Which of the following statements regarding the structure and function of cell membranes is correct? a. The phospholipid bilayer is arranged so that the hydrophilic heads of the phospholipid molecule face the extra and intracellular fluids. b. some proteins integrated into the membrane serve as channels for the passage of nonpolar molecules through the membrane. c. Peripheral membrane proteins function as channels associated with transport of ions through the membrane. d. cholesterol molecules function to transport ions form one side of the plasma membrane to the other. e. the plasma membrane is a layer of phospholipid molecules with their hyrophilic head groups in contact with the extracellular solution and the hydrophobic tail groups in contact with the intracellular solution.

Which of these compounds is most likely a lipid-soluble intranuclear first messenger? a. steroid hormone b. protein kinase c. glucose d. sodium ions e. cyclic AMP

Which would result from an increase in the extracellular concentration of K+ above normal? a. depolarization of resting nerve cells b. hyperpolarization of resting nerve cells c. The potassium equilibrium potential of nerve cells would become more negative. d. The sodium equilibrium potential would become less positive.

important mineral elements in teh body include Na, Ca, and K a. true b. false

Compared to type I (slow oxidative) skeletal muscle fibers, how are type IIb (fast-glycolytic) skeletal muscle fibers different? a. Type IIb fibers have more abundant mitochondria. b. Type IIb fibers fatigue more readily. c. Type IIb fibers have more abundant myoglobin. d. Type IIb fibers are smaller in diameter. e. Type IIb motor units contain fewer fibers per alpha motor neuron.

During isotonic contraction of a skeletal muscle fiber, tension increases but the fiber length stays the same. a. true b. false

Flexor muscles generally pull on bone and decrease the angle at a joint, whereas extensor muscles push the bone to increase the angle. a. true b. false

How is the strength of a stimulus encoded by neurons? a. by the size of action potentials b. by the frequency of action potentials c. by the duration of action potentials d. by whether the action potential peak is positive or negative.

Muscles used for delicate, finely controlled movements have larger motor units than muscles used for gross movements. a. true b. false

The cell membrane is composed principally of: a. cytosol b. phospholipids and proteins c. phospholipids and nucleic acids d. water e. proteins and glycocalyx

The decrease in mass and strength of muscle as a result of damage to the nerves innervating the muscle is called disuse atrophy. a. true b. false

The diameter of a skeletal muscle fiber has no relationship to the tension it can generate. a. true b. false

The prolonged electrical depolarization of cardiac muscle cells that occurs during contraction is due primarily to the persistent influx of what ion? a. sodium b. calcium c. nitrate d. chloride e. potassium

The site of Ca2+ storage in muscle cells is the lateral sacs of the transverse tubules. a. true b. false

What is the best description of a tetanic contraction in a skeletal muscle cell? a. A single action potential in the motor neuron causes a sustained contraction. b. Multiple action potentials in the motor neuron cause a sustained contraction. c. The action potential in the muscle cell is prolonged to last as long as the contraction. d. Repeated action potentials from the motor neuron summate into a sustained depolarization of the motor end plate, causing a sustained contraction. e. A very large amplitude action potential in the motor neuron causes a very strong contraction in the skeletal muscle cell.

Which best describes a myofibril? a. It is a single skeletal-muscle cell. b. It is a cylindrical cellular organelle composed of myofilaments. c. It is a hollow membranous structure that stores calcium. c. It is composed of a single type of protein and forms cross-bridges. e. It is a fibrous junction between a muscle cell and a tendon.

Which of the following is not one of the four general categories (histological types) of cells that make up the human body? a. epithelium b. membranes c. connective d. nervous e. muscle

Which of the following occurs first in hemostasis? A. activation of the fibrinolytic system B. platelet aggregation C. a clotting cascade that leads to the conversion of fibrinogen to stable fibrin D. conversion of prothrombin to thrombin E. conversion of plasminogen to plasmin

. NaCl is a molecule formed by the covalent bonding of a sodium atom to a chlorine atom. a. true b. false

A solute, X, is placed in compartment A of a two compartment container and allowed to diffuse to compartment B and attain diffusion equilibrium. At that point in time, a. there will be no further movement of any solute molecules between compartments. b. solutes will be moving in both directions equally. c. solutes will only continue to move from A to B. d. solutes will only continue to move from B to A. e. the concentration in compartment B will be much higher than that in compartment A

A solution with a pH of 8 is more acidic than one with a pH of 3. a. true b. false

An action potential in a membrane results in an electric current along an adjacent area of membrane and this current diminishes with distance from the site of the initial potential change. a. true b. false

An action potential in a neuronal membrane differs from a graded potential in that a. an action potential requires the opening of Ca2+ channels, whereas a graded potential does not. b. an action potential is propagated without decrement, whereas a graded potential decrements with distance c. an action potential has a threshold, whereas a graded potential is an all or none phenomenon. d. movement of Na+ and K+ across cell membranes mediate action potentials, while graded potentials do not involve movement of Na+ and K+ e. action potentials vary in size with the size of a stimulus, while graded potentials do not

Carbon-12 and carbon-14 are isotopes, but a. differ in the number of protons b. differ in the number of neutrons c. differ in the numbers of electrons d. they can form different numbers of chemical bonds e. differ in the number of orbitals.

Cocaine lowers the levels of a chemical messenger in the brain called enkephalin. Researchers have found the number of enkephalin receptors to be higher in cocaine addicts than non-addicted people. this is an example of: a. saturation b. up-regulation c. anagonism d. affinity e. down-regulation

During the rising (depolarizing) phase of a neuronal action potential, a. PK+ becomes much greater than PNa+. b. PNa+ becomes much greater than PK+. c. PK+ is the same as PNa+. d. Na+ efflux (flow out of the cell) occurs. e. K+ flows rapidly into the cell.

First messengers bind to voltage-gated ion channels, which promote a change in the membrane potential. a. true b. false

How does a chemical catalyst increase the rate of a reaction? a. by acting as one of the reactant molecules b. by decreasing the energy of activation c. by increasing the energy content of the product molecules d. by increasing the temperature of a solution e. by phosphorylating a reactant

Human beings can synthesize all twenty amino acids the body must have. a. true b. false

If a sports beverage advertises that it replaces the bodys electrolytes, what does the drink contain? a. sugars that were broken down for energy b. ionic forms of mineral elements c. lipids that form the membranes of cells d. oxygen and gases used by metabolism e. vitamins

If the amount of sodium in the blood decreases, what would a negative feedback control mechanism be expected to do? a. decreases the amount of sodium in the blood b. increase the amount of sodium in the blood c. leave the amount of sodium unchanged d. change the set point for sodium e. inhibit the ingestion of more sodium

In a metabolic pathway, the same enzyme ordinarily catalyzes several different reactions. a. true b. false

In general, polar molecules diffuse more rapidly across cell membranes than do nonpolar molecules. a. true b. fals

Ions are a. electrically neutral. b. electrically charged. c. formed by the gain or loss of protons from the nucleus. d. insoluble in water. e. nonpolar atoms.

Neuron X makes inhibitory axon-axon synaptic contact with neuron Y at the synapse of Y and neuron Z. Which will occur when action potentials are stimulated in neuron X? a. Neuron Y will be inhibited from reaching the threshold to fire an action potential. b. The release of neurotransmitter by neuron Y will be inhibited. c. The synapse between neurons Y and Z will be changed from an excitatory synapse to an inhibitory one. d. Neurons Y and Z will both be more likely to reach threshold and fire an action potential. e. Neurons Y and Z will both be less likely to reach threshold and fire an action potential.

Oils do not easily disperse in water, but rather clumps into oil droplets. Which of the following statements explains why this occurs? a. Oil is composed mainly of hydrophilic molecules. b. Oil is composed mainly of nonpolar molecules. c. Oil has no hydrogen in its molecular structure, so it can't form hydrogen bonds with water. d. Water is hydrophobic. e. Electrons are shared unequally between carbon and hydrogen atoms.

Organic molecules a. always contain oxygen b. always contain carbon c. are always macromolecules d. never contain hydrogen e. never contain oxygen

Organs are generally composed of only one kind of tissue. a. true b. false

Physiology is the study of a. interactions between organism b. functions in organisms c. spread of diseases d. structure of organisms

Reduction involves: a. loss of electrons b. gain of electrons c. gain of neutrons d. loss of neutrons

Ribosomes transcribe DNA into RNA. a. true b. false

Saturated fats contain carbon atoms linked by double bonds a. true b. false

Solutes that do not dissolve in water are called hydrophilic. a. true b. false

The Na+ and K+ channels that open during an action potential are ligand-gated (regulated). both opening in response to depolarization of the membrane. a. true b. false

The atomic number of an element refers to the total number of particles in its atomic nucleus. a. true b. false

The component of the plasma membrane that acts as a selective barrier to diffusion of polar molecules is the integral proteins. a. true b. false

The consequences of mutation are invariably harmful. a. true b. false

The four most common elements in the body are hydrogen, carbon, calcium, and oxygen. a. true b. false

The greater the concentration difference of a substance between two volumes separated by a permeable membrane, the lesser the magnitude of the net flux of the substance. a. true b. false

The hormone insulin enhances the transport of glucose into cells. Its secretion is controlled by a negative feedback system between the concentration of glucose in the blood and the cells that secrete insulin (beta cells in the Islets of Langerhans of the pancreas). Which of the following statements best represents this relationship? a. A decrease in blood glucose concentration will stimulate insulin secretion, which will in turn lower the blood glucose concentration still further. b. An increase in blood glucose concentration will stimulate insulin secretion, which will in turn lower the blood glucose concentration. c. A decrease in blood glucose concentration will stimulate insulin secretion, which will in turn increase the blood glucose concentration. d. An increase in blood glucose concentration will stimulate insulin secretion, which will in turn increase the blood glucose concentration still further.

The luminal side of an epithelial cell is also known as the basolateral side. a. true b. false

The only role of modulator molecules is to enhance the binding affinity of the functional site of an allosteric protein. a. true b. false

The plasma membranes of epithelial cells facing the lumen of hollow organs or tubes have the same transport proteins aas the plasma membranes that face the interstitial fluid. a. true b. false

The relative refractory period of an excitable membrane refers to the period of time during which no stimulus, however strong, will elicit a second action potential in the membrane. a. true b. false

Trace elements such as zinc and manganese are found in minute quantities in the body but do not serve any known function. a. true b. false

Two cell types having the same type of receptor for a chemical messenger will always respond to that messenger in the same way. a. true b. false

Water molecules can form covalent bonds with other water molecules. a. true b. false

What are the most common receptors for hydrophilic intercellular messenger molecules? a. peripheral membrane proteins b. integral membrane proteins c. specialized phospholipids within the membrane d. nucleic acids e. intracellular proteins

What is a codon? a. a triplet of deoxyribonucleotides b. a triplet of ribonucleotides c. a sequence of ribonucleotides on tRNA d. a very small gene e. a very small genome

What is the main function of cellular tight junctions? a. They resist fores that tend to pull cells apart. b. They form barriers that restrict the passage of materials through the extracellular space between cells. c. They are protein channels that allow the movement of ions between the cytosol of adjacent cells. d. They are spaces that allow movement of substances between the interior of the nucleus and the cytosol. e. They hold the genetic material in a tightly coiled conformation

Which describes the response of the voltage-gated channels when an axon is stimulated to threshold? a. K+ channels open before the Na+ channels b. Na+ channels are activated and then inactivated c. K+ channels open at the same time as the Na+ channels d. K+ channels are opened when Na+ binds to the channel e. K+ influx causes Na+ channels to inactivate

Which is the best definition of the term ligand? a. a receptor composed of protein b. a molecule or ion that binds to a protein c. any molecule found in the intracellular fluid d. any molecule found in extracellular fluid e. a carbohydrate molecule that binds weakly to membrane phospholipids

Which of the following is not true of glial cells? a. They form the myelin for axons b. Neurons outnumber glial cells 10 to 1 in the nervous system c. They deviler fuel molecules to neurons and remove the waste products of metabolism d. They are important for the growth and development of the nervous system. e. They regulate the composition of the extracellular fluid in the CNS.

Which of the following is not true of glial cells? a. they form the myelin for axons b. Neurons outnumber gial cells 8 to 1 in the nervous system. c. They deliver resources to neurons and remove the waste products of metabolism. d. They are important for the growth and development of the nervous system e. They regulate the composition of the extracellular fluid in the CNS.

Which of the following statements regarding endocytosis and exocytosis is correct. a. Endocytosis is a method by which large molecules may be secreted from a cell. b. Exocytosis is a method by which large molecules may be secreted from a cell. c. Pinocytosis is a form of endocytosis, phagocytosis is a type of exocytosis. d. Pinocytosis is a form of exocytosis, phagocytosis is a type of endocytosis e. pinocytosis an dphagocytosis are both types of exocytosis

Which of these would occur if the concentration of ATP were depleted in a typical nerve cell? a. Resting membrane potential would become more negative. b. Resting membrane potential would become less negative c. The concentration gradient for Na+ would remain the same. d. The resting membrane potential would eventually become positive inside with respect to outside e. There would be no change in the resting membrane potential

Which of these would occur if the concentration of ATP were depleted in a typical nerve cell? a. Resting membrane potential would become more negative. b. Resting membrane potential would become less negative. c. The concentration gradient for Na+ would remain the same. d. The resting membrane potential would eventually become positive inside with respect to outside. e. There would be no change in the resting membrane potential.

During concentric isotonic contraction of a skeletal muscle fiber, which of these occurs? a. sarcomeres lengthen b. A bands shorten c. I bands shorten d. A bands lengthen e. thin filaments shorten

In skeletal muscle cells, calcium initiates contraction by binding to: a. tropmyosin b. actin c. troponin d. myosin e. the thick filament

The equilibrium potential of K+ ions in nerve cells is about -90 mV. The membrane potential of typical nerve cells at rest is -70 mV, therefore, a. increasing the permeability of a resting neuronal membrane to K+ will make the membrane potential more negative inside with respect to the outside. b. in resting neurons, there is a net diffusion of K+ into the cell c. changing the resting membrane potential of a neuron to -80 mV would increase K+ diffusion rate out of the cell d. potassium is the only permanent ion at rest e. there must be another permanent ion with an equilibrium potential more negative than -90 mV

The plateau of the action potential in cardiac ventricular cells results from the opening of voltage-gated long-lasting ___________ channels in the plasma membrane of the cell. A. Na+ B. K+ C. Ca2+ D. Cl- E. glucose

What is the function of the transverse tubules in a skeletal-muscle fiber? a. They store the calcium ions that are the main source of activation for the cross-bridge cycle. b. They form the Z lines that mark the end of each sarcomere c. They allow action potentials to propagate deep into the center of skeletal muscle cells. d. They manufacture and store ATP e. They run in parallel with the myofibrils, and have abundant Ca2+-ATPase proteins for pumping Ca2+ back into the sarcoplasmic reticulum

When a muscle has been repeatedly contracting at a moderate intensity for an extended period of time (more than a few minutes), what is the primary source of ATP? a. transfer of energy and phosphate from creatine phosphate to ADP b. glycolysis c. oxidative phosphorylation d. breakdown of myosin e. uptake of ATP from the blood plasma

Which is a true statements about smooth muscle? a. smooth muscle is striated b. smooth muscle does not have thick and thin filaments c. smooth muscle does not use troponin-rropomysoin to regulate cross-bridge activity. d. Changes in cytosolic calcium do not regulate cross-bridge activity in smooth muscle. e. The mysoin in smooth muscle requires phosphorylation before it can bind to atp

Which membrane protein transport process plays an important role in terminating the contraction of cardiac muscle? a. Ca 2+-ATPase pumps move Ca2+ from the T-tubule back into the sarcoplasmic reticulum. b. Na+/K+-ATPase pumps move Na+ back into the cytosol and K+ back into the T-tubule lumen. c. Ca2+-ATPase pumps move Ca2+ from the cytosol back into the sarcoplasmic reticulum. d. Na+/Ca2+-exchangers move Na+ out of the cytosol in exchange for Ca2+ movement into the sarcoplasmic reticulum. e. Na+/K+-ATPase pumps move Na+ and K+ back out of the cell.

Which of the following statements about different kinds of skeletal muscle fibers is true? a. slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers. b. Fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers. c. A fast-glycolytic fiber can generate greater tension than a slow oxidative fiber d. Fast-glycolytic fibers and slow-oxidative fibers are innervated by alpha motor neurons of the smae diameter. e. To generate ATP, fast glyolytic fibers depend mainly on oxidative phosphorylation while slow oxidative fibers depend mainly on glycolysis

Which of the following statements about the cardiac cycle is true? A. The duration of systole is greater than that of diastole. B. During isovolumetric ventricular relaxation, blood flows from the atria into the ventricles. C. Closure of the atrioventricular valves occurs at the onset of ventricular systole. D. The QRS complex occurs at approximately the same time as the closure of the semilunar valves. E. The first valves to go from closed to open after the atrial kick are the atrioventricular valves.

Which of the following statements concerning the rate of action potential propagation is true? a. action potential propagation is faster in small-diameter axons than in large-diameter axons b. Action potential propagation is faster for a strong stimulus than for weak one. c. action potential propagation is faster in myelinated axons than in non-myelinated axons d. action potential propagation is faster in the dendrites than in the axon e. action potential propagation occurs at the same rate in all axons, regardless of their diameter.

Which of the following statements is false? a. Synaptic input onto skeletal muscle cells is always excitatory, whereas inputs to smooth muscle cells may be either excitatory or inhibitory. b. A single smooth muscle cell may be innervated by both a sympathetic neuron and a parasympathetic neuron. c. Contractile activity of smooth muscle cells does not normally require Ca2+. d. In the absence of any neural input, skeletal muscle cannot generate tension. e. Ca2+ that activates contraction of smooth muscles can come from either the ECF or from the sarcoplasmic reticulum.

Which of the following statements regarding contraction of a skeletal muscle fiber is true? a. Thick filaments shorten when muscle cells contract. b. Some contractions occur without cross-bridge activation. c. Contracting muscle fibers do not always shorten. d. Contraction does not always require the occurrence of an action potential. e. Contraction only occurs following summation of action potentials from many motor neurons.

Which of the following statements regarding the motor end plate of a skeletal muscle fiber is true? a. Muscarinic receptors in the end plate are activated by binding to acetylcholine. b. Temporal summation of multiple end plate potentials is required in order to trigger an action potential in the muscle-fiber membrane. c. Acetylcholinesterase in the end plate membrane catalyzes the breakdown of acetylcholine. d. Sympathetic nerve fibers terminate on skeletal muscle fibers at the motor end plate. e. The motor end plate under the axon terminal contains a large number of voltage-gated Na+ channels.

Which of these occurs during an isometric contraction of a skeletal muscle? a. The I bands shorten and the A bands stay the same length. b. The thick and thin filaments slide past each other. c. Sarcomere length does not change significantly. d. The A bands shorten and the I bands stay the same length. e. Cross-bridges lock onto actin, similar to what occurs in rigor mortis.

. Ion channels in cell membranes a. are nonspecific. b. are not affected by differences in electrical potential across the membrane. c. may open in response to binding a ligand. d. only allow ions to move from the extracellular fluid into the cell. e. only allow ions to move from the intracellular fluid out of the cell.

. Molecules that have properties of both polar and nonpolar molecules are called a. hydrophobic. b. hydrophilic. c. amphipathic. d. unipolar. e. bipolar.

A certain protein receptor is capable of binding the neurotransmitter epinephrine but does not bind to the neurotransmitters dopamine, glutamate, or serotonin. This is because the receptor displays what characteristic? a. saturation b. inhibition c. specificity d. acclimatization e. accommodation

A postsynaptic neuron has three presynaptic inputs from neurons X, Y, and Z. Stimulation of neuron X causes the postsynaptic neuron to depolarize by 0.5 mV. When X and Y are stimulated simultaneously, the postsynaptic neuron depolarizes by 1 mV. When X and Z are stimulated simultaneously, however, there is no change in the membrane potential of the postsynaptic neuron. What is most likely true about presynaptic neurons Y and Z? a. They are both excitatory. b. They are both inhibitory. c. Y is excitatory and Z is inhibitory. d. Z is excitatory and Y is inhibitory.

A threshold stimulus applied to an excitable membrane is one that is just sufficient to a. trigger an excitatory postsynaptic potential b. cause a change in membrane potential c. induce an action potential d. be conducted to the axon hillock e. depolarize a dendrite

ATP is a. formed during the hydrolysis of ADP b. used by cells for the storage of energy c. used to transfer energy within a cell d. a protein e. a molecule with less total energy content than ADP.

Ammonia is a. a waste product of fatty acid metabolism. b. exhaled by the lungs into the air. c. processed by the liver to form urea, a less toxic compound. d. a waste product of fatty acid metabolism and is excreted by the kidneys into urine. e. a polypeptide containing many amino acids.

Nucleic acids are a. polymers of subunits containing glucose an an amino acids. b. polymers of subunits containing glucose, a phosphate group, and an amino acid. c. polymers of subunits containing a phosphate group, a sugar, and a purine or pyrimidine base. d. polymers of subunits containing a phosphate group, a sugar, and an amino acid. e. long polymers of amino acids, folded into an alpha helix.

Protein channels that link the cytosol of adjacent cells and called ____ junctions. a. cadherin b. tight c. gap d. conjunction e. nexus

RNA synthesis from a DNA template: a. is called translation of the message. b. requires DNA polymerase. c. is called transcription. d. occurs in the nucleolus. e. occurs in the cytoplasm.

The energy currency of the cell is: a. FAD b. NAD+ c. ATP d. PGAL

The main role of calcium ions at chemical synapses is to a. depolarize the axon terimnal of the presynaptic cell b. bind to neurotransmitter receptors on the postsynaptic cell c. cause fusion of synaptic vesicles with the plasma membrane of the axon terminal d. interfere with IPSPs in the postsynaptic cell e. diffuse across the synaptic space and enter the postsynaptic cells

The organelles that digest engulfed bacteria and cell debris are the: a. vaults. b. endosomes. c. lysosomes. d. ribosomes. e. mitochondria.

The permeability of the plasma membrane to mineral ions is a. not influenced by channels formed by proteins. b. the same in all cell types. c. affected by differences in electrical charge on the two sides of the membrane. d. zero in all living cells. e. only possible because of the hydrophobic interior of the lipid bilayer.

What is "allosteric modulation"? a. regulation of physiological functions by the sympathetic division of the autonomic nervous system. b. modification of the functional state of a protein by temperature or pH. c. The change in the shape and functional state of a protein that occurs when a ligand binds to a regulatory site d. The fact that all binding sites on a protein must be occupied to have a biolgoical effect e. the ability of a single ligand-binding site to bind to molecularity similar ligands.

What second messenger most directly causes calcium ions to be released from intracellular stores? a. diaclyglycerol b. adenylyl cyclase c. inositiol triphosphate d. phospholipase A2 e. phospholipase C

Which is a series of reactions by which fatty acid catabolism occurs? a. glycolysis b. lipogenesis c. beta-oxidation d. glycogenolysis e. phosphorylation

Which is not typically a step in the cAMP second messenger system? a. A first messenger binds to a transmembrane receptor b. There is dissociation of G-protein subunits c. An activated G-protein subunit phosphorylates cAMP-dependent protein kinase d. Adenylyl cyclase coverts ATP into cAMP e. Active cAMP-dependent protein kinase phosphorylates cell proteins

Which is true about the resting membrane potential? a. It requires very many ions to be distributed unevenly b. It has the same value in all cells c. It is oriented so that the cell's interior is negative with respect to the extracellular fluid d. Only nerve and muscle cells have a potential difference across the membrane at rest. e. It is not altered by changing concentration gradients of permeating ions

Which is true about typical, resting membrane? a. The plasma membrane is most permeable to sodium ions. b. The concentrations of sodium ion is greater inside the cell than outside c. The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions. d. The plasma membrane is completely impermeable to sodium ions e. The plasma membrane is completely impermeable to potassium ions.

Which is true about typical, resting neurons? a. The plasma membrane is most permeable to sodium ions. b. The concentration of sodium ion is greater inside the cell than outside. c. The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions d. The plasma membrane is completely impermeable to sodium ions. e. The plasma membrane is completely impermeable to potassium ions.

Which of the following is not true about axon transport? a. It refers to the passage of materials from the cell body of a neuron to the axon terminals. b. It refers to the passage of materials from axon terminals to the cell body of a neuron. c. It refers to the transport of materials from the inside to the outside across the axonal membrane. d. It is especially important for maintaining the integritiy of neurons with long axons.

Which of the following statements is true? a. Glycolysis does not occur in the absence of O2. b. Glycolysis does not occur in the presence of O2. c. Glycolysis may result in the formation of two molecules of pyruvate for each molecule of glucose. d. Glycolysis is a multienzymatic pathway that occurs principally on the inner membrane of a mitochondrion e. Glycolysis is a metabolic reaction in which glucose is manufactured from large carbohydrates like glycogen.

Which statement is not true with regards to proteins? a. their roles in the body include acting as enzymes, providing structural support and signaling between cells. b. they make up a greater percentage of body mass than carbohydrates do c. they are composed of nucleic acids d. they are macromolecules with subunits linked by polypeptides bonds e. they are polymers made up of amino acids.

According to the Frank-Starling mechanism of the heart: A. the left ventricle ejects a larger volume of blood with each systole than the right ventricle. B. the intrinsic rate of the heart's pacemaker is 100 beats/min. C. cardiac output increases with increased heart rate. D. stroke volume increases with increased venous return. E. both ventricles contract simultaneously.

Following hemorrhage, reflexes are triggered that attempt to compensate for the blood loss. As a result of the blood loss and the reflex mechanisms, which of the following will be true, compared to prehemorrhage values? A. Both cardiac output and total peripheral resistance will be increased. B. Both cardiac output and total peripheral resistance will be decreased. C. Cardiac output will be increased and total peripheral resistance will be decreased. D. Cardiac output will be decreased and total peripheral resistance will be increased. E. Hematocrit will be increased.

Normally, the hydrostatic pressure difference between capillary fluid and interstitial fluid favors movement of fluid ________ a tissue capillary. The protein osmotic pressure difference between capillary fluid and interstitial fluid normally favors movement of fluid __________ a tissue capillary. A. into; into B. into; out of C. out of; out of D. out of; into

The removal of calcium ions from the cytosol of skeletal muscle causes a. the mysoin binding sites on actin to be uncovered by tropomyosin b. tropomyosin to change conformation and thereby move troponin moelcules over cross-bridge binding sites. c. troponin to change conformation and thereby expose cross-bridge binding sites. d. the mysoin binding sites on actin to be covered by tropomyosin e. None of the chocies is correct.

Which is a true statement about excitation-contraction coupling? a. In skeletal muscle cells, it requires the influx of extracellular calcium ions. b. In smooth muscle cells, it must be preceded by an action potential in the cell membrane c. In all kinds of muscle it requires the entry of calcium from the extracellular fluid. d. Calcium-induced calcium-release plays a release plays a role in cardiac muscle cells, as well as in some smooth muscle cells. e. In skeletal muscle cells, excitation-contraction coupling begins when an action potential propagates along the sarcoplasmic reticulum membrane.

Which is not true of myelin? a. Myelin is a fatty membranous sheath. b. Myelin is formed by glial cells c. Myelin influences the velocity of conduction of an electrical signal down an axon d. Myelin covers all parts of the neuron, including the axon, cell body and dendrites.

Which of the following statements regarding contraction in skeletal and smooth muscle is true? a. In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding directly to myosin. b. In skeletal muscle, calcium ions bind to a regulatory protein on thin filaments; in smooth muscle, calcium ions bind to a regulatory protein on thick filaments. c. In skeletal muscle, calcium initiates contraction by binding to myosin light-chain kinase, while in smooth muscle calcium initiates contraction by binding directly to tropomyosin. d. In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding to calmodulin. e. All of the choices are true.

Which of the following statements regarding skeletal muscle contraction is true? a. During a lengthening contraction, the tension exerted by the muscle exceeds the load on the muscle. b. In every isotonic muscle concentration, the length of the muscle remains constant. c. During every muscle contraction, muscle fivers change length. d. During every muscle contraction, tension is developed in the muscle e. Cross-bridge cycle faster during isometric contractions than during isotonic contractions

Which of the following statements regarding skeletal muscle is true? a. skeletal muscle fibers have a pacemaker activity b. Skeletal muscle fibers are joined together by gap junctions c. A given skeletal muscle fiber will contract when excitatory nervous stimuli sufficiently exceed inhibitory nervous stimuli at the motor end plate. d. A given skeletal muscle fiber will contract if excitatory synaptic inputs sufficiently exceed inhibitory synaptic inputs on the motor neuron that innervates that fiber and the motor neuron fires an action potential. e. Skeletal muscle contraction is inhibited by inhibotry motor neurons that synapse onto skeletal muscle fibers

Which of the following would be most likely to be determined with a patient's ECG recording? A. a heart murmur B. stroke volume C. cardiac output D. blockage of conduction of electrical signals between the atria and the ventricles E. a leaky atrioventricular valve

"Osmosis" refers to the movement of what substance across semipermeable membranes? a. glucose b. charged particles c. lipid molecules d. water e. solutes

A fat cells responds to the presence of the hormone epinephrine by increasing cytosolic cyclic AMP production, which leads to the catabolism of both glycogen and fat. What is the most likely explanation for this phenomenon? a. Epinephrine is binding to two types in the plasma membrane b. The activated receptor complex stimulates production of two different second messengers c. Cyclic AMP directly activates enzymes that catabolize glycogen and fat. d. Cyclic AMP-dependent protein kinase activates two kinds of enzymes

Amplification during a second-messenger cascade is beneficial because amplification: a. takes small molecules and makes polymers out of them. b. results in the production of more of the first messenger c. allows a cell to respond to more different hormones d. allows small amounts of hormones to produce large responses in target cells.

Before an amino acid can be broken down for energy a. the side chain must be removed. b. the carboxyl group must be removed. c. it must be converted to NAD+. d. the amino group must be removed. e. it must be phosphorylated.

Carbohydrates are stored in the liver and muscles in the form of a. cellulose. b. starch. c. triacylglycerol. d. glycogen. e. protein.

Compartments A and B are separated by a membrane that is premable to K+ but not to Na+ or Cl-. At time zero, a solution of KCl compartment A and an equally concentrated solution of NaCL is poured into comparment B. Which would be true once equlibrium is reached? a. The concentration of Na+ in A will be higher than it was at time zero. b. Diffusion of K+ from A to B will be greater than the diffusion of K+ from B to A. c. There will be a potential difference across the membrane, with side B negative relative to side a. d. The electrical potential difference and diffusion potential due to the concentration gradient for K+ will be equal in magnitude in direction. e. the concentration of Cl- will be higher in B than it was at time zero.

Describing a physiological variable as "homeostatic" means that it a. has varied from the normal value, and will remain constant at the new value. b. never varies from an exact set point value. c. is in an equilibrium state that requires no energy input to stay at the normal value. d. is n a state of dynamic constancy that is regulated to remain near a stable set point value. e. has no normal range, but will just change to match the outside environmental conditions.

Eating a bag of salty potato chips without increasing sodium excretion would result in what type of balanced? a. positive sodium balance b. negative sodium balance c. stable sodium balance d. It can't be determined without knowing the size of the sodium pool.

Epinephrine activates the cyclic AMP pathway in liver cells. In this example, epinephrine is a ______ and cyclic AMP is a ____. a. ligand, receptor b. first messenger, hydrophobic hormone c. second messenger, ion channel d. first messenger, second messenger e. enzyme, second messenger

Genes are a. uncoiled proteins that contain information necessary for the synthesis of other proteins. b. sequences of nucleotides in DNA that acts as an enzyme to digest proteins. c. sequences of peptides in the DNA that contains information needed to make RNA. d. sequences of nucleotides in DNA that contains information necessary for the synthesis of proteins.

In general, polar molecules diffuse more rapidly through the lipid bilayer part of cell membranes than do nonpolar molecules. This statement is a. true b. false, because polar molecules diffuse through less rapidly because the bilayer is polar throughout its width. c. false, because polar molecules diffuse through less rapidly because the bilayer is nonpolar throughout its width. d. false, because nonpolar molecules diffuse through more rapidly because much of the bilayer is nonpolar. e. false, because the rate of diffusion of nonpolar and polar molecules through the bilayer is essentially the same as long as the molecules are the same size.

The membrane potential of most neurons at rest is a. equal to the equilbrium potential for potassium b. equal to the equilibrium potential for sodium c. slightly more negative so that the cell's interior is negative with respect to the extracellular fluid d. more positive than the equilibrium potential for potassium e. more positive than the equilibrium potential for sodium

What codon of the RNA corresponds to (complements) the DNA sequence A-T-G? a. A-T-G b. G-T-A c. T-A-C d. U-A-C e. C-A-T

Which is NOT true about a binding site on a protein? a. It is an area of the protein with a shape complementary to that of a ligand. b. It is determined by the amino acid sequence of the protein. c. The binding of a ligand to a binding site typically changes the conformation of the protein. d. There can only be one binding site of a given protein. e. Binding of a ligand to the binding site typically activates or inactivates a protein's specific function

Which is false about interneurons? a. Interneurons receive synaptic input from other neurons in the CNS. b. Interneurons summate excitatory and inhibitory synaptic inputs. c. Interneurons deliver synaptic input on other neurons. d. Interneurons make synapses on effector organs in the PNS. e. Interneurons can transmit information between afferent neurons and efferent neurons.

Which is not a feature of the fluid-mosaic model of plasma membranes. a. Integral membrane proteins are embedded in the membrane. b. Phospholipids form a bilayer. c. Cholesterol associates with phospholipid molecules. d. Carbohydrates are linked to lipids and proteins on the interior surface, forming a glycocalyx layer. e. Peripheral membrane proteins associate with polar regions of integral membrane proteins.

Which of the following is true concerning the rate-limiting step in a metabolic pathway? a. It is likely to be the slowest reaction in the pathway, and it is always the last step in a metabolic pathway. b. It is likely to be the fastest reaction in the pathway, and it is always the last step in a metabolic pathway. c. It is always the first step in the pathway, and may be subject to end-product inhibition. d. It is likely to be the slowest reaction in the pathway and it may be subject to end-product inhibition. e. It is likely to be the fastest reaction in the pathway and it may be subject to end-product inhibition.

An action potential does not restimulate the adjacent membrane that was previously depolarized because a. stimulation is inhibited by the myelin sheath b. it is impossible for an action potential to be propagated along an axon toward the nerve cell body c. the resting membrane potential of the axon is to positive d. the resting membrane potential of the axon is too negative. e. that area of the membrane is in the absolutely refractory period

An inhibitory postsynaptic potential a. is produced by simultaneous increases in permeability to both Na+ and K_ b. occurs when a ligand-gated ion channel increases its permability to K+ c. is a small depolarization in a postsynaptic cell d. it can be summed with other IPSI to trigger an action potential in the postsynaptic cell e. is produced by an increase in permeability to only Na+

How is the length of a skeletal muscle cell releated to the force it can generate? a. The tension in a skeletal muscle cell is greatest when concentration occur at either very short or very long lengths. b. Skeletal muscle cells generate the same amount of force, regardless of their length. c. The shorter a skeletal muscle cell is when it begins to contract, the stronger the force generation will be. d. The longer a skeletal muscle cell is when it begins to contract, the stronger the force generation will be. e. Skeletal muscle cells generate the most force when the contraction occurs at an intermediate length.

If the arterial blood pressure in the brain is suddenly decreased, the flow through arterioles in the brain will immediately fall and then which of these will occur next? A. Brain arterioles will constrict to accelerate blood flow through the brain capillaries. B. Brain arterioles will dilate due to a decrease in levels of CO2. C. Blood flow will remain at the new, lower level due to reactive hyperemia. D. Blood flow will rise to levels above normal due to excess O2 levels. E. Blood flow will return toward its original level due to flow autoregulation.

The region of the brain that is the most important control area for homeostatic regulation of the internal environment is the a. thalamus. b. hippocampus. c. cerebrum. d. cerebellum. e. hypothalamus.

Which best defines the cardiac output? A. the end-diastolic volume minus the end-systolic volume B. the output of the aortic arch baroreceptors C. the volume of blood in the arterial tree at any moment in time D. the stroke volume divided by the heart rate E. the product of the heart rate and the volume ejected from the ventricle during a cardiac cycle

Which is TRUE regarding the regulation of heart rate? A. Stimulation of parasympathetic nerves to the heart causes a slowing of heart rate. B. Stimulation of sympathetic nerves to the heart causes an increase in heart rate. C. A person whose heart lacks autonomic innervation has a faster heart rate at rest than a person with a normally innervated heart. D. The slope of diastolic depolarization in SA node cell action potentials determines the heart rate. E. All of the choices are true.

Which of the following choices lists a correct sequence of events following the depolarization of transverse tubules in excitation-contraction coupling in cardiac muscle? a. calcium release into cytosol, calcium ion influx through sarcolemma, actin and myosin attach, thin filaments slide toward the middle of sarcomeres b. actin and myosin attach, thin filaments slide toward the middle of sarcomeres, calcium release into cytosol c. calcium release into cytosol, actin and myosin attach, calcium ion influx through sarcolemma, thin myofilaments slide toward the middle of sarcomeres d. calcium release into cytosol, actin and myosin attach, thin filaments slide toward the middle of sarcomeres, calcium ion influx through sarcolemma e. calcium ion influx through sarcolemma, calcium release into cytosol, actin and myosin attach, thin myofilaments slide toward the middle of sarcomeres

Which of the following does NOT correctly describe cardiac muscle cells? a. They are arranged in layers surrounding hollow cavities in the heart. b. They are much shorter than skeletal muscle fibers, and generally have a single nucleus. c. Their membranes are depolarized initially by the influx of sodium ions d. They depolarize prior to contraction e. They can contract in the absence of external calcium

Which of the following is NOT primarily a function of blood plasma? A. transport of hormones B. being in osmotic balance with red blood cells C. having plasma proteins that exert an osmotic pressure favoring fluid absorption into the capillaries D. providing clotting factors that are ready to be activated E. transport of oxygen

Which of the following is a feature that distinguishes active transport from facilitated diffusion? a.. saturation of transport rate b. requirement for a carrier molecule c. carrier molecules have specificity d. Presence of a transport maximum e. requirement for metabolic energy

Which of the following is not a determinant of whole-muscle tension? a. the number of muscle fibers contracting b. the tension produced by each contracting fiber c. the numbers of motor units recruited d. the frequency of motor neuron stimulation e. the proportion of the muscle fibers within each motor unit that are contracting at any given time

A covalent bond occurs when a. two atoms share inner-orbital electrons with each other b. a bond forms between water molecules c. a bond forms between two oppositely charged ions d. a bond forms between two free radicals e. two atoms share outer orbital electrons with each other

According to the chemioosmotic hypothesis, the flow of electrons through the respiratory system of carrier molecules released energy which drives postively charged hydrogen ions across the membranes of mitochondria and results in which the following? i. the generation of pH gradient ii. the formation of an electric potential gradient iii. the creation of a "protomotive force" iv. the formation of a hydrogen ion concentration gradient a. statements i, ii, and iii b. statements i and iii c. statements ii and iv. d. statement iv. e. All of the statements are correct

Amplification of a second messenger cascade can take place at which level of a signal cascade? a. one activated receptor can activate numerous g-proteins b. one activated g-protein can activate numerous effector enzymes c. one active effector enzymes can catalyze numerous reactions d. one activated protein kinase can allosterically modulate numerous proteins e. all of the chocies are correct

By what transport mechanism does glucose enter most cells? a. diffusion through the lipid bilayer b. primary active transport c. secondary active transport d. diffusion through a protein channel e. facilitated diffusion

Circadian rhythms are biological rhythms with what main characteristic? a. They are cyclical, like the 28-day female menstrual cycle. b. They are cyclical, like the rhythmic beating of the heart. c. They are voluntary rhythms, like the time you decide to eat lunch each day. d. They cease to occur when a person is in a dark environment. e. They repeat approximately every 24 hours, like daily spikes in hormone secretion.

Specificity is an important characteristic of intercellular communication, which of these best explains how it occurs? a. phospholipid composition of the plasma membrane differs among cells. b. protein receptors are only located on the surface of target cells. c. all cells have the same DNA, so any cell can express protein receptors for a specific chemical. d. Chemical messengers are all proteins, so bind only to receptors that are proteins. e. protein receptors for chemical messegners are only expressed in specific target cells.

The Golgi apparatus functions in a. modifying proteins synthesized on free ribosomes and storing calcium ions. b. digestion of engulfed bacteria and using oxygen to generate ATP. c. synthesizing lipids and intracellular storage of calcium ions. D. modifying proteins synthesized on free ribosomes and allowing the distribution of modified proteins throughout the cell in vesicles. e. modifying proteins synthesized on ribosomes associated with granular endoplasmic reticulum and allowing the distribution of modified proteins throughout the cell in vesicles.

The central nervous system includes the a. afferent nerves and spinal cord. b. efferent nerves and spinal cord. c. autonomic nervous system and the brain. d. brain stem and the autonomic nervous system. e. brain and spinal cord.

The organelle in which most of the ATP is generated within a cell is the a. nucleus b. plasma membrane c. endoplasmic reticulum d. Golgi apparatus e. mitochondria

The proability of a reaction occuring is increased a. by decreasing reactant concentration b. by increasing the activation energy c. by increasing the concentration of any of the products d. if the reaction uses a great deal of energy e. if the concentration of one of the reactants increase

The term "metabolism": a. is synonymous with the term "catabolism." b. is synonymous with the term "anabolism." c. refers to any chemical reaction that involves the production of energy. d. is defined as the covalent modification and activation of a protein with binding sites for organic molecules. e. refers to the synthesis and breakdown of organic molecules involved in cell structure and function.

What are desmosomes? a. low-resistance channel-like passages that let ions travel between the interiors of adjacent cells b. cell organelles that contain enzymes for digesting cellular debris and foreign microbes c. cellular organelles that transcribe RNA into DNA d. membrane-bound vesicles that pinch off from the plasma membrane and enter the cell e. dense plaques of proteins that maintain firm attachments between adjacent cells

What are the most common receptors for hydrophobic first messenger molecules? a. peripheral membrane proteins b. integral membrane proteins c. specialized phospholipids within the membrane d. nucleic acids e. transcription factors

What feature of phospholipids allows them to interact with aqueous cytosol and extracellular fluid, while still presenting a barrier to hydrophilic substances? a. They are polar molecules. b. They are nonpolar molecules. c. They are lipids. d. They are extremely rigid molecules. e. They are amphipathic molecules.

What is a genome? a. a cluster of genes that are all regulated in the same manner b. a measure of the genetic variability in a population c. a region of DNA that codes for a single protein d. all of the protein in a cell at a given point in time. e. the total genetic information in a typical cell of an organs

What is a role of calcium ions in the second-messenger cascade involving phospholipase C, deacylglycerol (DAG), and inositol triphosphate (IP3)? a. It splits and activates G-protein subuints b. It binds to the endoplasmic reticulum and causes the release of inositol triphosphate (IP3) c. It phosphorylates cell proteins d. It is the first messenger that binds to the integral membrane protein receptor e. Along with diacylglycerol, it activates protein kinase c

Which is NOT a function of the Golgi Apparatus? a. sorting of proteins destined for various locations in the cell. b. modifying proteins destined for secretion c. packaging enzymes destined for lysosomes d. addition of carbohydrate groups to protein e. transcribing a signal sequence into proteins destined for secretion

Which is false about the equilibrium potential of a given ion across a membrane? a. It is a function of the concentration of that ion on both sides of the membrane. b. It is the potential at which there is no net movement of that ion across the membrane c. It is the potential difference across the membrane at which an electric force favoring movement of the ion in one direction is equal in magnitude and opposite in direction to the diffusion force provided by the concentration difference of the ion across the membrane. d. A permeable ion will move in the direction that will tend to bring the membrane potential toward that ion's equilibrium potential. e. An anion that is in higher concentration inside the cell than outside the cell will have a negative equilibrium potential.

Which is most directly responsible for the falling (repolarization) phase of the action potential? a. voltage-gated Na+ channels are opened b. The Na+/K+ ATPase pump restores the ions to their original locations inside and outside of the cell. c. the permeability to Na+ increases greatly. d. ATPase destroys the energy supply that was maintaining the action potential at its peak. e. The permeability to K+ increases greatly while that to Na+ decreases

Which is not an example of a graded potential? a. a receptor potential in a sensory receptor cell b. a depolarizing excitatory postsynaptic potential c. a hyperpolarizing inhibirtory postsynaptic potential d. a depolarizing pacemaker potential e. a depolarizing action potential

Which is true about the Na+/K+ ATPase pump in neurons? a. It generates a small electrical potential such that the inside is made positive with respect to the outside. b. It maintains a concentration gradient for K+ such that diffusion forces favor movement of K+ into the cell. c. It maintains an electrical gradient at the equilibrium potential of K+ d. It transports equal numbers of sodium and potassium ions with each pump cycle e. It pumps 3 Na+ ions out of the cell for every 2 K+ ions it pumps in.

Which of components of a general reflex arc are listed in the order information typically flows through them following a stimulus. a. effector, afferent pathway, integrating center, efferent pathway, receptor b. effector, efferent pathway, integrating center, afferent pathway, receptor c. integrating center, receptor, afferent pathway, efferent pathway, effector d. receptor, efferent pathway, integrating center, afferent pathway, effector e. receptor, afferent pathway, integrating center, efferent pathway, effector

Which of the following are ways in which binding of an intercellular chemical messenger with a cells receptor can bring about a cellular response? a. opening or closing of specific ionic channels in the plasma membrane b. activation of an intracellular second-messenger system c. promoting or inhibiting the transcription of genes that code for the synthesis of cellular proteins d. activating or inhibiting intracellular enzymes e. all of the choices are correct.

Which of the following statements about the refractory period of a membrane is true? a. The absolute refractory period refers to the period of time during which another action potentials cannot be initiated in that part of the membrane that is undergoing an action potential, no matter how great the strength of the stimulus. b. The relative refractory period refers to the period of time during which another action potential can be initated in that part of the membrane that has just undergone an action potential if a stronger than normal stimulus is applied. c. The refractory period prevents the action potential from spreading back over the part of the membrane that just underwent an action potential d. The refractory period places an upper limit on the frequency with which a nerve cell can conduct action potentials. e. All of the above chocies are correct

Which of the follwoing statements about the Na+/K+ ATPase pump is false? a. it transports Na+ out of cells and K+ into cells. b. It binds to and hydrolyzes ATP c. It is constantly active in all cells d. Its activity requires the expenditure of metabolic energy e. it transports Na+ and K+ in a 1.1 ratio

Which of these is a second messenger? a. steroid hormone b. protein kianse c. glucose d. sodium ions e. cyclic AMP

Which organelles would you expect to be especially numberous in cells that utilize oxygen to generate a great deal of energy in the form of ATP? a. peroxisomes b. endosomes c. lyosomes d. ribosomes e. mitochondria

Enzymes a. are catalyst in chemical reactions b. can be carbohydrate molecules c. are not consumed (broken down) during chemical reactions they catalyst d. have names generally ending in the suffix "-ase". e. are polymers of ATP that store large amounts of energy f. More than one of the above are correct g. All of the above are correct

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