Deck 23: Molecular Cell Biology

Question 1

The vitamin involved most in coagulation is:

A) Vitamin A
B) Folicin
C) Niacin
D) Vitamin K
E) Tocopherol

Answer 1

Vitamin K

Question 2

All of the following statements concerning contraction are correct EXCEPT which one?

A) The conversion of chemical energy into mechanical energy is the result of protein conformational changes.
B) In the energized state, the myosin headpiece contains both ADP and Pi.
C) An early event in contraction is the binding of calcium to troponin.
D) The thick filament shortens in length to accommodate the thin filament.
E) The myosin binding sites on F-actin are physically blocked by tropomyosin in the resting state.

Answer 2

The thick filament shortens in length to accommodate the thin filament.

Question 3

Which of the following proteins involved in either clotting or fibrinolysis does not require Vitamin K for its completed production?

A) Factor X
B) Factor VII
C) Factor VIII
D) Factor IX
E) prothrombin

Answer 3

Factor VIII

Question 4

When at rest both skeletal and cardiac muscles satisfy their energy requirement mainly through

A) anaerobic glycolysis.
B) aerobic glycolysis.
C) oxidation of lactate.
D) oxidation of ketone bodies.
E) oxidation of free fatty acids.

Question 5

The principal action of thrombin in the human body is

A) association with activated factor V on membrane surface.
B) association with heparin and heparan sulfate.
C) hydrolysis of fibrinogen to fibrin.
D) hydrolysis of plasminogen to plasmin.
E) self-assembly to form a soft-thrombin clot.

Question 6

The conversion of fibrinogen to the fibrin monomer

A) is catalyzed by either plasmin or thrombin.
B) is catalyzed by thrombin and is accompanied by liberation of fibrin degradation products (FDP's).
C) is catalyzed by thrombin and is accompanied by liberation of peptides A and B
D) is catalyzed by active Factor XIII.
E) none of the above

Question 7

The high-energy compound that interacts most directly with the contractile proteins of muscle is

A) ATP.
B) GTP.
C) UDP-glucose.
D) creatine phosphate.
E) phosphoenolpyruvate.

Question 8

Which one of the following proteins are not present in smooth muscle?

A) Tropomyosin
B) Actin
C) Troponin
D) myosin
E) None of the above, all are present in smooth muscle

Question 9

Of the three classes of muscle which are striated?

A) Skeletal and cardiac
B) Cardiac only
C) Smooth and skeletal
D) Smooth only
E) Cardiac and smooth

Question 10

Thrombin, in its action on fibrinogen

A) requires the presence of thromboplastin.
B) causes the polymerization of native fibrinogen to give fibrin.
C) hydrolyzes certain specific peptide bonds in fibrinogen.
D) in the absence of calcium ions produces a fibrin clot insoluble in urea.
E) produces a clot that has all the required components for clot retraction.

Question 11

What is the function of the Protein C/Protein S complex in blood clotting?

A) Aggregation of platelets
B) Binding of heparin
C) Carboxylation of glutamate residues
D) Cleavage of prothrombin
E) Inactivation of Factors V and VIII

Question 12

Creatine phosphate in muscle serves as

A) an ATPase inhibitor
B) an ATP chelator
C) a storage form for high energy phosphate
D) a substrate for myosin ATPase

Question 13

Which one of the following statements would be true for a muscle containing all white fibers?

A) The myoglobin concentration would be high.
B) It would be capable of sustaining contractions over long periods of time.
C) It would contain a large number of mitochondria.
D) It would derive the majority of its energy from the catabolism of glucose.

Question 14

Receptors for the inhibitory neurotransmitters GABA and glycine:

A) are ligand-gated anion channels.
B) are ligand_gated cation channels.
C) permit hyperpolarization of neuronal cell membranes.
D) Both A and C are correct.
E) Both B and C are correct.

Question 15

Fibrin stabilizing factor (factor XIII) is activated by

A) prothrombin
B) thrombin
C) fibrinase
D) Stuart factor (factor X)

Question 16

In the activation of clotting factors

A) endothelial cells provide the phospholipid component in the intrinsic pathway of coagulation.
B) prothrombin molecules do not bind to phospholipids in the clotting activation process.
C) roughly, equal concentrations of plasma clotting factors participate in the coagulation cascade mechanism.
D) contact with a glass surface activates prothrombin (factor II).
E) usually, during activation of clotting factors, a one-chain molecule is cleaved into a two-chain molecule with the chains held together by S-S bonds.

Question 17

The photic step in the visual process

A) trans rhodopsin -> 11-cis rhodopsin.
B) 11-Cis rhodopsin -> all-trans rhodopsin.
C) all-trans retinol -> all-trans retinal.
D) lumirhodopsin -> metarhodopsin.
E) beta-carotene -> cis-retinal.

Question 18

Each of the following blood clotting factors requires vitamin K for its biosynthesis EXCEPT

A) Factor II (prothrombin)
B) Factor VII (pro-SPCA)
C) Factor VIII (antihemophilic factor)
D) Factor IX (Christmas factor)
E) Factor X (Stuart factor)

Question 19

Thrombin directly catalyzes the activation of the following by limited proteolysis except for:

A) Factor V
B) Factor VIII
C) Factor XIII
D) protein C
E) Factor X

Question 20

What is the first coagulation factor to be activated via the intrinsic pathway?

A) Factor II
B) Factor V
C) Factor VII
D) Factor XI
E) Factor XII

Question 21

The formation of a hard clot involves which of the following?

A) Transamidation
B) Reaction between allysine and lysine
C) Ionic links between gamma-carboxyglutamate on fibrin and Ca2+
D) Transamination
E) Glutaminase

Question 22

Which two blood clotting Factors are cofactors?

A) III and VI
B) V and VIII
C) VII and II
D) X and IX
E) XII and XI

Question 23

Contains an ATPase activity.

A) Calsequestrin
B) Actin
C) myosin
D) Troponin complex
E) Tropomyosin

Question 24

In retinal rod cells of the eye, the protein transducin:

A) catalyzes the covalent attachment of 11-cis retinal to the protein opsin.
B) contains three subunits, one of which serves to activate a phosphodiesterase.
C) inactivates photoexcited rhodopsin to prevent cyclic GMP hydrolysis.
D) Both A and B are correct.
E) Both B and C are correct.

Question 25

The following statements about retinol are true EXCEPT for:

A) It is toxic at high dosages.
B) It has hormone-like activity in that it has cellular receptors which act as transcription enhancers.
C) It can be oxidized in the body to retinoic acid.
D) It is an intermediate in the isomerization of trans-retinal to 11-cis-retinal in the "visual cycle" of the eye.
E) It can not be stored for long periods in the body.

Question 26

Vision

A) is a process that converts light energy into electrochemical energy
B) requires vitamin A derivatives
C) is a inherently low efficiency process due to sodium leakage and the low energy of photons in the visible spectrum
D) A and B
E) A, B and C

Question 27

Which factor can circulate in blood in its active form without promoting clotting?

A) thrombin
B) VIIa
C) Xa
D) XIIa
E) XIIIA

Question 28

All of the following statements regarding fibrinogen are true EXCEPT which one?

A) It consists of 6 peptide chains.
B) It aggregates into a clot with changes in pH.
C) It is changed into fibrin by the action of thrombin.
D) It carries a net negative charge.
E) It is synthesized in the liver.

Question 29

Which of the following is the major substrate used for energy by resting muscle?

A) fructose
B) nonesterified fatty acids
C) glycerol
D) beta-hydroxybutyrate
E) lactate

Question 30

The resting potential of a typical nerve cell membrane is determined primarily by a transmembrane equilibrium dominated by its permeability to:

A) Na+
B) K+
C) Ca2+
D) Both Na+ and K+
E) all three ions

Question 31

When prothrombin is cleaved to form thrombin

A) the calcium binding site is removed.
B) plasmin is required.
C) factor Xa cleaves the peptide bonds.
D) all of the above.
E) A and C are correct.

Question 32

What is the characteristic of surfaces that initiate the intrinsic pathway of blood clotting?

A) Anionic
B) Carbohydrate-containing
C) Cationic
D) Hydrophobic
E) Membranous

Question 33

The following proteins which participate in either clotting or fibrinolysis are proteases EXCEPT for:

A) Protein C
B) Plasmin
C) thrombin
D) Factor V
E) Tissue plasminogen activator

Question 34

Which thin filament protein is composed of three non-identical subunits?

A) Troponin
B) F-Actin
C) G-Actin
D) Tropomyosin

Question 35

Upon stimulation of a muscle to contract, which one of these events occurs following calcium ion binding to troponin?

A) Cross bridge formation
B) Depolarization of the sarcolemma
C) Depolarization of the T-tubules
D) Release of acetylcholine at the neuromuscular junction
E) calcium ion release from the sarcoplasmic reticulum

Question 36

All of the blood clotting factors below are serine proteases EXCEPT

A) thrombin.
B) Hageman factor (factor XII).
C) antihemophilic factor (factor VIII).
D) tissue thromboplastin (factor III).
E) Stuart factor (factor X).

Question 37

All of the following are considered to be components of the contractile protein of muscle EXCEPT which one?

A) Actin
B) myosin
C) Myogen A
D) Actomyosin
E) Actomyosin-ATPase

Question 38

During contraction, phosphocreatine is used

A) to phosphorylate ADP.
B) to phosphorylate glycogen.
C) directly in contraction.
D) to activate phosphofructokinase.
E) to phosphorylate fructose 6-phosphate.

Question 39

The formation of a soft clot (soluble fibrin) in the final stages of blood coagulation involves

A) the aggregation of fibrinopeptides A and B by end-to-end and side-to-side polymerization.
B) the action of thrombin on fibrin monomers in the presence of calcium ions.
C) a transamidation reaction between the side chains of glutamine and lysine residues catalyzed by fibrinase and calcium ions to form covalent linkages between fibrin monomers.
D) the proteolysis of fibrinogen to fibrin monomers catalyzed by fibrinase.
E) the thrombin-catalyzed conversion of fibrinogen to fibrin and the non-enzymic aggregation of fibrin monomers.

Question 40

For a relaxed muscle, which one of the following statements will be true?

A) The calcium ion concentration in the sarcoplasm is high.
B) The sarcoplasmic reticulum is permeable to calcium ions.
C) The sarcolemma is depolarized.
D) Very few, if any, cross bridges are formed.
E) acetylcholine is being released at the neuromuscular junction.

Question 41

During contraction of mammalian striated muscle

A) the A band shortens with no change in the I band.
B) the H band remains constant.
C) the actin filaments shorten with no change in the length of the myosin filaments.
D) the I band shortens with no change in the A band.
E) the distance between the Z and M lines remains constant.

Question 42

Normal coagulation is impaired by a deficiency of:

A) Ascorbate
B) Lysine
C) Pantothenate
D) Tocopherol
E) Vitamin K

Question 43

Is bound to both actin and the troponin complex in. skeletal muscle.

A) ATP
B) myosin
C) Tropomyosin
D) Troponin complex
E) Phosphocreatine (creatine phosphate)

Question 44

Which one of the following factors is NOT essential for the conversion of prothrombin to thrombin in the clot cascade?

A) Ca ion
B) Factor X
C) Phospholipid
D) Factor V
E) Factor XIII

Question 45

Which one of the following will potentiate the anticoagulant action of Warfarin?

A) chlorinated hydrocarbon insecticides
B) vitamin K
C) acetaminophen
D) aspirin
E) phenobarbital

Question 46

What possesses an ATPase site which is made more active by the binding of actin in skeletal muscle?

A) ATP
B) myosin
C) Tropomyosin
D) Troponin complex
E) Phosphocreatine (creatine phosphate)

Question 47

A protein involved in the dissolution of blood clots is

A) thrombin.
B) plasmin.
C) antithrombin III.
D) factor XIIIa.
E) heparin.

Question 48

In the visual cycle which molecule has GTPase activity?

A) Activated rhodopsin
B) Phosphodiesterase b subunit
C) Phosphodiesterase a subunit
D) Transducin Ta subunit
E) Transducin Tbg subunits

Question 49

Which one of the following terms is used to refer to the specialized endoplasmic reticulum of muscle cells?

A) Sarcoplasm
B) myofibrils
C) Sarcoplasmic reticulum
D) Sarcolemma
E) Sarcomere

Question 50

What function is common to all kinesins?

A) They cause contraction
B) They cause movement through space
C) They cause opening of vesicles
D) They cause transport across membranes
E) They interact with DNA

Question 51

Binds to myosin and causes the dissociation (detachment) of myosin from actin in skeletal muscle.

A) ATP
B) myosin
C) Tropomyosin
D) Troponin complex
E) Phosphocreatine (creatine phosphate)

Question 52

Active concentrations of all of the components of the blood clotting process listed below are decreased following dicoumarol administration EXCEPT for:

A) Factor X
B) Prothrombin
C) Factor VIII
D) Protein C
E) Factor VII

Question 53

Actin is released from its interaction with myosin by the addition of

A) ADP
B) magnesium ions
C) inorganic phosphate
D) ATP
E) calcium ions

Question 54

All of the following amino acids (or amino acid derivatives) neurotransmitters are activated by a reuptake mechanism EXCEPT which one?

A) GABA
B) Glycine
C) Aspartate
D) Histamine

Question 55

All of the following statements regarding the actions and inactivation of acetylcholine are true EXCEPT which one?

A) acetylcholine is inactivated by a reuptake mechanism operating in the presynaptic terminus.
B) acetylcholine is the neurotransmitter for the preganglionic neurons of the autonomic nervous system.
C) Postganglionic acetylcholine receptors are classified pharmacologically as either nicotinic or muscarinic.
D) acetylcholine is inactivated by hydrolysis by acetylcholinesterase.
E) Following synthesis in the presynaptic terminal, approximately one-half of the acetylcholine remains free in the cytoplasm.

Question 56

Ca2+ binds to this component of the thin filament of skeletal muscle, resulting in the interaction of actin and myosin, and thus, muscle contraction.

A) Calsequestrin
B) Actin
C) myosin
D) Troponin complex
E) Tropomyosin

Question 57

Calcium which is involved in control of muscle contraction is stored in the

A) transverse tubules.
B) mitochondria.
C) sarcoplasmic reticulum.
D) Z lines.
E) nerve terminals.

Question 58

Which of the following is involved in the conversion of a soft clot to a so-called hard clot?

A) Factor I
B) Factor VIII
C) Factor X
D) urokinase
E) Factor XIII

Question 59

What blood clotting Factor number is Tissue Factor?

A) I
B) II
C) III
D) IV
E) V

Question 60

Which of the following clotting factors are vitamin K+-dependent?

A) II, VII, IX, and X
B) VII, IX, fibrinogen, Antihemophilic factor
C) II, III, VII, and Hageman factor
D) VIII, IX, X, Prothrombin
E) None of the above group

Question 61

The following proteins which participate in either clotting or fibrinolysis are proteases EXCEPT for:

A) Protein C
B) Plasmin
C) thrombin
D) Factor V
E) Tissue plasminogen activator

Question 62

In the intrinsic pathway of blood coagulation, all of the following proteins are serine proteases EXCEPT

A) XIa.
B) IXa.
C) Xa.
D) thrombin.
E) fibrin.

Question 63

The following statements about retinoic acid are true EXCEPT for:

A) It can be metabolized in the body to retinol.
B) It can be metabolically derived in the body from dietary beta_carotene or retinol.
C) It cannot replace vitamin A in the diet.
D) It acts as a transcriptional co-activator by combining with cellular receptors which then go to the nucleus.

Question 64

Hydrolysis of 3',5'-cyclic-GMP in the retina involves all of the following except

A) transducin.
B) phosphodiesterase.
C) guanylate cyclase.
D) light.

Question 65

The neurotransmitter acetylcholine is

A) synthesized by the enzyme choline esterase.
B) hydrolyzed by the enzyme acetylcholine esterase at the synapse.
C) synthesized in the adrenal medulla.
D) the primary neurotransmitter in the brain.
E) competitively inhibited by diisopropylfluorophosphate.

Question 66

Hemophilia may be caused by a deficiency in which of the following clotting factors?

A) factor VIII
B) factor IX
C) factor XI
D) All of the above
E) None of the above.

Question 67

Energy transduction (conversion of chemical energy to mechano-chemical energy) in muscle contraction is due to

A) Random coil ->-> helix transition of the myosin molecule.
B) Activation by calcium ions of the myosin ATPase activity.
C) Splitting of ATP by a myosin dimer.
D) Interaction of actin with myosin.
E) Hydrolysis of ATP.

Question 68

What is the rate-limiting factor in the synthesis of acetylcholine?

A) The activity of choline acetyltransferase.
B) The availability of acetyl-CoA.
C) The activity of acetylcholinesterase.
D) The availability of choline.
E) The activity of butyrylcholinesterase.

Question 69

The thick filaments in muscle tissue contain

A) C protein.
B) protein of molecular weight about 42,000.
C) troponin.
D) creatine kinase.
E) none of the above.

Question 70

Which of the following blood clotting factors does not contain gamma carboxy glutamic acid?

A) fibrinogen
B) prothrombin
C) factor IX
D) factor VII
E) factor X

Question 71

Heparin has anticoagulant activity due to its ability to activate

A) thrombin.
B) plasmin.
C) vitamin K.
D) fibrinogen.
E) antithrombin.

Question 72

The two pocket model used to explain the activity of acetylcholinesterase

A) accounts for the changes in membrane potential.
B) accounts for an acetyl-enzyme intermediate.
C) suggests only a hydrophobic interaction with acetylcholine.
D) is required to explain the post-translation action on the enzyme.
E) requires covalent binding of choline.

Question 73

The following substances form either stable or transient compounds with acetylcholine esterase EXCEPT for:

A) acetylcholine.
B) Neostigmine.
C) DIPF.
D) Parathion.
E) Tetrodotoxin.

Question 74

Which of the following pairs are the structural units of the conjugate protein rhodopsin?

A) Opsin and beta-carotene
B) Opsin and vitamin A alcohol
C) myosin and retinal
D) myosin and beta-carotene
E) Opsin and cis-retinal

Question 75

The cross-striation in skeletal muscle is due to

A) the presence of microfibrils.
B) the presence of muscle fiber bundles.
C) the presence of actin and myosin.
D) the transverse angle of sectioning.
E) repeating sarcomere units.

Question 76

Aspirin exerts its effects on blood clotting by

A) binding to fibrinogen.
B) activating plasminogen.
C) blocking the action of phospholipase.
D) inhibiting cyclooxygenase.
E) stimulating the formation of thrombin.

Question 77

Dicoumarol is an anticoagulant which acts by

A) inhibiting the synthesis of vitamin K.
B) stimulating the synthesis of vitamin K.
C) stimulating the synthesis of gamma carboxyglutamic acid in clotting factors.
D) inhibiting the formation of gamma carboxyglutamic acid in clotting factors.

Question 78

The resting membrane potential (membrane polarization) of the neuron can be attributed, in part, to the relatively low permeability of the membrane to which cation?

A) Ca2+
B) K+
C) Mg++
D) Na+
E) SO4-

Question 79

That structural component of the eye which is characterized by a high rate of aerobic glycolysis is the

A) cornea.
B) retina.
C) sclera.
D) lens.
E) iris.

Question 80

All of the following statements are true regarding the blood clotting process in humans EXCEPT

A) phospholipids and Ca2+ are required.
B) it is a system of amplification.
C) it is delayed in vivo by dicoumarol.
D) it requires activation of zymogens.
E) it requires vitamin K for the biosynthesis of factor VIII.