U-World

What causes the power stroke to occur?

The dissociation of ADP and Pi causes the power stroke, which is the actual pivot of the actin-bound myosin head that drags the actin filament toward the center of the sarcomere. This directly results in shortening of the sarcomere (Choice C). The myosin head is now in its low-energy conformation. The release of ADT and Phosphate from the Myosin head.

oxidation reduction rule

As a general rule for organic compounds, C or S atoms that lose bonds to H are being oxidized. The S atom in Cys-247 loses a bond to H (gets oxidized), which means that the central S atom in S2O32− must be reduced in the process of losing the S-S bond.

Systole

Contraction of the heart

Under low ATP conditions, which of the following enzymes would be LEAST beneficial to the cell? A.Aldolase B.Enolase C.Glyceraldehyde 3-phosphate dehydrogenase D.6-Phosphogluconate dehydrogenase

D.6-Phosphogluconate dehydrogenase 6-Phosphogluconate dehydrogenase (6PGD) is the enzyme in the pentose phosphate pathway that catalyzes the conversion of 6-phosphogluconate to R5P. It is in this step that a carbon atom is converted to CO2, decreasing the overall potential ATP output. Therefore, 6PGD would be less beneficial to a cell deficient in ATP than would any glycolytic enzyme.

peritoneum

Double-layered membrane surrounding the abdominal organs is a tissue membrane and is therefore not a space/cavity into which GI contents may enter.

fructose-1,6-bisphosphatase,

which catalyzes the dephosphorylation of F1,6BP in gluconeogenesis

weaker bases such as amines are only protonated by _________

strong acids

Carboxylic acids, which are considered relatively strong organic acids, can be deprotonated by ________________

strong and weak bases.

phenols are much weaker acids that require _______________ to be deprotonate

strong bases

instantaneous velocity

the velocity of an object at some instant or at a specific point in the object's path STEEPEST SLOPE

terminal voltage of battery

the voltage that the battery supplies across the circuit. It is determined by calculating the drop in voltage across the battery itself due to its own internal resistance and subtracting this from the electromotive force. V = e - ir

paracellular transport

through junctions between adjacent cells Transport of materials through the interstitial space without interactions with the cytoplasm or cell membrane The paracellular transport of small, hydrophilic molecules is limited by the presence of tight junctions.

Decoupling ETC

"decoupling." Because fewer protons are being used to drive ATP synthase, the rate of ATP synthesis will decrease.

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection. Genetic drift is a mechanism of evolution; however, unlike natural selection, the variations in allele frequencies occur randomly by chance. Because smaller populations have a smaller gene pool, the random (good or bad) variations due to genetic drift cannot be buffered.

Axon

A threadlike extension of a neuron that carries nerve impulses away from the cell body.

Which expression gives the ion's radius of curvature in a magnetic field B for an ion with a mass of m, charge of q, and velocity of v? A.r = (m/q)(v2/B) B.r = (m/q)(v/B) C.r = (q/m)(v2/B) D.r = (q/m)(v/B)

B.r = (m/q)(v/B)

magnetic field (B)

B= μI/2πr

Brain frequencies is the wakeful state vs awake

Brain frequencies observed during most sleep stages are lower than brain frequencies observed during wakefulness.

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

Complex 3 of ETC

CoQH2 cytochrome c oxidoreductase also called *cytochrome reductase* this complexes allows the transfer of electrons from coenzyme Q to cytochrome c the steps involve the oxidation and reduction of cytochromes CoQH2 + 2 cytochrome c with Fe3+ --> CoQ + 2 cytochrome c with Fe2+ + 2H only on electron can be transferred to iron, which is why you need two cytochromes *q cycle is done here* - pumping *four protons*

gas-liquid chromatography

Gas-liquid chromatography is a technique that separates compounds in a mixture based on boiling point. The mobile phase is an inert gas, and the stationary phase is a liquid that coats the column, which is in a heated oven. The molecule with the lowest boiling point will reach the detector before molecules with higher boiling points

High Performance Liquid Chromatography (HPLC)

HPLC is optimal for small sample sizes and separates compounds based on their polarity, giving each compound a different affinity for the mobile and stationary phases and causing the compounds to pass through the column at different rates. Compounds are detected as they come off the column and go into the waste or are collected separately. Data is transmitted to the computer, creating a chromatograph.

HPLC vs Reverse HPLC

NP-HPLC is used to separate relatively nonpolar compounds and consists of a polar stationary phase (typically silica) and a nonpolar mobile phase. RP-HPLC is used to separate polar compounds and has a nonpolar stationary phase (typically C-18 alkyl hydrocarbon) and a polar mobile phase. Nonpolar compounds in a mixture will interact more with the stationary phase than polar compounds, causing nonpolar compounds to have a longer retention time.

Palmitate

Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is the most common saturated fatty acid found in animals, plants and microorganisms. Its chemical formula is CH₃(CH₂)₁₄COOH, and its C:D is 16:0. As its name indicates, it is a major component of the oil from the fruit of oil palms.

Upfield vs. Downfield

The chemical shift depends on the electronic environment around the proton. An electron cloud around the protons shields them from the external magnetic field, causing an upfield signal (small chemical shift). An electronegative substituent withdraws electrons and deshields neighboring protons from the magnetic field, causing a downfield signal (larger chemical shift).

peritoneal cavity

The peritoneal cavity is a potential space (ie, an area between two adjacent structures that may press together) between the parietal and visceral layers of the peritoneum. The peritoneal cavity is found within the abdomen and contains organs such as the liver, stomach, and intestines.

Fructose-1,6-bisphosphatase

What enzyme catalyzes the rate-limiting step in gluconeogenesis?

Dorsal Root Ganglion (DRG)

the cell bodies of neurons that are carrying afferent sensory signals to the central nervous system

perineum

perineum is the area between the anus and the scrotum (in males) or vulva (in females).

microRNAs

small single-stranded RNA molecules that can bind to complementary sequences in mRNA molecules on the translational level

Complex 2 of ETC

succinate CoQ oxidoreductase receives electrons from succinate as it is formed into fumerate FAD is covalently bonded to this and once succinate is oxidized into fumerate, FADH2 is formed iron sulfur protein oxidizes FADH2 back to FAD the iron sulfur protein transfers the electrons to coenzyme Q *no hydrogen pumping occurs here* net: succinate + CoQ + 2H --> fumerate +CoQH2

Strong organic bases form ionic salts easily when ___________ are added to a mixture

weak acid

parrallel evolution

Parallel evolution occurs when two more closely related species (ie, descended from a more recent common ancestor) continue to evolve the same characteristics to adapt to similar environments.

electromotive force (emf)

-voltage when no charge is moving b/w the 2 terminals of a cell that are at different potential values -Pressure to move exerted by the cell on the electrons 1V = J/C V= (emf) -i (R internal)

Suppose that a research technician wants to separate an aqueous mixture of CuF2 and BaF2 (Ksp = 3.0 × 10−6) by precipitating CuF2 from the solution. What should be added to the solution to perform the separation? A.Cu(NO3)2 B.NaF C.Ba(NO3)2 D.H2O

A.Cu(NO3)2 To separate a solution mixture of CuF2 and BaF2 by precipitating CuF2, Cu2+ ions can be introduced into the solution. The increased Cu2+ concentration disturbs the product side of the solubility equilibrium and causes it to shift toward the reactants (undissolved salt). Therefore, adding Cu(NO3)2 as a source of Cu2+ ions will selectively cause the CuF2 in the mixture to precipitate.

When the cell is in need of glucose, glycogenolysis is upregulated, beginning with the activation of glycogen phosphorylase. Glycogen phosphorylase catalyzes the production of which of the following molecules? A.UDP-glucose[ B.UDP-galactose C.Glucose 1-phosphate D.Glucose 6-phosphate

C.Glucose 1-phosphate Glycogen phosphorylase breaks the bond between two adjacent glucose molecules in a glycogen chain by phosphorolysis, or the addition of a phosphate molecule across a bond. The bond broken by this reaction is an α(1→4) linkage, so the phosphate must be added to either carbon 1 or carbon 4 of a glucose unit. The glucose unit that is released was attached by carbon 1, and it is to this carbon atom that phosphate is added, producing glucose 1-phosphate (G1P).

Researchers separate a mixture by both simple distillation and vacuum distillation. Which expression accurately describes the relationship of the boiling points (bp) in each distillation? A.Simple distillation bp = vacuum distillation bp B.Simple distillation bp < vacuum distillation bp C.Simple distillation bp > vacuum distillation bp D.Simple distillation bp = 2(vacuum distillation bp)

C.Simple distillation bp > vacuum distillation bp

In advanced ADPKD, all of the following components of physiological homeostasis would be disrupted EXCEPT: A.blood nitrogen levels. B.blood pH. C.leukocyte production. D.erythropoietin production.

C.leukocyte production. (Choice C) Production of leukocytes (white blood cells) occurs in the bone marrow, not the kidneys. Leukocytes are immune system cells that protect the body against infectious agents and foreign antigens. Consequently, leukocyte numbers are regulated by the presence or absence of cytokines released during active infection.

Suppose that a simple circuit comprising one voltage source and one metallic resistor yields current I. If the resistor were replaced with another resistor that is identical except that it has 75% lower conductivity, then I would: A.increase by a factor of 2. B.increase by a factor of 4. C.decrease by a factor of 2. D.decrease by a factor of 4.

Conductivity is an intensive property that quantifies the ease with which current flows through a material acting as an electric conductor. Conductivity is inversely proportional to resistivity. In this question, a voltage source generates a current (I) through one resistor in a simple circuit. Because resistivity and conductivity are inversely proportional, replacing the resistor with another that has ¼ the conductivity of the original is equivalent to increasing the resistivity of the resistor by a factor of 4. Given that the resistor is otherwise identical (ie, the same physical dimensions), the resistance of the resistor will also increase by a factor of 4. Ohm's law relates the current generated by such a simple circuit to the voltage (V) and resistance:

Which additional extraction steps would cause phosphatidylethanolamine and 2,6-dimethoxyphenol to enter the aqueous layer consecutively? A.Add 0.05 M NaOH(aq) to the organic layer followed by 0.01 M H2SO4(aq). B.Add 0.01 M NaHCO3(aq) to the organic layer followed by 0.05 M HCl(aq). C.Add 0.01 M H2CO3(aq) to the organic layer followed by 0.05 M NaHCO3(aq). D.Add 0.05 M H2SO4(aq) to the organic layer followed by 0.01 M NaOH(aq).

D.Add 0.05 M H2SO4(aq) to the organic layer followed by 0.01 M NaOH(aq). For phosphatidylethanolamine and 2,6-dimethoxyphenol to enter the aqueous layer consecutively, their ionic salts must be formed in sequence. Phosphatidylethanolamine contains an amine group that can be protonated to form a water-soluble ammonium salt; therefore, a strong acid such as H2SO4 or HCl should be added to protonate the amino group. In contrast, 2,6-dimethoxyphenol has a weakly acidic hydroxyl group on the benzene ring that must be deprotonated to form an ionic salt. Only strong bases such as NaOH or KOH are able to remove protons from phenols. Consequently, the correct sequence of extraction steps would involve the addition of a strong acid followed by a strong base.

dorsal root ganglion

a nodule on a dorsal root that contains cell bodies of afferent spinal nerve neurons

Which statement most accurately describes the role of T tubules in skeletal muscle cells? A.T tubules bind acetylcholine at the neuromuscular junction to generate a depolarizing stimulus. B.Depolarizing current reaches the sarcoplasmic reticulum by traveling down T tubules. C.Muscle contraction is driven by the sliding of T tubules across one another in the sarcomere. D.T tubules sequester Ca2+ out of the cytosol to prevent prolonged muscle contraction.

When acetylcholine (ACh) is released by the motor neuron at the neuromuscular junction, the following occur: ACh binds and opens ligand-gated ion channels in the sarcolemma (the plasma membrane of the muscle cell) (Choice A). Na+ flows down its electrochemical gradient and into the cell through the channel, resulting in depolarization of the sarcolemma and generation of an action potential that propagates along the muscle fiber in all directions. At certain locations along the muscle fiber, the sarcolemma burrows deep into the cells, forming a channel known as the transverse (T) tubule, which brings depolarizing current close to the sarcoplasmic reticulum (SR) (Choice B). The SR is a specialized smooth endoplasmic reticulum responsible for regulating cytosolic Ca2+ levels within the muscle cell. Action potential propagation through the T tubule ultimately leads to the opening of Ca2+ channels in the SR membrane. Because Ca2+ is more highly concentrated inside the SR than in the cytosol, the opening of these channels results in Ca2+ flowing down its concentration gradient and into the cytosol. Cytosolic Ca2+ ions then bind to troponin, which allows the actin and myosin filaments of the sarcomere to slide across one another. The sliding of the filaments results in shortening of the sarcomere and overall muscle contraction (Choice C). The Ca2+ channels in the SR membrane close when the depolarizing stimulus ceases. Active transport Ca2+ pumps sequester the Ca2+ back into the SR, which allows the muscle to return to its relaxed state as cytosolic Ca2+ concentration falls (Choice D).

thin filaments

actin

Electric Field lines point ________ in positive charges

away Electric field lines point out from positive charges and into negative charges

Preganglion and post ganglion send signals ______ from the CNS

away. The pre- and postganglionic fibers, which transmit impulses away from the spinal cord, make up the efferent component of the reflex arc. sensory organs make up the afferent port, nut ganglion is all part of the efferent response

Complex 4 of ETC

cytochrome c oxidase facilitates the final transfer of electrons from cytochrome c to oxygen (final electron acceptor) has subunits of cytochrome a, cytochrome a3 and Cu2+ ions cytochrome oxidase (a and a3) gets oxidized as oxygen gets reduced to water final location where proton pumping occurs - two protons are moved across the membrane net: 4 cytochrome c with Fe2+ + 4H+ + O2 --> 4 cytochrome c with Fe3+ + 2H2O

trypsin and chymotrypsin

major protein digesting endopeptidases of the small intestine, secreted by the pancreas

skeletal muscle

multinucleated

thick filaments

myosin

Which set of amino acids would most likely be found in the pore of the channel formed by PC2? (Assume the amino acids are at physiological pH.) (PC1 and PC2 interact via their C-terminal cytoplasmic tails to form a heteromer that modulates intracellular calcium homeostasis. ) A.D and E B.R and K C.V and L D.S and T

A.D and E Due to their charged nature, ions cannot freely cross the plasma membrane because the membrane contains a middle layer of uncharged fatty acid chains. Consequently, an ion must pass through the pore of an ion channel to enter the cell. Ion channels are transmembrane protein complexes that fluctuate between an open or closed conformation to facilitate ion transport. These channels exhibit selectivity as only specific ions may pass through the pore and down their concentration gradient (high to low). For a particular ion to go through a channel, the inside of the channel's pore must be lined by amino acid residues with charges opposite to the ion's charge. This is because oppositely charged species attract each other whereas identically charged species repel each other. In addition, the ion must be briefly pulled out of its hydration shell to pass from the aqueous environment outside the plasma membrane to the aqueous environment inside the cell. The opposite charges within the pore stabilize the charge of the newly dehydrated ion. Per the passage, PC2 forms a mechanically activated Ca2+ channel. For positively charged Ca2+ to pass, the inside of the pore must be lined by amino acid residues that are negatively charged at physiological pH. Aspartate (D) and glutamate (E) are the only amino acids that fit this criterion.

A mutant mouse is found to exhibit normal musculoskeletal function following the administration of anti-nAChR antibodies. Compared to a wild-type mouse, this mutant mouse is most likely to show which of the following changes at the neuromuscular junction? A.Decreased ACh degradation within the synapse B.Reduced expression of nAChR by skeletal muscle fibers C.Decreased reuptake of ACh degradation byproducts into the presynaptic neuron D.Reduced release of ACh from the presynaptic vesicles

A.Decreased ACh degradation within the synapse The interface between a somatic motor neuron and a skeletal muscle fiber is a specialized synapse known as the neuromuscular junction (NMJ). The basic function of the NMJ is to convert a motor neuron action potential into a muscle fiber action potential. Activity at the NMJ begins on the presynaptic side. The arrival of an action potential at the axon terminal of the presynaptic motor neuron triggers a series of processes that result in the release of ACh from presynaptic vesicles and into the synaptic cleft via exocytosis. ACh diffuses across the synaptic cleft to bind nicotinic ACh receptors (nAChRs) embedded within the membrane of the postsynaptic muscle fiber, eventually leading to muscle contraction. Unbound ACh may diffuse away from the synapse or be degraded by the enzyme acetylcholinesterase (AChE), terminating muscle fiber contraction. Based on the passage, anti-nAChR antibodies bind nAChR reversibly to block the interaction between ACh and nAChR, resulting in muscle weakness. Accordingly, administration of these antibodies in a wild-type mouse would temporarily prevent binding of ACh to its receptor. However, if a mutant mouse were to exhibit normal muscle contraction despite being treated with anti-nAChR antibodies, the most likely reason in this scenario is that ACh degradation within the mutant's synapse would be decreased compared to the wild-type. If ACh degradation is decreased, more ACh molecules will remain in the synapse for a longer time period and be able to bind nAChRs after these are no longer bound to anti-nAChR antibodies. This would result in muscle contraction that is delayed but still normal. In contrast, the following changes would magnify the inhibitory effect of anti-AChR antibodies on muscle contraction by decreasing the likelihood of ACh binding to nAChR: Fewer nAChR being present within the postsynaptic membrane decreases the binding sites available to synaptic ACh, resulting in muscle weakness (Choice B). Following motor neuron action potentials, reduced release of ACh from the presynaptic vesicles and decreased recycling of ACh breakdown products would decrease the quantity of ACh released into the synapse, also leading to muscle weakness (Choices C and D).

Which of the following best describes the high voltage plate if it accelerates positive ions away from it? A.It is positively charged, and its electric field lines point away from it. B.It is positively charged, and its electric field lines point toward it. C.It is negatively charged, and its electric field lines point away from it. D.It is negatively charged, and its electric field lines point toward it.

A.It is positively charged, and its electric field lines point away from it. Electric charges with the same sign repel, and charges with opposite signs attract. Electric field lines point out from positive charges and into negative charges. Therefore, a positively charged plate repels positively charged ions, and the electric field lines point away from a positively charged plate. Electric field lines are used to denote the direction that a positive charge would be accelerated in an electric field. Because positive charges repel positive charges, electric field lines point outward from positive charges and point toward negative charges (Choice B). Because the accelerating plate is positively charged, its electric field lines nearby must be pointing away, as shown in the figure.

Osteoporosis, a disease marked by decreased bone density and mass, is similar to OA in that it is a degenerative bone disorder correlated with old age. Which two skeletal system functions would OA and osteoporosis impair, respectively? A.Mobility and structural support B.Mobility and leukocyte production C.Calcium storage and structural support D.Calcium storage and leukocyte production

A.Mobility and structural support The primary functions of the skeletal system include mobility, structural support, physical protection of internal organs (eg, the skull protects the brain, the ribcage protects the lungs), mineral storage (primarily phosphate and calcium), blood cell production (hematopoiesis) in red bone marrow, and energy storage (fat stored in the yellow marrow). The passage states that the formation of bony growths (osteophytes) and narrowing of the joint space in OA limits movement. In contrast, osteoporosis is associated with a loss in bone density and mass, which likely leads to weakened bones that are more brittle and susceptible to fracture. Based on the given scenario, OA would limit mobility, and osteoporosis would compromise the structural integrity of bone and its ability to provide support (eg, fracture of weight-bearing bones that function as support pillars).

The drug cevimeline hydrochloride is a cholinergic agonist. Administration of cevimeline hydrochloride would be expected to cause:

A.increased salivation due to stimulation of mAChRs. Treatment with a drug that activates ACh receptors would be expected to increase salivation by activating the muscarinic acetylcholine receptors (mAChRs) present on secretory cells of the salivary gland.

Administration of canagliflozin most directly increases urinary output by increasing the: A.osmotic pressure of the tubular filtrate B.osmotic pressure of the peritubular capillaries C.hydrostatic pressure of the renal artery D.hydrostatic pressure of Bowman's space

A.osmotic pressure of the tubular filtrate Hydrostatic pressure and osmotic pressure are two opposing forces that regulate fluid movement between capillaries and the tissues that surround them. Hydrostatic pressure is the force exerted by a liquid on the walls of its container. Accordingly, the hydrostatic pressure of blood, or blood pressure (BP), is the force exerted by blood on the vessel walls. This pressure pushes fluid through capillary wall pores and into the interstitial fluid (the extracellular fluid surrounding cells of a tissue). The kidneys regulate BP by increasing water reabsorption (thereby increasing blood volume and, consequently, BP) when BP is low and by decreasing water reabsorption when BP is high. In contrast, osmotic pressure causes a solution to take in water by osmosis, the passive movement of water molecules from an area of low to an area of high solute concentration. Osmotic pressure increases as solute concentration (osmolarity) increases. When blood osmolarity is high, the kidneys respond by increasing water reabsorption and decreasing solute reabsorption. Conversely, when blood osmolarity is low, the kidneys react by decreasing water reabsorption and increasing solute reabsorption. The passage states that SGLTs transport glucose out of the proximal tubule so it can be returned to circulation through the peritubular capillaries. Administration of a SGLT inhibitor prevents glucose reabsorption, increasing solute concentration within the tubule and consequently increasing the osmotic pressure of the tubular filtrate. As a result, water is drawn back into the renal tubule, increasing urine output.

In the MS-MS separation chamber, the direction of the magnetic force on a moving ion is: A.perpendicular to both the ion's velocity and the direction of the magnetic field. B.perpendicular to the ion's velocity and parallel to the direction of the magnetic field. C.parallel to both the ion's velocity and the direction of the magnetic field. D.parallel to the ion's velocity and perpendicular to the direction of the magnetic field.

A.perpendicular to both the ion's velocity and the direction of the magnetic field. The quantity (v × B) is the cross product of the vectors v and B. The cross product of two vectors is a vector perpendicular to both vectors. Therefore, the direction of the magnetic force is perpendicular to both the ion's velocity v and the direction of the magnetic field B. The specific direction of a cross-product vector can be determined through the right-hand rule.

Lorentz force (force exerted on an ion in a magnetic field)

According to the passage, the centripetal force (F) exerted on an ion in MS-MS is related to the ion's mass (m) and velocity (v), and the radius (r) of the curved path (Equation 1): F= q*v*B and Fc= (mv^2)/r This force is a result of the force exerted on an ion in a magnetic field. This is known as the magnetic Lorentz force, and it is calculated as the product of the ion's charge (q), the ion's velocity (v), and the magnitude of the magnetic field (B): Because the force due to the magnetic field is the only force exerted on the ion, the centripetal force is equal to the Lorentz force: This equation shows that the ion's radius of curvature is directly proportional to its m/q ratio (Choices C and D). In addition, the radius increases with the ion's velocity and decreases with the strength of the magnetic field. Educational objective: The force exerted on a moving particle in a magnetic field is known as the magnetic Lorentz force, and it is equal to the product of the particle's charge, velocity, and strength of the magnetic field: F = qvB. This force is the centripetal force that curves the path of ions in MS-MS. Therefore, an expression for the radius of curvature can be determined by equating the Lorentz force and centripetal force equations.

Microglia

Act as phagocytes, eating damaged cells and bacteria, act as the brains immune system the macrophages of the central nervous system and consume waste.

Urinary retention in patients with poorly controlled diabetes mellitus is most likely the result of nerve damage impairing smooth muscle contraction in which of the following structures? A.Bladder B.Urethral sphincters C.Kidney D.Ureter

After urine is concentrated in the nephron, it is funneled from the collecting ducts into the renal calyces. The calyces then merge at the renal pelvis, which marks the beginning of the ureter (the tube connecting the kidneys to the bladder). Urine is stored in the bladder until filled, after which it exits the body via the urethra in a process called urination. Urination is controlled by musculature lining the urinary tract. During urine collection, the detrusor muscle (the layer of smooth muscle lining the bladder) is relaxed. At the same time, the internal urethral sphincter (IUS, a ring of smooth muscle surrounding the urethra) and the external urethral sphincter (EUS, a ring of striated muscle downstream of the IUS) are contracted to prevent urine flow down the urethra. The detrusor and IUS are under involuntary control; the EUS is under voluntary control. During urination, activity within stretch receptors in the bladder leads to: Contraction of the detrusor muscle, which pushes urine out of the bladder and into the urethra. Relaxation of the IUS, which opens the urethra and allows urine to pass. Nerve damage that impairs the contraction of the detrusor muscle of the bladder would impair emptying of the bladder and lead to urinary retention. (Choice B) Urine is able to pass through the remainder of the urethra and out the body when the EUS is relaxed. When contracted, both the IUS and EUS block urine flow through the urethra. Inability to contract these muscles due to nerve damage would facilitate, not impair, urine flow.

intercalated discs

Attachment sites between the transverse lines between cardiac muscle cells intercalated discs, which are regions of cell contact that contain both desmosomes (to prevent cells from separating during contraction) and gap junctions (to facilitate direct ion exchange for synchronized contraction).

Which evidence in Table 1 suggests that PTP and Abl are located close together on the chromosome? A. The two recombinant genotypes occur with similar frequency. B. Only a small percentage of the progeny are recombinant. C. Recombination did not occur in male gametes. D. The F1 generation has a high recombination frequency

B. Only a small percentage of the progeny are recombinant. If two genes are located close together on a chromosome (measured in centimorgans, or map units), they are relatively unlikely to be separated by a recombination event. This is because there is less distance between the two genes in which a recombination can occur. Therefore, substantially fewer progeny will have recombinant combinations than parental combinations. As a result, the recombinant progeny can be identified by the fact that there are fewer of them. Table 1 shows that only 43 of 500 flies (~9%) were recombinant. Given this small percentage of recombinant flies, it is likely that the PTP and Abl genes are close together on the chromosome. (Choice A) Recombination is the exchange of genes between homologous chromosomes, and always produces two recombinant chromosomes. Because each chromosome is equally likely to be passed on, recombinant genotypes always occur with equal frequency, regardless of genetic distance.

The misdirected transmission of a high-voltage electrical current is associated with a risk of accidental fire. To eliminate the risk of such accidents, the type of material that must be applied to the surface of bare wires is known as: A.an electrical conductor. B.an electrical insulator. C.a thermal conductor. D.a thermal insulator.

B. an electrical insulator. Electrical conductivity is a physical property that describes how easily electric charge flows through a given material. In solids, electrical conductivity is closely related to how readily electrons can move between atoms to produce an electric current. Electrons within metals are weakly attracted to their corresponding nuclei because the atomic number of many metals is such that the distance between positively charged protons and negatively charged valence electrons is relatively great. Consequently, electrons within metallic materials may be easily dislodged following exposure to an external electric field. Therefore, most metals are electrical conductors whereas most nonmetals are electrical insulators (materials that do not readily transmit electrical energy). In many cases, electrical fires begin as combustible foreign materials enter the electrical circuit, accumulate thermal energy from the high voltage source, and ignite. To prevent such accidental fires, electrical wires are coated in with an electrical insulator with high resistance, which does not transmit electrical energy and prevents electric current from easily exiting the circuit. (Choice A) Electrical conductors are used to facilitate current because the electric field that must be applied to a highly conductive material is less than that required for other materials, which conserves electrical potential energy (ie, voltage). (Choice C) Many metals are also thermal conductors, meaning that they readily act to transfer thermal (heat) energy via conduction. Facilitating thermal energy transfers between nearby atoms and molecules will not prevent adverse electrical events like electrical fires. (Choice D) Many thermal insulators are materials in which atoms and molecules are relatively sparse (eg, foam), making the exchange of thermal energy through conduction difficult. Thermal insulation is used to maintain the temperature of a region or object, not to prevent electrical accidents.

A charged particle is accelerated in a uniform electric field. When its velocity is 2 m/s, its electric potential energy is 100 J and its kinetic energy is 10 J. What is the particle's potential energy when its velocity reaches 4 m/s? A.25 J B.70 J C.90 J D.135 J

B.70 J Electric charges generate electric fields, regions of space that exert an electrostatic force on charges. Electrostatic force is conservative; the total energy of a charged particle in an electric field is conserved. In other words, the sum of the charge's electric potential energy (PE) and kinetic energy (KE) is constant. The total energy of the particle in the electric field is the sum of the given PE and KE: total energy=PEintial+KEintial total energy=100 J+10 J=110 J Kinetic energy is proportional to mass m and the square of velocity v: KE=1/2mv2 The velocity of the particle increases by a factor of 2, from 2 to 4 m/s. Therefore, its final KE increases by a factor of 2 squared, or 2^2 = 4: KEfinal=4(KE)=4(10 J)=40 J The final PE of the particle at 4 m/s is the difference between the overall total energy and its final KE: PEfinal=(total energy)−KEfinal PEfinal=110 J−40J=70 J

Which of the following changes could be made to this experiment to increase the relative signal intensity of peaks that correspond to smaller mass-to-charge (m/z) values? A.Increase the pH of the sample solvent B.Decrease the pH of the sample solvent C.Decrease the concentration of the sample D.Increase the concentration of the sample

B.Decrease the pH of the sample solvent Manipulating z (denominator) will have much higher influence than the numerator. In MS analysis, signal intensity, or the height of a data peak relative to other peaks, corresponds to the relative quantity of ions at each mass-to-charge ratio m/z. During electrospray ionization (ESI), particles are charged via protonation within droplets. Ions that have multiple charges have a smaller m/z ratio because the denominator (charge) has increased. In spectrometry data, this translates into greater signal intensities for these ions. Lowering the pH of the solvent increases the concentration of protons and results in a greater number of multiply charged molecules (z > 1). An increase in multiply charged molecules would therefore result in greater signal intensity for smaller m/z values.

OA commonly affects large, weight-bearing joints of the lower extremities such as the knee and hip. Based on the passage, which of the following would occur in a patient with OA involving the knees? A.Deterioration of the yellow bone marrow in affected bones B.Deposition of excess bone on the epiphyses of affected long bones C.Reduction of hematopoiesis in the red marrow of affected bones D.Degeneration of compact bone at the diaphysis of affected long bones

B.Deposition of excess bone on the epiphyses of affected long bones The human skeletal system is an endoskeleton (internal skeleton) that can be divided into axial and appendicular components. Long bones, one of the four bone types, are aptly named based on their appearance: their length is greater than their width. Long bones (eg, femur) serve to provide a framework for movement. The structure of long bones includes the following: Epiphyses are rounded ends that have joint surfaces covered by articular cartilage. The diaphysis is the hollow shaft (medullary cavity) filled with bone marrow. Metaphyses are the regions where the diaphysis and epiphyses meet. The epiphyseal (growth) plate, a cartilaginous structure that lies between the epiphyses and metaphyses, is present only during childhood and serves as the site of longitudinal growth. When growth ceases, the growth plate is replaced with mature bone and is referred to as the epiphyseal line. The periosteum is a thin layer of connective tissue that covers and protects the long bone. (Note: The periosteum does not cover joint surfaces.) The knee joint is the site where the femur and tibia meet. According to the passage, OA can result in the formation of osteophytes (bony growths) on the subchondral bone, which is the bone under the damaged articular cartilage. In other words, additional bone deposits on the epiphyses of the bones at the affected joint.

Which of the following characterize gas-liquid chromatography? Gas mobile phase Liquid stationary phase Separation based on polarity Room-temperature column conditions A.I only B.I and II only C.I and III only D.I, II, and IV only

B.I and II only Gas-liquid chromatography is a technique used to separate molecules in a mixture based on their boiling points. A gas chromatograph consists of an injection port, mobile and stationary phases, a column in a heated oven, a detector, and a computer for data analysis. The mobile phase is an inert gas such as helium or nitrogen (Number I), and the stationary phase is a liquid that coats a solid support on the inside of the column (Number II). A small amount of a liquid mixture is injected into the gas chromatograph, and the compounds in the mixture are vaporized by heating. The vapors then travel through the column in a heated oven to the detector. The most volatile molecules (low boiling points) spend more time in the gas phase than they spend interacting with the stationary phase of the column, so they migrate to the detector rapidly. However, molecules with higher boiling points condense more readily and spend more time interacting with the liquid stationary phase. These molecules make their way through the column slowly as the temperature in the oven increases.

The chemical process that occurs during acidosis can be replicated in vitro by adding a strong acid to an ammonia buffer solution. How will the pH change in the solution if 1.0 mL of 0.5 M H2SO4 is added to a 100 mL solution containing 1 M NH3 and 1 M NH4+? A.The pH will increase slightly (<0.1 pH units) because NH3 and NH4+ are a conjugate acid/base pair. B.The pH will decrease slightly (<0.1 pH units) because NH3 and NH4+ act as a buffer. C.The pH will increase significantly (>1.0 pH units) because NH3 is a strong base. D.The pH will decrease significantly (>1.0 pH units) because H2SO4 is a strong acid.

B.The pH will decrease slightly (<0.1 pH units) because NH3 and NH4+ act as a buffer. Buffer systems are comprised of a weak acid and its conjugate base or a weak base and its conjugate acid (often in equal concentrations). In either type of buffer, the mixture provides both acidic and basic species to counteract H+ or OH− ions from any strong acid or strong base that is added to the solution. This results in a much smaller change in pH than would have otherwise occurred without the buffer. The buffer species must be in much higher concentration than the amount of strong acid or strong base that is added to the system. If too much of a strong acid or base is added, too much of the weak acid or its conjugate base are consumed, and the buffer no longer resists changes to pH. In the experiment described in the question, a strong acid (H2SO4) is added to an ammonia buffer system. The amount of H2SO4 added is much less than the concentration of NH3 and will react with the NH3 to form NH4+ (a weak acid); therefore, the pH will decrease slightly but the ammonia buffer system will resist a large change in pH.

What happens to the pOH of the gastric acid entering the duodenum (pH 6.0) as a result of the introduction of bicarbonate ions from incoming pancreatic secretions? A.The pOH increases as [OH−] increases. B.The pOH decreases as [OH−] increases. C.The pOH increases as [OH−] decreases. D.The pOH decreases as [OH−] decreases.

B.The pOH decreases as [OH−] increases. Accordingly, lower pOH values indicate more alkaline solutions with higher [OH−]. This is opposite to the pH scale, in which lower pH values indicate more acidic solutions. Consequently, pH and pOH are inversely correlated. As pH rises, pOH falls (and vice versa) while maintaining the relationship pH + pOH = 14.

During Experiment 2, the subject lifts a ball with a mass m a vertical distance d1 and then lowers the ball a greater vertical distance d2. What is the net work done by gravity on the ball? A.W = 0 for all cases because gravity is a conservative force B.W = mg(d2 − d1), because gravity does work to lift and lower the ball C.W = mgd2, because gravity does work only to lower the ball D.W = mg(d1 + d2), because gravity does work only on the net vertical path

B.W = mg(d2 − d1), because gravity does work to lift and lower the ball Gravity is a conservative force; it depends on the initial and final position of the mass it acts on. The net work W done by a conservative force is the amount of energy transferred by the force F over a displacement d in the direction of the force: W = Fd Work and displacement are positive if they are in the same direction as the force, and gravity does work only along the vertical axis; W is positive when the ball is lowered because gravity acts downward. The ball's net downward displacement is the difference between the lowered distance d2 and the raised distance d1: d = d2 − d1 W = F(d2 − d1) The force due to gravity on the ball is its weight, which is the product of its mass m and the acceleration due to gravity g: F = mg. Therefore, the net work done by gravity is W = mg(d2 − d1)

Renal studies in mice have revealed that a mutation in various sodium transporters causes impaired active transport of NaCl from the filtrate within the loop of Henle to the medulla. If mice with wild-type sodium transporters were compared to mice with the mutated sodium transporters, the mutant mice would likely exhibit all of the following EXCEPT: A.decreased saltiness of the medulla. B.decreased urine output. C.decreased renal water reabsorption. D.decreased blood pressure.

B.decreased urine output. Each kidney, divided into an outer cortex and inner "salty" medulla, contains many functional units known as nephrons. In the renal cortex, blood is first filtered through glomerular capillaries into the Bowman's capsule (a cup-shaped structure) of each nephron. The filtered fluid (filtrate) then flows through the tubular segments of the nephron. The proximal tubule is the first segment the filtrate traverses. Next, the filtrate flows into the loop of Henle, a two-limbed structure stretching into the medulla that reabsorbs water and salt (NaCl) from the filtrate into the body via countercurrent multiplication: Filtrate flows through the descending limb of the loop, which is highly permeable to water but impermeable to NaCl. Water will move from areas of low solute concentration to areas of high solute concentration. Accordingly, because salt concentration in the medulla is high, water is passively reabsorbed (via osmosis) from the filtrate flowing through the descending limb into the salty medulla, where it is taken up by blood vessels. Filtrate then flows into the ascending limb, which is highly permeable to NaCl but impermeable to water. Initially, NaCl is passively reabsorbed into the medulla as filtrate moves up the ascending limb. However, as the ascending limb nears the cortex, NaCl is actively transported from the filtrate into the medulla, preserving the medulla's high salt concentration. Because water follows NaCl, the saltiness of the medulla promotes continued water reabsorption from the descending loop of Henle and the collecting duct. Following passage through the loop of Henle, filtrate travels through the distal tubule into the collecting duct, where water and salt reabsorption continue. Remaining filtrate flows to the bladder and is excreted from the body as urine. Studies in mice indicate that sodium transporter mutations impair active transport of NaCl from the loop of Henle into the medulla. Accordingly, compared to wild-type mice, mice with mutated sodium transporters would exhibit a decrease in both medullary salt concentration and water reabsorption (Choice C), a decrease in blood pressure (Choice D), and an increase in urine output (Choice B).

An infant who experiences seizures and has lactic acid buildup is shown to have deficient pyruvate dehydrogenase complex (PDHC) activity. Genetic analysis shows that both the maternal and paternal alleles for all PDHC subunits are normal. These results could indicate: A.overexpression of one or more PDHC subunits. B.impaired ability to synthesize lipoic acid. C.upregulated acetyl-CoA entry into the Krebs cycle. D.an unusually low rate of pyruvate fermentation.

B.impaired ability to synthesize lipoic acid. Because lipoic acid is a necessary cofactor of the PDHC, impaired lipoic acid production would result in decreased activity of the PDHC complex.

Microscopic examination of tissue samples obtained from the type of bone that becomes exposed in advanced OA is most likely to reveal all of the following EXCEPT: A.Volkmann canals connecting haversian canals. B.mature chondrocytes. C.canaliculi. D.osteocytes situated within lacunae.

B.mature chondrocytes. Based on the passage, the degradation of articular cartilage in advanced OA can ultimately result in complete exposure of the cortical portion of the underlying subchondral bone. A shell of cortical (compact) bone generally surrounds cancellous (spongy) bone. Therefore, the compact bone becomes exposed in advanced OA. Compact (hard) bone is organized into structural units called osteons, or haversian systems, which are made up of lamellae (concentric rings of bone matrix) that surround a central haversian canal, a cylindrical channel that runs parallel to the long axis of bone and through which blood vessels and nerves traverse. Volkmann canals, which run perpendicular to the long axis of bone, allow the passage of blood vessels and nerves between different haversian canals (Choice A). Other cellular components of bone include osteogenic (osteoprogenitor) cells, osteoblasts, osteocytes, and osteoclasts. During bone remodeling, old bone is resorbed (broken down) by osteoclasts and new bone is deposited by osteoblasts. Osteogenic cells are the mitotically active stem cells in bone that initially differentiate into osteoblasts. The osteoblasts then secrete the proteins that form the unmineralized bone matrix called osteoid. Although it is primarily composed of collagen, osteoid eventually becomes mineralized through the precipitation of calcium salts on the surfaces of its collagen fibers. These deposited calcium salts mature into hydroxyapatite crystals, the mineral responsible for bone hardness. Osteoblasts continue to build successive concentric layers of bone, but as the osteoid mineralizes, some osteoblasts become trapped within lacunae (spaces) in the lamellar matrix and are known as (mitotically inactive) osteocytes at this stage. Within each osteon of compact bone, lacunae connect to one another via microscopic channels called canaliculi, which allow osteocyte waste exchange and nutrient delivery (Choices C and D).

The cheetahs that survived the environmental catastrophe that occurred 12,000 years ago are at greater risk of extinction because of: A.naturally selected changes in allele frequencies. B.random changes in allele frequencies. C.changes in allele frequencies due to migration. D.changes in allele frequencies due to random mating.

B.random changes in allele frequencies. Genetic drift describes the natural variations in allele frequencies of a population due to random genetic changes that are not related to natural selection (eg, sampling error, chance event). Although all populations are affected by genetic drift, its effects are more significant in smaller populations because they have a reduced gene pool. The smaller gene pool cannot buffer random (good or bad) variations in allele frequencies that occur due to chance events. In other words, the probability of a beneficial allele being removed by genetic drift increases for populations whose genetic diversity is low. Similarly, drift increases the probability of a deleterious allele becoming fixed within the population. According to the passage, cheetahs experienced a catastrophic event that drastically reduced their population size; this is known as a bottleneck event. Bottlenecks (due to environmental events or human action) greatly reduce the genetic diversity of a population. Consequently, the smaller population of cheetahs has a reduced ability to buffer the negative impacts of random changes in allele frequencies (genetic drift) that may result in extinction. (Choice A) Natural selection is an evolutionary mechanism by which only beneficial alleles are selected for while unfavorable traits are selected against. These selected changes alter the population's allele frequencies, which improves the species' fitness. Consequently, these populations have an improved probability for survival rather than an increased probability for extinction.

action potential & voltage gated channels locations in myelinated vs unmylineated axons

Biologist 1 stained neurons with myelinated axons (which contain voltage-gated ion channels that are clustered at the nodes of Ranvier) whereas Biologist 2 stained unmyelinated axons (which contain voltage-gated ion channels that are evenly distributed across the entire axon). Due to the lack of myelination, the axons studied by Biologist 2 were fully exposed to extracellular space (Choice B), were more susceptible to rapid weakening of the electrical signal (Choice A), and conducted APs at a slower rate (Choice C).

Uniform magnetic fields created by advanced medical imaging devices most likely come from the: A.nuclear decay of device materials. B.electric forces generated by charged particles. C.motion of electrons along a circular pathway. D.storage of electrical charges at small distances.

C.motion of electrons along a circular pathway. Magnetic fields are vector quantities representing the magnetic influence that electrical currents and magnetized materials would experience at a location in three-dimensional space. Common sources of magnetic fields include electromagnetic radiation and permanent magnets, materials in which sustained north and south magnetic poles are present intrinsically or formed through magnetic induction (ie, magnetization). Electric current is another source of magnetic fields. Current traveling along a straight wire generates magnetic field lines that encircle the wire lengthwise, the orientation of which can be determined by the right-hand rule. The magnitude of the magnetic field (B) generated by electric current relates to the current (I), the distance from the axis of the wire (r), and the permeability constant (µ) of the medium: B= μI/2πr Furthermore, current flowing along a circular wire generates unidirectional magnetic field lines within the interior of the coil. Among other applications, this principle is useful to medical imaging technologies. Specifically, the core of an MRI (magnetic resonance imaging) machine is composed of sequential conductive coils in which current flows in the same clockwise or counterclockwise direction. Therefore, the use of circular current generates a uniform magnetic field that interacts with anatomical structures to enable the collection of medical imaging data.

More polar, carboxylic acid or alcohol?

Carboxylic acids are more polar than alcohols because there are two oxygen atoms present in a carboxylic acid molecule.

carrier mediated transport

Carrier-mediated transport (facilitated diffusion and active transport) allows for the passage of large or hydrophilic molecules such as glucose, amino acids, and nucleosides. ...Endocytosis is used to transport molecules in bulk.

Which of the following statements is NOT true about hyaline cartilage? A.It lacks innervation. B.It gives rise to bone through endochondral ossification. C.It serves as an attachment that holds bones to muscle. D.It is avascular and receives nutrients from surrounding fluids.

Cartilage is a connective tissue composed of cells known as chondrocytes that secrete an extracellular matrix called chondrin, which contains collagen fibers, proteoglycans, and water. Cartilage may be classified as hyaline, elastic, or fibrous cartilage depending on its composition. The firm but flexible structure of cartilage is resistant to compression and stretching. Hence, most of the cartilage in the body is found in parts that require cushioning (eg, joint surfaces, spine) and on the articulating surfaces of bone ends. Specifically, hyaline cartilage is the most abundant cartilage type in the body and is found on the ends of long bones as well as in the ribs, nose, trachea, and larynx. Because cartilage lacks nerves (ie, is not innervated) and is avascular (ie, lacks its own blood supply), it must receive nutrients and oxygen via diffusion from surrounding fluids or vascularized areas (Choices A and D). Cartilage also plays a role in certain mechanisms of bone development. The process of endochondral ossification utilizes hyaline cartilage as a template for bone deposition (Choice B). During fetal development, hyaline cartilage composing the fetal skeleton is replaced by bone (ie, it calcifies). In children and adolescents, the epiphyseal (growth) plate of long bones is formed from hyaline cartilage and serves as the site of bone lengthening. In contrast, bone formation can also occur via intramembranous ossification, a process in which bone is formed directly from fibrous connective tissue (not hyaline cartilage). Mesenchymal (connective tissue) stem cells within this connective tissue differentiate into osteoblasts and secrete the bone matrix. (Choice C) Ligaments and tendons are important connective tissue structures at joints. Tendons (not hyaline cartilage) tautly anchor muscle to bone. Tendons are strong, fibrous bands of connective tissue that transmit a force generated by contracting muscle to the bone, permitting locomotion (movement). In contrast, ligaments are strong bundles of connective fibers that connect bones to other bones and stabilize and hold structures together.

What is the force felt by a doubly ionized particle in a 2,000-N/C electric field? (Note: The charge of an electron is e = 1.6 × 10−19 C.) A.1.6 × 10−22 N B.3.2 × 10−22 N C.3.2 × 10−16 N D.6.4 × 10−16 N

Charged particles are accelerated in electric fields by a force known as the electric Lorentz force. The force exerted on a particle in an electric field is equal to the product of the particle's charge (q) and the electric field strength (E): F=qE The charge of a doubly ionized particle will be twice the charge of an electron (1.6 × 10−19): q=2(1.6×10−19 C)=3.2×10−19 C Using the above charge as q and the given electric field strength of 2,000 N/C as E, the force exerted on the particle is: F=(3.2×10−19 C)(2,000 NC)=6.4×10−16 N (Choice C) This value (3.2 × 10−16 N) is the force exerted on a singly ionized molecule. However, the question asks for the force exerted on a doubly ionized molecule, which has twice the charge and therefore experiences twice the force.

Which complexes pump protons?

Complexes I, III, and IV pump protons into the intermembrane space against their concentration gradient, but Complex II does not pump protons against their gradient, and therefore does not contribute to the decrease in pH in the intermembrane space.

Ligaments

Connect bone to bone This is why All surgeries can still let someone move, since you only need muscle to move. But they can also make your knees bend in crazy ways.

Tendon

Connects muscle to bone

Which of the following regulatory mechanisms helps increase net glucose catabolism in the liver after a meal? A.Inhibition of hexokinase by glucose-6-phosphate B.Allosteric supression of phosphofructokinase-1 by ATP binding C.Hormonal suppression of fructose-2,6-bisphosphate synthesis D.Allosteric inhibition of fructose-1,6-bisphosphatase catalysis

D.Allosteric inhibition of fructose-1,6-bisphosphatase catalysis Allosteric inhibition of fructose-1,6-bisphosphatase catalysis The well-fed state is characterized by the release of insulin in response to high levels of glucose in the blood. Insulin stimulates glucose catabolism (glycolysis) by activating synthesis of fructose-2,6-bisphosphate (F2,6BP). F2,6BP allosterically activates phosphofructokinase-1 (PFK-1), which catalyzes the rate-limiting step of glycolysis. In the liver, F2,6BP also inhibits fructose-1,6-bisphosphatase, which catalyzes the dephosphorylation of F1,6BP in gluconeogenesis. Inhibiting gluconeogenesis in the liver leads to increased net glucose catabolism.

During anaerobic exercise, the Cori cycle connects which two metabolic pathways? A.Glycogenolysis and the citric acid cycle B.The urea cycle and gluconeogenesis C.The pentose phosphate pathway and glycogenesis D.Gluconeogenesis and glycolysis

D.Gluconeogenesis and glycolysis During glycolysis, NAD+ is converted to NADH by the enzyme glyceraldehyde-3-phosphate (GAP) dehydrogenase. For glycolysis to continue, NAD+ must be regenerated. Under aerobic conditions, electrons from NADH can be transferred to the electron transport chain (ETC) and ultimately to oxygen. However, in anaerobic conditions, NAD+ cannot be regenerated by the ETC because there is insufficient oxygen to accept electrons. Consequently, NADH donates electrons to pyruvate, which is reduced to lactate in the process. Lactate that builds up from this mechanism must be removed from the system because it can lead to muscle pain and nausea. The lactate in muscles enters the bloodstream, which carries it to the liver. In the liver, lactate is converted to glucose during gluconeogenesis and is carried back to muscles by the blood. The process of carrying lactate from the muscle to the liver and moving regenerated glucose from the liver back to muscles is called the Cori cycle, which connects gluconeogenesis and glycolysis.

Which organ synthesizes a compound that facilitates the mechanical digestion of lipids? A.Pancreas B.Salivary glands C.Gallbladder D.Liver

D.Liver The liver synthesizes bile, a nonenzymatic solution stored in the gallbladder and released into the small intestine to aid in the mechanical digestion of lipids. Bile is composed of bile salts, bile pigments (eg, bilirubin), and cholesterol. Bile salts act as detergents to solubilize fats during digestion and possess both a hydrophobic region that associates with the surface of lipids and a hydrophilic region that associates with water. Consequently, bile salts break down large lipid globules into smaller droplets (micelles) in a process known as emulsification. Emulsification is an example of mechanical digestion, which physically breaks down food particles into smaller pieces. Additional examples of mechanical digestion include chewing in the mouth and churning in the stomach due to peristaltic waves.

Cirrhosis of the liver is characterized by hepatic cell death, tissue scarring, and altered liver function. All of the following would be disrupted by cirrhosis of the liver EXCEPT: A.the production of ketone bodies. B.the metabolism of most drugs. C.the oncotic pressure within capillaries. D.the secretion of digestive proteolytic enzymes.

D.the secretion of digestive proteolytic enzymes.

Fatty Acid Transport into Mitochondria

Entry into the mitochondrial matrix is tightly regulated by transport proteins in the inner mitochondrial membrane. Fatty acids must be activated with coenzyme A followed by carnitine to enter the mitochondrial matrix. Activation requires ATP hydrolysis.

magnetic Force (Fb)

F = qvB sinθ where θ is the angle < 180 degrees between the velocity and the magnetic field

If lower phospholipid levels in ME patients are due to inhibition of fatty acid synthesis, researchers would most likely observe which of the following? A.Increased cytosolic NADPH. B.Decreased mitochondrial acetyl-CoA. C.Decreased mitochondrial fumarate. D.Increased cytosolic lysine.

Fatty acid synthesis is an anabolic process that builds lipids in the cytosol. Anabolic processes generally require energy, reducing power, and sufficient precursor molecules: in fatty acid synthesis these requirements are satisfied by ATP, NADPH, and acetyl-CoA, respectively. During fatty acid synthesis, NADPH is oxidized to NADP+ to reduce the carbonyl groups and carbon-carbon double bonds on each acetyl-CoA molecule added to the fatty acid chain. If fatty acid synthesis is inhibited in ME patients, the conversion of NADPH to NADP+ will occur less frequently, and cytosolic NADPH will build up. (Choice B) Fatty acid synthesis takes place in the cytosol, not the mitochondria. In addition, cytosolic acetyl-CoA levels would most likely increase when fatty acid synthesis is inhibited because less acetyl-CoA is consumed. (Choice C) Fumarate concentration is not directly related to fatty acid synthesis and will most likely be unaffected. (Choice D) Lysine is not directly involved in fatty acid synthesis. In addition, figure 1 shows that category II amino acids, including lysine (K), have decreased levels in ME patients. Educational objective: Acetyl-CoA, NADPH, and ATP are the reactants needed to generate fatty acid chains during lipid synthesis. The pentose phosphate pathway generates the NADPH needed to reduce the carbonyl groups from each molecule of acetyl-CoA that is added to a fatty acid chain.

In the combined population of 15 X chromosomes and 5 Y chromosomes, which of the following alleles, if any, would be most susceptible to loss due to random chance alone? A.An allele on the Y chromosome B.An allele on the X chromosome C.An allele on either the X or Y chromosome D.Allele loss due to random chance alone would only occur in nonsex chromosomes

Genetic drift is the fluctuation of allele frequencies within a population due to chance events. This can lead to random loss of alleles within a population. In general, low-frequency alleles have an increased probability of being eliminated by random events than do high-frequency alleles. Because alleles on the Y chromosome exist at the lowest frequencies, they are most susceptible to loss by random chance alone.

Light

In general, the perceived color of a substance is complementary to the color of the wavelength that is maximally absorbed by that substance. When the basic colors of the visible spectrum (red, orange, yellow, green, blue, and violet, or ROYGBV) are arranged in a wheel with red and violet next to each other, a color's complement is the color directly across from it on the wheel.

A solution of Compound 1, shown below, absorbs light maximally at 448 nm in the absence of copper(II) ions but shifts to a 623 nm absorption maximum upon the addition of Cu2+. Which of the following best describes this process? A.Changes in electronic structure cause the solution to change from yellow to blue. B.Changes in vibrational modes cause the solution to change from green to yellow. C.Changes in the mass-to-charge ratio (m/z) cause the solution to change from violet to orange. D.Changes in nuclear spin cause the solution to change from colorless to violet.

In general, the perceived color of a substance is complementary to the color of the wavelength that is maximally absorbed by that substance. When the basic colors of the visible spectrum (red, orange, yellow, green, blue, and violet, or ROYGBV) are arranged in a wheel with red and violet next to each other, a color's complement is the color directly across from it on the wheel. The question states that Compound 1 absorbs light with a 448 nm wavelength, which corresponds to violet light and to yellow as the complement. After Cu2+ is added, the absorption maximum changes to 623 nm and corresponds to orange light, the complement of which is blue. Therefore, upon the addition of Cu2+, Compound 1 must undergo a change in electronic structure that causes the solution to change from yellow to blue.

Fructose-2,6-bisphosphate (F2,6BP)

Insulin stimulates glucose catabolism (glycolysis) by activating synthesis of fructose-2,6-bisphosphate (F2,6BP). F2,6BP allosterically activates phosphofructokinase-1 (PFK-1), which catalyzes the rate-limiting step of glycolysis.

mass spectrometry

Ions in TOF-MS are separated by their travel time to the detector, which is proportional to its m/q ratio. Ions in MS-MS are separated by their radius of curvature, which is directly proportional to its m/q ratio. Therefore, an ion that takes less time to reach the detector in TOF-MS has a small m/q ratio and a smaller radius of curvature in MS-MS.

Insulin increases fatty synthesis

Liver cells, in particular, respond to insulin by increasing their rates of lipid synthesis and mobilization. In the mitochondria, insulin activates pyruvate dehydrogenase (PDH), which converts pyruvate into acetyl-CoA. The accumulated acetyl-CoA is transported to the cytoplasm by combining with oxaloacetate to form citrate, which can exit the mitochondria. In the cytoplasm, citrate is converted back to acetyl-CoA and oxaloacetate. Insulin activates both acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), which convert acetyl-CoA to malonyl-CoA and catalyze the synthesis of 16-carbon fatty acid chains from malonyl-CoA, respectively.

****HOW ELECTRONS ARE PASSED IN THE ETC****

Mitochondria are double membrane-bound cellular organelles that house several connected metabolic reactions. The citric acid cycle takes place inside the mitochondrial matrix and produces two reduced electron carriers, NADH and FADH2. These two carriers then pass their electrons to ubiquinone (UQ), which is reduced to ubiquinol (UQH2). UQH2 passes its electrons to oxidized cytochrome C (cyt-Cox), regenerating UQ and forming reduced cytochrome C (cyt-Cred). Finally, cyt-Cred transfers electrons to oxygen, regenerating cyt-Cox and forming water.

During muscle contraction, the power stroke is the pivoting motion of the myosin head that pulls the actin filament inward to shorten the sarcomere. Given this, which of the following events immediately precedes the power stroke? A.The binding of ATP to the myosin heads B.The hydrolysis of myosin-bound ATP to ADP and Pi C.The release of ADP and Pi from the myosin head D.The binding of Ca2+ to tropomyosin

Muscle contraction is dependent on the interaction between the myosin (thick) and actin (thin) protein filaments in the sarcomere, the basic contractile unit of muscle tissue. To generate muscle contraction, the sarcomere functions as follows: When the muscle fiber is at rest, the myosin head is in its high-energy conformation (upright and bound to ADP and Pi), and the actin filaments are bound by the regulatory proteins tropomyosin and troponin. Tropomyosin is an elongated protein that wraps around the actin filament to block myosin-binding sites on this thin filament. Troponin is a small protein complex associated with tropomyosin. Following a depolarizing stimulus by a motor neuron, Ca2+ ions are released from the sarcoplasmic reticulum into the cytosol. The abundant cytosolic Ca2+ ions bind troponin, causing a conformational change that ultimately pulls on tropomyosin and exposes the myosin binding sites on the actin filaments (Choice D). When the active sites are exposed, the myosin head is able to bind strongly to the actin filament, forming a cross-bridge and promoting the release of ADP and Pi. The dissociation of ADP and Pi causes the power stroke, which is the actual pivot of the actin-bound myosin head that drags the actin filament toward the center of the sarcomere. This directly results in shortening of the sarcomere (Choice C). The myosin head is now in its low-energy conformation. A new ATP molecule binds the myosin head and the cross-bridge disassembles (Choice A). Hydrolysis of the ATP molecule allows the myosin head to shift back into its upright, high-energy conformation in preparation for a new cycle of contraction (Choice B). The cycle of cross-bridge formation and disassembly continues until motor neuron signaling ceases, and Ca2+ is sequestered back into the sarcoplasmic reticulum.

In neurons, action potential propagation occurs along the axon. The analogous structure in skeletal muscle fibers that enables action potential propagation is the: A.actin filament. B.transverse tubule. C.motor endplate. D.myelin sheath.

Muscle fiber action potentials propagate along the sarcolemma, the plasma membrane of the muscle fiber. The sarcolemma burrows deep into the muscle fiber, forming hollow structures known as transverse (T) tubules. Action potentials propagate along T-tubules just as they propagate along the superficial sarcolemma, resulting in the rapid and complete depolarization of the muscle fiber. This promotes calcium release from the sarcoplasmic reticulum, leading to muscle fiber contraction.

Complex 1 of ETC

NADH CoQ oxidoreducatse oxidation of NADH transfer of electrons/ H- to the coenzyme Q (CoQ) has two major subunits 1. iron sulfur cluster 2. flavoprotein with FMN (flavin mononucleotide) coenzyme FMN has similar structure to FAD as NADH gets oxidized to NAD+ FMN goes to FMNH2 (reduced) FMNH2 gets oxidized to FMN iron sulfur cluster gets reduced reduced iron sulfer subunit gives electrons to CoQ/ ubiquinone CoQ --> CoQH2 *four protons are moved to the intermembrane space* net: NADH + H+ + CoQ --> NAD+ + CoQH2

Native PAGE (polyacrylamide gel electrophoresis)

Polyacrylamide gel electrophoresis (PAGE) can be used to separate DNA molecules by size. A native PAGE gel contains no denaturants or reducing agents, and allows double-stranded DNA molecules to traverse the gel in their native (unaltered) state.

reflex arc

Reflex arcs begin with the stimulation of a sensory neuron, which leads to an electrical impulse that travels toward the spine along a sensory nerve. This impulse enters the spine via the dorsal root ganglia and can be transmitted in one of two ways: Directly to the effector neuron (ie, a monosynaptic reflex arc), or Indirectly through an interneuron that interfaces with the effector neuron (ie, a polysynaptic reflex arc) Subsequently, electrical impulses initiated in the effector neuron leave the spinal cord through the ventral root and travel along the effector neuron's axon to synapse with and stimulate a muscle fiber, gland, or ganglionic neuron. When the effector neuron synapses with a muscle fiber, it is referred to as a motor neuron. Reflexes can be modulated (dampened or enhanced) by input from the brain. Descending signals from higher areas in the central nervous system (CNS) travel along spinal tracts to act on neurons in the reflex arc whose cell bodies lie within the spine. Based on the gustatory-salivary reflex arc depicted in Figure 1, the cell bodies of both the interneuron and the preganglionic neuron lie within the spine. Therefore, descending input could act on either of these two neurons to alter the gustatory-salivary reflex.

Diastole

Relaxation of the heart

stereospecific reactions

Stereospecific reactions produce chiral molecules, which have chiral centers in a specific conformation. The conversion of citrate into isocitrate by aconitase and the transformation of fumarate into malate by fumarase are stereospecifc reactions.

Acid base requirements for extractions

Strong organic bases form ionic salts easily when weak acids are added to a mixture. On the other hand, weaker bases such as amines are only protonated by strong acids. Likewise, carboxylic acids, which are considered relatively strong organic acids, can be deprotonated by strong and weak bases. However, phenols are much weaker acids that require strong bases to be deprotonated.

electrical synapse vs chemical

Synapses in the nervous system can be either electrical or chemical. Information transmitted across electrical synapses is conveyed in the form of an ionic current that passes directly from neuron to neuron via a gap junction, which is a cluster of channels that connects the cytoplasms of adjacent cells. Due to this cytoplasmic continuity and the mere 2- to 4-nm gap between the pre- and postsynaptic membranes, the current passes almost instantaneously from one neuron to another. Cytoplasmic continuity also allows signals (ions) to flow bidirectionally across the synapse. In contrast, information transfer is typically unidirectional at chemical synapses, and the cytoplasms of the two neurons are not continuous. Depolarization of the presynaptic neuron results in the release of chemical messengers (neurotransmitters) that diffuse across the synaptic cleft (the 20- to 40-nm space between the pre- and postsynaptic membranes) and bind to postsynaptic membrane receptors to generate a new ionic current in the postsynaptic cell. Signal transmission across chemical synapses is slower than transmission across electrical synapses because the signal must be modified (electrical to chemical to electrical) and must cross a larger intercellular distance. Therefore, Set A depicts a chemical synapse because there is a delay between the pre- and postsynaptic action potentials (APs). Set B, which shows nearly instantaneous firing of the postsynaptic cell, corresponds to an electrical synapse.

Ganglia (ganglion)

cluster of neurons in PNS

The force exerted on a particle in a uniform electric field

The force exerted on a particle in a uniform electric field is the product of its charge and the magnitude of the electric field: F = qE.

Which change would result in the greatest decrease in the volumetric blood flow rate within a mesenteric vessel? A.Decrease the viscosity of the blood by a factor of 4 B.Increase the length of the vessel by a factor of 9 C.Decrease the radius of the vessel by a factor of 2 D.Increase the pressure difference by a factor of 6

The greatest decrease in blood flow rate is achieved when the radius is reduced by a factor of 2 because Poiseuille law has a fourth-power dependence on r and a linear (first-power) dependence on all the other variables. Therefore, blood flow rate Q decreases by a factor of 16 when the vessel's radius r is halved.

How to separate a racemic mixture

The separation of enantiomers, such as those in the racemic mixture of albuterol, requires the addition of a resolving agent (a chiral molecule). When a resolving agent is added to a racemic mixture, it reacts with each enantiomer, forming a covalent bond or an ionic salt. Because the resolving agent is chiral, it incorporates a new chiral center into each enantiomer, creating a pair of diastereomers. Diastereomers can be separated from each other because, unlike enantiomers, they have different physical properties. Once the diastereomers are separated, the resolving agent is removed, yielding the original molecules as single enantiomers.

transcellular transport

The transcellular route refers to the passage of relatively small, lipophilic molecules by passive transport (diffusion). Nonpolar gases such as CO2 and O2 as well as steroid hormones such as testosterone pass easily through epithelial cells and therefore readily enter the brain through the transcellular route.

Human cardiac muscle differs from skeletal muscle because it: A.appears striated. B.requires acetylcholine to contract. C.contains intercalated discs. D.contains cells with multiple nuclei.

The walls of the heart are composed primarily of cardiac muscle fibers, which function to generate powerful, coordinated contractions that are responsible for the continuous pumping of blood through the vessels of the circulatory system. Microscopically, cardiac muscle appears striated due to the regular arrangement of actin and myosin filaments into small contractile units called sarcomeres, and each cardiac muscle cell contains one or two nuclei. Cardiac muscle is unique in that each cell is connected to adjacent cells via intercalated discs, which are regions of cell contact that contain both desmosomes (to prevent cells from separating during contraction) and gap junctions (to facilitate direct ion exchange for synchronized contraction). (Choice A) Cardiac and skeletal muscle both appear striated due to the presence of sarcomeres. (Choice B) Cardiac muscle is under involuntary control and is myogenic, meaning that it does not require nervous system input to contract. Instead, specialized cells in the sinoatrial node spontaneously depolarize to produce electrical impulses that spread through the cardiac muscle via its intercalated discs. However, cardiac muscle contraction can be regulated by neural and hormonal input. For example, parasympathetic signaling slows the rate of contraction, and sympathetic and hormonal signaling can increase heart rate. Skeletal muscle, on the other hand, is under voluntary control and must be stimulated by the acetylcholine-releasing motor neurons of the somatic nervous system to contract. (Choice D) Cardiac and skeletal muscles are alike in that both contain cells that have multiple nuclei. Cardiac muscle cells typically have no more than 2 nuclei, but skeletal muscle cells, which fuse during development, can contain hundreds of nuclei.

Researchers analyzing gene expression in connective tissue samples are likely to obtain gene expression profiles for all of the following tissues EXCEPT: A.bone tissue. B.blood tissue. C.adipose tissue. D.muscle tissue.

There are four main tissue types in the human body: epithelial, muscle, connective, and nervous tissue. Connective tissue, consisting of specialized cells that secrete and maintain an extensive extracellular matrix, has several functions. Connective tissue serves to attach tissues and organs to one another and is essential for the protection and support of surrounding structures. In the given scenario, researchers are analyzing gene expression in connective tissue samples. Therefore, they may obtain gene expression profiles for several subtypes of connective tissue, including: Bone, which makes up the skeletal system and provides structural support and physical protection for internal organs as well as a framework for mobility. Bone comprises osteoblasts (matrix-secreting cells that build bone), osteoclasts (bone-degrading cells), and osteocytes (mature bone cells) (Choice A). Blood, which transports gases, cells (ie, erythrocytes, leukocytes), nutrients, wastes, and other materials (eg, hormones) throughout the body via blood vessels. Although mature erythrocytes have no nucleus, gene expression profiles can still be obtained from leukocytes (Choice B). Adipose tissue, which is responsible for the storage of fats as well as providing cushioning for organs and insulation to prevent heat loss (Choice C). Muscle tissue, classified into three types, is under the control of the nervous system and allows for movement. Although connective tissue comes into contact with muscle tissue, muscle is not considered to be a type of connective tissue. Therefore, researchers analyzing gene expression in connective tissue samples would not obtain gene expression profiles for muscle tissues.

best indicator in titrations

To visually detect when a titration is complete, an indicator that has an endpoint (color change) near the pH of the equivalence point can be added to the solution. Different indicators change color across a particular pH range (endpoint range). The best indicator for a given titration is one that has a pH range that corresponds most closely to the pH of the equivalence point.

Fructose 2,6-bisphosphate

activates PFK-1 which increases glycolysis and inhibits fructose 1,6-bisphosphatase (decreasing gluconeogenesis). Insulin causes an increase in PFK-2 which causes an increase in Fructose 2,6-bisphosphate.

Autonomic Nervous system can never be part of the _________.

central nervous system. Since it is part of the Peripheral nervous System, which is composed of your autonomic and somatic nervous system. Furthermore, the autonomic nervous system is divided into the parasympathetic and sympathetic branches. The passage states that the gustatory-salivary reflex is part of the parasympathetic division of the nervous system. Therefore, the gustatory-salivary reflex is also part of the peripheral and autonomic branches of the nervous system

Equivalent Hydrogens

hydrogens that have the same chemical environment In the splitting pattern formula n+1, n stands for the # of ____ ___ that will split an adjacent signal

Osmotic pressure

if something is more concentrated, it has a higher osmotic pressure since it wants more water to come in an reach equilibrium

Heterozygosity

in a population, the average proportion of genes for which a randomly chosen individual is heterozygous decreased heterozygosity hints are inbreeding increased heterozygosity hints are selective outbreeding

variable expressivity

individuals with the same genotype may have different phenotypes. Expressivity refers to the range of symptoms observed in individuals with a given genetic condition. If the tlr4(d) allele had variable expressivity, the mutation would result in a range of different phenotype characteristics.

Electric Field lines point ________ in negative charges

into Electric field lines point out from positive charges and into negative charges

Cori Cycle

the cycle of lactate to glucose between the muscle and liver

synapsis

the pairing of homologous chromosomes during meiosis In prophase I of meiosis, homologous chromosomes recognize each other and line up side by side during synapsis. Because each homologous chromosome consists of two identical (sister) chromatids, this adjacent chromosomal alignment forms a tetrad (four chromatids total). Tetrads arise when a synaptonemal complex (protein structure) forms between homologous chromosomes and holds them together tightly. The tetrad structure allows physical contact between the paternal and maternal chromosomes at the chiasma, a point where a chromosome segment can break off and rejoin with the opposite homologous chromosome. This exchange of DNA is the hallmark feature of the process called crossing over.

electromotive force

the rate at which energy is drawn from a source that produces a flow of electricity in a circuit

glycogen phosphorylase

the rate-limiting step in glycogenolysis

Transmination

the transfer of an amino group from one amino acid to a keto acid, producing a new nonessential amino acid and a new keto acid Male patients with ME undergo more transamination reactions than female patients because protein catabolism is increased. The transamination reaction produces an α-keto acid from the amino acid by transferring the NH3 group to α-ketoglutarate, forming glutamate. The glutamate produced in this process is then deaminated, releasing ammonia (NH3), which enters the urea cycle. The urea formed in this cycle is released in urine.