Phy/Chem Jack Westin Exam Practice
In a nucleophilic addition reaction, the nucleophile
(Nu) donates its electron pair to the electrophile (E), forming a new covalent bond.
A Detectable Range Measurement Precision
A Detectable Range refers to the range of substrate concentrations where the color change produced is measurable and can be accurately translated back to the actual concentration. It's a limitation of the chromogenic substrate itself. If the substrate concentration is too high, the resulting color might be too intense to measure accurately. Conversely, if the concentration is too low, the color change might be too faint to detect reliably. . Measurement Precision refers to how close repeated measurements of the same sample concentration are to each other. It reflects the random error inherent in any measurement process. . However, regardless of how many times the measurement is taken, if the actual substrate concentration is outside the detectable range, the color change will still be too faint to detect reliably. Increasing the number of measurements won't amplify the signal or make it appear within the detectable range. . Chromogenic substrate gives a detectable signal only within a certain concentration range: Dilute the colored solution up to the linear range of the calibration curve. Optimize Protac concentration to activate Protein C more potently. Change the enzyme concentration to increase the sensitivity of the assay.
Beta - Decay, Beta + decay and electron capture. Radiolabeled mNAs contain Carbon-11 isotopes that undergo positron decay and yield: . Nitrogen-11 Boron-11 Oxygen-15 Beryllium-7
Beta- decay, a neutron turns into proton, the atomic number goes up by one! . Beta + decay; a proton converts into neutron, the atomic number goes down by 1, . Electron capture: a proton converts into neutron, the atomic number goes down by 1 . C-11 has 6 protons and 5 neutrons. During positron decay, one proton gets converted into a neutron. This conversion results in a new nucleus with 5 protons (original 6 - 1 converted proton) and 6 neutrons (original 5 neutrons + 1 gained neutron). The new nucleus perfectly matches the composition of Boron-11 (⁵B₁₁), which has 5 protons and 6 neutrons.
Brønsted-Lowry vs Arrhenius vs Lewis
Brønsted-Lowry: Focuses on proton transfer; important in titrations and buffering systems. . Arrhenius: Emphasizes ion formation in water; useful for simple neutralization reactions. . Lewis: Expands to include electron pair transfer; important for complex reactions, catalysis, and understanding molecular interactions. . Brønsted-Lowry:Buffer system: . CH3COOH+OH−→CH3COO−+H2O . Acid: CH3COOH Base: OH− . Arrhenius:Neutralization: . HCl+NaOH→NaCl+H2O Acid: HCl, Base: NaOH . Lewis:Complexation: Ag++2NH3→[Ag(NH3)2]+ Acid: Ag+ Base: NH3
Capacitor
Capacitor Design: A capacitor consists of two conductive plates separated by an insulating material (dielectric). . Charging Process: When a capacitor is connected to a voltage source, the source pushes positive charges onto one plate and pulls electrons (negative charges) away from the other plate. . Opposing Charges: This creates a situation where one plate has an excess of positive charges and the other has a deficit of electrons, resulting in a negative charge. However, the total amount of positive charge added to one plate is exactly equal to the amount of negative charge removed from the other plate. . Net Charge: Since the charges are equal and opposite, the overall net charge on the capacitor remains zero. There's no net gain or loss of charge, just a redistribution within the system. . Imagine a seesaw with two children of equal weight sitting on opposite ends. The seesaw remains balanced (net force of zero) even though one side is pushed up (positive) and the other down (negative). In the capacitor, the charges act like the children, and the voltage difference between the plates acts like the force on the seesaw.
A sine wave with an amplitude of 2 combines with a sine wave with an amplitude of 1. The waves are otherwise the same, having no phase difference and a period of 2π. If this second wave is phase-shifted by π, by how much does the amplitude of the resultant wave change?
Changes by 2. 3-1 is 2. When two waves combine, they interfere with one another. Constructive interference occurs when the crests of one wave align in space with the crests of another wave, resulting in the sum of their amplitudes. . Destructive interference occurs when the crests of one wave correspond to the troughs of another wave, resulting in an amplitude that is the difference between both amplitudes. More generally, interference is the sum of every amplitude along two waves moving along a common axis. . when they say shifted by pi; it means it swaps to opposite axis, so if it's +1, it's -1.
What are Grignard reagents?
Grignard reagents are strong nucleophiles and bases. Used in organic synthesis to form carbon-carbon bonds. . React with carbonyl compounds to form alcohols after hydrolysis. . Example Reaction: Grignard reagent reacts with a ketone: R2C=O+RMgX→R2C(OH)R'R2C=O+RMgX→R2C(OH)R' . Where: R22C=O: Ketone. R'MgX: Grignard reagent. R22C(OH)R': Tertiary alcohol after hydrolysis. . Summary: Grignard reagents are versatile in organic chemistry for forming new C-C bonds, making them valuable for synthesis.
Explain the key difference between Cytosine, Guanine, Uracil, Thymine and Adenine; in respect to structure.
Guanine modification into inosine involves the removal of the NH2 group from guanine. Guanine has two key functional groups for hydrogen bonding: an amine (NH2) group and a carbonyl (C=O) group. These groups form hydrogen bonds with cytosine during normal base pairing. Removing the NH2 group eliminates one of the key hydrogen bonding sites.
Hydrogen bonds Salt bridges Covalent bonds Disulfide bridges
are a type of weak chemical bond that forms between a hydrogen atom bonded to a highly electronegative atom, like oxygen or nitrogen, and another electronegative atom in a nearby molecule. . are ionic bonds between oppositely charged functional groups within or between different molecules. In proteins, these interactions typically involve charged side chains of amino acids. For instance, between Aspartic acid (-) and Arg (+), . are the strongest type of chemical bond formed by sharing electrons between two atoms. Non-polar: less than 0.5, polar between 0.5 to 1.7. Greater than 1.7 is ionic bonds; electron transfer. . are a specific type of covalent bond between a protein's sulfur atoms of two cysteine residues. .
Anionic proteins are
are negatively charged proteins. The anionic proteins in BGM could attract the positively charged regions shown in Figure 1 of the SNAPP molecules, causing them to clump together. Therefore, removing anionic proteins from the BGM reduces the attraction between the SNAPPs and these proteins, allowing them to remain larger and potentially more effective.
A beta-barrel (β barrel) is a specific type of protein fold characterized by a cylindrical shape formed from
beta sheets. . Hydrogen bonds form between the peptide backbone's carbonyl (C=O) and amino (N-H) groups within each beta-strand. These intra-strand hydrogen bonds create a pleated sheet structure, giving the individual strands their flat, stable conformation. . Additionally, hydrogen bonds can form between adjacent beta strands in the barrel. These inter-strand hydrogen bonds occur between the carbonyl group of one strand and the amino group of another, typically in an antiparallel fashion. These inter-strand bonds link the strands together, contributing significantly to the overall stability and rigidity of the entire beta-barrel structure.
The complete metabolism of a monosaccharide involves its breakdown into
carbon dioxide (CO2) and water (H2O) with oxygen (O2). For each carbon atom in the monosaccharide, the reaction produces an equal mole of carbon dioxide in aerobic respiration. . We are given that 0.1 mol of a monosaccharide is metabolized, producing 0.4 mol CO2 and 0.4 mol H2O. . Since 0.1 mol of the monosaccharide produces 0.4 mol CO2, each monosaccharide molecule (CxHyOz) must have 4 carbon atoms (x = 4) based on the coefficient in the balanced equation.
Aggregation refers to the
clumping together of particles or molecules. In this case, the aggregation of SNAPPs could affect their efficacy in combating bacteria. . This is because removing anionic proteins could reduce aggregation, allowing SNAPPs to remain smaller and more effective. Aggregation likely decreases their efficacy, so reducing factors that promote aggregation would be beneficial. . MBC (Minimum Bactericidal Concentration): The lowest concentration of an antimicrobial that kills a particular bacterium.
The equilibrium constant (Keq) of a reaction is defined as the ratio of the
concentrations of the products to the concentrations of the reactants, each raised to the power of their respective stoichiometric coefficients. . Since H2O is a liquid, its concentration remains constant under normal conditions. Water acts as both solvent and reactant, yet only the minimal reacting portion is considered in the equilibrium expression. Given the very small equilibrium constant (K), the amount of water used is negligible. . Thus, the water concentration remains unchanged from its pure state (55.6 mol L⁻¹). As a result, changes in the concentration of H2O do not affect the Keq value. Therefore, Keq is independent of H2O, and the Keq equation.
Sigma (σ) and pi (π) bonds are the two main types of: A sigma bond and pi bond:
covalent bonds. . A sigma bond is a strong, cylindrically symmetrical covalent bond formed by the head-on overlap of atomic orbitals. The overlap occurs along the internuclear axis, which is the imaginary line connecting the nuclei of the bonded atoms. . A pi bond is a weaker covalent bond formed by the sideways overlap of p orbitals. The overlap occurs above and below the internuclear axis, creating a delocalized electron cloud.
iquid-liquid extraction relies on the
different solubilities of the target substance (solute) in two immiscible liquids (solvents). Immiscible refers to two substances (typically liquids) that do not mix or form a homogeneous mixture when combined. Instead, they separate into distinct layers, with each substance retaining its phase. . One solvent, often water (polar), preferentially dissolves the solute if it's more polar. The other solvent, typically an organic (non-polar), will dissolve the solute if it's more non-polar. By choosing solvents with different polarities and shaking the mixture, the solute partitions between the two phases are based on their relative solubility in each. . A classic example of immiscible liquids is oil and water. When mixed, oil and water do not form a uniform phase; instead, the oil will float on top of the water, forming two distinct layers. This immiscibility is due to the differences in polarity and intermolecular forces between oil molecules (nonpolar) and water (polar) molecules. . In conclusion, the key to separation in liquid-liquid extraction is exploiting the differences in solubility of the target substance and other components of the mixture in the chosen immiscible solvents.
An electric field is a physical field produced by
electric charges that exert a force on other charged particles within the field. . The force can either be attractive or repulsive. It has units of newtons per coulomb (N/C) or volts per meter (V/m). . For a uniform electric field between two parallel plates, the electric field (E) anywhere within that field is equal to the voltage across the plates (ΔV) divided by the distance between the plates (d). . E = ΔV/d
Isoelectronic ions share the same number of
electrons, regardless of their atomic number (number of protons).
Constitutional (or structural) isomers,
have the same molecular formula but display different connectivity of their atoms. . Knowing this, we can simply count the number of different atoms of the main compound, and see which answer choice has the same molecular formula.
Proteolytic cleavage involves
hydrolysis, where water acts as a nucleophile attacking the carbonyl carbon of the peptide bond
tautomerization; enol and keto forms
is a chemical reaction where a molecule exists in equilibrium between two isomeric forms that differ only in the position of a hydrogen atom and a double bond. . The rearrangement of bonds within a compound, usually by moving a hydrogen and forming a double bond . involves rearranging a double bond and a hydrogen atom . Keto Form: This is the form where a carbonyl group (C=O) is present. In keto tautomers, the carbonyl group is typically more stable due to the double bond's strong polar character and resonance stabilization. Ketone . Enol Form: The enol form features a double bond (C=C) adjacent to an alcohol group (OH). This form is generally less stable than the keto form because it lacks the extensive resonance stabilization that the keto form enjoys. However, in some chemical environments or under certain conditions, the enol form can be more stable or significantly populated. OH-C=C-Ch3,
Kirchoff's current law states that
the sum of the currents entering a junction in a circuit equals the sum of the currents exiting that junction. . Notice that each parallel branch within the circuit eventually travels through the capacitor. . At the capacitor, the total current must equal the sum of the currents in each circuit branch. . Given that the current due to the flow of sodium ions is in the direction opposite to the other currents, its value must be subtracted from the sum of the currents due to the flow of chloride and potassium.
Power is the rate at which work is completed, or energy is consumed. Accordingly, energy is equivalent
to power times time. . P = E/T . Whenever power appears in a question or passage, remember that you may need to manipulate time to find energy instead of power. . Energy unit Joules,
Which of the following compounds has a seesaw molecular geometry? . I - SF4 II - (ClF4)+ III - (ClF4)- . A. I only . B. II only . C. I and II only . D. I and III only .
A seesaw molecular geometry arises when a central atom forms four bonds with one lone pair of electrons. This creates a structure resembling a playground seesaw, with the lone pair occupying an equatorial position for minimal repulsion with the bonding electrons. . SF4 has a central Sulfur atom (S) bonded to four Fluorine (F) atoms with one lone pair of Sulfur. . ClF4+ has a chlorine (Cl) atom; the central atom has four fluorine (F) atoms bonded to it and a positive charge. The positive charge signifies the loss of one electron, essentially creating a situation similar to having a lone pair (acting like an empty orbital). . ClF4 has a chlorine atom, which gains one electron (negative charge); it fills an empty orbit and no longer has a lone pair. With four bonding pairs of electrons around the Chlorine, and two lone pairs bonded to Cl, the expected geometry becomes a tetrahedral shape, not a seesaw. . If the extra electron is used in bonding (or to fill an empty d orbital, making chlorine's valence shell effectively utilize more electrons), and assuming there are no lone pairs on chlorine: . The molecular geometry would then be determined purely by the four bonding pairs from the four fluorine atoms.
How to know a bacterial species is most effective in accordance to concentration? Let's see various solutions of different bacteria was added.
A. baumannii had the least minimum bacterial concentration, meaning that A. baumannii required the least concentration of Magainin II to cause 99.9% cell death. Therefore, A. baumannii was most affected by Magainin II.
ATP synthesis requires the energy produced by ETC to proceed at any temperature. Which of the following would best explain this phenomenon?
ATP is less disordered than ADP. . For the reaction to be nonspontaneous, - TdS must be positive, implying that dS (entropy change) must be negative. Since dS = S Product (ATP) - S reactant (ADP + Pi), we can infer that the S reactant is larger than the S product, meaning that dS of ADP is larger than dS of ATP. . In other words, ADP is more disordered than ATP. In other words, adding a phosphate group to ADP (to form ATP) decreases disorder and increases order. Therefore, the entropy change (dS) is negative.
An initially uncharged solid conductor is placed between the plates of the cell membrane parallel plate capacitor. The electric field inside the solid conductor will be: . A. zero, because excess charge within the conductor moves to the external surface. . B. zero, because charges within a conductor are fixed to their current position. . C. equal to the electric field of the capacitor, because excess charge within the conductor moves to the external surface. . D. equal to the electric field of the capacitor, because charges within a conductor are fixed to their current position.
At equilibrium, the electric field is generally zero at any point within a conducting material. Resistive materials (generally non-metals) contain electrons that are mostly fixed in place, whereas conductive materials contain both fixed and free electrons. In a conductive material, the core electrons of atoms are typically fixed in place, while the outer electrons are typically free to move. . In conductive materials (e.g., metals such as copper), free electrons react directly to the forces exerted by external electric fields. In an initially uncharged solid, free electrons will be distributed evenly around the surface of the solid because they are repelled from one another, according to Coulomb's law. Suppose an electric field is applied to a solid after establishing this static equilibrium. In that case, the free electrons will rearrange themselves on the conductor surface in the orientation needed to produce an electric field of zero within the solid. . (Choice B) Conductive materials contain both fixed and free electrons. . (Choice C) While excess charge accumulates on the surface, the electric field inside the conductor itself becomes zero. . (Choice D) Similar to B, conductive materials contain both fixed and free electrons.
Active site interactions
Considering the versatility, specificity, and reversibility of hydrogen bonds, they are likely the more prominent interaction for substrate binding and catalysis within the active site. . Covalent bonds wouldn't be ideal for most interactions in the enzyme's active site. While some enzymes utilize transient covalent bonds during catalysis, PK doesn't form them in its phosphate transfer reaction. The active site needs to bind, release, and react with substrates repeatedly, and breaking and reforming covalent bonds wouldn't be efficient for this process. . Disulfide bridges are more used to stabilize protein structures, particularly between distant parts of the polypeptide chain. They are less common within active sites, as they wouldn't directly participate in catalysis. The Beta barrel structure might contain disulfide bridges to maintain its overall fold, but these wouldn't be the most prominent interactions in the PK active site.
Electronic geometry vs molecular geometry (shape)
EG: bonded and lone pairs treated the same, MShape: lone pairs take up less space than a bond to another atom. Electronic geometry describes the spatial arrangement of all pairs of electrons around the central atom, both bonding and lone pairs . Molecular geometry describes the spatial arrangement of only the bonding pairs of electrons ex. NH3 . Electronic G = tetrahedral Molecular S = trigonal pyramidal
When transition metals form ions, they generally lose electrons from the s orbital before the d orbital, contrary to the order of filling.
Fe²⁺ (Iron(II)): [Ar] 3d⁶ (loses two electrons from the 4s orbital) . Mn²⁺ (Manganese(II)): [Ar] 3d⁵ (Manganese in its neutral state is [Ar] 4s² 3d⁵; loses the 4s electrons) . Co²⁺ (Cobalt(II)): [Ar] 3d⁷ (Cobalt in its neutral state is [Ar] 4s² 3d⁷; loses the 4s electrons) . Cr²⁺ (Chromium(II)): [Ar] 3d⁴ (Chromium in its neutral state is [Ar] 4s¹ 3d⁵; it loses one 4s and one 3d electron) . Special Cases Chromium (Cr) and Copper (Cu) have exceptions in their electron configurations due to electron-electron repulsions and exchange energyvoptimization: . Chromium: [Ar] 4s¹ 3d⁵ (instead of [Ar] 4s² 3d⁴) . Copper: [Ar] 4s¹ 3d¹⁰ (instead of [Ar] 4s² 3d⁹)
The Grignard reagent is an organometallic compound with the general formula RMgX, where R is an organic group, typically an alkyl (like isobutyl) or aryl (like benzyl) group, Mg is magnesium, and X is a halogen (like chlorine or bromine).
Isobutyl is a branched alkyl group with the formula (CH3)2CHCH2-. It comprises a three-carbon chain with a methyl group (CH3) attached to the second carbon. . Benzyl is an aryl group derived from benzene. It consists of a phenyl ring (C6H5) attached to a methylene group (CH2-). So, the structure looks like C6H5-CH2-. . Acyl is a functional group consisting of a carbonyl group (C=O) bonded to another group (R). The "R" can be various things like an alkyl group (e.g., CH3-C=O, acetyl group), an aryl group (e.g., C6H5-C=O, benzoyl group), or even a hydrogen atom (H-C=O, formyl group). Essentially, it's a carbonyl group acting as a bridge to another atom or group. . Halide is an atom from the halogen group (Group 17) of the periodic table. The most common halides encountered in organic chemistry are chlorine (Cl), bromine (Br), iodine (I), and fluorine (F). They can form single bonds with carbon atoms in organic molecules.
The 3d valence electron configuration below would belong to which transition metal?
M(II) indicates a loss of 2 electrons to form a positively charged ion. For Fe, Mn, Co, and Cr (first-row transition metals), losing electrons follows this order: . Lose 2 electrons from the 4s orbital (higher energy level). . The remaining electrons occupy the 3d subshell. . Iron (Fe) has an atomic number of 26. In its neutral state, it has 26 electrons. Losing 2 electrons (M(II)) leaves 24 electrons. The configuration becomes [Ar]3d⁶ (after losing 2 from 4s). . Manganese (Mn) has 25 electrons. Losing 2 leaves 23 electrons, resulting in [Ar]3d⁵ (one less than Fe). . Cobalt (Co) has 27 electrons. Losing 2 gives [Ar]3d⁷ (one more than Fe). . Chromium (Cr) has 24 electrons. Losing 2 leaves 22 electrons, resulting in [Ar]3d⁴ (two less than Fe). . Therefore, only Fe(II) has the specific 3d⁶ configuration due to the number of electrons it possesses after losing two from the 4s orbital.
Vitamins serve as coenzymes in many enzyme-catalyzed reactions. Which of the following enzymatic reactions most likely utilizes niacin (vitamin B3) as a coenzyme? . A. Lactate dehydrogenase . B. Pyruvate decarboxylase . C. Enolase . D. Phosphofructokinase .
Niacin functions as a precursor for the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These coenzymes participate in numerous oxidation-reduction (redox) reactions within the cell. . Lactate Dehydrogenase (LDH) catalyzes the conversion of pyruvate (a three-carbon molecule) into lactate (a three-carbon molecule) during anaerobic respiration. This reaction involves the transfer of a hydrogen atom from pyruvate to NAD, reducing NAD to NADH. . LDH converts pyruvate to lactate utilizing NAD as a coenzyme, accepting a hydrogen atom and transforming it into NADH. Niacin serves as a precursor for NAD synthesis, making it directly relevant to LDH function. . Pyruvate decarboxylase converts pyruvate to acetaldehyde and carbon dioxide, not involving NAD as a coenzyme. Plays a key role in alcoholic fermentation in yeast and some bacteria. Part of the fermentation pathway, allowing organisms to regenerate NAD⁺ under anaerobic conditions. Not found in humans; humans convert pyruvate to acetyl-CoA instead. . Bicarbonate+pyruvate = oxaloacetate by pyruvate carboxylase, uses biotin and ATP, . Enolase catalyzes the conversion of phosphoenolpyruvate (PEP) to phosphoglycerate (PGA) in glycolysis. It doesn't utilize NAD or NADP. . Phosphofructokinase regulates a step in glycolysis by phosphorylating fructose-6-phosphate. It doesn't involve NAD or NADP; it uses ATP
Which of the following occurs during the proteolytic cleavage of S2366? "presence of a colorless chromogenic substrate, S2366"
Nitrogen of 4-nitroaniline acts as a nucleophile and attacks arginine. . The second paragraph of the passage describes S2366 as "a colorless chromogenic substrate." This means it has two key components: a peptide sequence that can be cleaved by the enzyme (proteolytic cleavage) and a chromophore (4-nitroaniline) that generates a colored product upon cleavage. Proteolytic cleavage involves hydrolysis, which is a reaction where a water molecule breaks a peptide bond between two amino acids. . The actual mechanism of proteolytic cleavage often involves a nucleophilic attack by a side chain within the enzyme on the carbonyl carbon of the scissile bond (the bond being broken). This initiates a series of reactions leading to hydrolysis.
Nucleophiles vs. Electrophiles
Nucleophiles: Donate electrons, attack electrophiles (e.g., OH−OH−, NH3NH3). Br-, Cl-, I-, . Electrophiles: Accept electrons, attacked by nucleophiles (e.g., H+H+, R−XR−X).
Formula for power (watts)
P = W/t P = (VI) P = (I^2)(R)
electron-donating group . Nitrogen involved in hydrogen bonding in uracil has a pKa of 9.45. Which of the following can be inferred regarding its pKa in T1?
The methyl group in thymine is an electron-donating group. This means it pushes electron density towards the nitrogen atom in the ring structure. Since the methyl group donates electrons, the nitrogen atom is slightly more negative. As a result, the nitrogen atom holds onto the proton a little more tightly, making it a weaker acid. . Therefore, the pKa of the nitrogen atom in thymine (T1) will be higher than the pKa of the nitrogen atom in uracil. This translates to a smaller numerical value for the pKa in T1.
Further increasing the voltage across the cell membrane (V0) will have what effect on the circuit shown by Figure 1? add the figure on desktop. . A. The capacitance of the capacitor will increase. . B. The number of charges stored by the capacitor will decrease. . C. The capacitor will store more energy. . D. The net charge of the capacitor will increase. .
This question asks how increasing the voltage across the cell membrane (V0) in the circuit model will affect the capacitor's behavior. . The energy (U) stored by a capacitor of capacitance C increases exponentially as the voltage (V) across that capacitor increases. This is given mathematically by the equation U = ½ CV2. In other words, a capacitor experiencing a greater voltage drop will store more charges and thus more energy. . (Choice A) The physical properties of the plate determine capacitance: namely, how large the plates are (more room for charge to spread out), how far apart the plates are (how well positive charge on one plate can attract negative charge on the other plate), and the presence of a dielectric, which reduces the effective electric field experienced by the plate at a given applied voltage and allowing for greater charge storage. . (Choice B) The number of charges Q stored on a capacitor is determined by the Q = CV, where C is capacitance, and V is voltage. Increasing the voltage will increase the number of charges stored by the capacitor. . (Choice D) Whether charged or uncharged, the net charge of a capacitor is zero because each plate stores an equal amount of opposing charges. The positive charges stored on one plate of the capacitor cancel out the negative charges on the other plate. . A capacitor functions by storing equal and opposite charges on its two plates
Which element would have the largest radius when forming its most stable ion? . Ca . S . Cl . K .
This question asks which element forms the biggest ion when it gains or loses electrons to become stable. . We can infer the number of electrons of each element from the periodic table through the atomic number, which represents the number of protons in a neutral atom. In neutral atoms, the number of electrons equals the number of protons. The group number signifies the number of valence electrons in the outermost shell. Since atoms strive for a full outer electron shell (usually 8 electrons) to be stable, we can deduce the number of electrons each element would gain or lose to reach its most stable form. . Calcium has 20 electrons and loses two electrons (Ca²⁺) to reach 18 electrons. Sulfur has 16 electrons and gains two electrons (S²⁻) to achieve 18 electrons. Chlorine has 17 electrons and gains one electron (Cl⁻) to reach 18 electrons. Potassium has 19 electrons and loses one electron (K⁺) to attain 18 electrons. We can notice that all the ions above have the same number of electrons (18). Isoelectronic ions. , Protons in the nucleus have a positive charge that attracts the negatively charged electrons. The more protons an atom has (higher atomic number), the stronger the electrostatic attraction between the nucleus and the electrons. This stronger attraction pulls the electrons closer to the nucleus, leading to a smaller atomic radius. Therefore, in isoelectronic species, the one with the largest atomic number (most protons) will indeed have the smallest radius. . Knowing that calcium's atomic number is 20, sulfur's is 16, chlorine's is 17 and potassium's is 19, we can infer that the element with the smallest atomic number would have the largest radius. In this case, sulfur has the largest radius.
obtaining the FT-IR spectra beforehand, the researchers can identify the presence and track the changes in the
To be able to differentiate the substrate and product . To convert the wavenumber to wavelength in meters. This is done using the equation Wavelength (λ) = 1 / Wavenumber (cm-1) and multiplying it by 10-2 to convert it into meters. . λ = (1 / 1560) x 10-2 = 6.41 x 10-6 m
Concentration is the amount of a substance (solute) present in a certain volume of solution (solvent).
Whether you have 100 ml, 1 liter, or any other volume of blood, as long as the concentration remains the same (70 nM), the p[PC] value remains the same.
Hydrostatic pressure refers to the pressure exerted by
a fluid at rest due to gravity. . In Heron's fountain, the pressure in container 3 is caused by the weight of the water column above it in container 2. The fluids in containers 1 and 3 are regarded as one water column as they are interconnected. . Ha represents the height difference between the water surfaces in containers 2 and 3. A larger Ha signifies a taller water column in container 2. . According to the principle of hydrostatic pressure, P = ⍴gd, where ⍴ is the density of the fluid, g is a constant, and d is the depth below the surface of the fluid. A taller water column exerts a greater force due to gravity, leading to higher pressure at the bottom. . Because of this, raising container 1 above the other container will raise the fluid's surface height and consequently increase d in ⍴gd, which will raise the hydrostatic pressure that the fluid in container 3 experiences. This distance and hydrostatic pressure will grow with an increase in the terms Ha or Hw.
A fluorophore is a molecule that can
absorb light at a specific wavelength and then re-emit light at a different, usually longer, wavelength. This process is called fluorescence. . Fluorophores typically have a structure with alternating single and double bonds between carbon atoms. This creates a "conjugated system" that allows electrons to move freely across the molecule. . This free movement of electrons is essential for efficient light absorption and emission. Many fluorophores contain aromatic rings because they contribute to the conjugated system and enhance light absorption properties. . Therefore, we need to look for the molecule with the highest conjugation.
The Acid Dissociation Constant (Ka)
is a constant that represents how much an acid dissociates in water to release a proton (H+). . A higher Ka value indicates a stronger acid that dissociates more readily. . The Negative Logarithm (base-10) is a mathematical function used to express numbers as exponents. Taking the negative of the logarithm flips the relationship between the original value and the exponent. . So, pKa gives you a more manageable way to work with acid strength. A lower pKa value corresponds to a higher Ka value, meaning the acid dissociates more easily and is, therefore, stronger. A higher pKa value indicates a lower Ka value, signifying a weaker acid that dissociates less in water.
A blank solution is a solution that contains
no reactants and is used to calibrate the experiment. . If the absorbance of the blank solution was not nearly zero, this would mean that there might be some interference or contribution from the solvent itself. . The purpose of the blank solution is to measure the background absorbance of the solvent. . In this case, the solvent used for acetamide contains a carboxyl group, which could potentially absorb at or near the same wavelength as the product (acetic acid).
Cofactors are
non-protein molecules that aid enzymes in their catalytic activity. In the case of T7 RNAP, Mg2+ stabilizes the binding of the triphosphate groups (building blocks of RNA) to the enzyme. It facilitates the phosphodiester bond formation between the RNA nucleotides during transcription. . Therefore, Mg2+ (iron ion) is the most likely candidate to further enhance T7 RNAP's transcription capacity. . EDTA chelates metal ions like Mg2+. If added, it would remove existing Mg2+ from the reaction mixture, potentially hindering transcription instead of enhancing it.
Protein-substrate affinity refers to the strength of the interaction between the
protein (enzyme) and its substrate. A higher affinity signifies a tighter binding between the two, allowing for more efficient catalysis (substrate conversion to product). Low Km: high affinity, high Km, low affinity . Mutations can alter the protein's structure and chemical properties, potentially affecting its ability to bind to the substrate effectively. The impact of a mutation depends on its location within the protein structure.
What is the approximate reaction rate when D35A variant is incubated with 25 nm chromogenic substrate in nm.min-1?
reaction rate is Vo, to find Vo you gotta use the MMequation; which is Vo = Vmax [S]/Km+[S], . Km is half of Vmax, if it's given on table or chart then that's good, if not then half of Vmax is Km in order to find the reaction rate,
The buffering capacity of a buffer solution refers to its ability to
resist changes in pH upon the addition of acids or bases. . Enzymes often have a specific pH range where they function optimally. Fluctuations in pH can significantly affect enzyme activity. Buffers maintain a stable pH environment to optimize enzyme activity. . "Each APC variant (2 nm) was incubated with multiple concentrations of S-2366 in 20 mm 1 ml Tris/HCl (pKa=8.1)." This means that the original experiment used a Tris/HCl buffer with a pKa of 8.1. This buffer effectively resists pH changes around this pKa value. . The proposed experiment uses a MOPS buffer with a pKa of 7.15, which is slightly lower than Tris/HCl. . Both MOPS and Tris/HCl are commonly used biological buffers. While their pKa values differ slightly, they both have sufficient buffering capacity around physiological pH (pH 7.4). As long as the MOPS buffer concentration is chosen appropriately to maintain the desired pH range (around 7.4), it should be able to buffer the solution similar to Tris/HCl adequately. The enzyme activity likely wouldn't be significantly affected by this small change in pKa. . Therefore, the proposed experiment would work because the buffering capacity of MOPS and Tris/HCl coincide. . MOPS: Better suited for slightly acidic to neutral pH applications, making it particularly effective just below physiological pH. . Tris: More effective slightly above physiological pH, due to its higher pKa, making it suitable for experiments that might naturally drift towards more basic conditions.
