FL3 LLJ

Periodic Trends

property of the elements that can be predicted from the arrangement of the periodic table

ion exchange chromatography

-stationary phase is made of either negatively or positively charged beads (attract & bind compounds that have opposite charge) -salt is added to elute proteins stuck to column

Thin Layer Chromatography (TLC)

A type of chromatography that uses silica gel or alumina on a card as the medium for the stationary phase

Gas chromatography (GC)

A type of chromatography used to separate vaporizable compounds; the stationary phase is a crushed metal or polymer and the mobile phase is a nonreactive gas.

Imine

A double bond between a carbon and a nitrogen

column chromatography

Chromatography in which the substances to be separated are introduced onto the top of a column packed with an adsorbent (as silica gel or alumina), pass through the column at different rates that depend on the affinity of each substance for the adsorbent and for the solvent or solvent mixture, and are usually collected in solution as they pass from the column at different times

Q2 Physics Comprehension/application

During inspiration, contraction of the diaphragm and external intercostal muscles leads to expansion of the thoracic cavity and a decrease in intrapleural pressure. This negative pressure, relative to atmospheric pressure at the entry of the upper airway, generates airflow through the respiratory tree and to its terminal extension—the alveoli. The elastic recoil force of the airway and the surface tension of the water lining the airway oppose expansion of the alveoli due to the influx of atmospheric pressure. Pulmonary surfactant adsorbed to the air-water-alveoli interface, reducing surface tension and the total force resisting expansion. This increases pulmonary compliance—a measure of lung volume change at a given pressure of inspired air—and decreases the work required to expand the lungs at a given atmospheric pressure.

Question 25 What is the exclusion limit of the SEC column used to create the calibration curve shown in Figure 2?

Figure 2 indicates that the exclusion limit of the SEC column is at log (MW) = 6. If true, the molecular weight can be found by taking the inverse log of 6, 106 D = 1000 kD.

Question 14 I knew this one, but couldn't remember the kinematic equations it would of been easy points

However, pay close attention here as they are round the square root of 25 to 5 - since they are "estimating" - important to notice. Since the crate is initially at rest, the Vi = 0 m/s, the acceleration a = 2.0 m/s2, and the displacement = 6 m. The appropriate kinematic equation is vf2 = vi2 + 2ad. Substituting the variables gives: vf2 = 02 + 2(2)(6) vf2 = 24 vf = ~5 m/s

Q3 Gen Chem This is kind of hard to understand, like where doe they get that Delta H and Delta G should have opposite signs?

Let's work out this problem in the following steps: * For a process to be spontaneous, the Gibbs free energy change of the reaction should be negative, i.e., ∆G < 0. Since ∆G = ∆H - T∆S, for a spontaneous process, ∆H - T∆S < 0. * Since the given interaction is spontaneous, ∆G < 0. Also, it is given that ∆H and ∆G have opposite signs. This means that ∆H > 0 for the process. * Now, the left side of the equation ∆G = ∆H - T∆S, i.e., ∆G is negative and ∆H is positive, so the term - T∆S must be negative (or T∆S must be positive) only then the whole ∆H - T∆S term can be negative. Since temperature is also positive, a positive T∆S means a positive ∆S. Therefore, the true statements are: I. ∆H > ∆G (because ∆H is positive and ∆G is negative.) II. 0 < ∆S

Question 21 Gen Chem content

Longer-wavelength light corresponds to lower-energy light. If the energy required to excite electrons present in the CPV fluorophore exceeded that which is emitted when the electrons relaxed, then energy must have been lost during the return to the ground state following excitation separately from the energy of the emission. Only choice B, which states that there is a loss of vibrational energy during the transition, provides a possible explanation consistent with this requirement

On the MCAT, there are several ways by which you can estimate the entropy of a system:

Reactions that increase the number of moles of substances in the system (or produce more gas particles) typically increase the entropy of the system. Entropy generally increases when a solid or liquid is dissolved in a solvent. Entropy increases when the solubility of a gas decreases and it escapes from a solvent. Entropy generally increases as molecular complexity increases (KOH vs. Ca(OH)2) due to the increased movement of electrons. Adapted from Blueprint MCAT Chemistry and Organic Chemistry Ch. 4, where more information on this topic can be found.

C/P

Review

Q1 - General Chemistry This is an easy question, that had I compared the correct info then I could have gotten it correctly - what it came down to was to look at the top number where there were no carbs, and see what happened when there were carbs added, and obviously they all decreased across the board

Reviewed

reactions, which - contrary to what you may expect - take place in two distinct steps.

SN1 Let's begin with SN1 reactions, which - contrary to what you may expect - take place in two distinct steps. In the first step, the leaving group dissociates from the target substrate molecule, leaving behind an unstable carbocation. Since the product is so unstable, this step is slow and thus rate-determining. (This is where the "1" in SN1 comes from; it denotes the fact that only one molecule - the substrate - is involved in this first step.) In the second step, the nucleophile attacks the carbocation to form a more stable product molecule. Since the carbocation intermediate is planar, or lacks stereochemistry, SN1 reactions with chiral substrates produce an even mix of enantiomers termed a racemic mixture. Carbocation stability is the primary factor in SN1 reaction rate. For this reason, SN1 reactions favor tertiary substrates (as tertiary is the most stable carbocation structure) and occur to a negligible extent with primary substrates.

reactions are even simpler, as they take place in a single step.

SN2 SN2 reactions are even simpler, as they take place in a single step. In this mechanism, the strong nucleophile displaces the leaving group by attacking from the rear, often described as a "backside attack." This reverse attack inverts the relative stereochemistry of the molecule. (The absolute stereochemistry - namely R vs. S configuration - is inverted as well, provided that the priority of the nucleophile matches the priority of the leaving group, which is nearly always the case.) For a brief instant before the leaving group fully dissociates, the central carbon of the substrate is at least partially bound to five substituents. This high-energy state is known as a pentavalent transition state. With everything happening at once, steric hindrance is a major limiting factor of SN2 reactions, with primary substrates reacting the most rapidly.

ionization energy

The amount of energy required to remove an electron from an atom

Q5 Gen chem - see pic content

The azimuthal, or angular momentum, quantum number (l) describes the subshell of the principal quantum number in which the electron is found, with values ranging from 0 to n - 1, where l = 0 is the s subshell, l = 1 is the p subshell, l = 2 is the d subshell, and l = 3 is the f subshell.

. The slope of a graph of velocity vs. time corresponds to

acceleration

To make sense of this statement, let's review the steps involved in cancer development, or oncogenesis.

The term "tumor" describes any abnormal proliferation of cells. Benign tumors remain localized, whereas malignant tumors (which are what the term "cancer" properly refers to) can invade other organs and tissues in the body in a process called metastasis. The first step in oncogenesis, tumor initiation, involves changes that allow a single cell to proliferate abnormally. This means that the cell must develop the ability to bypass regulatory steps of the cell cycle that normally help to limit mitotic proliferation. Tumor progression occurs as a cell develops the ability to proliferate even more aggressively, such that its descendants are selected for and come to predominate the growing tumor. In addition, malignant cells often undergo mutations that promote their own growth and the development of blood vessels to feed them (angiogenesis). Oncogenesis is most often associated with mutations that occur by random chance (and elude the normal DNA repair machinery in the cell) or as a result of mutagenic compounds known as mutagens or carcinogens. (Examples of mutagens include ultraviolet light and certain chemicals, such as reactive oxygen species.) These mutations alter the functionality of crucial genes in the cell. However, oncogenesis is also associated with dysregulation of gene expression, as the abnormally elevated expression of genes involved in growth and proliferation can help contribute to the development of a tumor. The genes involved in oncogenesis can be divided into two groups: oncogenes and tumor suppressor genes. The basic difference between them is that oncogenes function to promote abnormal growth and proliferation, leading to cancer, while tumor suppressor genes function to prevent tumorigenic properties. Oncogenes can arise from the mutation of other genes, termed proto-oncogenes. If not mutated, proto-oncogenes do not promote cancer, but certain mutations or inappropriately elevated gene expression can effectively turn them into oncogenes.

Q6 - Physics content

The visible spectrum contains electromagnetic signals with wavelengths ranging from 400 nm to 700 nm. The wavelength of light emitted during a particular electronic transition is determined by the energy difference (∆E) between the final and initial energy levels. The energy of each level can be determined using Equation 1 and the principal quantum number in question. For light to be emitted at all, an electron must travel from a higher to a lower level, a process that releases energy.

When an atom does not gain or lose any protons, and only the neutron count is changed, a new_______is formed.

There are a number of ways that this can happen, and when it does, the atom is forever changed. There is no going back - the process is irreversible. There are four primary types of decay: alpha decay, beta decay (β+ and β−), gamma decay, and electron capture. In alpha decay, an alpha particle, containing two protons, two neutrons, and a +2 charge, is emitted. In beta-minus decay, a neutron is converted into a proton in the nucleus, and a β− particle (an electron) is ejected to maintain charge balance. In beta-plus decay, a proton is converted into a neutron, and a β+ particle (a positron) is emitted to preserve charge. Gamma decay involves the emission of a gamma ray, which is a high-energy photon, from an excited nucleus. Finally, in electron capture, a nucleus "grabs" an electron, which changes a proton into a neutron.

Question 10 A hospital purchases brand-new GKS-Co and GKS-X machines. Five years after installation, what is the expected ratio of the total atomic mass of material in the Co machine to that in the X machine, assuming both machines start with the same mass of radioactive material?

When reading questions, be careful not to read too quickly. In this case, fast but inefficient reading will lead us to assume that it is asking about the percentage of a certain isotope that is left after radioactive decay. However, the question is asking about atomic mass. While β-decay does cause a nuclear transmutation of protons to neutrons (β-plus) or neutrons to protons (β-minus), the atomic mass lost in these processes is negligible. This means that whether after one (Co) or five (X) half-lives, the atomic mass will be the same in both samples.

beta particle

a high-speed electron or positron emitted in the decay of a radioactive isotope

Positron

a particle with the mass of an electron but a positive charge

gel chromatography

differential migration of biomolecules in a gel based on their size and/or charge

Normality equation

equivalents/L

paper chromatography

method of separating a mixture of different colours. The liquid soaks through the paper and carries the mixture with it. Some substances are carried faster than others so the substances are separated along the paper

Molality

moles of solute/kg of solvent

Question 23 Gen Chem - comprehension but content also because I had no idea that cells change pH

pH may change over time in the same cell. If the biosensor is pH-sensitive, then changes in cellular pH over the course of a measurement could confuse changes in the energy balance of the cell, as reflected by the cell's ATP-to-ADP ratio.

size exchange chromatography

relies on porous beads; larger molecules elute first because they are not trapped in small pores

Question 19 Ochem - This would of been an easy point had I slowed down and assigned the proper value to what it was asking

slow down, focus and apply the information give - I think over time my comprehension should improve some what According to the passage, the spectral ratio of the peaks of the excitation spectrum of a Y32-expressing cell directly reflects its cellular ATP-to-ADP ratio. The peak absorbance of the B-state, which is favored in the Mg2+-ATP-bound conformation, is near 500 nm, while the peak absorbance of the A-state, which favors the ADP-bound conformation, is near 420 nm. Thus, the ratio of the fluorescence emission intensities when Y32 is excited at 500 nm versus when it is excited at 420 nm serves as a direct indicator of the cellular ATP-to-ADP ratio.

High Pressure Liquid Chromatography (HPLC)

the column and solution use an apparatus that puts the system under high pressure

affinity chromatography

uses a bound receptor or ligand and an eluent with free ligand or a receptor for the protein of interest

. The slope of a graph of displacement vs. time corresponds to

velocity

enthalpy change symbol

ΔH

Gibbs free energy equation

∆G = ∆H - T∆S

Hess's law:

∆Hrxn = Σ∆Hproducts - Σ∆Hreactants.

Entropy symbol

∆S