blueprint exam chemistry

The association constant, Ka, of Epithelial Growth Factor Receptor (EGFR) binding to Epithelial Growth Factor (EGF) is 5.61 x 106. What is Keq for the reaction EGFR-EGF → EGFR + EGF? A. 1.78 x 10^-7 B. 8.42 x 10^-6 C. 5.61 x 10^6 D. 1.12 x 10^7

1.78 x 10^-7 We are asked for the equilibrium constant for the dissociation reaction, which is 1/Ka. The association constant is the same as the equilibrium constant, so for dissociation, Keq = 1 / (5.61 x 106) = 1.78 x 10-7

What is a chiral carbon

A chiral carbon must be sp3 hybridized and attached to four different substituents.

what is the effect of a forced change in body temperature, give an example

A forced change in body temperature results when an environmental stress is sufficient to overcome the thermoregulatory systems of the body. For example, prolonged time in cold water results in forced hypothermia, while prolonged time in hot water results in hyperthermia. A regulated change in body temperature occurs when the hypothalamic "temperature setting" is shifted, as when a fever results from infection by a pathogen.

What is the electron transport chain

A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP. In the electron transport chain, electrons are passed from species with a less positive reduction potential to those with a more positive reduction potential.

Which of the following correctly describes the orbital hybridization of XeF4 and NH3, respectively? A. sp3d2, sp3 B. sp3, sp3 C. sp3, sp2 D. sp3d2, sp2

A) One way to determine the orbital hybridization around the central atom is to count the number of bonds and lone pairs. For example, the central nitrogen atom in ammonia has three bonds and one lone pair, for a total of four groups. Thus, ammonia is sp3 hybridized, eliminating choices C and D. Next, xenon is a noble gas in period 5. As such, XeF4 has a total of eight electrons in its s and p orbitals. Four of the electrons form bonds to fluorine, leaving two lone pairs around the central xenon atom. Six electron groups produce sp3d2 hybridization.

The transcription factor AP-1 is a heterodimer consisting of c-jun and c-fos. C-jun and c-fos are soluble proteins that can be localized to either the cytosol or nucleus of a cell. C-jun and c-fos dimerize through a leucine zipper motif. In this motif, every 7 amino acid residues, or two full turns of an alpha helix, are leucine residues. Leucine and other amino acids on one face of the helix come together to form an opposite alpha helix that has a similar arrangement of leucine and other amino acids. Which solvent would be LEAST favorable for c-fos/c-jun dimerization? A. Hexane B. Ethanol C. Water D. Phosphate-buffered saline

A. Leucine residues on different parts of a molecule form a dimer. Leucine is hydrophobic, since its side chain contains only carbon and hydrogen. If the solvent were also hydrophobic, the face of a leucine zipper could interact just as favorably with the solvent as with the opposite alpha helix. Some leucine residues would likely interact only with the solvent, preventing formation of the dimer entirely. Because hexane is a nonpolar hydrocarbon, it would be expected to interfere with dimerization.

The association constant, Ka, of Epithelial Growth Factor Receptor (EGFR) binding to Epithelial Growth Factor (EGF) is 5.61 x 106. What is Keq for the reaction EGFR-EGF → EGFR + EGF? A. 1.78 x 10-7 B. 8.42 x 10-6 C. 5.61 x 106 D. 1.12 x 107

A. We are asked for the equilibrium constant for the dissociation reaction, which is 1/Ka. The association constant is the same as the equilibrium constant, so for dissociation, Keq = 1 / (5.61 x 106) = 1.78 x 10-7.

What are purines?

Adenine and Guanine

What is the role of Aldosterone and cortisol

Aldosterone, regulates fluid and salt levels, and cortisol affects blood glucose levels as part of the long-term stress response. These three functions of steroid hormones are sometimes known as the three "S's": sex, salt, and sugar.

Where are all steroid hormones derived from

All steroid hormones are derived from cholesterol, which means they share a four-ring lipid structure and are permeable to the cell membrane. Since steroid hormones are hydrophobic, they are typically transported throughout the body using plasma proteins in the blood. Steroid hormones are synthesized by the adrenal cortex and the gonads, in the mitochondria and smooth endoplasmic reticulum.

Researchers have developed a novel enzyme that is able to catalyze the reduction of any partially oxidized nitrogen in the six-atom ring found in the structure of the adenine base pair. Which of the following changes might you expect to see in the base pairs of DNA as a consequence of the action of this enzyme? A. Adenine will preferentially form a base pair with Uracil. B. Adenine will preferentially form a base pair with Cytosine. C. Adenine will preferentially form a base pair with Guanine. D. Adenine will preferentially form a base pair with itself.

B) Adenine will preferentially form a base pair with Cytosine. In DNA, A and T form a base pair, as do G and C. The AT base pairing has two hydrogen bonds between the nitrogenous bases and the GC base pairing has three hydrogen bonds between them. However, with the reduction of nitrogen through the action of the described enzyme, adenine now has the ability to form 3 or 4 hydrogen bonds with a complementary pyrimidine. Because Cytosine is a pyrimidine that can form three hydrogen bonds, we can conclude that the best answer choice is that Adenine preferentially forms a base pair with Cytosine.

what is base pairing

Base pairing is caused by the formation of hydrogen bonds between complementary nucleotides. Cytosine (C) pairs with guanine (G), while adenine (A) pairs with thymine (T) in DNA and with uracil (U) in RNA. Two hydrogen bonds are formed between A and T, and three are present between C and G. A result of this is that sequences in which C and G bases predominate require higher temperatures for the strands to denature (or separate). Another important point to note is that purines pair with pyrimidines and vice versa. The specificity of complementary base pairing allows one strand to serve as a template for another; this property is integral to DNA replication and the transcription of DNA into mRNA.

Hypobromite

BrO⁻

Bromite

BrO₂⁻

Bromate

BrO₃⁻

Perbromate

BrO₄⁻

Which of the following is closest to the bond angle between the carbon atoms in a molecule of acetone? A) 90° B) 109.5° C) 120° D) 180°

C) 120° Acetone has a central carbon atom that is double-bonded to an oxygen and that has single bonds to two carbon atoms. The bonds form three groups, so the central carbon is sp2 hybridized. This corresponds to a trigonal planar molecular geometry and a bond angle of 120º.

Nitrogen is primarily present in the atmosphere as a diatomic gas. Which of the following is true about this form of nitrogen? A) The presence of a lone pair of electrons on each nitrogen atom in the molecule allows it to act as a strong Lewis base. B) The triple bond of electrons creates a region of high electron density that allows N2 to be very reactive as a nucleophile. C) Diatomic nitrogen gas is relatively inert and can be used in the atmosphere in laboratory reactions to prevent unwanted side reactions. D) Atmospheric nitrogen reacts spontaneously with carbon dioxide, which keeps atmospheric CO2 levels at a relatively low level of 0.04% (on a molar basis) of the atmosphere.

C. The MCAT will expect you to know that N2 is an inert gas. As such, it serves as a good atmosphere when working with reagents that might react with oxygen or other gasses.

Acetate

CH₃CO₂⁻

Cyanide

CN⁻

Chlorite ion

ClO2 -1 charge

Clorate Ion

ClO3 -1

Hypochlorite

ClO⁻

Chlorite

ClO₂⁻

Chlorate

ClO₃⁻

Perchlorate

ClO₄⁻

Which pair of amino acids would best provide disulfide links to stabilize the folded form of collagen?

Disulfide linkages only form between the side chains of cysteine (C) residues. When not part of such a linkage, cysteine side chains contain a thiol group (S-H). Through the process of oxidative folding, two thiol groups can interact and form an S-S bond, as shown below. These linkages are an important part of protein tertiary and quaternary structure

what are electron poor molecules

Electron-poor molecules function as electrophiles in reactions that yield covalent bonds, as Brønsted-Lowry acids when making a bond to an H+, or as Lewis acids when coordinate bonds are formed.

what are electron rich molecules

Electron-rich molecules tend to act as nucleophiles when a covalent bond is being made. They also tend to act as Brønsted-Lowry bases when making a bond to an H+, or as Lewis bases when a coordinate bond is formed. Such bonds are so weak that they repeatedly form and dissociate at standard temperatures.

what are amines? nucleophiles or electrophiles what about carbonyl carbon groups

For example, amines are good nucleophiles due to the presence of a lone pair of electrons. The carbons in carbonyl groups (C=O) are electron-poor, making them good electrophiles. One of the first steps to take when determining electron density is to look for C atoms bound or near to highly electronegative atoms (O, F, N) and for pi bonds, which can undergo resonance, allowing for molecules to be better nucleophiles.

Hydrogen carbonate\n(or bicarbonate)

HCO₃⁻

Hydrogen sulfate\n(or bisulfate)

HSO₄⁻

dihydrogen phosphate

H₂PO₄⁻

What is distillation?

If all are liquids, one may be able to utilize distillation, which aims to separate liquids by utilizing the difference between their boiling points.

What are the common suffixes for steroid hormones

If you encounter an unknown hormone on Test Day, the suffix of the name provides some clues. Generally, steroid hormones end in -ol, -one, or -en (e.g., testosterone, cortisol, and estradiol).

What is the induced fit model regarding enzymes interactions

In the induced fit model, the enzyme and substrate are seen as affecting each other; the initial stages of binding induce conformational shifts that allow closer attachment and more efficient catalysis.

What is Infrared (IR) spectroscopy

Infrared (IR) spectroscopy is a method used to identify specific functional groups present on an unknown molecule. Group frequencies are vibrations that are associated with certain functional groups.

What are ligases

Ligases are used in catalysis where two substrates are stitched together (i.e., ligated) via the formation of C-C, C-S, C-N or C-O bonds while giving off a water (condensation) molecule.

Ammonium

NH₄ (+) charge= +1 (cation)

What is the correct order of the five para substituents on the carbocation intermediate, if arranged from most stabilizing to least stabilizing? A. F > H > CH3 > OCH3 > NO2 Show Explanation B. CH3 > NO2 > OCH3 > H > F Show Explanation C. NO2 > OCH3 > CH3 > H > F Show Explanation D. NO2 > CH3 > OCH3 > F > H Show Explanation

NO2 > OCH3 > CH3 > H > F The stabilizing effects of the substituents can be determined from the relative stabilization energy (RSE), which can be found in Table 1. The more negative the RSE, the greater the stabilization; thus, the substituents should be ordered from most negative to least negative (or most positive) RSE. From Table 1, this corresponds to Compound 5 > Compound 1 > Compound 2 > Compound 3 > Compound 4, which matches this answer choice.

Is Uracil a purine or pyrimidine?

Pyrimidine (A is a purine, so must be paired with a pyrimidine, also U replaces T, and T is a pyrimidine)

what are radiation, conduction and convention determined by

Radiation, conduction, and convection are determined by the difference between the skin temperature and the ambient temperature. The rate of heat body heat loss depends primarily on the surface temperature of the skin, which is in turn a function of cutaneous blood flow.

what are situations where entropy is increased

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.

What is Recrystallization

Recrystallization is used to purify a solid product that contains impurities. This process involves the dissolution of the solid in a solvent and subsequent heating. The solid then dissolves and is cooled, causing it to solidify (crystallize) again. As the lattice structures of solids tend to exclude impurities, each subsequent recrystallization results in a progressively purer compound.

What is the difference between sulfite and sulfate

SO3^2- is sulfite SO4^2- is sulfate

sulfate ion

SO4 charge -2

What is Simple diffusion

Simple diffusion refers to the tendency for solutes to diffuse directly through a membrane and down their concentration gradient; that is, from an area of high solute concentration to an area of low concentration.

What are the symbols for spontaneity

Spontaneous reaction will lead to more products being present than reactants. It is important to automatically recognize that spontaneity is equivalent to ∆G < 0, Keq > 1, and E° > 0.

What bond angle is tetrahedral

Tetrahedral molecules contain four electron-rich areas and four bonded atoms, at angles of 109.5°. Methane (CH4) is a classic example of tetrahedral geometry.

what is our body's thermostat

The anterior hypothalmic-preoptic area! Remember, more heat sensitive neurons in hypothalamus than cold. Heat exchange is determined by convection, conduction, evaporation, and radiation.

how does your body gain or loses heat

The body can lose heat by increasing cutaneous blood flow and sweating, or by decreasing the basal metabolic rate through thyroid signaling. It can gain heat by decreasing cutaneous blood flow, increasing muscular activity (through movement and shivering), increasing the basal metabolic rate through thyroid signaling, metabolizing brown adipose (in infants only), or triggering piloerection of the hair on the body (goosebumps).

what are things does the body have to maintain

The body must maintain homeostasis of many parameters, including osmolality, pH, energy, and temperatur

Who has a higher boiling point. Aldehyde or carboxylic acid

The boiling point of the aldehyde is about 170°C The boiling point of carboxylic is about 300°C

What is the lock-and-key theory regarding enzymes interactions

The lock-and-key theory proposes that the active site of an enzyme and the substrate fit together like puzzle pieces, with no change in tertiary or quaternary structure. However, it eventually became clear that the lock-and-key theory was not sufficient to adequately explain enzyme-substrate interactions

What does carbonyl groups (C=O) and hydroxyl groups (OH) look like on an IR spectra

The most high-yield IR spectra for the MCAT are those of carbonyl groups (C=O) and hydroxyl groups (OH). The figure below shows the IR spectra for these important functional groups.

what is Chargaff's rule

The regularity of the base pairing rules leads to an interesting generalization This rule can be formulated in two ways. More generally, purines and pyrimidines will be present in a cell at a 1-to-1 ratio. This is because purines always pair with pyrimidines, and vice versa. the fact that C pairs with G and A pairs with T means that the amount of C in a cell's genome will equal the amount of G, and the amount of A will equal that of T. This means that you can use information about one nucleotide to infer information about the others. For instance, if we know that 15% of a cell's DNA is T, then we can infer that 15% must be A. The remaining 70% must be equally divided between C and G, so the overall composition will be 15% T, 15% A, 35% C, and 35% G.

What is Hess's Law?

The total enthalpy change of a reaction is independent of the route taken. The enthalpy (H) of a reaction is the heat energy it contains. The most important law when looking at enthalpy is Hess's law: ΔHrxn = Σ∆Hproducts - ΣΔHreactants. This equation illustrates that enthalpy, like entropy, is a state function. This means that the ∆H accompanying a chemical reaction is independent of the mechanism by which the reaction occurs. That is, when reactants are converted into products, the overall enthalpy change is the same whether it is done as one step or multiple steps

what is the difference between enthalpy and entropy

a key distinction is made between enthalpy (heat energy in a system) and entropy (energy in a closed system that is unavailable to do work)

Define boiling point

boiling point is defined as the temperature at which the vapor pressure of a solution is equal to the atmospheric pressure.

What is centrifugation

centrifugation utilizes a rapidly spinning apparatus to separate particles by density. More dense particles, such as cells, gravitate toward the bottom of the spun tube, while less dense substances remain at the top in a liquid termed the supernatant. This liquid can then be poured off, and further separation or analysis can be conducted.

from what can we infer chemical behavior

chemical behavior can be largely understood as the movement or shifting of electrons on a molecule Understanding general patterns of electron behavior is useful for predicting the outcomes of novel reactions and the activity of unfamiliar compounds..

What is the third law of thermodynamics?

he third law of thermodynamics allows us to calculate absolute entropy, but not absolute enthalpy. The enthalpy of a substance can only be calculated relative to other substances, and therefore enthalpy does not approach 0 as temperature

If a person drank a large quantity of hypersaline ocean water, the person could die because absorption of salt into the blood will cause it to become:

hypertonic compared with the cytosol of the body's cells, causing osmosis of water out of the cells.

Tucson, Arizona is well known for its sunny, dry weather. A 33ºC day in Tucson can feel relatively cool and pleasant compared to a similar temperature in a humid city like Tampa, Florida. The phenomenon of "dry heat" feeling subjectively cooler is a result of: A. decreased evaporation from the skin helping to keep the body cool. B. increased evaporation from the skin helping to keep the body cool. C. decreased cardiac output in response to dehydration lowering cutaneous perfusion. D. increased cardiac output in response to dehydration lowering cutaneous perfusion.

increased evaporation from the skin helping to keep the body cool. One of the body's primary ways of regulating heat is through sweating. The evaporation of liquid is an endothermic process that keeps the body from overheating. In a dry climate, the low humidity allows water to evaporate more readily, increasing the effects of evaporative cooling.

What is a polyatomic ion?

ions that are made of more than one atom

how do you know that a polyatomic ion has hydrogen ions in it

it has the word hydrogen in it it has a prefix (bi) in it

polyatimic ions that end with the suffix (ous) have (----) charge compared to polyatomic ions that end with (ic) 1. lesser 2. greater

lesser charge, meaning that if you have a polyatomic ion that end with a ic it has a greater charge than that ends with ous

what are oxyanions

polyatomic ions that contain oxygen

Boiling chips and vacuum distillation, respectively, are used in distillations to...

provide nucleation sites that give the liquid a place to start forming bubbles to prevent superheating; lower the boiling points of the substances to be distilled.

During the experiment, scientists noted that several of the reaction beakers became hot to the touch. All of the following reactions could cause this result EXCEPT:

reaction d In order for a reaction to cause the beaker to get hot to the touch, it must be exothermic. All exothermic reactions have a negative ∆Hreaction. The ∆Hreaction can be found using Hess's law and the Hf , where ∆Hreaction = ∆Hf products - ∆Hf reactants. Since this is an EXCEPT question, the correct answer should be endothermic and have a positive value for ∆Hreaction. The standard enthalpy of formation of any pure element in its standard state, such as C (graphite), N2 (g), O2 (g), and so on, is zero. Thus, the only Hf values required are the ones found in Table 1. This question does not require an exact solution; any reaction with an Hf for the products that is greater than Hf reactants will lead to a positive value for ∆Hreaction. The Hf for the products in choice D is 10.1 J/mol, while the Hf for the reactants is -18.8 J/mol. Because 10.1 J/mol (Hf products) > -18.8 J/mol (Hf reactants), the reaction is endothermic.

Which of the following correctly describes the orbital hybridization of XeF4 and NH3, respectively? A. sp3d2, sp3 Show Explanation B. sp3, sp3 Show Explanation C. sp3, sp2 Show Explanation D. sp3d2, sp2 Show Explanation

sp3d2, sp3 One way to determine the orbital hybridization around the central atom is to count the number of bonds and lone pairs. For example, the central nitrogen atom in ammonia has three bonds and one lone pair, for a total of four groups. Thus, ammonia is sp3 hybridized, eliminating choices C and D. Next, xenon is a noble gas in period 5. As such, XeF4 has a total of eight electrons in its s and p orbitals. Four of the electrons form bonds to fluorine, leaving two lone pairs around the central xenon atom. Six electron groups produce sp3d2 hybridization

what are suffix of polyatomic ions that indicate it is an oxyanion

suffix (ite) suffix (ate) - contains greater number of oxygen than ones that end with ite

What is thermoregulation?

the maintenance of body temperature is known as thermoregulation. This process relies on multiple systems within the human body, including the endocrine, cardiovascular, integumentary, and respiratory systems.

The preferred ion configuration of many elements on the periodic table is determined by:

the tendency of elements to gain or lose electrons until they have the same valence electron configuration as the nearest noble gas.

What are pyrimidines?

thymine and cytosine