The________, becomes epidermis, hair, nails and the epithelia of the nose, mouth, and anal canal, as well as the nervous system (including the adrenal medulla) and the lens of the eye.
ectoderm
The________, becomes much of the musculoskeletal, circulatory, and excretory systems. It also gives rise to the gonads and the muscular and connective tissue layers of the digestive and respiratory systems, as well as the adrenal cortex.
mesoderm
The_______ becomes much of the epithelial lining of the respiratory and digestive tracts, and parts of the pancreas, thyroid, bladder, and distal urinary tracts.
endoderm
The notochord induces a group of overlying ectodermal cells to slide inward to form the neural folds, which surround the neural groove. The neural folds grow toward one another until they fuse into a _______, which gives rise the central nervous system.
neural tube
Name a bodily structure that is derived from the same germ layer as the kidneys?
Kidneys are derived from the mesoderm: blood, endothelium, heart, kidney, reproductive system, bones, skeletal, smooth muscle and connective tissues. Mesoderm also contributes to tendons, ligaments, dermis and cartilage.
Converging Lense
the image is real if the object sits outside the focal length.all objects view by the eye sit outside the focal lengththe image is reduced in sizethe image is inverted
What is the difference between alpha-D- glucose and beta-D glucose?
alpha-D- glucose and beta-D glucose are a pair of two anomers, and by definition anomers differ only in the absolute configuration at their anomeric carbon.
When blood is donated, it is important that no active antibodies are transferred along with the red blood cells. In order to accomplish this, a reducing agent, which breaks the disulfide bonds that maintain the quaternary structure of antibodies, is added to donated blood. This is effective because:
When cystine accepts electrons, it separates into two cysteine groups that are located on separate polypeptides.Remember, the quatenary structure exists when multiple polypeptides interact to form a single protein with multiple subunits.In the case of protein, disulfide bonds occure between two cysteine amino acids to form a single unit known as cystine.Reducing means gaining electrons
A catalyst
can only lower the activation energies of a reaction1 and 2 are the activation energy of the reaction3 and 4 are the potential energies of the reactants and products, and 5 is the potential energies difference of the reaction.
If a reaction proceeds spontaneously to the right, the equilibrium constant must be......
greater than one
If delta G were greater than zero, the reaction would not be
spontaneous
On a globular protein, what are the preferred locations for leucine and phenylalanine?
Leucine and phenylalinine have hydrophobic side chains and thus prefer to be buried on the interior.
Which of the following statements correctly describes the separation of the compounds below by extraction into dichloromethane and water.
If the solution were basic, caffeine would be more soluble in dichloromethane than in waterbecause in basic condition caffeine is uncharged (neutral) and water doesn't love neutral like organic solvants do. If it were negatively charged it would be more soluble in water.
The action of phenylalanine hydroxylase on pheylalanine results in:
conservation of steriochemistry, since the primary chiral center is not altered
Which of the following compounds is expected to have the highest melting point?A. GlycineB. ValineC. EthanolD. Butane
B. ValineValine is not only the largest in this group, but it is also capable of strong dipole-dipole interactions.
What is chromatography? What is the difference between thin-layered chromatography and column chromatography?
Chromatrography is about the affinity of a substance for the mobile and stationary phase, except for exclusion chromatography where small compounds are retained longer than larger compounds.
A scientist uses thin-layer chromatography on silica plates to separate a mixture of phenylalanine and tyrosine. Does phenylalanine have a higher or lower Rf than tyrosine?
Higher, because Tyrosine is more polar than phenylalanine which means that tyrosin will not migrate and phenylalanine will. Silica plates are very polar, thus the stationary phase is polar and so molecules with an affinity for polar-stationary phase will have a lower RfRf means the distance the spot migrates to relative to the front.
In the absence of a pH meter, which of the flowing indicator solution is most appropriate for a titration of stomach acid with NaOH?
The stomach produces HCL, a strong acid. The titrant is NaOH, a strong base, the equivalence point is 7. II. Phenol red is the only indicator that corresponds with pH of 7.
What is the most common reason for performing a titration?
To discover the concentration of an known reactant in a solution.There are four types of titrations but MCAT only focuses on, acid-base, oxidation-reduction.
What is the approximate Ka of acid T?
To find the Ka look at the half equivalence point, which occurs at 25ml. at the half equivalence point the pH = pKa and pka= - log (Ka). If the pKa is 4 the Ka= 1x 10-4
The denaturation of a protein by stomach acid involves the breaking of?
h-bonds
D-amino acids and L-amino acids have the same
physical properties
DD-transpeptidase is a bacterial enzyme that cross-links peptidogylcan chains to form rigid cell walls. Threonine is often found in these interbridges. Which of the following is also a likely component?A. HistidineB. IsoleucineC. PhenylalanineD. Serine
The question is essentially asking for the amino acid most similar to threonine. Serine, is the most similar.They are amino acids with polar side chains: So That Apple Grows ColdSerine, Threonine, Asparagine, Glutamine, Cysteine
What is bomb calorimetry?
is a very ineffiecent way to determine the bond enthalpies within a compound when not starting from a standard state. In order to do so, we would need all of the information provided above (temperature, mass of reactants, mass of water, heat of formation etc), plus the heat of formation of the products and background information on bond energies contained within either the reactants or products.
Selenium is often an active compound of treatments for scalp dermatitis. Selenium is aA. metalB. transitional metalC. halogenD. nonmetal
D. nonmetals
Boyle's Law
(Diver) Even at a constant depth and temperature, a shift occurs inducing a net upward force. Assuming no changes are made to the buoyancy compensator, this is best explained because
Since the divers depth is constant, that means he remains relatively still in relation to the earth, so the only changes in gravitational force will result from changes in mass.
As oxygen is consumed underwater, the body also produces carbon dioxide. This has the effect of:
decreasing the pH of the bloodAn increase in carbon dioxide production in the body leads to more carbonic acid in the blood stream, lowering the pH of the blood.
isotopes differ in their number of?
neutrons
A conservationist would like to tes the acidity of a sample of rainwater by titrating it with 0.05 M NaOH. What additional information is needed to calculate the initial number of moles of H2CO3?I. Volume of NaOH used to reach the end pointII. Ka of H2CO3III. Initial volume of rainwater in the sample
I. Volume of NaOH used to reach the end pointThe goal is to find the # of moles of H2CO3 , not the concentration. Therefore it is only necessary to know how many moles of NaOH were required to reach equivalence.
If a neuron is first measured at resting potential but later is found to require application of +3mA of current to return to -60mV, which of the following could explain the neuron's net ion flow between the two measurements?
Answer was B. Positive ions flowed out of the cell.The applied current is positive into the cell, so the cell is itself negative. The axon becomes more negative when positive ions leave the cell or when negative ions move into it.
The response of the skeletal system to increased levels of PTH include.
Systems that respond to PTH do so with the goal of raising blood calcium.Stimulation of osteoclasts breaks down bone, releasing calcium from bone into the blood.Thus, osteoclast activity increases because bone breakdown will raise blood calcium levels
Which of the following is most likely true regarding the primary structure of PTH?A. A high percentage of PTH's amino acids are serinesB. PTH has a cleavage site close to its amino terminusC. PTH and the products of its degradation are excreted by the liverD.The short half life of PTH is due to the absence of disulfide bridges.
B. PTH has a cleavage site close to its amino terminusIn order to remove biological activity from a hormone, the amino terminus must be destroyed. In other words, there must be a hydrolytic cleavage site near the amino terminus.
In order to be excreted in the urine, a substance must be..
water-solubleWater insoluble compounds are either stored in the body, converted to water-soluble products, or eliminated in the feces.
In order to get into the urine, a molecule must be filtered from the blood through the____________ and into the renal tuble for transport to the ureter and bladder.
glomerulus
Suppose a healthy individual experiences a surge in plasma calcium. Subsequently, where would one expect to fine the greatest amount of hydrolyzed PTH?
If plasma calcium in a healthy individual is above normal, the body will respond by excreting calcium and PTH by-products. Excretion occurs in the kidneys, making the nephron a good prediction.
The diagram below illustrates the relationship between interstitial (extracellular) fluid pressure and lymph flow. Would an increase in interstitial fluid protein cause an increase in lymph flow?
yes, because an increase of pressure will result in an increase of fluid movement out of the capillaries.
Which of the following graphs best describes the relationship between reaction velocity and temperature in an enzyme-catalyzed reaction?A. B.
A. In enzymatic reactions, reaction velocity and temperature are directly proportional, as temperature increases, so does the rate of the reaction. But if temperature gets too high the protein will denature. The graph should begin with an upward slope followed by a sharp descending slope.
Despite the importance of mitochondria, scientist have demonstrated that human mitochondrial DNA mutates at a fairly high rate. The mutations are most likely to be:
point mutations.
As non-polar protein groups cluster in water, the water experiences a(n):
increase in entropyThe organization of the solvation layer causes a decrease in entropy, so the clustering of non-polar groups, by virtue of diminishing the layer, causes a favorable increase in entropy.
In the experiments described in the passage, how does water most likely react to the polar protein groups?
By forming a solvation layer to a lesser exten than around non-polar groups
Hydrophobic interactions have the LEAST significant role in?
The secondary structure of globular proteinsThe secondary structure of any protein is determined primarily by local h-bonds; hydrophobic interactions play a more significant role in tertiarty structure of proteins; the stability of intracellular vesicles, the spontaneous fomation of micelles, the immiscbility of oil and water etc
Which of the following does NOT derive from the neural crest?A. Adrenal medullaB. Schwann cellsC. Melanocyte cellsD. Erythrocyte cells
D. Erthrocyte cellsSince the neural crest is derived from the ectoderm, knowing all structure types that drive from the ectoderm all you to rule out all choices except Erythrocytes
A man with type AB blood marries a woman with type O blood. Which of the following are blood types that their children might inherit?
Type A and BA woman with type O blood has two O alleles and therefore produces gametes of the O allele. So if these two people have children they only two genotypes their children can inherit are AO and BO, which correspond to the phenotype A blood and type B blood.
What is the Jacob-Monod Model?
It describes the function of operons.Operons are a cluster of genes made from different DNA that come together to get transcribed. The cluster of genes include the: structural gene which codes for the protein of interest, The operator, a nontranscribable region of DNA that is capable of binding a repressor protein. Promotor site, and further upstream lives the regulator gene.
What is an inducible system? (Gene control in prokaryotic cells)
structural genes can only be transcribed if inducer binds to repressor before repressor binds to operator.
The lac Operon
is induced by the presence of lactose. These genes are only transcribed (read) when useful to the cell.
What is a repressible system (control of gene expression in prokaryotes)?
A repressible system allows for the continuous production of something because the repressor molecule is inactive unless it is bound to a corepressor. It usually serves as negative feedback, thus the final product will code for the production of the corepressor in order to stop transcription.
Eukaryotic proteins may be toxic to bacteria when produced in large amounts. As such, scientist find it useful to insert eukaryotic proteins into bacterial DNA at a site where the protein may be induced. Scientist use the lac operon to control eukaryotic protein expression. What occurs in the absense of allolactose?
Allolactose is called an inducer because it turns on, or induces the expression of, the lac genes.The repressor binds the operator, preventing RNA polymerase from transcribing the eukaryotic genes. Allolactose binds to an allosteric site on the repressor protein causing a conformational change. As a result of this change, the repressor can no longer bind to the operator region and falls off. RNA polymerase can then bind to the promoter and transcribe the lac genes.
At temperatures below 85 C, the renaturation of the organism's DNA is:
Spontaneous and exothermicThe denaturation process is endothermic (heat must be applied for the bonds to break) and the renaturation process is exothermic.No additional energy is necessary for the reannealing process, so this is best described as spontaneous.
The GTP used by tubulin could come directly from the products of:
the citric acid cycle
When in mitosis do tubulin fibers shorten?
Anaphase
Which of the following mitochondrial genome characteristics differs most from the charateristics of the nuclear genome?
Almost every base in mitochondrial DNA codes for a product
When action potential induces muscle contraction, what occurs?
Ca 2+ is released into the cytosol; Ca 2+ binds to troponin complex
What's the difference between nuclear DNA and mitochondrial DNA?
competitive acetylcholine receptor antagonist.agonist promotes promotes twitchesan anatagonist inhibits them
In order to prevent the net movement of water between blood and the dialyzing fluid, the dialyzing fluid:
is isosmotic to bloodIf the dialyzing fluid is isosmotic, it has the same concentration of particles and thus, the same osmotic pressure exists on either side of the membrane. if the osmotic pressure is the same, the net movement between blood and the dialyzing fluid is zero.
The semi-permeable membrane of the dialysis machine function in a manner most analogous to which part of the kidney?
The glomerulus, functions like a sieve allowing the filtration (movement from the circulation into the nephron tubule) of small molecules while blocking filtration of the plasma proteins. The semi-permeable membrane serves an analogous function in the dialysis machine.
A patient with renal failure has nephrons which lack the ability to actively secrete or reabsorb any substances. Which of the following actions will the patient's kidney most likely still be able to perform?
Excretion of salt in urineRemember that the fluid in the Bowman's capsule is isotonic to plasma. Without reabsorption or secretion, isotonic urine can still be produced. Glucose is normally filtered and then actively reabsorbed in the proximal convoluted tube, so this patient could not conserve glucose.
If mRNA is not able to attach itself to ribosome, it will inhibit
translation of a gene.translation happens after transcription.
DNA methylation
is the process by which methyl groups are added to the DNA molecule. Methylation can change the activity of the DNA segment without changing the sequence. When located on a gene promoter, DNA methylation typically acts to repress transcription.
A researcher studying plasma membrane proteins uses a detergent to disrupt cellular membranes. Why might the researcher choose erythrocytes for this study?
The plasma membrane is only a fraction of a typical cell's membranesThe question asks us to explain why a researcher studying plasma membrane proteins might work with erythrocytes. Erythroctyes, or red blood cells lack organelles. Organelles have membranes and membrane proteins. Thus, in order to study plasma membrane proteins and not organelle membrane proteins the researcher has chosen red blood cells.
The Schachter-Singer theory differs from the James-Lange theory of emotion because the Schachter-Singer theory states that:
it is necessary to understand and label the physiological arousal changes that occur in response to an emotion.Although both Schachter-Singer theory and James-Lange think physiological arousal is needed in order to experience emotion, the S S theory also say's that cognitive interpretation is needed in order to experience emotion.Body and Mind
What are the three muscle types?
Describe skeletal muscle type I fibers (slow-twitch muscle fiber):
Describe skeletal moderate fast-twitch fibers IIa:
Describe skeletal muscle fast-twich fibers type IIx:
Name the organs of the digestive system and describe their function:
Initial mechanical and chemical digestion
What are the three main cell types in the stomach?
What is the name and function of the enzymes/hormones in duodenum?
Which of the following do disacchridases NOT digest?
glucose
Pancreatic juice is secreted by which pancreatic cells?
Acinar
List the enzymes secreted by the pancreas and describe their function
What are the functions of the liver?
What are the functions of the gallbladder?
Stores bile. Without bile salts the body would not be as affective in lipid/ fat digestion
Jejunum and Illeum
How does the body maintain plasma osmolarity and volume?
Two major hormones ADH and Aldosterone
What other hormones regulate glucose levels beside insulin and glucagon?
Cortisol: its produced by the adrenal cortex stimulated by ACTH enhances gluconegenesis and antagonizes insulinEpinephrine: is produced by the adrenal medulla stimulated by the sympathetic nervous system promotes glycogenolysis and fatty acid release from adipose tissue
Thryoxine
Thyroxine is a hormone the thyroid gland secretes into the bloodstream. Once in the bloodstream, thyroxine travels to the organs, like the liver and kidneys, where it is converted to its active form of triiodothyronine. Thyroxine plays a crucial role in heart and digestive function, metabolism, brain development, bone health and muscle control. It affects almost all of the body's systems, which means proper thyroxine levels are vital for health. This is why many doctors will test T4 levels along with the more common T3 levels when testing for thyroid disorders.
Calcium is controlled by:
What are mineralcorticoids?
mineral corticoids like aldosterone promote sodium reabsorption in the distal convoluted tubule and collecting duct, thus increasing water reabsorption. If someone is definicient in mineralcorticoids tthey are likely to suffer from hypertension
Which tropic hormones is likely secreted to great excess in congenital adrenal hyperplasia?
ACTH (adrenocorticotropic hormone)
Increased insulin sensitivity results in
decreased weight gain and increased blood glucose
Patients with high cortisol levels often suffer from obesity: Which of the following is a likely explanation
Cortisol increases levels of circulating blood glucose resulting in increased insulin levels and the deposition of fat.
Type I diabetes results from a lack of secretion of insulin, while Type II diabetes results from impaired sensitivity to insulin. Which of the following most accurately represents the relationships between type of diabetes and body habitus?
Type I diabetics are likely to be underweight, while Type II diabetics are likely to be overweight.And type one diabetes the lack of insulin causes high blood sugar which leads to dehydration and weight loss because your body isn't using sugar for energy so it starts to use fat.
ACTH, prolactin, TSH, and growth hormone are all secreted by the
the anterior pituitary
Which of the following is a hormone likely to trigger a second messenger cascade?A. AldosteroneB. CortisolC. SomatostatinD. Progesterone
D. SomatostatinSomatostatin is a hormone that inhibits the secretion of several other hormones, including growth hormone, thyroid stimulating hormone, cholecystokinin and insulin.A second messenger cascade is a series of events that occur intracellularly following the binding of a hormone to a receptor. Thus, in order for this to occur, the hormone must be a hormon that binds to a receptor on the plasma memberane. Thus, the hormone does not enter the cell. Peptide hormones do not enter the cell. Thus, the correct answer will be a peptide hormone. All the other hormones are steriod hormones.
Human placental lactogen often increases insulin resistance in pregnancy women. Which of the following abnormalities may be present in a woman as a result of this?
Increased blood glucose levels
What is an Arrhenius acid?
In eukaryotic proteins, phosphorlation usually occurs on which amino residues?
Serine, Threonine, Tyrosine and Histidine
microfilaments are composed of ______ while microtubles are composed of______
actin: tubulin