MCAT BIOLOGY PRACTICE QUESTIONS EXAM QUESTIONS WITH CORRECT SOLUTIONS||100% GUARANTEED PASS!! ALREADY GRADED||BRAND NEW VERSION

MCAT BIOLOGY PRACTICE QUESTIONS EXAM QUESTIONS WITH CORRECT SOLUTIONS||100% GUARANTEED PASS!! ALREADY GRADED||BRAND NEW VERSION INSULIN RESISTANCE Mixed inhibition is when the inhibitor binds with unequal affinity to the enzyme and the enzyme-complex, how does this affect Vmax and Km values - ANSWER Vmax ↓ Km ↑ or ↓ depending on if the inhibitor has a higher affinity for the ENZYME or the ES complex How does phosphorylation affect substrates in a catabolism reaction vs those in anabolism - ANSWER Catabolism: Phosphorylation = ACTIVE Anabolism: Phosphorylation = INACTIVE Zymogens are precursors to enzymes, how do they get activated - ANSWER They are secreted in a an inactive form and are ACTIVATED by CLEAVAGE i.e angiotensinogen secreted from liver, is cleaved into angiotensen I by renin and further cleaved into angiotensin II by ACE Cell Adhesion Molecules (CAM) allow cells to bind to other cells or surfaces, what are the three main types - ANSWER Cadherins: calcium dependent glycoproteins that hold SIMILAR CELLS (cell to cell) together Integrins: have two membrane spanning chains and permit CELLS to adhere to PROTEINS in the extracellular matrix Selectins: Allow cells to adhere to CARBOHYDRATE on the surfaces of other CELLS, mostly commonly used in the IMMUNE SYSTEM (doesn't bind as tightly as integrins) Beer-Lambert Law - ANSWER Used to relate the concentration of colored solutions to the amount of visible light they absorb. True or False: Nearly all carbohydrates in nature are in the L-configuration - ANSWER False Nearly all carbohydrates in nature are in the D-configuration. Compared to amino acids which are found in the L-configuration Diastereomers are any stereoisomer that is not an enantiomer, what are epimers and anomers - ANSWER Epimers: subtype of diastereomers that differ exactly at ONE CHIRAL CARBON Anomers: subtype of epimers that differ at the ANOMERIC CARBON Sucrose - ANSWER glucose + fructose alpha glycosidic bond 1,2 linkage How does the saturation of fatty acid tails affect cell membranes - ANSWER Saturation of the fatty acid tails determines the fluidity of the membrane SATURATED FA = LESS FLUID What does the backbone of phospholipids typically contain - ANSWER Mostly Glycerol Sometimes sphinogosine Prostaglandins are autocrine and paracrine signaling molecule, what do they regulate - ANSWER cAMP levels - plays a huge role in signal transductions Affect smooth muscle contraction, body temp, sleep-wake cycle, fever, pain structure of steroids - ANSWER 4 fused carbon rings 3 CYCLOHEXANE, 1 CYCLOPENTANE Most of DNA is B-DNA, forming a right-handed helix, under what conditions can Z-DNA form - ANSWER Low concentrations of Z-DNA, with a ZIGZAG shape may be seen with HIGH GC content or HIGH SALT concentration DNA polymerase proofreads its work and excises incorrectly matched bases. How is the daughter strand identified - ANSWER The daughter strand is identified by its LACK of METHYLATION and corrected accordingly When does mismatch repair occur? - ANSWER G2 phase What kinds of things does the Nucleotide Excision Repair - ANSWER Fixes helix deforming lesions on DNA such as THYMINE DIMERS Cut and Patch process What type of DNA repair is used to fix nondeforming lesions of the DNA helixes such as cytosine deamination - ANSWER Base Excision repair DNA repair that first excises modified bases (leaves a APRUNIC/APYRIMIDIC (AP) site) and then replaces the entire nucleotide Operons are inducible or repressible clusters of genes transcribed as a single mRNA, describe inducible and repressible systems - ANSWER Inducible Systems: under normal conditions, they are bonded to REPRESSOR, turned on when INDUCER pulls the repressor off, so they can be transcribed (i.e lac operon) Repressible System: TRANSCRIBED under normal, can be turned off by a COREPRESSOR (i.e trp operon) True or False: promoters are within 25 bp of transcription initiation site - ANSWER True Enhancers are more than 25 base pairs away from transcription initiation site Hemidesmosomes - ANSWER attach epithelial cells to the basement membrane Unlike desmosomes which bind adjacent cells by anchoring to their cytoskeleton True or False: the outer mitochondrial membrane is not permeable to metabolic molecules and small proteins - ANSWER False The OMM is HIGHLY PERMEABLE to metabolic molecules and small proteins GLUT 2 vs GLUT 4 - ANSWER GLUT-2: in liver (for glucose storage), has ↑Km (lower binding affinity) - INSULIN INDEPENDENT GLUT-4: found in adipose tissue and muscle. Stimulated by insulin. Has ↓Km Why can is ADH Always Digging Holes - ANSWER ADH regulates the volume of blood by allowing the distal convoluted tubule and the collecting ducts to be MORE PERMEABLE to water which allows water to move out of the ducts and into the BLOOD What is the primary neurotransmitter in the parasympathetic system - ANSWER Acetylcholine "Calico Cat's Contract Muscles" - ANSWER Calcium Cation attaches to Calmodulin, which activates myosin True or False: the circulatory system behaves as a CLOSED system with nonconstant flow - ANSWER True The nonconstant flow = our pulse How does velocity relate to cardiac output and cross sectional area - ANSWER v = Q/A Q= cardiac output A = cross-sectional area pressure in circulatory system - ANSWER ∆P = Q x R ∆P = vAR If pressure increases, how will this affect velocity, area and resistance - ANSWER They would increase Pressure is DIRECTLY RELATED to velocity, area and resistance However, area is INVERSELY related to resistance and velocity True or False: inspiration and expiration create a pressure gradient only for the respiration system - ANSWER False They create a pressure gradient for the RESPIRATION system and for the CIRCULATORY system Does air at the alveoli have an speed - ANSWER No, air at the alveoli has essentially ZERO speed True or False: conjugation is a feature of Gram-positive bacteria - ANSWER False Conjugation is a feature of Gram-NEGATIVE bacteria. It allows for sexual reproduction on the bacterium What is needed in order for conjugation to occur in bacteria - ANSWER A PILUS (SEX pilus) A F factor plasmid (FERTILITY Plasmid) Remember a plasmid is a separate EXTRAGENOMIC strand of DNA that is not incorporated into the bacteriums own DNA True or False: Myoglobin is only found in the muscle - ANSWER True. What two compounds allosterically inhibits hemoglobin - ANSWER CO2 and H+ They trigger the heme group to release its O2 because H+ changes the conformation of hemoglobin- this makes sense because a situation where there is a lot of H+ and CO2 means there is a need for O2, so they will need to be lowered binding affinity of O2 to hemoglobin so it can be released What happens when CO2 enters into the RBC, where carbonic anhydrase resides (the enzyme for the bicarbonate buffer) - ANSWER The CO2 COMBINES with the H2O, forming H2CO3, which dissociates into H+ and HCO3-