MCAT TEST PAPER 2025/2026 QUESTIONS WITH
SOLUTION GRADED A+
✔✔rate double per 10 degree C increase in temperature until what? - ✔✔optimum temp
✔✔what occurs after optimum temperature is reached? - ✔✔activity falls sharp
✔✔what occurs to enzymes at high temperatures? - ✔✔it denatures
✔✔blood pH - ✔✔7.4
✔✔pH 7.3 indicates: - ✔✔acidosis
✔✔pH values - ✔✔basic >7>acidic
✔✔competitive inhibition - ✔✔-binds active site
-overcome by adding substrate
-increase Km
✔✔noncompetitive inhibition - ✔✔-binds other than active site
-cannot be overcome
-Km unchanged
-Vmax decreased
✔✔zymogens - ✔✔regulatory domain must be removed/altered to expose active site
✔✔autotrophs - ✔✔-use sun energy to make organic molecules
-do not require organic compounds
✔✔heterotrophs - ✔✔break bonds in organic molecules for energy
✔✔Intermediates - ✔✔-ADP,NAD+,FAD
-high-energy electron shuttles between cytoplasm and mitochondria
✔✔ATP aka - ✔✔adenosine triphosphate
✔✔ATP - ✔✔-primary energy currency of cell
-generated during glucose catabolism
-energy stored in high-energy phosphate bonds
✔✔why are ATP phosphate bonds high energy? - ✔✔it is energetically unfavorable to
have negatives close together
✔✔NAD+ and FAD - ✔✔-coenzymes/electron acceptors
,-does not provide energy by itself
✔✔reduction - ✔✔-decrease oxidation state
-add hydrogens
✔✔oxidation - ✔✔-increase oxidation state
-remove hydrogen
✔✔glycolysis - ✔✔-break down glucose into 2 smaller molecules
-occurs in cytoplasm
-presence or absence of oxygen
✔✔where does glycolysis occur? - ✔✔in the cytoplasm
✔✔input of glycolysis - ✔✔6-carbon glucose
✔✔output of glycolysis - ✔✔2 molecules of 3-carbon pyruvate
✔✔ATP output of glycolysis - ✔✔4 total
net of 2
✔✔Net glycolysis reaction - ✔✔glucose+2ADP+2P+2NAD-->2
pyruvate+2ATP+2NADH+2H+2water
✔✔2 pyruvate fates - ✔✔aerobic
and
anaerobic
✔✔aerobic pyruvate fate - ✔✔-further oxidation via mitochondrial ETC
✔✔anaerobic pyruvate fate - ✔✔fermentation
✔✔aerobic - ✔✔oxygen present
✔✔anaerobic - ✔✔no oxygen present
✔✔Fermentation process - ✔✔-pyruvate-->ethanol or lactic acid
-reduce pyruvate and oxidize NADH to NAD+
✔✔Alcohol fermentation - ✔✔-Pyruvate (3C)-->CO2+ Acetaldehyde(2C)
-Acetaldehyde+NADH+H-->ethanol(2C) and NAD+
✔✔input of alcohol fermentation - ✔✔pyruvate (3C)
,✔✔Lactic Acid fermentation - ✔✔pyruvate (3C)+NADH+H-->Lactic Acid+NAD
✔✔lactic acid influence on pH - ✔✔lowers pH
✔✔symptoms of lactic acid in the body - ✔✔burning and fatigue when running
✔✔Cori cycle - ✔✔lactic acid-->pyruvate
✔✔cellular respiration - ✔✔-produces ATP
-uses electron transport chain
-oxygen as final electron acceptor
✔✔what is the final electron acceptor of cellular respiration? - ✔✔oxygen
✔✔is cellular respiration aerobic or anaerobic? - ✔✔aerobic
✔✔ATP output per glucose - ✔✔36-38
✔✔3 phases of cellular respiration - ✔✔1. pyruvate decarboxylation
2. citric acid cycle
3. electron transport chain
✔✔pyruvate decarboxylation - ✔✔-from cytoplasm to mitochondrial matrix
-anaerobic itself but requires aerobic commitment
✔✔is pyruvate decarboxylation aerobic? - ✔✔anaerobic itself but requires aerobic
commitment
✔✔pyruvate decarboxylation procedure - ✔✔pyruvate decarboxylated to acetyl (2C)
-acetyl + coenzyme A=acetyl CoA
✔✔what is the NAD output of pyruvate decarboxylation? - ✔✔1 NAD--> NADH per
pyruvate
✔✔Overall pyruvate decarboxylation reaction - ✔✔2 pyruvate(3C) + 2 CoA + 2 NAD--
>2NADH + 2 Acetyl CoA + 2 CO2
✔✔Citric acid cycle aka - ✔✔krebs cycle
TCA
✔✔Citric acid cycle procedure - ✔✔acetyl CoA (2C)+ oxaloacetate (4C)-->citrate (6C)
+2CO2
✔✔intermediates output of citric acid cycle - ✔✔1 ATP and 1 GTP
, 6 NADH
2 FADH
✔✔why is the citric acid cycle important? - ✔✔generates high-energy electrons carried
by NADH and FADH2
✔✔Electron transport chain - ✔✔-oxidative phosphorylation
-cytochrome carriers
✔✔oxidative phosphorylation - ✔✔electrons from NADH and FADH2 passed along
assembly line and release free energy
✔✔cytochrome complexes - ✔✔1) NADH dehydrogenase (complex I)
2) b-c1 complex (complex III)
3) cytochrome oxidase (complex IV)
✔✔ETC steps - ✔✔1) electrons from NADH to FMN (complex I)
2) electrons to carrier Q (ubiquinone)
3) electrons to complex III
4) electrons to complex IV (cytochrome a3)
5) electrons to oxygen and 2 H+ to water
✔✔carrier Q - ✔✔-ubiquinone
-hydrophobic molecule
-not an enzyme
✔✔NADH=____ ATP molecules - ✔✔3
✔✔FADH2=____ATP molcules - ✔✔2
✔✔FADH2 electrons skip complex I - ✔✔directly to complex II (succinate-Q oxido
reductase)
✔✔cyanide on ETC - ✔✔blocks the final transfer of electrons to oxygen
✔✔dinitrophenol (DNP) effect on ETC - ✔✔destroy mitochondria's ability to generate H+
gradient
✔✔How does ATP synthesis within oxidative phosphorylation occur? - ✔✔-proton
gradient across inner mitochondrial membrane links NADH and FADH2 oxidation to
ATP production
✔✔what does the hydrogen on the intermembrane space cause? - ✔✔positive charge
and acidic
SOLUTION GRADED A+
✔✔rate double per 10 degree C increase in temperature until what? - ✔✔optimum temp
✔✔what occurs after optimum temperature is reached? - ✔✔activity falls sharp
✔✔what occurs to enzymes at high temperatures? - ✔✔it denatures
✔✔blood pH - ✔✔7.4
✔✔pH 7.3 indicates: - ✔✔acidosis
✔✔pH values - ✔✔basic >7>acidic
✔✔competitive inhibition - ✔✔-binds active site
-overcome by adding substrate
-increase Km
✔✔noncompetitive inhibition - ✔✔-binds other than active site
-cannot be overcome
-Km unchanged
-Vmax decreased
✔✔zymogens - ✔✔regulatory domain must be removed/altered to expose active site
✔✔autotrophs - ✔✔-use sun energy to make organic molecules
-do not require organic compounds
✔✔heterotrophs - ✔✔break bonds in organic molecules for energy
✔✔Intermediates - ✔✔-ADP,NAD+,FAD
-high-energy electron shuttles between cytoplasm and mitochondria
✔✔ATP aka - ✔✔adenosine triphosphate
✔✔ATP - ✔✔-primary energy currency of cell
-generated during glucose catabolism
-energy stored in high-energy phosphate bonds
✔✔why are ATP phosphate bonds high energy? - ✔✔it is energetically unfavorable to
have negatives close together
✔✔NAD+ and FAD - ✔✔-coenzymes/electron acceptors
,-does not provide energy by itself
✔✔reduction - ✔✔-decrease oxidation state
-add hydrogens
✔✔oxidation - ✔✔-increase oxidation state
-remove hydrogen
✔✔glycolysis - ✔✔-break down glucose into 2 smaller molecules
-occurs in cytoplasm
-presence or absence of oxygen
✔✔where does glycolysis occur? - ✔✔in the cytoplasm
✔✔input of glycolysis - ✔✔6-carbon glucose
✔✔output of glycolysis - ✔✔2 molecules of 3-carbon pyruvate
✔✔ATP output of glycolysis - ✔✔4 total
net of 2
✔✔Net glycolysis reaction - ✔✔glucose+2ADP+2P+2NAD-->2
pyruvate+2ATP+2NADH+2H+2water
✔✔2 pyruvate fates - ✔✔aerobic
and
anaerobic
✔✔aerobic pyruvate fate - ✔✔-further oxidation via mitochondrial ETC
✔✔anaerobic pyruvate fate - ✔✔fermentation
✔✔aerobic - ✔✔oxygen present
✔✔anaerobic - ✔✔no oxygen present
✔✔Fermentation process - ✔✔-pyruvate-->ethanol or lactic acid
-reduce pyruvate and oxidize NADH to NAD+
✔✔Alcohol fermentation - ✔✔-Pyruvate (3C)-->CO2+ Acetaldehyde(2C)
-Acetaldehyde+NADH+H-->ethanol(2C) and NAD+
✔✔input of alcohol fermentation - ✔✔pyruvate (3C)
,✔✔Lactic Acid fermentation - ✔✔pyruvate (3C)+NADH+H-->Lactic Acid+NAD
✔✔lactic acid influence on pH - ✔✔lowers pH
✔✔symptoms of lactic acid in the body - ✔✔burning and fatigue when running
✔✔Cori cycle - ✔✔lactic acid-->pyruvate
✔✔cellular respiration - ✔✔-produces ATP
-uses electron transport chain
-oxygen as final electron acceptor
✔✔what is the final electron acceptor of cellular respiration? - ✔✔oxygen
✔✔is cellular respiration aerobic or anaerobic? - ✔✔aerobic
✔✔ATP output per glucose - ✔✔36-38
✔✔3 phases of cellular respiration - ✔✔1. pyruvate decarboxylation
2. citric acid cycle
3. electron transport chain
✔✔pyruvate decarboxylation - ✔✔-from cytoplasm to mitochondrial matrix
-anaerobic itself but requires aerobic commitment
✔✔is pyruvate decarboxylation aerobic? - ✔✔anaerobic itself but requires aerobic
commitment
✔✔pyruvate decarboxylation procedure - ✔✔pyruvate decarboxylated to acetyl (2C)
-acetyl + coenzyme A=acetyl CoA
✔✔what is the NAD output of pyruvate decarboxylation? - ✔✔1 NAD--> NADH per
pyruvate
✔✔Overall pyruvate decarboxylation reaction - ✔✔2 pyruvate(3C) + 2 CoA + 2 NAD--
>2NADH + 2 Acetyl CoA + 2 CO2
✔✔Citric acid cycle aka - ✔✔krebs cycle
TCA
✔✔Citric acid cycle procedure - ✔✔acetyl CoA (2C)+ oxaloacetate (4C)-->citrate (6C)
+2CO2
✔✔intermediates output of citric acid cycle - ✔✔1 ATP and 1 GTP
, 6 NADH
2 FADH
✔✔why is the citric acid cycle important? - ✔✔generates high-energy electrons carried
by NADH and FADH2
✔✔Electron transport chain - ✔✔-oxidative phosphorylation
-cytochrome carriers
✔✔oxidative phosphorylation - ✔✔electrons from NADH and FADH2 passed along
assembly line and release free energy
✔✔cytochrome complexes - ✔✔1) NADH dehydrogenase (complex I)
2) b-c1 complex (complex III)
3) cytochrome oxidase (complex IV)
✔✔ETC steps - ✔✔1) electrons from NADH to FMN (complex I)
2) electrons to carrier Q (ubiquinone)
3) electrons to complex III
4) electrons to complex IV (cytochrome a3)
5) electrons to oxygen and 2 H+ to water
✔✔carrier Q - ✔✔-ubiquinone
-hydrophobic molecule
-not an enzyme
✔✔NADH=____ ATP molecules - ✔✔3
✔✔FADH2=____ATP molcules - ✔✔2
✔✔FADH2 electrons skip complex I - ✔✔directly to complex II (succinate-Q oxido
reductase)
✔✔cyanide on ETC - ✔✔blocks the final transfer of electrons to oxygen
✔✔dinitrophenol (DNP) effect on ETC - ✔✔destroy mitochondria's ability to generate H+
gradient
✔✔How does ATP synthesis within oxidative phosphorylation occur? - ✔✔-proton
gradient across inner mitochondrial membrane links NADH and FADH2 oxidation to
ATP production
✔✔what does the hydrogen on the intermembrane space cause? - ✔✔positive charge
and acidic
