MCAT- Biological and
Biochemical foundations of
living systems correct
answers 2025/2026
(* Genetics)
Inbreeding - correct answerInbreeding occurs when mates have a large proportion of
shared ancestry. The small population of flies that was left after the drought did not
necessarily share the same ancestry.
(*Anatomy)
Autocrine signaling - correct answerCell signaling. Cell secretes hormone/chemical
messenger (autocrine agent) to bind to cell's autocrine receptors, leading to changes
in the cell.
(*Anatomy)
Chief cells - correct answerStomach cells. These produce pepsinogen and gastric
lipase.
(*Anatomy)
D cells - correct answerProduce somatostatin. When D cells are destroyed,
somatostatin production decreases, inhibition of G cells decreases, gastric production
increases, # of mature parietal cells increases. Ultimately, luminal pH decreases.
(*Anatomy)
G cells - correct answerProduce Gastin, promote HCl release from parietal cells, this
chemical messenger also simulates parietal cell maturation and growth.
(*Anatomy)
Parasympathetic neurotransmitter - correct answer(E.g. ACh/acetylcholine) A
chemical messenger of the parasympathetic nervous system i.e. "rest & digest"
activity.
,(*Anatomy)
Parietal cels - correct answerStomach cells that produce gastric acid
(*Anatomy)
Somatostatin - correct answerAn inhibitory hormone secreted by pancreas & pituitary
gland, inhibits gastric secretion and somatotropin release. (somatotropin is a growth
hormone secreted by the pituitary gland) In somatostatin absence, gastric cells
operate with freedom. Somatostatin produces a net decrease in gastric/duodenal
digestive activity
(*Anatomy)
What is active gastric digestion characterized by? - correct answerGastric distention,
active secretion of hydogen ions (HCl), and a consequently low gastric pH.
(*Biochemistry)
alpha-amino acids - correct answerThese are the 20 naturally occurring/essential
amino acids. All amino acids are chiral and therefore are optically active. Glycine is
achiral because the r-group is a hydrogen.
(*Biochemistry)
How do enzymes affect the kinematics and thermodynamics of a reaction - correct
answerEnzymes do not change any thermodynamic properties of a reaction, they
instead lower the activation energy of a reaction, making the reaction more kinetically
favorable.
(*Biochemistry)
Iso-electric point - correct answerThe point at which an amino acid exhibits neutral
pH. At this point, the amino acid has no net charge. Above the iso-electric point, the
amino acid is overally negative, the -COOH loses the H+ forming -COO-. Below the iso-
electric point, the amino acid is overally positive, the -NH2 group picks up a proton and
forms NH3+.
(*Biochemistry)
Transition state analogues - correct answerMolecules that closely resemble a
subtrate's transition state structure in a reaction catalyzed by enzymes. Transition
state analogues are often the most tightly bound substrates for any enzyme, exhibit
highest affinity for the enzyme.
(*Biochemistry)
Which stage of an enzyme reaction is highest in energy? - correct answerThe
transition state is highest in energy (Ea is energy required to reach the transition
state) The reactants are higher than products for exothermic reactions and lower for
endothermic reactions
, (*Biochemistry*)
Glycogen phosphorylase - correct answerEnzyme that releases glucose from
glycogen. If a deficiency in glycogen phosphorylase occurs, glucose is not released
from glycogen, which decreases the production of ATP by glycolysis. Thus, any ATP
used in muscles during exercise is not replenished, leading to an accumulation of ADP
and Pi.
Once anaerobic exercise gives way to aerobic exercise, glycolysis is no longer the
primary source of ATP production. Aerobic exercise allows fatty acids to be used as an
energy source, generating ATP from oxidative phosphorylation.
(*Ecology)
Analogous structures - correct answerAnalogous structures are structures that serve
the same function, but come from a different evolutionary origin.
(*Ecology)
Artificial Selection ("selective breeding") - correct answerDoes not occur naturally,
has outside individual literally choosing which traits in an individual will be passed on.
e.g farmers picking better crop varieties for seeds, scientist adding genes that help
with pest resistance to crops
(*Ecology)
Assortive mating - correct answerAssortive mating is when mates are not chosen
randomly, but instead certain individuals are selected over others possibly because of
phenotype or location.
(*Ecology)
Coevolution - correct answerCoevolution occurs when two species evolve alongside
each other and exert evolutionary pressures on one another.
(*Ecology)
Convergent evolution - correct answerConvergent evolution occurs when two
populations that don't share a recent common ancestor start to resemble each other
as they adapt to the same or similar environments (e.g. a dolphin and a fish).
(*Ecology)
Differential reproduction - correct answerDifferential reproduction is the idea that
certain individuals are more likely to reproduce than others, and will therefore have
their genetic traits expressed at a higher rate in future generations.
(*Ecology)
Biochemical foundations of
living systems correct
answers 2025/2026
(* Genetics)
Inbreeding - correct answerInbreeding occurs when mates have a large proportion of
shared ancestry. The small population of flies that was left after the drought did not
necessarily share the same ancestry.
(*Anatomy)
Autocrine signaling - correct answerCell signaling. Cell secretes hormone/chemical
messenger (autocrine agent) to bind to cell's autocrine receptors, leading to changes
in the cell.
(*Anatomy)
Chief cells - correct answerStomach cells. These produce pepsinogen and gastric
lipase.
(*Anatomy)
D cells - correct answerProduce somatostatin. When D cells are destroyed,
somatostatin production decreases, inhibition of G cells decreases, gastric production
increases, # of mature parietal cells increases. Ultimately, luminal pH decreases.
(*Anatomy)
G cells - correct answerProduce Gastin, promote HCl release from parietal cells, this
chemical messenger also simulates parietal cell maturation and growth.
(*Anatomy)
Parasympathetic neurotransmitter - correct answer(E.g. ACh/acetylcholine) A
chemical messenger of the parasympathetic nervous system i.e. "rest & digest"
activity.
,(*Anatomy)
Parietal cels - correct answerStomach cells that produce gastric acid
(*Anatomy)
Somatostatin - correct answerAn inhibitory hormone secreted by pancreas & pituitary
gland, inhibits gastric secretion and somatotropin release. (somatotropin is a growth
hormone secreted by the pituitary gland) In somatostatin absence, gastric cells
operate with freedom. Somatostatin produces a net decrease in gastric/duodenal
digestive activity
(*Anatomy)
What is active gastric digestion characterized by? - correct answerGastric distention,
active secretion of hydogen ions (HCl), and a consequently low gastric pH.
(*Biochemistry)
alpha-amino acids - correct answerThese are the 20 naturally occurring/essential
amino acids. All amino acids are chiral and therefore are optically active. Glycine is
achiral because the r-group is a hydrogen.
(*Biochemistry)
How do enzymes affect the kinematics and thermodynamics of a reaction - correct
answerEnzymes do not change any thermodynamic properties of a reaction, they
instead lower the activation energy of a reaction, making the reaction more kinetically
favorable.
(*Biochemistry)
Iso-electric point - correct answerThe point at which an amino acid exhibits neutral
pH. At this point, the amino acid has no net charge. Above the iso-electric point, the
amino acid is overally negative, the -COOH loses the H+ forming -COO-. Below the iso-
electric point, the amino acid is overally positive, the -NH2 group picks up a proton and
forms NH3+.
(*Biochemistry)
Transition state analogues - correct answerMolecules that closely resemble a
subtrate's transition state structure in a reaction catalyzed by enzymes. Transition
state analogues are often the most tightly bound substrates for any enzyme, exhibit
highest affinity for the enzyme.
(*Biochemistry)
Which stage of an enzyme reaction is highest in energy? - correct answerThe
transition state is highest in energy (Ea is energy required to reach the transition
state) The reactants are higher than products for exothermic reactions and lower for
endothermic reactions
, (*Biochemistry*)
Glycogen phosphorylase - correct answerEnzyme that releases glucose from
glycogen. If a deficiency in glycogen phosphorylase occurs, glucose is not released
from glycogen, which decreases the production of ATP by glycolysis. Thus, any ATP
used in muscles during exercise is not replenished, leading to an accumulation of ADP
and Pi.
Once anaerobic exercise gives way to aerobic exercise, glycolysis is no longer the
primary source of ATP production. Aerobic exercise allows fatty acids to be used as an
energy source, generating ATP from oxidative phosphorylation.
(*Ecology)
Analogous structures - correct answerAnalogous structures are structures that serve
the same function, but come from a different evolutionary origin.
(*Ecology)
Artificial Selection ("selective breeding") - correct answerDoes not occur naturally,
has outside individual literally choosing which traits in an individual will be passed on.
e.g farmers picking better crop varieties for seeds, scientist adding genes that help
with pest resistance to crops
(*Ecology)
Assortive mating - correct answerAssortive mating is when mates are not chosen
randomly, but instead certain individuals are selected over others possibly because of
phenotype or location.
(*Ecology)
Coevolution - correct answerCoevolution occurs when two species evolve alongside
each other and exert evolutionary pressures on one another.
(*Ecology)
Convergent evolution - correct answerConvergent evolution occurs when two
populations that don't share a recent common ancestor start to resemble each other
as they adapt to the same or similar environments (e.g. a dolphin and a fish).
(*Ecology)
Differential reproduction - correct answerDifferential reproduction is the idea that
certain individuals are more likely to reproduce than others, and will therefore have
their genetic traits expressed at a higher rate in future generations.
(*Ecology)
