MCAT- BIOLOGICAL AND
BIOCHEMICAL FOUNDATIONS
OF LIVING SYSTEMS
(*Molecular Biology)
Hydrolases - ANSWERS-Enzymes that catalyze reactions between a
specific substrate and water in order to break a covalent bond.
(*Molecular Biology)
pI (Isoelectric point) of an amino acid - ANSWERS-The pH at which
an amino acid carries no electrical charge (average of the pKa's of the
carboxyl and amino group)
(*Genetics)
Silent Mutations - ANSWERS-Mutations that do not change the
amino acid sequence
(*Molecular Biology)
When are Amino acid substitutions least disruptive? - ANSWERS-
These are least disruptive to protein structure when the R-group
maintains the previous amino acid's non-polar or polar properties
(*Genetics)
,In x-linked inheritance, how are alleles distributed? - ANSWERS-
Males receive one allele from the mother (on X) and none from the
father (provides Y).
(*Genetics)
How do dominant disorders proceed across generations? -
ANSWERS-They do not skip generations
(*Genetics)
What form of transmission is characteristic of X-linked disorders? -
ANSWERS-Mother to Son transmission
(*Genetics)
What are the sources of alleles in recessive diseases? - ANSWERS-A
diseased allele must be received from each parent in autosomal
disorders and it must be received just from the mother in X-linked
disorders
(*Genetics*)
What is the allelic basis for rare recessive genetic disorders? -
ANSWERS-It is most likely X-linked. It is much more rare to get two
carriers marrying into one family i.e. autosomal disorder
(*Anatomy)
Autocrine signaling - ANSWERS-Cell signaling. Cell secretes
hormone/chemical messenger (autocrine agent) to bind to cell's
autocrine receptors, leading to changes in the cell.
,(*Anatomy)
Somatostatin - ANSWERS-An 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)
Chief cells - ANSWERS-Stomach cells. These produce pepsinogen
and gastric lipase.
(*Anatomy)
Parietal cels - ANSWERS-Stomach cells that produce gastric acid
(*Anatomy)
G cells - ANSWERS-Produce Gastin, promote HCl release from
parietal cells, this chemical messenger also simulates parietal cell
maturation and growth.
(*Anatomy)
D cells - ANSWERS-Produce 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)
What is active gastric digestion characterized by? - ANSWERS-
Gastric distention, active secretion of hydogen ions (HCl), and a
consequently low gastric pH.
(*Anatomy)
Parasympathetic neurotransmitter - ANSWERS-(E.g.
ACh/acetylcholine) A chemical messenger of the parasympathetic
nervous system i.e. "rest & digest" activity.
(*Biochemistry)
How do enzymes affect the kinematics and thermodynamics of a
reaction - ANSWERS-Enzymes 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)
Which stage of an enzyme reaction is highest in energy? -
ANSWERS-The 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)
Transition state analogues - ANSWERS-Molecules that closely
resemble a subtrate's transition state structure in a reaction catalyzed
by enzymes. Transition state analogues are often the most tightly
BIOCHEMICAL FOUNDATIONS
OF LIVING SYSTEMS
(*Molecular Biology)
Hydrolases - ANSWERS-Enzymes that catalyze reactions between a
specific substrate and water in order to break a covalent bond.
(*Molecular Biology)
pI (Isoelectric point) of an amino acid - ANSWERS-The pH at which
an amino acid carries no electrical charge (average of the pKa's of the
carboxyl and amino group)
(*Genetics)
Silent Mutations - ANSWERS-Mutations that do not change the
amino acid sequence
(*Molecular Biology)
When are Amino acid substitutions least disruptive? - ANSWERS-
These are least disruptive to protein structure when the R-group
maintains the previous amino acid's non-polar or polar properties
(*Genetics)
,In x-linked inheritance, how are alleles distributed? - ANSWERS-
Males receive one allele from the mother (on X) and none from the
father (provides Y).
(*Genetics)
How do dominant disorders proceed across generations? -
ANSWERS-They do not skip generations
(*Genetics)
What form of transmission is characteristic of X-linked disorders? -
ANSWERS-Mother to Son transmission
(*Genetics)
What are the sources of alleles in recessive diseases? - ANSWERS-A
diseased allele must be received from each parent in autosomal
disorders and it must be received just from the mother in X-linked
disorders
(*Genetics*)
What is the allelic basis for rare recessive genetic disorders? -
ANSWERS-It is most likely X-linked. It is much more rare to get two
carriers marrying into one family i.e. autosomal disorder
(*Anatomy)
Autocrine signaling - ANSWERS-Cell signaling. Cell secretes
hormone/chemical messenger (autocrine agent) to bind to cell's
autocrine receptors, leading to changes in the cell.
,(*Anatomy)
Somatostatin - ANSWERS-An 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)
Chief cells - ANSWERS-Stomach cells. These produce pepsinogen
and gastric lipase.
(*Anatomy)
Parietal cels - ANSWERS-Stomach cells that produce gastric acid
(*Anatomy)
G cells - ANSWERS-Produce Gastin, promote HCl release from
parietal cells, this chemical messenger also simulates parietal cell
maturation and growth.
(*Anatomy)
D cells - ANSWERS-Produce 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)
What is active gastric digestion characterized by? - ANSWERS-
Gastric distention, active secretion of hydogen ions (HCl), and a
consequently low gastric pH.
(*Anatomy)
Parasympathetic neurotransmitter - ANSWERS-(E.g.
ACh/acetylcholine) A chemical messenger of the parasympathetic
nervous system i.e. "rest & digest" activity.
(*Biochemistry)
How do enzymes affect the kinematics and thermodynamics of a
reaction - ANSWERS-Enzymes 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)
Which stage of an enzyme reaction is highest in energy? -
ANSWERS-The 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)
Transition state analogues - ANSWERS-Molecules that closely
resemble a subtrate's transition state structure in a reaction catalyzed
by enzymes. Transition state analogues are often the most tightly
