USABO Open eXAM STUDY GUIDe 2025/2026
COMpLeTe QUeSTIOnS WITH VeRIFIeD CORReCT
AnSWeRS/ 100% GUARAnTeeD pASS
1. What binding partner do integrins require in the extracellular matrix of an
animal cell? - ANSWER Integrins would most likely require firm attachment
to Actin.
2. Which molecular motor protein is involved in the contractile ring during
cytokinesis? - ANSWER Myosin.
3. What is the ratio of the concentration of protonated to deprotonated forms of
an acid with a pKa of 4.76 in a pH environment of 6.8? - ANSWER 1 : 100.
4. In oxidative phosphorylation, which chemical species is oxidized in choice
A? - ANSWER H2O.
5. In oxidative phosphorylation, which chemical species is reduced in choice
A? - ANSWER NAD+.
6. In oxidative phosphorylation, which chemical species is phosphorylated in
choice A? - ANSWER ATP.
7. Which of the following correctly describes how the lifespan of a protein is
regulated?
A. The part of the sequence coded for by the UTR tags it for destruction.
B. Giant protein complexes called ubiquitins destroy proteins after they
have remained in the cell for a certain time.
C. Proteins are methylated over time; heavily methylated proteins are
destroyed by proteasomes.
, D. Proteins are tagged with ubiquitins, which are recognized by
proteasomes; the proteasomes destroy the proteins.
E. Proteins tagged with methyl groups are destroyed by ubiquitins. -
ANSWER D. Proteins are tagged with ubiquitins, which are
recognized by proteasomes; the proteasomes destroy the proteins.
8. Of the following amino acids, which is least likely to form strong
interactions with other amino acids that contribute to the tertiary structure of
a given protein?
A. Histidine
B. Glutamate
C. Cysteine
D. Glycine
E. Serine - ANSWER D. Glycine
1. Thymine dimers arise when two adjacent thymine bases become covalently
linked. This interferes with normal DNA geometry and will cause replication
errors. Which of the following agents is the primary cause of the thymine
dimers?
A. Chemical mutagens
B. Beta emissions from radioactive decay
C. Gamma rays
D. X-rays
E. UV rays - ANSWER E. UV rays
2. Which of the following oligonucleotides would have the highest melting
point when paired with the proper complementary strand?
A. 5'-AAAAAAAA-3'
B. 5'-ATGCATGC-3'
C. 5'-CGCGCGCG-3'
D. 5'-TTTTGGGG-3'
, E. 5'-TATATATA-3' - ANSWER C. 5'-CGCGCGCG-3'
3. Which of the following is a way in which the cell increases gene expression
in the nucleus?
A. Acetylation of histone tails
B. DNA methylation
C. Locating a gene within heterochromatin
D. Dephosphorylating DNA
E. Alternative splicing - ANSWER A. Acetylation of histone tails
4. Which of the following statements about cellular ultrastructure is FALSE?
A. Nonmotile eukaryotic cilia are composed of 9 doublets of
microtubules in a ring, with no microtubules in the center ('9+0').
B. Bacterial flagella are composed of 9 doublets of microtubules in a
ring, with two microtubules in the center ('9+2').
C. Motile eukaryotic cilia are composed of 9 doublets of microtubules in
a ring, with two microtubules in the center ('9+2').
D. Centrioles are composed of nine triplets of microtubules arranged in a
ring.
E. The basal bodies of eukaryotic flagella are composed of nine triplets
of microtubules arranged in a ring. - ANSWER B. Bacterial flagella
are composed of 9 doublets of microtubules in a ring, with two
microtubules in the center ('9+2').
5. Which of the following chemicals or groups of chemicals is not a major
determinant of flower color?
A. Flavonols
B. Carotenoids
C. Cyanidin
D. Phytoalexins
E. Betacyanins - ANSWER D. Phytoalexins
, 6. Which of the following is not a characteristic of cycads?
A. Secondary growth from a vascular cambium
B. Fruit
C. True leaves
D. Insect pollination
E. Presence of neurotoxins and carcinogens in plant tissues - ANSWER
B. Fruit
7. . Which of the following does not take part in the light reactions of
photosynthesis?
A. Photosystem I
B. Photosystem II
C. Rubisco
D. ATP synthase
E. Cytochrome complex - ANSWER C. Rubisco
8. Lettuce seeds receive flashes of far red and red light in this order: far red,
red, far red, red, red, red, red, far red. The seeds will
A. Germinate since far red light induces germination.
B. Germinate since the first flash of light determines germination.
C. Germinate since there are more flashes of red light.
D. Not germinate since the flashes of light have destroyed the seeds.
E. Not germinate since only the last flash of light determines
germination. - ANSWER E. Not germinate since only the last flash of
light determines germination.
9. Which of the following statements about alternation of generations in land
plants is TRUE?
A. The gametophyte produces haploid cells by meiosis.
COMpLeTe QUeSTIOnS WITH VeRIFIeD CORReCT
AnSWeRS/ 100% GUARAnTeeD pASS
1. What binding partner do integrins require in the extracellular matrix of an
animal cell? - ANSWER Integrins would most likely require firm attachment
to Actin.
2. Which molecular motor protein is involved in the contractile ring during
cytokinesis? - ANSWER Myosin.
3. What is the ratio of the concentration of protonated to deprotonated forms of
an acid with a pKa of 4.76 in a pH environment of 6.8? - ANSWER 1 : 100.
4. In oxidative phosphorylation, which chemical species is oxidized in choice
A? - ANSWER H2O.
5. In oxidative phosphorylation, which chemical species is reduced in choice
A? - ANSWER NAD+.
6. In oxidative phosphorylation, which chemical species is phosphorylated in
choice A? - ANSWER ATP.
7. Which of the following correctly describes how the lifespan of a protein is
regulated?
A. The part of the sequence coded for by the UTR tags it for destruction.
B. Giant protein complexes called ubiquitins destroy proteins after they
have remained in the cell for a certain time.
C. Proteins are methylated over time; heavily methylated proteins are
destroyed by proteasomes.
, D. Proteins are tagged with ubiquitins, which are recognized by
proteasomes; the proteasomes destroy the proteins.
E. Proteins tagged with methyl groups are destroyed by ubiquitins. -
ANSWER D. Proteins are tagged with ubiquitins, which are
recognized by proteasomes; the proteasomes destroy the proteins.
8. Of the following amino acids, which is least likely to form strong
interactions with other amino acids that contribute to the tertiary structure of
a given protein?
A. Histidine
B. Glutamate
C. Cysteine
D. Glycine
E. Serine - ANSWER D. Glycine
1. Thymine dimers arise when two adjacent thymine bases become covalently
linked. This interferes with normal DNA geometry and will cause replication
errors. Which of the following agents is the primary cause of the thymine
dimers?
A. Chemical mutagens
B. Beta emissions from radioactive decay
C. Gamma rays
D. X-rays
E. UV rays - ANSWER E. UV rays
2. Which of the following oligonucleotides would have the highest melting
point when paired with the proper complementary strand?
A. 5'-AAAAAAAA-3'
B. 5'-ATGCATGC-3'
C. 5'-CGCGCGCG-3'
D. 5'-TTTTGGGG-3'
, E. 5'-TATATATA-3' - ANSWER C. 5'-CGCGCGCG-3'
3. Which of the following is a way in which the cell increases gene expression
in the nucleus?
A. Acetylation of histone tails
B. DNA methylation
C. Locating a gene within heterochromatin
D. Dephosphorylating DNA
E. Alternative splicing - ANSWER A. Acetylation of histone tails
4. Which of the following statements about cellular ultrastructure is FALSE?
A. Nonmotile eukaryotic cilia are composed of 9 doublets of
microtubules in a ring, with no microtubules in the center ('9+0').
B. Bacterial flagella are composed of 9 doublets of microtubules in a
ring, with two microtubules in the center ('9+2').
C. Motile eukaryotic cilia are composed of 9 doublets of microtubules in
a ring, with two microtubules in the center ('9+2').
D. Centrioles are composed of nine triplets of microtubules arranged in a
ring.
E. The basal bodies of eukaryotic flagella are composed of nine triplets
of microtubules arranged in a ring. - ANSWER B. Bacterial flagella
are composed of 9 doublets of microtubules in a ring, with two
microtubules in the center ('9+2').
5. Which of the following chemicals or groups of chemicals is not a major
determinant of flower color?
A. Flavonols
B. Carotenoids
C. Cyanidin
D. Phytoalexins
E. Betacyanins - ANSWER D. Phytoalexins
, 6. Which of the following is not a characteristic of cycads?
A. Secondary growth from a vascular cambium
B. Fruit
C. True leaves
D. Insect pollination
E. Presence of neurotoxins and carcinogens in plant tissues - ANSWER
B. Fruit
7. . Which of the following does not take part in the light reactions of
photosynthesis?
A. Photosystem I
B. Photosystem II
C. Rubisco
D. ATP synthase
E. Cytochrome complex - ANSWER C. Rubisco
8. Lettuce seeds receive flashes of far red and red light in this order: far red,
red, far red, red, red, red, red, far red. The seeds will
A. Germinate since far red light induces germination.
B. Germinate since the first flash of light determines germination.
C. Germinate since there are more flashes of red light.
D. Not germinate since the flashes of light have destroyed the seeds.
E. Not germinate since only the last flash of light determines
germination. - ANSWER E. Not germinate since only the last flash of
light determines germination.
9. Which of the following statements about alternation of generations in land
plants is TRUE?
A. The gametophyte produces haploid cells by meiosis.
