Unit 2 Practice Exam Questions

Question 1

Small signaling molecules such as NO bind to surface receptors on target cells (T/F)

Answer 1

False, these small molecules interact directly with enzymes in the cytoplasm

Question 2

If chorionic villus testing returns a result of 47,XY,+21, then it can be concluded that the fetus has down syndrome. TF?

Answer 2

False, results from CVS testing could reflect an anomoly in the placenta only (confined placental mosacism). All abnormal results from CVS must be confirmed by amniocentesis

Question 3

23
.
For the enzymatic reaction shown below, the following rate constants were determined:  
k1 = 10 mM-1 sec
k2 = 20sec
k3 = 40sec-1

What is the dissociation constant of the
enzyme-substrate complex?

Answer 3

dissociation constant = k2/k1

20/10 = 2nM

Question 4

It has been shown that chromosomal breakage and rearrangement are key
characteristics of 
cancer.
A. 
True
B.
False

Answer 4

true

Question 5

Hexokinase and glucokinase are isozymes that carry out the initial step of glucose metabolism, conversion of glucose to glucose-6-phosphate. Hexokinase has a Km for glucose of 0.1 mM and glucokinase has a Km
for glucose of 5 mM. Cytosolic glucose
(substrate) concentration is 2 mM in a fasting subject and 6 mM in a subject who has just eaten a large meal. Which of the following conclusions can be drawn from this in formation?

A. The rate of the hexokinase reaction will triple when the glucose concentration goes
from 2 mM to 6 mM.
B. The rate of the glucokinase reaction will triple when the glucose concentration goes
from 2 mM to 6 mM.
C. At 2 mM glucose, 2/7 of the active sites on glucokinase are bound to substrate.
D. All of the above are true.
E. None of the above are true

Answer 5

C, use equation Fe=[s]/(km+[s])

Question 6

total enzyme concentration = 1nm
inhibitor = 2nm

Uninhibited enzyme = slope 4, y int of 1
+2mM inhibitor A = slope 8, y int of 1
+2mM inhibitor B = slope 8, y int of .5

what can be concluded from this data?

A.Both inhibitor A and inhibitor B are competitive inhibitors.
B. Both inhibitor A and inhibitor B have the same Ki
C.The plot for inhibitor A will have the same x intercept as the plot for the uninhibited
enzyme.
D.The Ki for inhibitor B will double if the total enzyme concentration is doubled

Answer 6

both have same Ki

both have same slope and same concentration

plug into alpha = 1+ I/Ki

Question 7

Activated T cells express _______________, which binds to B7 with 20 times higher affinity than CD28 and results
in _____________ of T cell activity and proliferation.

Answer 7

CTLA, Suppression

Question 8

Superantigens are…

Answer 8

bacterial toxins that activate T-cells at a 100x greater rate than other antigens

Question 9

Describe the drug used for immune rejection

Answer 9

CTLA fused to Fc region of an Ig molecule

Question 10

Patient had a helminth infection resulting in high levels of IFN gamma and activated macrophages. Patients serum had high levels of IgG. Pronogis?

Answer 10

Poor, due to prescence of a TH1 response.

Need TH2 for helminths (IgE)

Question 11

A cyclin molecule can best be described as…

Answer 11

the regulatory subunit of a protein kinease

Question 12

After prolonged exposure to a high concentration of a hormone, you find that a specific tissue shows a greatly
decreased response to the hormone (adaptation). What is most likely to be responsible?

Answer 12

a change in the number of receptors on each cell

Question 13

patient presents with tumor, DNA reveals novel mutations in kknown/suspected receptors associated with tumor tissue. Which type of receptor is frequently the target of oncogenic mutations and therefor most likely to be linked to the tumor growth in this patient?

Answer 13

Receptor Tyrosine Kineases

Question 14

EBV vs CMV?

Answer 14

EBV causes severe sore throat more often

Question 15

Which of the following statements about herpesvirus latency is CORRECT?
A: Latency is a hindrance to vaccine development because the virus genome is maintained in the cell for the life of the infected
person.
B: Latency is established before symptoms of the primary infection are apparent.
C: Reactivation from latency may not be apparent to the infected person.
D: The genome is present in a cell but infectious virions are absent.
E: All of the above
F: None of the above

Answer 15

all of the above

Question 16

After polio binds GI receptors. When does infection begin and what happens next?

Answer 16

infection begins when genome enters cytoplasm

Polio’s genome is +ssRNA which is recognized by ribosomes, so the next step involves translation of genomic mRNA into viral polyprotein by host ribosomes

Question 17

child has recurrent infections with labs showing absence of large granular lymphocytes. Flow cytometry shoes normal numbers of CD3+, CD19+, and lack of CD56+ cells. What ist he probable mechanism?

Answer 17

mutation of an essential transcription factor

NK cells are “large granular lymphocytes” with a cd56+ receptor

Question 18

Which statement about rotovirus is correct?

1. incidence peaks during summer
2. Gastroenteritis is most common in infants and toddlers
3. icosahedral, enveloped, -ssRNA virus
4. heat killed injectable rotovirus vaccine is used in the US; the live, attenuated, rotavirus vaccine is used in other countries

Answer 18

b - Gastroenteritis caused by the virus is most common in infants/toddlers

Question 19

icosahedral capsid with spikes at verticies with no envelope, double stranded DNA

most likely is?

Answer 19

adenovirus

Question 20

the bronchus of a dead smoker has respiratory epithelium likely replaced with?

Answer 20

stratified squamous epithelium (like skin)

Question 21

protection from tumor cells of the cervix has been demonstrated in women who have
received the Gardasil. The major components of the vaccine are capsid proteins from a DNA virus. The
pre-neoplastic lesions do not express capsid proteins, but instead express viral oncoproteins
analogous to the

Answer 21

t antigen of merkel cell polyomavirus

Question 22

Both chromosome breakage syndromes and HNPCC (hereditary non-polyposis colon cancer) are associated with

Answer 22

mutations in dna repair genes

Question 23

To kill bacteria that are adapted to survive inside of phagocytes, the most important immune response
is____________________.

Answer 23

TH1 response and activation of macrophages

Question 24

Which of the following junction types is MOST IMPORTANT for determining epithelial tissue permeability

Answer 24

tight

Question 25

Expression of the ribozyme called telomerase in cancer cells may prevent cellular senescence by

Answer 25

stimulating RNA templated extension of the parental DNA strand

Question 26

which is not a component of the BCR? cd2, cd19, cd21, cd81

Answer 26

cd2 - this is an adhesion molecule found on T cells and NK cells

Question 27

14 year old gets a thymectomy, likely outcome?

Answer 27

will likely survive with functional immune system

Question 28

A newborn in the neonatal intensive care unit has features consistent with Patau syndrome. The perinatologist requests that the
diagnosis be confirmed by karyotype analysis. It is important to determine the karyotype of the baby because .
􁅞􀀃A: it will reveal which parent is the source of the abnormality, which is important for future family planning
􁅚􀀃B: it is possible that this child has a normal chromosome constitution and is actually affected by an autosomal recessive phenocopy. In addition, if the child has a chromosome rearrangement involving chromosome 13, the chromosome imbalance could place future pregnancies at risk
􁅞􀀃C: if the child is a mosaic, the mutation cannot be due to an error in meiosis, and therefore the recurrence risk in future pregnancies will be negligible
􁅞􀀃D: if the disease causing duplication can be identified, it will reveal which of the parents is a carrier of that mutation which is important for future
family planning
􁅞􀀃E: it will aid in his/her care

Answer 28

it is possible that this child has a normal chromosome constitution and is actually affected by an autosomal recessive phenocopy. In addition, if the child has a chromosome rearrangement involving chromosome 13, the chromosome imbalance could place future pregnancies at risk

Answer B: The diagnosis of Patau syndrome at birth would be done by clinical assessment. It is always a good idea to have the
chromosome complement confirmed by karyotype analysis, but, more important, is the confirmation that the trisomy is the result of a meiotic
nondisjunction event giving rise to 3 individual copies of chromosome 13. The recurrence risk for this is quite low. However, the trisomy could also be
the result of a nondisjunction error if one of the parents is a carrier of a Robertsonian translocation involving chromosome 13. Clinically there is no way
to tell the difference between a translocation trisomy and a three chromosome trisomy, but if a parent is a carrier of a rearrangement, then he/she is at
risk of having another child with a trisomy. Knowing that there is a recurrence risk is an important piece of information for future family planning.
Learning Outcomes: Genetics

Question 29

A 24-year-old woman who is 18 weeks pregnant is meeting with her obstetrician to discuss prenatal screening for chromosomal
abnormalities. This is her first pregnancy and she has no family history of chromosomal disorders. Which of the following should
be offered and discussed with the patient?

Answer 29

amniocentesis

This patient is in her 2nd trimester and amniocentesis is the only listed procedure that is carried out in the 2nd trimester. All others are 1st
trimester procedures/screens.
Learning Outcomes: Genetics

Question 30

A 45-year-old patient presents with an acute leg cramp that has become worse over several days, along with evidence of restricted
circulation in his leg. After further investigation, it is determined that he has a deep vein thrombosis (a clot has formed in a leg
vein). He is prescribed the drug coumadin. Coumadin has a structure similar to Vitamin K and acts as an anticoagulant. This was
not the first time that this patient had a deep vein thrombosis. After he recovered, his physician suggested that he be tested for a
deficiency in one of the factors involved in regulation of coagulation. Genetic deficiency in which of the following
is MOST LIKELY to cause the tendency toward thrombosis (excessive clotting) in this patient?

Answer 30

anti-thrombin ATIII deficiency

Question 31

in a LV, steeper the curve, the ____ the Km

Answer 31

higher the Km of the enzyme, less affinity

Question 32

Preferential binding of the transition state by the enzyme is a major catalytic strategy, which is utilized by most enzymes and also
exploited in drug design. Which of the following statements BEST describes this catalytic strategy?

Answer 32

The enzyme lowers the activation energy for the reaction by stabilizing the highest energy structure that occurs during the reaction.

Question 33

You proceed to explain that gastrulation is the process during which

Answer 33

􁅚􀀃D: the three germ layers of the trilaminar embryo are established

Question 34

Which mechanism of immune evasion is used by BOTH trypanosoma brucei (sleeping sickness) and hepatitis C virus?

Answer 34

they exhibit antigenic variation

Question 35

How are subcutaneous mycoses USUALLY contracted?

Answer 35

soil contamination of injuries, rose pickers disease

Question 36

Which of the following is MOST LIKELY to describe the HIV protease isolated from a patient who has become resistant to an HIV
protease inhibitor after a prolonged antiretroviral treatment that included this inhibitor?
􁅞􀀃A: The active site of the protease has several amino acid changes that make the active site cleft more hydrophilic.
􁅚􀀃B: The kcat/Km of the protease is similar to the wild-type protease.
􁅞􀀃C: The protease has a lower Ki for the inhibitor than the wild-type protease.
􁅞􀀃D: The protease has a single mutation at its active site aspartate.

Answer 36

Kcat/Km of the protease is similar to the Wild Type protease

Question 37

The Iditarod dog sled race commemorates a 1925 effort by dog sledders to get medication to children in Nome, Alaska who were
dying of Diphtheria. Which of the following is the medication that "the Mushers􀂴􀀃transported to Nome?
􁅚􀀃A: Antiserum to Diphtheria toxin
􁅞􀀃B: Diphtheria toxin
􁅞􀀃C: Recombinant Diphtheria proteins
􁅞􀀃D: Tetanus toxoid
􁅞􀀃E: TNF-alpha
Learning Outcomes:

Answer 37

antiserum to diphteria toxin

Question 38

What syndrome results in thymic aplasia (congenital deficiency of the thymus)?
􁅞􀀃A: Acquired Immunodeficiency Syndrome
􁅞􀀃B: Bare Lymphocyte Syndrome
􁅚􀀃C: DiGeorge Syndrome
􁅞􀀃D: Down Syndrome
Learning Outcomes: Immunology

Answer 38

digeorge syndrome

Question 39

Patients with Ehlers-Danlos Type IV syndrome may display aortic and intestinal ruptures and have a defect in the gene for

Answer 39

collagen type III

Question 40

Jeremy has been diagnosed with velocardiofacial syndrome (VCFS). If you compare his DNA with that of his parents, you would
MOST LIKELY find evidence of ________________ in Jeremy’s DNA.

Answer 40

a deletion

Question 41

how does malaria evade the immune system?

Answer 41

antigenic variation = a single nucleotide point replacement/mutation.

organisms can carry upwards of 1,000 different genes allowing for expression of distinct surface molecules

Question 42

what group of parasites have an intracellular phase in their life cycle to conceal antigens?

Answer 42

plasmodium species

trypnosoma cruiz, leishmania, cryptosporidum parvum

Question 43

hookworms are what type of parasite?

Answer 43

obligatory parasite

Question 44

example of opportunitist pathogen?

Answer 44

toxoplasma gondii

Question 45

one of the most important mediators released by mast cells when they bind ____

Answer 45

mast cells bind IgE, release eosinophil chemotactic factor which attracts eosinophils to the area of infection.