USMLE Step 1 Qs (1)
For those of you who love all things biology and living organisms especially anatomy and how features work in the human body then this is the quiz for you. If you are prepared to test your knowledge, try it out.
- 1.. The secondary oocyte enters the second meiotic division and proceeds as far as metaphase. Which of the following is the stimulus required for continuation of the second meiotic division to produce the haploid ovum?
- A.
Elevation of progesterone titers
- B.
The environment of the oviduct and uterus
- C.
Expulsion from the mature follicle
- D.
Fertilization by a spermatozoon
- E.
The presence of human chorionic gonadotropin (hCG)
- 2.
The structures shown in the accompanying photomicrograph are derived from which of the following?- A.
A combination of fetal and maternal tissues
- B.
Endometrial glands
- C.
Endometrial stroma
- D.
Fetal tissues
- E.
Maternal blood vessels
- 3.Which of the following is responsible for the prevention of polyspermy, the fertilization of an oocyte by more than one sperm?
- A.
Resumption of the first meiotic division
- B.
Resumption of the second meiotic division
- C.
Capacitation
- D.
The zona reaction
- E.
The release of enzymes from the sperm acrosome
- 4.Oogonia reach their maximum number at which of the following stages of human development?
- A.
Five months of fetal life
- B.
Birth
- C.
Puberty (12 to 14 years of age)
- D.
Adolescence (16 to 20 years of age)
- E.
Early adulthood (21 to 26 years of age)
- 5.Blood from the placenta is about 80% oxygenated. However, mixture with unoxygenated blood at various points reduces the oxygen content. Which of the following vessels contains blood with the highest oxygen content?
- A.
Abdominal aorta
- B.
Common carotid arteries
- C.
Ductus arteriosus
- D.
Pulmonary artery
- E.
Pulmonary vein
- 6.Which of the following hematopoietic tissues or organs develops from endoderm?
- A.
Thymus
- B.
Tonsils
- C.
Bone marrow
- D.
Spleen
- E.
Blood islands
- 7.Which of the following processes is responsible for fusion of the paired dorsal aortae?
- A.
Lateral folding
- B.
Craniocaudal folding
- C.
Gastrulation
- D.
Neurulation
- E.
Looping of the heart tube
- 8.
The region labeled with the arrow in the accompanying electron micrograph of the plasma membrane is responsible for which of the following functions?
- A.
Creation of a barrier to water-soluble molecules
- B.
Specific cellular receptors for ligands
- C.
Catalyzing membrane-associated activities
- D.
Transport of small ions
- E.
Connections to the cytoskeleton
- 9.Which of the following increases membrane fluidity under normal conditions?
- A.
Restriction of rotational movement of proteins and lipids in the membrane
- B.
Binding of integral membrane proteins with cytoskeletal elements
- C.
Transbilayer movement of phospholipids in the plasma membrane
- D.
High cholesterol content of the plasma membrane
- E.
Binding of an antibody to a cell surface receptor
- 10.
Members of the multiple-pass, G protein–linked family of receptors include the muscarinic, cholinergic, and -adrenergic receptors. Which of the following characterizes these receptors?
- A.
They possess intrinsic enzyme activity
- B.
They possess an arrangement of hydrophobic membrane-spanning segments
- C.
They possess an intracellular ligand-binding domain
- D.
They possess a single hydrophobic transmembrane segment
- E.
They are arranged so that both the amino- and carboxy-terminals are located intracellularly
- 11.Which of the following is the primary function of intermediate filaments?
- A.
Generate movement
- B.
Provide mechanical stability
- C.
Carry out nucleation of microtubules
- D.
Stabilize microtubules against disassembly
- E.
Transport organelles within the cell
- 12.Which of the following mechanisms is used to establish the mitochondrial electrochemical gradient?
- A.
The action of ATP synthase
- B.
Pumping of protons into the mitochondrial matrix by respiratory chain activity
- C.
Transport of ATP out of the matrix compartment by a specific transporter
- D.
Proton-translocating activity in the inner membrane
- E.
Transfer of electrons from NADH to O2 in the intermembrane space
- 13.Chloroquine is a weak base that neutralizes acidic organelles. In a pancreatic beta cell, which of the following would be a direct effect of chloroquine treatment?
- A.
Increased proinsulin content in secretory vesicles
- B.
Increased release of C peptide
- C.
Increased number of amylase-containing secretory vesicles
- D.
Reduced translation of glucagon mRNA
- E.
Increased stability of insulin mRNA
- 14.Which of the following is the function of the nucleosomes?
- A.
Package genetic material in a condensed form
- B.
Transcribe the DNA
- C.
Form pores for bilateral nuclear-to-cytoplasmic transport
- D.
Form the nuclear matrix
- E.
Hold together adjacent chromatids
- 15.
Which of the following is the primary function of the structure labeled between the arrows in the photomicrograph?
- A.
Extensive movement of substances over cell surfaces
- B.
Increase in surface area for absorption
- C.
Cell motility
- D.
Transport of intracellular organelles through the cytoplasm
- E.
Stretch
- 16.Which of the following is a function of the basement membrane?
- A.
Molecular filtering
- B.
Contractility
- C.
Excitability
- D.
Modification of secreted protein
- E.
Active ion transport
- 17.Which of the following types of epithelium typically line the urinary system?
- A.
Simple columnar epithelium
- B.
Stratified squamous epithelium
- C.
Transitional epithelium
- D.
Pseudostratified ciliated epithelium
- E.
Simple squamous epithelium
- 18.The extracellular matrix and the cytoskeleton communicate across the cell membrane through which of the following structures?
- A.
Proteoglycans
- B.
Integrins
- C.
Cadherins
- D.
Intermediate filaments
- E.
Microtubules
- 19.Which of the following is the function of fibronectin in the extracellular matrix?
- A.
Structural support
- B.
Binding of signaling molecules
- C.
Selectivity for passage of molecules
- D.
Elasticity
- E.
Adhesion and cell attachment
- 20.Ehlers-Danlos syndrome occurs in several forms. In type IV disease there is a defect in type III collagen synthesis. Which of the following symptoms would be most expected in a patient with this disorder?
- A.
Rupture of the intestinal or aortic walls
- B.
Hyperextensibility of the integument
- C.
Hypermobility of synovial joints
- D.
Increased degradation of proteoglycans in articular cartilages
- E.
Imperfections in dentin formation (dentinogenesis imperfecta)
- 21.. Which of the following is the primary function of brown adipose tissue?
- A.
To store unilocular energy
- B.
To provide thermal insulation
- C.
To mobilize lipid for export as fatty acids
- D.
To initiate the shivering-induced mobilization of lipid
- E.
To produce heat
- 22.Which of the following is a major contributor to the tensile strength of collagen?
- A.
Interactions with the FACIT collagens
- B.
The double helical arrangement of collagen
- C.
Electrostatic interactions
- D.
Intramolecular and intermolecular cross-links
- E.
Low concentrations of lysine
- 23.A patient with rheumatoid arthritis would exhibit which of the following joint changes?
- A.
Loss of the proteoglycan matrix and fibrillation in the articular cartilage during the early stages
- B.
Decreased levels of fibrinogen in the synovial fluid
- C.
Formation of osteophytes at the articular margins and eburnation of large weight-bearing joints in the later stages
- D.
Decreased number of leukocytes including PMNs in the synovial fluid
- E.
Heterologous autoantibodies deposited in joint surface
- 24.Patients with Cushing's syndrome often show osteoporotic changes. Which of the following is involved in the etiology of osteoporosis induced by Cushing's syndrome?
- A.
Decreased glucocorticoid levels that result in decreased quality of the bone deposited
- B.
Excess deposition of osteoid
- C.
Stimulation of intestinal calcium absorption
- D.
Decreased PTH levels
- E.
Bone fragility resulting from excess bone resorption
- 25.The collagenous protein in bone subserves which of the following functions?
- A.
Growth factor
- B.
Binding of ionic calcium and physiologic hydroxyapatite
- C.
Formation of the three-dimensional lattice of the matrix
- D.
Cell attachment
- E.
Binding of mineral components to the matrix
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