ENADE Ciências Biológicas Practice Questions - ENADE Ciências Biológicas - Bacharelado and Licenciatura Exam - ENADE Ciências Biológicas Practice Questions - ENADE Ciências Biológicas

Question 1

According to the fluid mosaic model, plasma membranes consist of a dynamic lipid bilayer embedded with proteins. How does cholesterol regulate plasma membrane fluidity across varying physiological temperatures in eukaryotic cells?

It acts as a bidirectional fluidity buffer, restraining phospholipid movement at high temperatures and preventing close packing/crystallization of acyl chains at low temperatures. It permanently solidifies the lipid bilayer at elevated temperatures by covalently cross-linking adjacent sphingolipids and unsaturated fatty acids. It promotes constant passive ion leakage at low temperatures by forming transmembrane aqueous pore complexes across the hydrophobic core. It exclusively increases membrane fluidity at high temperatures by accelerating lateral phospholipid exchange and decreasing transition temperature.

Correct Answer:

It acts as a bidirectional fluidity buffer, restraining phospholipid movement at high temperatures and preventing close packing/crystallization of acyl chains at low temperatures.

Question 2

In animal epithelial cells, the apical uptake of D-glucose against its concentration gradient is coupled with the influx of sodium ions via the SGLT1 symporter. What mechanism provides the fundamental driving force that sustains this secondary active transport?

Direct enzymatic hydrolysis of cytosolic ATP by the catalytic nucleotide-binding domain of the SGLT1 symporter protein itself. The electrochemical Na+ gradient maintained across the basolateral membrane by primary active transport via the Na+/K+ ATPase pump. Passive facilitated diffusion of K+ out of the cell through apical voltage-gated potassium channels down its chemical gradient. Generation of an alkaline intracellular pH gradient driven by mitochondrial vacuolar-type H+-ATPases.

Correct Answer:

The electrochemical Na+ gradient maintained across the basolateral membrane by primary active transport via the Na+/K+ ATPase pump.

Question 3

During the synthesis and sorting of secretory and lysosomal proteins in eukaryotic cells, which molecular sequence of events directs the nascent polypeptide to the lumen of the rough endoplasmic reticulum (RER)?

A C-terminal KDEL retrieval signal binds to cytoplasmic importin-alpha receptors, directing the ribosome directly to nuclear pore complexes. A core oligosaccharide is transferred to cytosolic lysine residues by chaperone BiP, triggering passive diffusion through peroxisomal pores. An N-terminal hydrophobic signal sequence emerges from the ribosome, is recognized by the Signal Recognition Particle (SRP), halts translation, and docks onto the SRP receptor at the Sec61 translocon. Clathrin triskelions assemble around the ribosome on the cytosolic face, driving endocytic engulfment into cis-Golgi cisternae.

Correct Answer:

An N-terminal hydrophobic signal sequence emerges from the ribosome, is recognized by the Signal Recognition Particle (SRP), halts translation, and docks onto the SRP receptor at the Sec61 translocon.

Question 4

In human cellular pathology, I-cell disease (mucolipidosis type II) is a severe autosomal recessive disorder characterized by the absence of multiple hydrolytic enzymes in lysosomes and their aberrant hypersecretion into the extracellular fluid. What is the underlying biochemical defect causing this cellular phenotype?

Constitutive activation of dynamin GTPase, resulting in premature fusion of late endosomes with the mitochondrial outer membrane. Defect in the Sec61 translocon channel, preventing the entry of newly synthesized acid hydrolases into the lumen of the rough endoplasmic reticulum. Total absence of the vacuolar H+-ATPase (V-ATPase) proton pump in the lysosomal membrane, leading to an alkaline lysosomal lumen. Mutation in the gene encoding UDP-N-acetylglucosamine:lysosomal-enzyme N-acetylglucosaminyl-1-phosphotransferase, preventing the generation of mannose-6-phosphate (M6P) targeting signals in the cis-Golgi.

Correct Answer:

Mutation in the gene encoding UDP-N-acetylglucosamine:lysosomal-enzyme N-acetylglucosaminyl-1-phosphotransferase, preventing the generation of mannose-6-phosphate (M6P) targeting signals in the cis-Golgi.

Question 5

The eukaryotic cell cycle is tightly controlled by cyclin-dependent kinases (CDKs) and their regulatory cyclin subunits. What molecular event is required for a mammalian cell to pass the G1/S restriction point (R-point) and commit to DNA replication?

Hyperphosphorylation of the Retinoblastoma protein (pRb) by Cyclin D-CDK4/6 and Cyclin E-CDK2 complexes, releasing active E2F to transcribe S-phase genes. Dephosphorylation of the Retinoblastoma protein (pRb) by protein phosphatase 1, which locks the E2F transcription factor in a repressive complex. Proteasomal degradation of the Anaphase-Promoting Complex/Cyclosome (APC/C) triggered by high levels of Cyclin B1. Direct ubiquitin-mediated destruction of DNA polymerase delta and single-stranded DNA binding protein RPA by the p53 tumor suppressor.

Correct Answer:

Hyperphosphorylation of the Retinoblastoma protein (pRb) by Cyclin D-CDK4/6 and Cyclin E-CDK2 complexes, releasing active E2F to transcribe S-phase genes.

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Prepare with the ENADE Ciências Biológicas Practice Questions - ENADE Ciências Biológicas - Bacharelado and Licenciatura Exam practice quiz. This question bank includes 100 questions covering cells, such, physiological, eukaryotic, and human. Use it to review important concepts, identify knowledge gaps, and build confidence for the related exam, course, or assessment.

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ENADE Ciências Biológicas Practice Questions - ENADE Ciências Biológicas - Bacharelado and Licenciatura Exam

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