MCQs

Lipoproteins feature a hydrophilic protein shell that encloses a hydrophobic lipid core, allowing transport in aqueous blood plasma.

Galactolipids and cerebrosides, which are types of glycolipids, are heavily concentrated in the nervous system's myelin sheath.

Histones are basic proteins that bind tightly to the acidic phosphate backbone of DNA, creating a conjugated nucleoprotein complex.

Immunoglobulins (antibodies) and cell-surface receptors are functionally classified as glycoproteins due to their oligosaccharide chains.

Glycolipids are formed when carbohydrate groups (oligosaccharides) attach covalently to fatty acids or glycerol backbones within membranes.

Conjugated molecules consist of a basic biomolecule chemically bound to a distinct, non-protein or structural component termed a prosthetic group.

Replacing the 2'-OH group removes the nucleophile required for autophilic attack, making the synthetic RNA highly resistant to ribonuclease degradation.

Converting a CAA codon (coding for glutamine) into a UAA codon introduces a premature stop signal, producing a shorter, tissue-specific protein.

Promoter hypermethylation creates a structural barrier that blocks the binding of transcription factors and RNA polymerase, shutting down transcription.

The creation of a cryptic splice site inside an intron leads the spliceosome to misidentify the intron boundaries, incorporating junk sequence into the mature mRNA.

Telomerase is a reverse transcriptase that carries its own internal RNA molecule to serve as a structural template for lengthening chromosome ends.

The branch-point sequence contains an adenine residue whose 2'-OH attacks the 5' splice site, a critical step for lariat formation during splicing.

Puromycin structurally mimics an aminoacyl-tRNA, entering the A site and forming a premature peptide link that causes the peptide chain to detach.

The 2'-OH group on the ribose ring structurally prevents the RNA-DNA hybrid from matching the B-form geometry, forcing it into an A-form configuration.

Without a protective 3' poly-A tail, newly exported cytoplasmic mRNA molecules are quickly targeted and broken down by cellular exonucleases.

Alternative splicing allows exons to be skipped or combined in different ways, creating diverse protein products from one primary transcript.

The ribosome checks only the codon-anticodon match. The 3'-UUG-5' anticodon will pair with a 5'-AAC-3' codon, incorrectly introducing methionine.

In basic solutions, the 2'-OH group of ribose is deprotonated, launching a nucleophilic attack on the adjacent phosphorus atom that breaks the RNA backbone.

The sigma subunit is a transient initiation factor that grants the core prokaryotic RNA polymerase structural specificity to bind promoters.