multiple choice like

What is the significane of the protease active site?

determines substrate specificity

How can the fate of a newly synthesized protein be predicted?

by analyzing its N-terminal sequence

Why is the CRP protein responsive to both high cAMP and low glucose levels?

to regulate the lac operon when glucose is not available

How does the 19S particle of the eukaryotic 26S proteasome function?

regulates access to proteases

In the context of the lac operon, what does ligand-regulated deactivation accomplish?

turns off gene expression when appropriate

How does ligand-regulated de-repression function as a mode of regulation?

removes inhibition of gene expression

What does the binding of the lac repressor to DNA accomplish?

creates a loop in the DNA structure

What is the relationship between glucose availability and CRP-cAMP signaling?

low glucose increases cAMP levels activating CRP

Describe the catalytic activity of the peptidyl transferase reaction.

23S RNA (ribozyme) acts as an enzyme and catalyzes formation of peptide bond using energy stored in ester bond of aa-tRNA

What is the relationship between transcription and translation in terms of timing?

co-transcriptional translation can occur during mRNA synthesis

What happens to the P site tRNA after peptide bond formation occurs?

it is deacylated and released from the ribosome

In the peptidyl transferase reaction, which tRNA molecule attacks the other? (the tRNA in the ___ site attacks the ___ site tRNA)

the tRNA in the A site attacks the P site tRNA

What is the primary catalytic function of ribosomal RNA during protein synthesis?

forms peptide bonds between amino acids

Which position of the tRNA anticodon is known for its flexibility in base pairing?

first position (5' end)

Which position of the mRNA codon is known for its flexibility in base pairing?

third position (3' end)

In the context of RNA processing, what is the role of ribozymes?

catalyzing splicing + modifying tRNAs

What is the primary function of aminoacyl-tRNAs synthetases in protein synthesis?

activating amino acids and matching them with proper tRNA molecules

How does the 7-methyl guanosine cap protect nascent DNA in eukaryotes?

protecting from degradation via 5’ triphosphate linkage

Which structural feature of tRNA allows for wobble pairing with mRNA codons?

modified bases in the anticodon loop

What is added post-transcriptionally to the 3’ end of tRNA molecules?

CCA sequence

Where do aminoacyl-tRNA synthetases send mismatched tRNAs?

into editing site

How does TFIIH contribute to the initiation of transcription in eukaryotes?

unwinds DNA and phosphorylates the CTD of RNA Pol II

In the two-stage process of aminoacyl-tRNA synthetase activation, which stage involves forming the aminoacyl-adenylate intermediate?

stage 1: amino acid activation (adenylation)

stage 2: transfer to tRNA

intermediate forms during the first stage of aminoacyl-tRNA synthetase catalysis, when the amino acid is activated by ATP to form aminoacyl-AMP

carboxyl group of aa

What structural modification in the anticodon loop facilitates wobble pairing?

modified bases like inosine

What roles do Mg2+ ions play in the DNA Pol function?

activate water molecules for nucleotide incorporation

What is the functional significane of minor groove contacts in DNA recognition?

allow specific recognition of base sequences by proteins

What is the primary function of guanine nucleotide exchange factors in signal transduction?

activate monomeric GTPases and catalyze exchange of GDP for GTP

What structural feature of DNA ensures fidelity of genetic information and prevents mutations?

presence of thymine instead of uracil despite being more energetically costly (remember that thymine can spontaneously be deaminated into uracil, risking mutations)

What is the relationship between nicotinamide adenine dinucleotide (NAD) and cellular metabolism?

serves as an electron carrier in metabolic pathways

How do human milk oligosaccharide function in immune defense?

compete with bacterial glycans for human receptors by physically blocking them

How does the chemiosmotic theory explain ATP synthesis in mitochondria?

electron flow pumps protons creating a gradient that ATP synthase uses

What is the functional significance of citrate as a negative regulator in glycolysis?

signals sufficient energy availability and inhibits further glucose breakdown

Which step in glycolysis represents the first substrate-level phosphorylation?

conversion of 3-phosphoglycerate to 1,3-biphosphoglycerate

What structural feature allows membrane proteins to form stable alpha helices in nonpolar environments?

peptide backbone hydrogen bonds satisfied WITHIN helix structure

Why does lowering temperature require bacteria to alter their membrane phospholipic composition?

to maintain fluidity by reducing van der Waals interactions

What role do hydrophobic interactions play in protein folding?

drive folding by providing favorable entropy change

Why does an uncompetitive inhibitor decrease both Vmax and Km proportionally?

shifts equilibrium E + S ⇌ ES toward ES; traps enzyme in ESI complex, which cannot make product

Why do cis double bonds lead to lower melting temperatures than trans double bonds?

cis double bonds kink the hydrocarbon chain and prevents tight packing (weaken intermolecular forces and lower the melting temperature)

What is one way unfavorable reactions are pushed forward?

using multistep routes instead of one big transformation