Biochemistry & Cell Biology

Biochemistry & Cell Biology

Plants that take up high amounts of metal elements from soil and store them in their aerial tissue are known as (A) hype

Hyperaccumulators are plants accumulating metals >100-fold normal concentrations in shoots exceeding thresholds like 1000 mg/kg. Metallophytes tolerate metal-rich soils, many being hyperaccumulators used in phytoremediation. Chelators are chemical agents, reducers are not metal accumulator plant categories.

Ref: Begon, Townsend and Harper, Ecology: From Individuals to Ecosystems, 4th Edition, and Taiz and Zeiger, Plant Physiology, 6th Edition, Chapter 26, Mineral Nutrition discusses hyperaccumulators and metallophytes as metal-accumulating plants for phytoremediation, published by Wiley and Sinauer Associat

View Details

Biochemistry & Cell Biology

Transport proteins associated with facilitated diffusion process include (A) Uniporters (B) Pump motors (C) Ion channels

Facilitated diffusion is passive down gradient requiring no energy input. Uniporters carry single solute bidirectionally and ion channels form aqueous pores for ions, both passive. Pump motors and transport motors use ATP or cytoskeletal energy for active transport, not facilitated diffusion processes physiologically.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 11, Membrane Transport discusses uniporters and ion channels as facilitated diffusion carriers versus pumps for active transport, published by Garland Science.

View Details

Biochemistry & Cell Biology

When aligning sequences that are highly divergent best results will be obtained with which substitution matrix?

PAM matrices model evolutionary distance. Low numbers like PAM1 reflect short divergence retaining high identity. PAM250 corresponds to 250 mutations per 100 residues, modeling distant relationships with greater tolerance for substitutions, thus optimal for highly divergent sequences compared to PAM1 or PAM25.

Ref: Durbin et al., Biological Sequence Analysis, 1998, Chapter 3 and Mount, Bioinformatics Sequence and Genome Analysis, 2nd Edition, Chapter 3, Substitution Matrices discusses PAM matrices where high numbers like PAM250 best for divergent alignments, published by Cambridge University Press.

View Details

Biochemistry & Cell Biology

The PDB-ID or PDB code is of ________ character and is represented as ________.

Protein Data Bank identifiers consist of four alphanumeric characters, typically starting with digit followed by letters and numbers, for example 1TIM. This code uniquely identifies experimentally determined macromolecular structures deposited, enabling retrieval from RCSB PDB database quickly across worldwide archives.

Ref: Berman et al., The Protein Data Bank, Nucleic Acids Research, Volume 28, Issue 1, 2000, and RCSB PDB official documentation explains PDB ID as four-character alphanumeric code uniquely identifying entries, published by Oxford University Press and RCSB.

View Details

Biochemistry & Cell Biology

In the FASTA format the definition line start with

FASTA format widely used for nucleotide and protein sequences. Each entry begins with header line initiated by greater-than symbol > followed by identifier and description. Subsequent lines contain sequence data. Symbols # and @ denote other formats like SAM or FASTQ.

Ref: Pearson and Lipman, Improved tools for biological sequence comparison, Proceedings of National Academy of Sciences, 1988 and Pevsner, Bioinformatics and Functional Genomics, 3rd Edition, Chapter 3, Sequence Formats describes FASTA format with > as definition line starter, published by Wiley-Blackwel

View Details

Biochemistry & Cell Biology

Which algorithm is used for global alignment?

Global alignment aligns entire sequences end-to-end maximizing overall similarity, suitable for similar length sequences. Needleman-Wunsch dynamic programming uses scoring matrix and gap penalties to find optimal global alignment. Smith-Waterman finds local alignments, therefore Needleman-Wunsch is correct for global strategy.

Ref: Mount, Bioinformatics: Sequence and Genome Analysis, 2nd Edition, Chapter 3 and Durbin et al., Biological Sequence Analysis, Probabilistic Models, Chapter 2, Alignment describes Needleman-Wunsch algorithm for global sequence alignment versus Smith-Waterman local, published by Cold Spring Harbor Labo

View Details

Biochemistry & Cell Biology

Chose a compound with best docking score.

Molecular docking scoring approximates binding free energy ΔG. More negative values indicate stronger spontaneous protein-ligand interaction with lower free energy, better affinity and stability. Therefore -9.0 kcal/mol represents strongest binding compared to -3.0, -4.5 and positive unfavorable +6.2 kcal/mol scores.

Ref: Leach, Molecular Modelling Principles and Applications, 2nd Edition, Chapter 9, Docking and Virtual Screening and Morris et al., AutoDock, Journal of Computational Chemistry, discuss binding free energy where more negative docking score indicates higher affinity, published by Prentice Hall.

View Details

Biochemistry & Cell Biology

Which one of the following is an experimental method for determining three dimensional structure of a protein?

X-ray crystallography experimentally determines atomic coordinates by diffracting X-rays through protein crystals and calculating electron density maps. Threading, homology modeling and ab-initio methods are computational predictions requiring templates or energy minimization, not direct experimental structure determination methods.

Ref: Branden and Tooze, Introduction to Protein Structure, 2nd Edition, Chapter 3, Structure Determination and Alberts et al., Molecular Biology of the Cell, 6th Edition, explains X-ray crystallography as experimental method for protein structure determination versus modeling, published by Garland Scienc

View Details

Biochemistry & Cell Biology

In chronic kidney disease, hyperkalemia is often a concern due to impaired renal excretion. Which hormone’s decreased ac

Aldosterone via mineralocorticoid receptor increases Na+ reabsorption and K+ secretion in collecting duct principal cells. CKD reduces renal mass and impairs RAAS, lowering aldosterone responsiveness and K+ excretion. Hypoaldosteronism thus worsens hyperkalemia, especially with diabetes or ACE inhibitor use.

Ref: Guyton and Hall, Textbook of Medical Physiology, 14th Edition, Chapter 77, Mineralocorticoids and Harrison's Principles of Internal Medicine, Chapter 310, discuss aldosterone regulation of potassium excretion and hyperkalemia in chronic kidney disease, published by Elsevier and McGraw-Hill Education

View Details

Biochemistry & Cell Biology

The ATP-dependent pathway of protein degradation in eukaryotic cells is quite different, involving the protein ubiquitin

Ubiquitin is activated by E1 ubiquitin-activating enzyme using ATP forming thioester. It transfers to E2 conjugating enzyme, then E3 ligase provides substrate specificity, catalyzing isopeptide bond formation between ubiquitin C-terminus and lysine of target protein for proteasomal degradation.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 6, Protein Degradation via Ubiquitin-Proteasome System describes E1 activating, E2 conjugating and E3 ligase enzymes mediating ubiquitination for proteolysis, published by Garland Science.

View Details

Biochemistry & Cell Biology

The most sensitive test among thyroid function test for detecting primary hypothyroidism?

Primary hypothyroidism results from thyroid failure reducing T4 T3, removing negative feedback on pituitary. TSH rises earliest and most sensitively even when free T4 still normal, due to log-linear relationship. Thus elevated TSH is earliest marker before total T4 or T3 declines.

Ref: Harrison's Principles of Internal Medicine, 21st Edition, Chapter 383, Thyroid Function Tests and Guyton and Hall, Textbook of Medical Physiology, 14th Edition, discusses TSH as most sensitive test for primary hypothyroidism due to feedback amplification, published by McGraw-Hill and Elsevier.

View Details

Biochemistry & Cell Biology

From the following statements, match the correct statements about the mechanism of action of antibiotics given below: Li

Tetracycline binds 30S ribosome blocking A-site aminoacyl-tRNA entry in bacteria. Chloramphenicol inhibits bacterial 50S peptidyl transferase sparing cytosolic eukaryotic ribosomes. Cycloheximide blocks 80S eukaryotic peptidyl transferase. Streptomycin aminoglycoside causes mRNA misreading and initiation inhibition at high concentrations.

Ref: Prescott et al., Microbiology, 10th Edition, Chapter 34, Antimicrobial Chemotherapy and Nelson and Cox, Lehninger Principles of Biochemistry, Chapter 28, discuss antibiotic targets including tetracycline A-site, chloramphenicol, cycloheximide and streptomycin misreading, published by McGraw-Hill Edu

View Details