Board-style MCQs and short questions in the BIEK / Sindh Board pattern. Tap an option to check yourself instantly. Solved questions are at the bottom.
Multiple-choice questions
Solved short questions & self-assessment
What is a peptide bond and how is it formed?
A peptide bond is the –CO–NH– link joining two amino acids.
It forms by condensation: the –COOH of one amino acid reacts with the –NH₂ of the next, releasing one molecule of water.
Distinguish DNA from RNA
DNA: deoxyribose sugar · double helix · bases A, T, G, C · stores heredity.
RNA: ribose sugar · single strand · bases A, U, G, C · carries the code to build proteins.
Base pairing in DNA: A = T (2 H-bonds), G ≡ C (3 H-bonds).
Explain the lock-and-key model of enzyme action
An enzyme is a biological catalyst with an active site of a particular shape.
Only a substrate that fits the active site (like a key in a lock) can bind and react → this explains enzyme specificity. Products leave and the enzyme is reused.