IBDP Biology: Core Medium Concepts

Front

Explain the role of induced fit in enzyme catalysis.

Back

Induced fit occurs when the substrate binds to the active site, causing the enzyme to change shape and tighten around the substrate. This stabilizes the transition state, lowers the activation energy, and ensures precise positioning of catalytic groups, increasing reaction efficiency.

Front

Distinguish between competitive and non-competitive inhibition.

Back

Competitive inhibitors resemble the substrate and bind to the active site, blocking substrate binding; their effect can be overcome by increasing substrate concentration. Non-competitive inhibitors bind to an allosteric site, changing the enzyme's shape so the active site no longer functions; increasing substrate concentration does not reverse this inhibition.

Front

Compare the structure and stability of DNA and RNA.

Back

DNA is double-stranded, forming a double helix with complementary base pairing (A-T, C-G), making it chemically stable and ideal for long-term storage. RNA is usually single-stranded, contains Uracil instead of Thymine, and has a ribose sugar with an extra -OH group, making it more reactive and less stable, suitable for short-term functions like protein synthesis.

Front

Explain how anti-parrallel strands and complementary base pairing facilitate DNA replication.

Back

The anti-parallel nature (5' to 3' vs 3' to 5') allows DNA polymerase to synthesize new strands only in the 5' to 3' direction, creating leading and lagging strands. Complementary base pairing ensures that the genetic code is copied accurately, as each strand serves as a template for the exact sequence of nucleotides on the new strand.

Front

Define: Gene Mutation (Silent, Missense, Nonsense).

Back

These are point mutations involving a single base substitution: Silent codes for the same amino acid (no effect); Missense codes for a different amino acid (may alter protein function); Nonsense codes for a stop codon (premature termination, usually non-functional protein).