IB Biology 2

Question 1

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Answer

Helicase breaks the hydrogen bonds between complementary bases to unwind and separate the two strands of the double helix.

Question 2

What is the role of the rough endoplasmic reticulum (rER) in protein secretion?

Accepted Answer

Synthesizing proteins on attached ribosomes

Answer

The rough ER bears ribosomes on its surface where secretory proteins are synthesized and threaded into the ER lumen.

Question 3

In which stage of meiosis do homologous chromosomes separate?

Accepted Answer

Meiosis I anaphase

Answer

During anaphase I, spindle fibers pull homologous chromosome pairs to opposite poles, reducing the chromosome number by half.

Question 4

Which type of selection leads to two distinct phenotypic peaks in a population?

Accepted Answer

Disruptive selection

Answer

Disruptive selection favors extreme phenotypes at both ends of the distribution, often splitting a population into two distinct groups.

Question 5

What is the primary reason temperature affects enzyme activity?

Accepted Answer

High temperatures denature the enzyme's active site

Answer

Excessive heat breaks the bonds maintaining the tertiary structure of the enzyme, distorting the active site so substrate can no longer bind effectively.

IB - International Baccalaureate Practice Test

IB - International Baccalaureate Practice Test

IB Biology 2