Biology Key Concepts Flashcards

What is the role of the enzyme rubisco in the Calvin cycle?

Answer: It catalyses the fixation of CO₂ by combining it with ribulose bisphosphate (RuBP)

Rubisco (ribulose bisphosphate carboxylase/oxygenase) catalyses the carboxylation of RuBP, combining it with CO₂ to form two molecules of glycerate-3-phosphate (GP). It is the most abundant enzyme on Earth.

Which type of immunity is provided by vaccination?

Answer: Artificial active immunity

Vaccination introduces antigens (weakened/dead pathogens or their fragments) to stimulate the immune system to produce memory cells and antibodies. It is 'artificial' because it involves deliberate exposure, and 'active' because the body mounts its own immune response.

During meiosis, when does crossing over occur?

Answer: Prophase I

Crossing over occurs during prophase I when homologous chromosomes pair up (synapsis) and form bivalents. Sections of non-sister chromatids exchange, producing recombinant chromosomes and increasing genetic variation.

What is the net gain of ATP from one molecule of glucose during glycolysis?

Answer: 2 ATP

Glycolysis produces 4 ATP in total but uses 2 ATP in the phosphorylation of glucose and fructose-6-phosphate, giving a net gain of 2 ATP per glucose molecule.

In the Hardy-Weinberg equation p² + 2pq + q² = 1, what does 2pq represent?

Answer: The frequency of heterozygous individuals in the population

In Hardy-Weinberg equilibrium, p² represents homozygous dominant frequency, q² represents homozygous recessive frequency, and 2pq represents heterozygous frequency. The equation models allele frequencies in a non-evolving population.

Which cells in the immune system are responsible for producing antibodies?

Answer: Plasma cells (differentiated B lymphocytes)

Plasma cells are fully differentiated B lymphocytes that secrete large quantities of specific antibodies. After antigen presentation and T helper cell activation, B cells clonally expand and differentiate into plasma cells and memory B cells.