Biology: Membranes, Genetics, Energy and Homeostasis
Akita biology questions link molecular mechanisms to whole-organism effects: membrane transport, enzyme kinetics, Mendelian and molecular genetics, photosynthesis and respiration, homeostasis and ecology. Expect data interpretation from tables, pedigrees and cross diagrams, with answers that must name the mechanism, not just the outcome.
Core rules and concepts
- Enzymes lower activation energy; rate rises with substrate concentration then plateaus as active sites saturate. Denaturation changes shape and destroys activity.
- Photosynthesis: light reactions produce ATP and NADPH; the Calvin cycle fixes CO₂ using RuBP.
- Respiration: glycolysis in the cytoplasm; the Krebs cycle and oxidative phosphorylation in the mitochondria.
- Independent assortment applies to genes on different chromosomes.
- Homeostasis uses negative feedback: effectors counteract the deviation.
Worked example
In a cross AaBb × AaBb with independent assortment, what fraction of offspring show dominant A and recessive b?
Reasoning: treat each gene separately. Aa × Aa gives 3/4 A_ (AA or Aa) and 1/4 aa. Bb × Bb gives 1/4 bb. Because the genes assort independently, multiply: 3/4 × 1/4 = 3/16.
Traps that cost marks
- Confusing the genotype ratio 1:2:1 with the phenotype ratio 3:1.
- Forgetting that "A_" covers two genotypes.
- Assuming linkage when the question states independent assortment.
- Placing glycolysis in the mitochondria.