About Biology Question and Answers

1. Explain the difference between prokaryotic and eukaryotic cells.

Answer: Prokaryotic cells lack a nucleus and membrane-bound organelles (e.g., bacteria), while eukaryotic cells have a nucleus and organelles (e.g., plant and animal cells).

2. Describe the structure and function of the mitochondrion.

Answer: Mitochondria have a double membrane; the inner membrane has folds called cristae. They produce ATP through cellular respiration.

3. What are the main stages of cellular respiration, and where do they occur?

Answer: Glycolysis (cytoplasm), Krebs cycle (mitochondrial matrix), and Electron Transport Chain (inner mitochondrial membrane).

4. How does photosynthesis convert light energy into chemical energy?

Answer: Chlorophyll captures light energy to produce ATP and NADPH in the light reactions; the Calvin cycle uses them to make glucose from CO.

5. Compare mitosis and meiosis.

Answer: Mitosis produces 2 identical diploid cells for growth/repair; meiosis produces 4 non-identical haploid gametes for sexual reproduction.

6. What are the central dogma steps of molecular biology?

Answer: DNA RNA Protein; DNA is transcribed into RNA, which is translated into protein.

7. Explain the role of enzymes and how temperature or pH affects them.

Answer: Enzymes lower activation energy for reactions. Extreme temperature or pH can denature enzymes, reducing activity.

8. Difference between DNA replication and transcription?

Answer: DNA replication copies DNA for cell division; transcription makes RNA from a DNA template for protein synthesis.

9. How do competitive and non-competitive inhibitors affect enzyme activity?

Answer: Competitive inhibitors bind the active site; non-competitive inhibitors bind elsewhere, changing enzyme shape.

10. Describe the plasma membrane structure and function.

Answer: Phospholipid bilayer with embedded proteins; controls transport of substances in/out of the cell.

11. Explain signal transduction.

Answer: Cells receive signals (ligands), activate receptors, and trigger intracellular pathways to respond.

12. How do ligand-gated ion channels work in neurons?

Answer: Binding of a neurotransmitter opens the channel, allowing ions to flow and generate an electrical signal.

13. Compare oxidative phosphorylation and substrate-level phosphorylation.

Answer: Oxidative phosphorylation uses the electron transport chain and chemiosmosis; substrate-level phosphorylation directly transfers a phosphate group to ADP.

14. Differences between protein structures.

Answer: Primary = amino acid sequence; secondary = alpha helices & beta sheets; tertiary = 3D folding; quaternary = multiple polypeptide chains.

15. How does gene regulation differ in prokaryotes vs. eukaryotes?

Answer: Prokaryotes use operons for coordinated gene expression; eukaryotes have complex regulation with transcription factors and epigenetics.

16. Role of RNA splicing.

Answer: Removes introns from pre-mRNA to produce mature mRNA for translation.

17. What is the Hardy-Weinberg principle?

Answer: Allele frequencies remain constant in a population without evolution, assuming no mutation, migration, selection, or genetic drift.

18. How do antibodies recognize and neutralize antigens?

Answer: Antibodies bind specifically to antigens, blocking pathogens or marking them for destruction by immune cells.

19. Describe feedback mechanisms in hormone regulation.

Answer: Negative feedback reduces hormone production when levels are high; positive feedback increases hormone production (e.g., oxytocin in labor).

20. Difference between sympatric and allopatric speciation.

Answer: Sympatric speciation occurs in the same area (behavioral/genetic isolation); allopatric speciation occurs due to geographic isolation.