Edexcel A Level Biology B Topic 2: Cells, Viruses and Reproduction of Living Things Exam Questions

About Edexcel A Level Biology B Topic 2: Cells, Viruses and Reproduction of Living Things

Topic 2 of Edexcel A Level Biology B covers how cells are organised and how living things reproduce. You compare eukaryotic and prokaryotic cells, use microscopy and calculate magnification, and learn the structure and replication of viruses. The cell cycle and mitosis explain growth and repair, while meiosis explains how gametes are made and how genetic variation arises. You then study sexual reproduction in mammals, including gamete structure and fertilisation, and in flowering plants, including pollen tube growth and double fertilisation. Core practical work on preparing and observing a root tip squash to see mitosis is commonly assessed, along with microscope calculations.

What you need to know

• Eukaryotic and prokaryotic cells Eukaryotic cells have a nucleus and membrane-bound organelles (mitochondria, ER, Golgi apparatus, lysosomes). Prokaryotes have circular DNA, plasmids, 70S ribosomes and a peptidoglycan cell wall.
• Microscopy Magnification = image size / actual size. Electron microscopes have higher resolution than light microscopes. Use an eyepiece graticule calibrated with a stage micrometer.
• Viruses Viruses consist of DNA or RNA inside a protein capsid, sometimes with an envelope. They replicate only inside host cells, through lytic or lysogenic (latent) cycles.
• Cell cycle and division Interphase includes DNA replication. Mitosis (prophase, metaphase, anaphase, telophase) gives identical diploid cells. Meiosis gives four haploid cells, with variation from crossing over and independent assortment.
• Reproduction in mammals Sperm and eggs are adapted for their roles. At fertilisation, the acrosome reaction allows the sperm to penetrate the zona pellucida and the cortical reaction prevents more sperm entering.
• Reproduction in plants Pollen grains land on the stigma, a pollen tube grows down the style, and two male nuclei enter the ovule: one fuses with the egg cell (zygote), the other with the polar nuclei (endosperm).

Common mistakes in Topic 2: Cells, Viruses and Reproduction of Living Things

• Saying viruses are prokaryotes; they are non-cellular.
• Stating that chromosomes split during anaphase of mitosis; sister chromatids separate.
• Confusing homologous chromosomes with chromatids in meiosis.
• Forgetting that double fertilisation in plants involves two male nuclei.
• Calculating magnification without converting units to match.

Try three Topic 2: Cells, Viruses and Reproduction of Living Things exam-style questions