AQA GCSE Biology 4.1.1 Cell Structure Exam Questions

About AQA GCSE Biology 4.1.1 Cell Structure

Cell structure is the opening section of AQA GCSE Biology and is examined on Paper 1. You need to compare eukaryotic and prokaryotic cells, name the parts of animal, plant and bacterial cells and explain how specialised cells are adapted to their jobs. The section also covers light and electron microscopy, magnification calculations and standard form, and (Biology only) culturing microorganisms using aseptic technique. These ideas underpin almost every other topic, from transport in cells to respiration and photosynthesis. Examiners regularly set magnification calculations, unit conversions between mm, micrometres and nm, and questions on the microscopy and microorganism required practicals.

What you need to know

• 4.1.1.1 Eukaryotes and prokaryotes Eukaryotic cells (plants, animals) have a nucleus containing the genetic material. Prokaryotic cells (bacteria) are much smaller, have no nucleus, and their DNA is a single loop with extra small rings called plasmids.
• 4.1.1.2 Animal and plant cells Animal and plant cells contain a nucleus, cytoplasm, cell membrane, mitochondria (aerobic respiration) and ribosomes (protein synthesis). Plant cells also have chloroplasts, a permanent vacuole filled with cell sap and a cellulose cell wall.
• 4.1.1.3 Cell specialisation Learn examples such as sperm cells (tail, many mitochondria), nerve cells (long axon, branched endings), muscle cells, root hair cells (large surface area), xylem (hollow, lignified) and phloem (sieve plates, companion cells).
• 4.1.1.4 Cell differentiation Cells differentiate to become specialised. Most animal cells differentiate early in development, while many plant cells keep the ability to differentiate throughout life. In mature animals, cell division is mainly for repair and replacement.
• 4.1.1.5 Microscopy Electron microscopes have much higher magnification and resolving power than light microscopes, so they reveal subcellular structures such as ribosomes. Magnification = size of image / size of real object. Required practical: use a light microscope to observe, draw and label cells with a scale magnification.
• 4.1.1.6 Culturing microorganisms (Biology only) Bacteria divide by binary fission, as often as every 20 minutes in ideal conditions. Use sterile Petri dishes and agar, sterilise inoculating loops in a flame and incubate at 25 degrees C in school labs. Required practical: investigate the effect of antiseptics or antibiotics using clear zones, and calculate area with pi r^2 (Biology only).

Common mistakes in 4.1.1 Cell Structure

• Saying plant cells have chloroplasts but not mitochondria. Plant cells respire too, so they have mitochondria as well as chloroplasts.
• Mixing up magnification and resolution. Resolution is the ability to distinguish between two points close together; higher resolution gives more detail, not just a bigger image.
• Getting unit conversions wrong. 1 mm = 1000 micrometres and 1 micrometre = 1000 nm, so convert both measurements to the same unit before using the magnification equation.
• Saying bacteria have a nucleus or that plasmids are the main DNA. Bacterial DNA is a single loop free in the cytoplasm; plasmids are small extra rings.
• Saying cultures are incubated at 37 degrees C in schools. Incubate at 25 degrees C to reduce the chance of growing human pathogens.

Try three 4.1.1 Cell Structure exam-style questions