Cells & Transport is a core part of A-Level Biology. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
CellThe smallest unit of life; carries out the functions needed to live.
Eukaryotic cellA cell with a nucleus enclosed in a membrane; e.g. animal, plant, fungus cells.
Prokaryotic cellA smaller cell with no nucleus; DNA is a loop in the cytoplasm; e.g. bacteria.
Subcellular structuresParts inside a cell with specific jobs: nucleus, mitochondria, ribosomes, chloroplasts.
Specialised cellsCells adapted for a specific role, e.g. red blood cell, sperm, root hair.
Stem cellUndifferentiated cell that can divide to form many cell types.
ProkaryoteCell with no nucleus, 70S ribosomes, circular DNA — e.g. bacteria
EukaryoteCell with nucleus and membrane-bound organelles, 80S ribosomes
Rough ERStudded with ribosomes — synthesises and folds proteins
Smooth ERNo ribosomes — synthesises lipids and steroids
Golgi apparatusModifies, packages and labels proteins into vesicles
LysosomeVesicle of hydrolytic enzymes — breaks down waste
G1 phaseCell growth, organelle replication, protein synthesis
S phaseDNA replication — each chromosome becomes 2 sister chromatids
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What is the key structural difference between prokaryotic and eukaryotic cells?✗ Prokaryotes have no DNA — that's why they have no nucleus. ✓ Eukaryotes have a membrane-bound nucleus and membrane-bound organelles; prokaryotes do not.
What is the main role of mitochondria in a cell?✗ Mitochondria produce energy by creating it from nothing. ✓ To carry out aerobic respiration, producing ATP that cells use as an energy currency.
What is the key difference between mitosis and meiosis?✗ Mitosis and meiosis both produce gametes; they are basically the same. ✓ Mitosis produces two genetically identical diploid cells; meiosis produces four genetically different haploid cells (gametes).
In osmosis, which direction does water move?✗ Water moves from high solute concentration to low solute concentration. ✓ From a region of higher water potential (less concentrated solution) to lower water potential.
What is a stem cell?✗ Stem cells are taken only from embryos and cannot be found in adults. ✓ An undifferentiated cell capable of dividing to produce more stem cells or differentiating into specialised cell types.
Practise Cells & Transport — free games
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