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A-Level Biology Flashcards: Cell Biology

A-Level Biology — Cell Biology Flashcards

20 flashcards with spaced repetition. Press Space to flip, rate 1-4.

What These Flashcards Cover

Cell biology is the foundation of A-Level Biology. These flashcards test your knowledge of cell structure, organelle function, membrane dynamics, and the processes that allow cells to communicate and divide.

Key areas:

  • Cell Structure: Prokaryotic cells lack a nucleus and membrane-bound organelles. Eukaryotic cells have a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, and a cytoskeleton. Plant cells additionally have a cell wall, chloroplasts, and a large permanent vacuole.
  • Organelles and Their Functions: Mitochondria are the site of aerobic respiration (ATP production). Ribosomes are the site of protein synthesis (80S80S in eukaryotes, 70S70S in prokaryotes). The rough ER has ribosomes and processes proteins; the smooth ER synthesises lipids. The Golgi apparatus modifies, packages, and secretes proteins.
  • Cell Membrane Structure: The fluid mosaic model: a phospholipid bilayer with embedded proteins (integral and peripheral), cholesterol, and glycolipids/glycoproteins. The membrane is selectively permeable.
  • Membrane Transport: Passive transport (diffusion, osmosis) requires no energy. Active transport requires ATP and carrier proteins. Endocytosis (phagocytosis and pinocytosis) brings material in; exocytosis sends material out.
  • Cell Division: Mitosis produces two genetically identical daughter cells (growth and repair). Meiosis produces four genetically different haploid gametes (sexual reproduction). Key stages: prophase, metaphase, anaphase, telophase. Crossing over and independent assortment create genetic variation in meiosis.
  • Cell Signalling: Cells communicate through chemical messengers (hormones, neurotransmitters). Lock-and-key model: the signal molecule fits a specific receptor. Signal transduction pathways convert the signal into a cellular response. Gap junctions allow direct communication between adjacent animal cells; plasmodesmata do the same in plant cells.

Intuition

Think of a cell as a factory. The nucleus is the management office (holds the plans/DNA). Ribosomes are the assembly line workers (build proteins). The ER is the production floor (rough ER for proteins, smooth ER for lipids). The Golgi apparatus is the packaging and dispatch department. Lysosomes are the recycling centre. Mitochondria are the power station.

The cell membrane is the security gate — it controls what enters and leaves. Like a bouncer at a club, it lets some things in freely (small non-polar molecules), some things in with a ticket (facilitated diffusion), and some things only if they pay (active transport).

Common Pitfalls

  1. Confusing plant and animal cells. Plant cells have a cell wall (cellulose), chloroplasts, and a large permanent vacuole. Animal cells have centrioles and lysosomes (which plant cells lack). Do not attribute animal cell features to plant cells or vice versa.
  2. Mixing up mitosis and meiosis. Mitosis produces 2 diploid cells (identical). Meiosis produces 4 haploid cells (genetically different). Meiosis involves two divisions; mitosis involves one.
  3. Forgetting that active transport requires energy. Diffusion and osmosis are passive (no ATP). Active transport moves substances against their concentration gradient and requires ATP and carrier proteins.
  4. Confusing pinocytosis and phagocytosis. Phagocytosis (“cell eating”) engulfssolid particles. Pinocytosis (“cell drinking”) engulfs fluid. Both are forms of endocytosis, but they differ in what is taken in.

Cross-References

  • Biological Molecules: Cell structures are built from biological molecules
  • Ecology: Cellular processes scale up to organism and ecosystem levels