π¬ Cell Biology
- Basic biology β concept that cells are the fundamental unit of life
- State the three principles of cell theory and explain why cells are fundamental to life
- Identify 7+ organelles and describe their functions
- Compare animal and plant cells using a table
- Describe the stages of mitosis and contrast it with meiosis
Think of a cell as a miniature city: nucleus = city hall (stores DNA), mitochondria = power plants (produce ATP), ribosomes = factories (build proteins), Golgi apparatus = post office (sorts and ships materials), cell membrane = city walls (controls entry and exit).
Cells are the fundamental units of life. Our bodies contain about 37 trillion cells, and cancer is essentially uncontrolled cell division. COVID-19 works by binding to cell membrane receptors, and insulin signals cells to absorb glucose. Understanding cells means understanding disease, medicine, and life itself. Every field of biology, medicine, and pharmacology begins at the cellular level.
- Cell membrane: selective permeability. Nucleus: DNA storage + control. Mitochondria: ATP production
- Ribosomes: protein synthesis. Golgi apparatus: packaging + secretion. ER: transport
- Plant-only: cell wall (cellulose) + chloroplasts (photosynthesis) + large central vacuole
- Animal-only: lysosomes (digestion) + centrioles (cell division orientation)
- Mitosis: 1 cell β 2 identical. Meiosis: 1 cell β 4 with half chromosomes
1. Cell Theory
- All living things are made of cells.
- The cell is the basic unit of life.
- All cells come from pre-existing cells.
2. Cell Organelles AP Exam
- Cell Membrane: Phospholipid bilayer; controls what enters and exits (selectively permeable).
- Nucleus: Contains DNA; the "command center" that directs cell activities.
- Mitochondria: Site of cellular respiration; produces ATP ("powerhouse of the cell").
- Ribosomes: Synthesize proteins from mRNA instructions.
- Endoplasmic Reticulum (ER): Rough ER (studded with ribosomes) processes proteins; Smooth ER synthesizes lipids.
- Golgi Apparatus: Packages and ships proteins/lipids ("post office of the cell").
- Lysosomes: Digest waste and worn-out organelles (animal cells mainly).
- Vacuoles: Storage organelles; large central vacuole in plant cells maintains turgor pressure.
3. Animal Cell vs. Plant Cell AP Exam
| Structure | Animal Cell | Plant Cell |
|---|---|---|
| Cell wall | Absent | Present (cellulose) |
| Chloroplasts | Absent | Present (photosynthesis) |
| Central vacuole | Small or absent | Large |
| Lysosomes | Common | Rare |
| Centrioles | Present | Absent (most) |
4. Cell Division
Stages: Interphase (DNA replication) β Prophase (chromosomes condense) β Metaphase (align at center) β Anaphase (sister chromatids separate) β Telophase (nuclear envelopes reform) β Cytokinesis (cytoplasm divides).
Meiosis: Division of reproductive cells (gametes) β 1 cell becomes 4 haploid cells (half the chromosome count). Creates genetic diversity.Practice Questions
Answer: Chloroplasts (for photosynthesis) and cell wall (for structural support). The large central vacuole is also plant-specific.
Answer: 23 chromosomes β meiosis halves the chromosome number to produce haploid gametes.
- Animal vs plant cells: only plants have cell wall, chloroplasts, large vacuole
- Organelles: mitochondria (energy/ATP) vs chloroplasts (photosynthesis)
- Cell membrane: phospholipid bilayer β selectively permeable
- Osmosis: water moves from low solute concentration to high
Review this material at increasing intervals to commit it to long-term memory.