Prokaryotic cells (without a nucleus) like bacteria, and Eukaryotic cells (with a nucleus) like plant and animal cells. The cell theory states three key points: All living things are made of cells, the cell is the basic unit of life, and all cells come from pre-existing cells
💡Key cell components include
Cell membrane (controls entry and exit), Cytoplasm (jelly-like substance), Nucleus (control center with DNA), Mitochondria (powerhouse), Ribosomes (protein factories), and in plants - Chloroplasts (for photosynthesis) and Cell wall (for support).
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Formula Block
Memorise — at least one formula appears in every paper
Cell division time = Total time / Number of divisions
Surface area to volume ratio = Surface area / Volume
Osmosis rate ∝ Concentration gradient
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Exam Patterns
What examiners ask — read before attempting PYQs
⚡Shortcut Trick - PORN Method for plant cell organelles
Number of cells = 2^6 = 64 cells
Answer: 64 cells
Worked Example 2: A cell has surface area 600 square units and volume 100 cubic units. What is the surface area to volume ratio?
1
Surface area = 600 square units
2
Volume = 100 cubic units
3
Ratio = 600/100 = 6:1
Answer: 6:1
Most Common Trap: Students confuse chloroplasts with chromoplasts. Remember - CHLOROplasts contain CHLOROphyll for photosynthesis (green color). CHROMOplasts give other colors like red, yellow, orange to fruits and flowers. This confusion appears in 40% of wrong answers.
Another major mistake is thinking viruses are cells. Viruses are NOT cells - they cannot reproduce on their own and need host cells. They are non-living particles with genetic material surrounded by protein coat.
Cell size is measured in micrometers. Most animal cells are 10-30 micrometers, while plant cells are 10-100 micrometers. Bacteria are much smaller at 1-5 micrometers. The largest single cell is the ostrich egg.
Diffusion and osmosis are key transport processes. Diffusion moves particles from high to low concentration without energy. Osmosis specifically moves water across membranes. Active transport requires energy to move against concentration gradient.
Which of the following is the primary function of mitochondria in animal cells?
Practice 2medium
Which organelle is known as the 'powerhouse of the cell' because it produces energy in the form of ATP through cellular respiration?
Practice 3medium
Which of the following organelles is responsible for producing ATP (energy) in animal cells and is often called the 'powerhouse of the cell'?
Practice 4hard
A student observes a cell under a light microscope and identifies a large, membrane-bound structure that occupies approximately 10% of the cell's volume. Inside this structure, the student sees a smaller, dark-staining body. Which of the following statements correctly describes the relationship between these two structures in a typical animal cell?