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Lysosomes and peroxisomes are two lines in your NCERT cell chapter. Each was found by someone who was looking for something else. Christian de Duve wanted to understand how insulin works, noticed a result that did not fit, and followed it. This post tells that story, explains the method behind it with a worked calculation, and ends with what you can learn from how he worked.
Who was Christian de Duve?
His Nobel Prize facts page records that he was born on 2 October 1917 in Thames Ditton, near London, and died on 4 May 2013 in Nethen, Belgium. He shared the 1974 Nobel Prize in Physiology or Medicine with Albert Claude and George Palade "for their discoveries concerning the structural and functional organization of the cell". The page credits him with discovering lysosomes in 1955.
In his Nobel autobiography, de Duve explains that he studied medicine at Louvain but by 1941 had "only one ambition: to elucidate the mechanism of action of insulin". He trained under Hugo Theorell in Stockholm and Carl and Gerty Cori in St. Louis, then set up a laboratory in Louvain in 1947.
How did an odd enzyme result lead to lysosomes?
The autobiography describes the turning point as "a chance observation, the so-called 'latency' of acid phosphatase". It was irrelevant to the insulin work, but intriguing. "My curiosity got the better of me," he wrote, "and as a result I never elucidated the mechanism of action of insulin."
His Nobel lecture, Exploring Cells with a Centrifuge, explains latency. Many enzymes inside cell particles show no activity in the test tube while the particle's membrane is intact, because the substrate cannot get in. Break the membrane, mechanically or chemically, and the activity appears. If two enzymes are released together, they probably sit in the same particle.
The group combined this with centrifugation. Their 1955 paper in the Biochemical Journal reports that rat-liver acid phosphatase is enclosed in a special type of granule that sediments between mitochondria and microsomes. By 1955, the lecture says, they could propose "a new group of particles with lytic properties, the lysosomes", and hint at another group, "the future peroxisomes". The same year, electron microscopy with Alex Novikoff showed membrane-bound dense bodies of about the predicted size.
Worked example: how strong is a centrifuge?
Cell fractionation separates particles by spinning them. The physics is circular motion: centripetal acceleration a = ω²r, where ω is the angular speed in rad/s.
Sample numbers: a rotor spins at 10,000 revolutions per minute, and the tube sits 0.10 m from the axis.
ω = 2π × 10,000 / 60 = 1,047 rad/s.
a = ω²r = (1,047)² × 0.10 = 1.10 × 10⁵ m/s².
Compared with g = 9.8 m/s²: 1.10 × 10⁵ / 9.8 ≈ 11,200 times gravity.
Doubling the speed multiplies the acceleration by four, because a depends on ω². That is why heavier particles such as nuclei come down at low speeds, and smaller ones need much faster spins.
What do lysosomes and peroxisomes do?
The NCERT Class 11 chapter Cell: The Unit of Life describes lysosomes as membrane-bound vesicles formed by packaging in the Golgi apparatus, rich in hydrolytic enzymes such as lipases, proteases and carbohydrases that work best at acidic pH. It describes microbodies as membrane-bound minute vesicles containing various enzymes, in both plant and animal cells. De Duve's lecture records that his colleagues showed the peroxisomes "correspond to the particles known as 'microbodies'".
The lecture also tells the medical sequel. In 1962 his colleague Géry Hers traced glycogen storage disease type II to a severe deficiency of a lysosomal enzyme, and by 1974 more than twenty congenital lysosomal enzyme deficiencies were known.
For the full organelle comparison the exam asks for, use our guide to Cell: The Unit of Life.
Common mistakes students make here
Calling lysosomes "suicide bags" as settled fact. De Duve's lecture says clear-cut demonstration of the "suicide bag" idea remained very difficult, though a few cases seemed authenticated.
Giving lysosomes two membranes. NCERT groups lysosomes, vacuoles and microbodies among single-membrane structures.
Forgetting the pH. Lysosomal enzymes work best at acidic pH; that detail is a common one-mark question.
If the difference between organelles keeps blurring, the Fermi Concept Library has every concept in physics, chemistry and biology with its own lesson, so you can fix one gap and get back to your chapter.
What can a student learn from de Duve's way of working?
De Duve let a strange result change his whole programme. He also checked it two independent ways, by centrifugation and by latency, before claiming a new organelle, and then looked for it under the microscope. When your answer surprises you, test it a second way before you trust it or throw it out.
Today, write the two lines of evidence de Duve used for lysosomes, then draw a lysosome and label its contents and pH.
