Biology · Cell: The Unit of Life · NEET
A lysosome is very rich in hydrolytic enzymes, also called hydrolases. NCERT names three types: lipases (break down lipids/fats), proteases (break down proteins) and carbohydrases (break down carbohydrates). It also has nucleases that break down nucleic acids. These enzymes digest almost all types of biomolecules, which is why the lysosome is the cell's main digestion centre.
A lysosome is bound by a SINGLE membrane. This is a very common NEET trap. Mitochondria and chloroplasts are double-membrane, and the nucleus has a nuclear envelope (two membranes), but the lysosome has only one membrane. In NEET 2016 the answer to 'which organelle is enclosed by a single membrane' was Lysosomes.
Lysosomes are formed by the process of PACKAGING in the Golgi apparatus, NOT the endoplasmic reticulum. The enzymes are made on ribosomes of the rough ER, but the finished lysosome is packaged and pinched off from the Golgi. NEET repeatedly puts 'lysosomes are formed by packaging in the endoplasmic reticulum' as the WRONG (incorrect) statement to catch students.
Lysosomal hydrolytic enzymes are optimally active at an ACIDIC pH (low pH, around 5). This acidic environment is kept inside the lysosome so the enzymes can digest material. If a lysosome bursts, its enzymes are much less active in the cell's neutral cytoplasm, which partly protects the cell.
A lysosome is nicknamed the 'suicidal bag' because it holds powerful digestive enzymes. If the cell is old, damaged or dying, the lysosome membrane can break and release its enzymes, which digest the cell's own contents (autolysis). Note: 'suicidal bag' is a popular name, not the main NCERT wording, so in NEET always trust the direct NCERT facts first.
No, lysosomes do NOT contain DNA. Only mitochondria and chloroplasts have their own DNA among cell organelles, plus the nucleus which holds the main DNA. In NEET 2019 the pair of organelles that do NOT contain DNA was 'Lysosomes and Vacuoles'.
A lysosome is a small vesicle packed with hydrolytic enzymes that DIGESTS biomolecules. A vacuole is a larger membrane-bound space (bounded by the tonoplast in plants) that STORES water, sap, and traps waste/excretory products. So lysosome = digestion, vacuole = storage. Both are single-membrane and both lack DNA.
Yes. The endomembrane system includes the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles, because their functions are coordinated. Mitochondria, chloroplasts and peroxisomes are NOT part of it because their functions are not coordinated with these. NEET tests this list very often.
A cell organelle containing hydrolytic enzymes is
Which one of the following cell organelles is enclosed by a single membrane?
Which of the following statements is not correct?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Its main function is intracellular digestion. Using hydrolytic enzymes, it breaks down proteins, lipids, carbohydrates and nucleic acids, and helps digest old or damaged cell parts and foreign material.
Remember the three NCERT-named hydrolases: lipases (fats), proteases (proteins) and carbohydrases (carbohydrates), plus nucleases (nucleic acids). All are optimally active at acidic pH.
Lysosomes are mainly found in animal cells. In many plant cells, the large central vacuole carries out similar digestive and storage roles, so typical lysosomes are less prominent.
The Golgi apparatus. The enzymes are produced on the rough endoplasmic reticulum, then sent to the Golgi where they are packaged into lysosomes.
Yes, it is a single membrane-bound vesicular structure. This single membrane keeps the digestive enzymes safely separated from the rest of the cell.
