Which of the following statements is correct regarding cell theory?
A. All cells have a nucleus.
B. Only plant cells contain cell walls.
C. Cells arise spontaneously.
D. All living organisms are composed of cells and products of cells.
Answer: Option D
Solution (By JKSSB Mock Tests)
Modern cell theory states that all living organisms are composed of cells and cell products, the cell is the basic unit of structure and function, and all cells arise from pre-existing cells (Omnis cellula e cellula). Not all cells have a nucleus (e.g., prokaryotes, mature RBCs). Cell theory was formulated by Schleiden, Schwann, and Virchow. Spontaneous generation was disproved.
Explanation:
The conversion of milk to curd (yogurt) is a fermentation process primarily caused by lactic acid bacteria (LAB), such as Lactobacillus. These bacteria ferment the lactose (milk sugar) into lactic acid. The lactic acid lowers the pH, causing the milk protein (casein) to coagulate and solidify, forming curd. It also improves the nutritional value by producing Vitamin B12.
Explanation:
Seminal vesicles produce a fructose-rich fluid (energy for sperm), and the prostate gland adds a milky, alkaline fluid to form semen. The testis produces sperm, epididymis stores them, vas deferens transports.
Explanation:
Hybridoma technology fuses antibody-producing B cells with immortal myeloma cells to create hybridomas that produce monoclonal antibodies. Developed by Kohler and Milstein.
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