The enzyme telomerase is highly active in which type of cells?
A. Somatic cells
B. Stem cells and cancer cells
C. Neurons
D. Mature red blood cells
Answer: Option B
Solution (By JKExamLibrary)
Telomerase is a ribonucleoprotein enzyme that adds repetitive nucleotide sequences to the ends of chromosomes (telomeres), preventing them from shortening during DNA replication. It is highly active in germ cells, stem cells, and most cancer cells, granting them replicative immortality. In most normal somatic cells, telomerase is inactive, leading to gradual telomere shortening and cellular aging.
Explanation:
Osmosis is the special case of diffusion of water across a semipermeable membrane down its concentration gradient (from high to low water potential). It does not require energy. Diffusion refers to solute movement, active transport requires energy against a gradient, and plasmolysis is the shrinking of protoplasm due to water loss.
Explanation:
Simple permanent tissues (parenchyma, collenchyma, sclerenchyma) consist of a single cell type. Meristematic tissues are dividing and have thin walls; xylem/phloem are complex; epidermis is dermal.
Consider the following statements about blood:
1. Red blood cells transport oxygen.
2. White blood cells are involved in immunity.
3. Platelets help in blood clotting.
Which of the above is/are correct?
Explanation:
All three statements are correct: RBCs contain hemoglobin for oxygen transport, WBCs (leukocytes) defend against pathogens, and platelets (thrombocytes) initiate blood clotting.
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