The phenomenon that explains the movement of water from roots to leaves against gravity is mainly:
A. Active transport
B. Root pressure
C. Transpiration-cohesion-tension mechanism
D. Capillary action
Answer: Option C
Solution (By JKSSB Mock Tests)
The cohesion-tension theory (transpiration pull) is the primary mechanism for water ascent in tall trees. Transpiration creates negative pressure (tension) in leaves, water molecules cohere, and the column is pulled up. Root pressure and capillary action play minor roles. The cohesion of water is due to hydrogen bonds.
Assertion (A): The large central vacuole in plant cells helps maintain turgor pressure.
Reason (R): It stores water and solutes, creating osmotic pressure that pushes the cytoplasm against the cell wall.
A.Both A and R are true, and R is the correct explanation.
B.Both A and R are true, but R is not the correct explanation.
Explanation:
The vacuole’s solute concentration draws water, generating turgor pressure that maintains cell rigidity. This is essential for support in plants. R explains A.
Explanation:
In prokaryotes, DNA polymerase I has 5'→3' exonuclease activity that removes the RNA primer and fills the gap with DNA. DNA polymerase III adds nucleotides to the growing strand. Ligase seals the nicks. Helicase unwinds DNA. In eukaryotes, RNase H removes primers and DNA polymerase δ fills the gap.
Explanation:
Biotin is a coenzyme for carboxylation enzymes, including pyruvate carboxylase (gluconeogenesis) and acetyl-CoA carboxylase (fatty acid synthesis). Thiamine (B₁) is for decarboxylation, riboflavin (B₂) for redox, folate (B₉) for one-carbon transfers. Biotin is often bound to lysine in enzymes.
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