#Question id: 10346
#Unit 6. System Physiology – Plant
Nitrite reductase will convert nitrite to ammonium. There are two types of nitrite reductase characteristics given below;
a) Both nitrite reductase consist of a single 63kD polypeptide
b) In leaf chloroplasts and root plastids contain different forms of the nitrite reductase enzyme
c) In shoot nitrite reductase directly dependent on the light reaction by the ferredoxin, it activates nitrite reductase in choloroplast
d) NADPH in the roots is provided by pentose phosphate pathway, it also activate nitrite reductase in the plastids
Which of the correct statement about nitrite reductase characteristics?
#Question id: 16391
#Unit 7. System Physiology – Animal
#Question id: 16314
#Unit 7. System Physiology – Animal
#Question id: 641
#Unit 1. Molecules and their Interaction Relevant to Biology
Which of the following does NOT describe a mechanism that cells use to regulate enzyme activities?
A. Cells control enzyme activity by phosphorylation and dephosphorylation.
B. Cells control enzyme activity by the binding of small molecules.
C. Cells control the rates of diffusion of substrates to enzymes.
D. Cells control the rates of enzyme degradation.
E. Cells control the rates of enzyme synthesis.
F. Cells control the targeting of enzymes to specific organelles.
#Question id: 10920
#Unit 6. System Physiology – Plant
The pressure-flow model, first proposed by Ernst Münch, Phloem loading at the source and phloem unloading at the sink establish the pressure gradient.
a.) In source tissues, an accumulation of sugars in the sieve elements generates a lower or negative solute potential (ψs).
b.) source tissue, causes a steep drop in the water potential (ψ), due to water potential gradient, water enters the sieve elements and causes turgor pressure (ψp ) decrease.
c.) In sink tissues, phloem unloading leads to a lower sugar concentration in the sieve elements, generating a higher or less negative solute potential.
d.) As the water potential of the phloem rises above that of the xylem, water tends to leave the phloem in response to the water potential gradient, causing a decrease in turgor pressure in the sieve elements of the sink.
Which of the following statements of sink and source tissue is FALSE?