Allosteric regulation of enzyme multisubunit or multiactive site shows cooperativity with the sigmoidal graph between substerate conc. v/s Activity,

a) Cell contain NADH, FADH2 and ATP, that inhibits the allosteric enzyme activity by lowering the affinity with its substate, graph shifts towards B from control

 b) A- shows low ATP, the Km for fructose 6-phosphate is relatively low, the affinity of the enzyme with its substate is relatively high

 c) Haemoglobin, Phosphofructokinase, Phosphate dehydrogenase complex, α-ketoglutarate dehydrogenase complex, these all enzymes shows characteristics of sigmoidal graph

 d) When ATP is high, Km for fructose 6-phosphate is greatly increased- this activity shown by B in the graph

 e) fructose 2,6-bisphosphate binds to its allosteric site on PFK-1, it increases the enzyme’s affinity for its substrate fructose 6-phosphate and reduces its affinity for the allosteric inhibitors ATP and citrate- shown in graph by A

 Which of the following  combination of the enzyme activity with its substate correctly shown;

#Question id: 10916

#Unit 6. System Physiology – Plant

A photosynthetic sugar sucrose can be hydrolyzed into glucose and fructose in the apoplast by a sucrose-splitting enzyme, this enzyme known as;

#Question id: 10917

#Unit 6. System Physiology – Plant

Photosynthetic sugar molecules are transported via phloem to other parts of the plants. The following aspects are associated with sucrose unloading in phloem and its transport;

a) The presence of plasmodesmata is assumed to provide apoplastic transport. An absence of plasmodesmata between cells indicates an nonfunctional symplastic continuity

b) Phloem unloading and short-distance transport can occur via symplastic as well as apoplastic pathways

c) Both unloading and the short-distance pathway appear to be completely symplastic in some young eudicot leaves, such as sugar beet and tobacco

d) An apoplastic step is required in developing seeds because there are no symplastic connections between the maternal tissues and the tissues of the embryo

Which of the following combination is INCORRECT?

#Question id: 10918

#Unit 6. System Physiology – Plant

The import into sinks such as developing roots, tubers, and reproductive structures, In many ways the events in sink tissues are simply the reverse of the events in sources. The following steps are involved in the import of sugars into sink cells such as;

#Question id: 10919

#Unit 6. System Physiology – Plant

Both of these observations—________X__________and________Y__________—support the existence of mass flow in the sieve elements of the phloem.

#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?

#Question id: 10921

#Unit 6. System Physiology – Plant

The mechanism of phloem translocation in angiosperms is best explained by which method?