Practice Questions

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#Question id: 643

The hydrolysis of lactose is catalysed by b-galactosidase as given below

Which of the following could be correct mechanism for this hydrolysis reaction?

A. Nucleophilic attack by the carboxylate group of Glu/Asp on the C-1 carbon atom of the galactose moiety within glucose, releasing glucose and forming an intermediate with the galactose linked to the enzyme through an ester linkage. Water then attacks this carbon atom, displacing the glutamate carboxylate and releasing galactose.

B. Electrophilic attack by the carboxylate group of Glu/Asp on the C-1 carbon atom of the galactose moiety within glucose, releasing glucose and forming an intermediate with the galactose linked to the enzyme through an ester linkage. Water then attacks this carbon atom, displacing the glutamate carboxylate and releasing galactose.

C. Nucleophilic attack by the carboxylate group of Lys/Arg/His or bivalent cation on the C-1 carbon atom of the galactose moiety within glucose, releasing glucose and forming an intermediate with the galactose linked to the enzyme through an ester linkage. Water then attacks this carbon atom, displacing the glutamate carboxylate and releasing galactose.

#Unit 1. Molecules and their Interaction Relevant to Biology

A & C could be correct
Only A could be correct
B&C could be correct
Only C could be correct

More Questions

TLS Online TPP Program

#Question id: 12670

#Unit 6. System Physiology – Plant

Changement in the physiology or morphology of the individual is a nonpermanent or temporary and that can be reversed if the prevailing environmental conditions change is termed as

TLS Online TPP Program

#Question id: 12671

#Unit 6. System Physiology – Plant

When genetic changes in an entire plant population have been fixed over many generations by selective environmental pressure, those changes are referred to as,

TLS Online TPP Program

#Question id: 12711

#Unit 6. System Physiology – Plant

Various sensors monitor ROS levels in cells; an increase in ROS activates a signal transduction network. ROS scavenging is carried out by antioxidant molecules ____X_________and by antioxidant enzymes such as____Z_________

TLS Online TPP Program

#Question id: 12713

#Unit 6. System Physiology – Plant

Following are certain statements related to plants water deficit condition;

a) Inhibits Leaf Abscission

b) Enhances Root Extension into Deeper, Moist Soil

c) Limits Photosynthesis within the Chloroplast

d) decreases Resistance to Liquid-Phase Water Flow

e) Increases Wax Deposition on the Leaf Surface

f) Alters Energy Dissipation from Leaves

Which of the following combination given statements is correct

TLS Online TPP Program

#Question id: 12714

#Unit 6. System Physiology – Plant

Physiological and biochemical perturbations in plants caused by fluctuations in the abiotic environment, given column I with environmental factor and with its effects in the form of primary effects in column II and secondary effects in column III

COLUMN I

(environmental factor )

COLUMN II

(primary effects)

COLUMN III

(secondary effects)

A) Water deficit

i) Hypoxia, Anoxia

a) Membrane dysfunction

B) High temperature

ii) ROS production

b) Reduced cellular and metabolic activities,

Leaf abscission,

Ion cytotoxicity and Cavitation

C) Trace element toxicity

iii) Photo inhibition

c) Reduced respiration,

Fermentative metabolism, Inadequate ATP production ,

ROS production and

Stomatal closure

D) Flooding and soil compaction

iv) Membrane destabilization

d) Inhibition of PSII repair

E) Chilling

v) Cell dehydration and Hydraulic resistance

e) Disruption of metabolism

F) High light intensity

f) Photosynthetic and respiratory inhibition, ROS production

Find out the correct combination of given above column;

TLS Online TPP Program

#Question id: 12716

#Unit 6. System Physiology – Plant

Some cis-elements of target genes, which are involved in the Signal perception of stress (Drought/salinity and cold) to activating tolerance,

These cis-elements are____