The lac operon, which stands for Lactose operon is known as an inducible system. It is the an operon required for the transport and metabolism of lactose some enteric bacteria (Echerichia coli for example). The Lac operon is only activated in the presence of a key molecule. The key molecule is lactose.
From the given options the following best describes the Lac operon:
D. The repressor is freed from the operator when lactose is present.
 
        
             
        
        
        
Answer:
Structure of large intestine: Large intestine is the part of digestive system which comes in the end. It consist of four parts. Large intestine length is 150 cm and width is 5 cm. 
Function of large intestine: It performs two main functions. 
1) Large intestine helps in the absorption of water and nutrients from the food which cannot be digested in the stomach. 
2) It removes the waste material from the body in the form of feces. 
 
        
             
        
        
        
Answer: Coastal estuary 
Explanation:
Euryhaline animals are able to live in the wide range of salinity.These animals have the ability to live in the variety of water mostly fresh water.
The coastal estuary is one of the habitat of such animals. The green crab, molly fish are some example of the animals found in this environment.
Some of the euryhaline animals are also found in the salt and brackish water, fresh water, moderately haline et cetera.
 
        
             
        
        
        
Answer: adenylyl cyclase inositol triphosphate mainly known as IP3 causes the release of Calcium ions directly from the inracellular stores and causea contraction.
Explanation:
IP3, inositol phosphate is a second messenger a signaling molecule. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the plasma membrane, by an enzyme phospholipase C.
IP3 binds to the calcium channels and opens Ca2+ channels that are embedded in the ER membrane, releasing Ca2+ into the cytosol. Calcium ions released may cause contraction and regulate the Ca2+ channels in the membranes.