What is the most abundant form of nitrogen in nature?

345

Under which form is nitrogen fixed by the living beings.

260

Explain what does a beaver build?

938

How many tropic levels can a food chain have?

459

What is a characteristic feature of a carrier protein in a plasma membrane?

1061

When it functions as a "second messenger", cAMP a) acts outside the cell to influence cellular processes. b) acts "second in importance" to AMP. c) activates all cytosolic protein kinases. d) activates the cAMP-dependent protein kinase.

2393

What are some examples of chemical changes?

874

How can a great biological diversity protect an ecosystem from environmental damages?

305

What is the secondary structure of intron ?

2170

What is the reaction characterized by degranulation of mast cells as a result of antigen-antibody complexes affixed to cell surfaces?

2623

Which are the molecules that make possible active transport through membranes?

931

How to Prepare cultures of known concentration ?

2162

Describe the stem cell culture ?

1937

Why does thermal inversion increases air pollution?

303

Explain why the tropical forests are also known as stratified forests?

371