Which of the following regarding proteins is incorrect?
a. they form peptide bonds
b. all are enzymes
c. play a role in transport of material across a membrane
d. may serve as structural proteins

b. All are enzymes  

Explanation:

"Every enzyme is a protein, but not every protein is an enzyme." You may have heard that phrase already.

With the exception of one group of RNA molecules with enzymatic activity, every enzyme is a protein.

Proteins, in addition to enzymes, can perform many other functions in the cell, such as structural and transport functions. Protein is a type of substance formed from a set of linked amino acids (called peptide bonds). In other words, proteins are composed of carbon, hydrogen, oxygen and nitrogen molecules.

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.