Protein sequence A shows a string of leucines (hydrophobic amino acids) at one end and a string of arginine (hydrophilic amino acids) at the opposite end, whereas protein sequence B contains purely hydrophilic amino acids. It is known that both proteins are membrane proteins. Which of the following statements best classifies Protein A and Protein B?
a. Protein A is a surface protein; Protein B is a transmembrane protein.
b. Protein A is a transmembrane protein; Protein B is a peripheral membrane protein.
c. Protein A is a transmembrane protein; Protein B is also a transmembrane protein.
d. Protein A is a transmembrane protein; Protein B is a peripheral membrane protein that can only be situated on the outer side of the membrane.
e. Protein A is a transmembrane protein; Protein B is a peripheral membrane protein that can only be situated on the inner side of the membrane.

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.