Question

Question: Which of the following metabolic processes can occur without a net influx of energy from some other process?

1. \({\rm{ADP}}\,{\rm{ + }}\,{\rm{Pi}}\, \to {\rm{ATP}}\,{\rm{ + }}\,{{\rm{H}}_{\rm{2}}}{\rm{O}}\)
2. \({{\rm{C}}_{\rm{6}}}{{\rm{H}}_{{\rm{12}}}}{{\rm{O}}_{\rm{6}}}\,{\rm{ + }}\,{\rm{6}}{{\rm{O}}_{\rm{2}}}{\rm{ }} \to {\rm{6C}}{{\rm{O}}_{\rm{2}}}{\rm{ + 6}}{{\rm{H}}_{\rm{2}}}{\rm{O}}\)
3. \({\rm{6C}}{{\rm{O}}_{\rm{2}}}{\rm{ + 6}}{{\rm{H}}_{\rm{2}}}{\rm{O}} \to \,{{\rm{C}}_{\rm{6}}}{{\rm{H}}_{{\rm{12}}}}{{\rm{O}}_{\rm{6}}}\,{\rm{ + }}\,\,{\rm{6}}{{\rm{O}}_{\rm{2}}}\)
4. \({\rm{Amino}}\,{\rm{acids}}\, \to {\rm{Proteins}}\)

Short answer

1. The option “\({\rm{ADP}}\,{\rm{ + }}\,{\rm{Pi}}\, \to {\rm{ATP}}\,{\rm{ + }}\,{{\rm{H}}_{\rm{2}}}{\rm{O}}\)” is false.
2. The option “\({{\rm{C}}_{\rm{6}}}{{\rm{H}}_{{\rm{12}}}}{{\rm{O}}_{\rm{6}}}\,{\rm{ + }}\,{\rm{6}}{{\rm{O}}_{\rm{2}}}{\rm{ }} \to {\rm{6C}}{{\rm{O}}_{\rm{2}}}{\rm{ + 6}}{{\rm{H}}_{\rm{2}}}{\rm{O}}\)” is true.
3. The option “\({\rm{6C}}{{\rm{O}}_{\rm{2}}}{\rm{ + 6}}{{\rm{H}}_{\rm{2}}}{\rm{O}} \to \,{{\rm{C}}_{\rm{6}}}{{\rm{H}}_{{\rm{12}}}}{{\rm{O}}_{\rm{6}}}\,{\rm{ + }}\,\,{\rm{6}}{{\rm{O}}_{\rm{2}}}\)” is false.
4. The option “\({\rm{Amino}}\,{\rm{acids}}\, \to {\rm{Proteins}}\)”isfalse.

Step-by-step solution

Metabolic reactions are either exergonic or endergonic

Some metabolic reactions in the cell require the input of energy to occur. These reactions are called endergonic reactions. Other metabolic processes release energy and are called exergonic reactions.

Thus, metabolic reactions are either exergonic or endergonic.

Explanation of option (A)

In the given equation, ATP (adenosine triphosphate) is formed from ADP (adenosine diphosphate) and Pi (inorganic phosphate).The process of chemiosmosis forms ATP.

This process requires energy to build the bond between an additional phosphate and ADP. Thus, chemiosmosis cannot occur without the input of energy.

Therefore, the given option is false.

Explanation of option (B)

In the given equation,glucose degrades to produce carbon dioxide and water. Glucose is the source of energy in the cell.

Thus, the breakdown of glucose occurs without an influx of energy.

Therefore, the given option is true.

Explanation of option (C) 

In the given equation, glucose is produced from carbon dioxide and water. The formation of one glucose molecule requires 18 molecules of ATP and 12 molecules of NADPH (nicotinamide adenine dinucleotide phosphate hydrogen).

Thus, the formation of glucose requires an enormous amount of energy.

Therefore, the given option is false.

Explanation of option (D)

In the given equation, the proteins are synthesized from amino acids. Protein synthesis is a demanding energy process because peptide bonds are formed in proteins that require energy input.

Thus, proteins cannot be formed without the input of energy.

Therefore, the given option is false.