Which of the following metabolic processes can occur without a net influx of energy from some other process?
A. [tex]$6 CO _2+6 H _2 O \rightarrow C _6 H _{12} O _6+6 O _2$[/tex]
B. [tex]$C _6 H _{12} O _6+6 O _2 \rightarrow 6 CO _2+6 H _2 O$[/tex]
C. [tex]$ADP + P _{ i } \rightarrow ATP + H _2 O$[/tex]
D. Amino acids [tex]$\rightarrow$[/tex] Protein
Answer (2)
Identify exergonic reactions as those occurring without net energy influx.
Analyze each reaction: photosynthesis (endergonic), cellular respiration (exergonic), ATP synthesis (endergonic), and protein synthesis (endergonic).
Determine that only cellular respiration releases energy spontaneously.
Conclude that the reaction that can occur without a net influx of energy is: C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O .
Explanation
Identifying Exergonic Reactions We need to determine which of the given metabolic processes can occur without a net influx of energy. This means we are looking for exergonic reactions, which release energy and can occur spontaneously.
Analyzing Each Reaction Let's analyze each reaction:
6 C O 2 + 6 H 2 O → C 6 H 12 O 6 + 6 O 2 : This is photosynthesis, where plants use energy from sunlight to convert carbon dioxide and water into glucose and oxygen. This process requires energy input, so it is endergonic.
C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O : This is cellular respiration, where glucose and oxygen are converted into carbon dioxide and water, releasing energy in the process. This process releases energy, so it is exergonic.
A D P + P i → A TP + H 2 O : This is the synthesis of ATP (adenosine triphosphate) from ADP (adenosine diphosphate) and inorganic phosphate. ATP is the main energy currency of the cell, and its synthesis requires energy input, so it is endergonic.
Amino acids → Protein: This is protein synthesis, where amino acids are linked together to form a protein. This process requires energy input, so it is endergonic.
Conclusion Therefore, the only reaction that can occur without a net influx of energy is cellular respiration.
Examples
Understanding exergonic and endergonic reactions is crucial in various fields. For example, in designing biofuel production systems, optimizing exergonic reactions can lead to more efficient energy extraction. Similarly, in drug development, understanding the energy requirements of biochemical reactions helps in designing drugs that can either inhibit or promote specific metabolic pathways. For instance, the breakdown of glucose during exercise ( C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O ) provides the energy needed for muscle contraction, illustrating an exergonic reaction powering a biological process.
The metabolic process that can occur without a net influx of energy is cellular respiration, which is represented by the equation C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O . This reaction releases energy, while photosynthesis, ATP synthesis, and protein synthesis all require energy input. Therefore, option B is correct.
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