TRUE OR FALSE
A coupled reaction is a pair of reactions, one exothermic and one endothermic.
ATP contains less energy than ADP.
In the ATP-ADP cycle, when the phosphate is removed, energy is released.
In coupled reaction, an endothermic reaction supplies the energy needed to drive an exothermic reaction.
Chlorophyll absorbs green light.
The correct answer and explanation is :
Here are the statements you provided with the correct answers and explanations:
1. A coupled reaction is a pair of reactions, one exothermic and one endothermic.
Answer: TRUE
Explanation: A coupled reaction involves pairing an exothermic (energy-releasing) reaction with an endothermic (energy-absorbing) reaction. In biological systems, such as cellular metabolism, the energy released from an exothermic reaction, like the hydrolysis of ATP, is used to drive an endothermic reaction, such as the synthesis of macromolecules or the active transport of substances across membranes. The two reactions are “coupled” because the energy from the exothermic reaction makes the endothermic reaction energetically favorable.
2. ATP contains less energy than ADP.
Answer: FALSE
Explanation: ATP (adenosine triphosphate) contains more energy than ADP (adenosine diphosphate). ATP has three phosphate groups, while ADP has only two. The high-energy bond between the second and third phosphate groups in ATP stores a significant amount of energy. When ATP is hydrolyzed to ADP and an inorganic phosphate (Pi), energy is released, which can then be used for various cellular processes, such as muscle contraction, protein synthesis, and active transport.
3. In the ATP-ADP cycle, when the phosphate is removed, energy is released.
Answer: TRUE
Explanation: The ATP-ADP cycle is central to cellular energy metabolism. When ATP is hydrolyzed (broken down) by the enzyme ATPase, the bond between the second and third phosphate groups is broken, releasing energy. This energy is used by the cell for various functions. The resulting ADP can later be converted back into ATP by adding a phosphate group through cellular processes like cellular respiration or photosynthesis.
4. In a coupled reaction, an endothermic reaction supplies the energy needed to drive an exothermic reaction.
Answer: FALSE
Explanation: In a coupled reaction, it is the exothermic reaction that supplies the energy needed to drive the endothermic reaction, not the other way around. The energy released from an exothermic reaction (like ATP hydrolysis) is used to fuel the energy-requiring (endothermic) process (such as the synthesis of molecules or the pumping of ions against a concentration gradient).
5. Chlorophyll absorbs green light.
Answer: FALSE
Explanation: Chlorophyll does not absorb green light well; instead, it primarily absorbs red and blue light in the visible spectrum. Green light is reflected, which is why plants appear green to us. Chlorophyll’s absorption of red and blue light is essential for photosynthesis, where light energy is converted into chemical energy.
In summary:
- Coupled reactions involve both exothermic and endothermic reactions, with the exothermic reaction driving the endothermic one.
- ATP has more energy than ADP.
- ATP hydrolysis releases energy.
- Endothermic reactions are driven by exothermic ones, not the other way around.
- Chlorophyll reflects, not absorbs, green light.