Question

A molecule in which the energy of metabolism is stored is (a) glucose; (b) DNA; (c) RNA; (d) glycerol; (e) ATP.

Short answer

The correct answer is (e) ATP.

Step-by-step solution

Understanding Metabolism and Energy Storage

Comprehending the process of metabolism is important. Metabolism involves all the chemical reactions in a cell that are necessary to sustain life. These reactions involve breaking down substances to obtain energy (catabolism) and building new cellular structures and molecules (anabolism). Energy obtained from catabolism is often stored in another molecule, so it can be used by the cell when needed.

Analyzing The Choices

Now each of the options can be analyzed: (a) Glucose - This is a sugar molecule used as a source of energy, but it is not the principal store of energy. (b) DNA - This is the molecule that contains our genetic information, not a store of energy. (c) RNA - RNA is involved in protein synthesis and other functions but it doesn't store energy. (d) Glycerol - It is a component of fats but is not where energy is stored. (e) ATP - Known as Adenosine triphosphate, it is the primary molecule for storing and transferring energy in cells.

Identifying The Correct Molecule

As it was analyzed in the previous step, among the given options, Adenosine triphosphate (ATP) is the main molecule that cells use to store and transfer energy. Therefore, ATP is the correct answer.

Key concepts

Energy Storage

Metabolism is the umbrella term for all chemical reactions within cells that allow an organism to sustain life. One of the essential aspects of metabolism is energy storage. The energy from the foods we eat needs to be stored efficiently, as it is not always required immediately. Energy storage enables cells to save excess energy during times of abundance and release it when needed.

Cells primarily store energy in chemical bonds. These bonds, when broken, release energy that cells can use for various functions. Energy storage is crucial because it supports processes such as growth, repair, and maintaining homeostasis.

• Short-term energy storage tends to be in the form of chemical compounds, like Adenosine triphosphate (ATP).
• Long-term energy storage occurs in forms such as glycogen and lipids (fats).

This mechanism ensures that energy is readily available when needed, thereby sustaining life without requiring constant energy intake.

ATP (Adenosine triphosphate)

ATP, or Adenosine triphosphate, is often referred to as the "energy currency" of the cell. It plays a crucial role in metabolism by acting as an energy transfer molecule. The structure of ATP consists of three phosphates and a ribose sugar, connected to an adenine base.

The bonds between its phosphate groups are high-energy, meaning that when they break, a significant amount of energy is released that can be harnessed for cellular activities. ATP allows for energy transfer within the cell, powering various processes such as:

• Muscle contraction.
• Active transport across cell membranes.
• Synthesizing complex molecules from simpler ones.

When the cell needs energy, ATP releases a phosphate group, transforming into ADP (Adenosine diphosphate) and releasing energy. The cell can then regenerate ATP from ADP through metabolic pathways like cellular respiration, ensuring a continuous supply of energy for cellular processes.

Catabolism and Anabolism

Metabolism can be divided into two broad categories: catabolism and anabolism. These categories capture the dual nature of cellular reactions, which are all about breaking down and building up substances.

Catabolism involves the breakdown of complex molecules into simpler ones. This process releases energy, which cells then capture and store, primarily in the form of ATP. Catabolic reactions include digestion and cellular respiration, where nutrients are oxidized for energy.

• Catabolic processes help extract energy from nutrients.
• They play a role in removing waste products.

On the other hand, anabolism is all about building up. It involves synthesizing complex molecules from simpler precursors, and these reactions require energy, which is often supplied by ATP. Anabolic processes include protein synthesis, DNA replication, and the creation of cell membranes.

• Anabolism is essential for cellular growth and repair.
• It contributes to the production of components vital for cellular functions.

Together, catabolism and anabolism interconnect to form a balanced state of energy and material flow within the cell, maintaining the cell's activities efficiently.