Cellular Localization of Enzymes Quiz

The Energy of Life

• The living cell is a miniature chemical factory where thousands of reactions occur, extracting energy and applying energy to perform work.

Metabolism

• Metabolism is the totality of an organism's chemical reactions, an emergent property of life that arises from interactions between molecules within the cell.
• Metabolic pathways begin with a specific molecule and end with a product, with each step catalyzed by a specific enzyme.

Catabolic and Anabolic Pathways

• Catabolic pathways release energy by breaking down complex molecules into simpler compounds, such as cellular respiration (the breakdown of glucose in the presence of oxygen).
• Anabolic pathways consume energy to build complex molecules from simpler ones, such as the synthesis of protein from amino acids.

Bioenergetics

• Bioenergetics is the study of how organisms manage their energy resources.
• Energy can be converted from one form to another, and exists in various forms, including kinetic energy (associated with motion), heat (thermal energy), potential energy (possessed due to location or structure), and chemical energy (potential energy available for release in a chemical reaction).

Enzymes and Metabolic Pathways

• Enzymes act as catalysts, lowering the activation energy required for a chemical reaction to occur.
• Specific localization of enzymes within the cell helps bring order to metabolic pathways.
• Enzymes can act as structural components of membranes or reside in specific organelles, such as mitochondria.

Thermodynamics

• The first law of thermodynamics states that energy can be transferred and transformed, but not created or destroyed.
• The second law of thermodynamics states that every energy transfer or transformation increases the entropy (disorder) of the universe.
• Living organisms create ordered structures from less ordered materials, but the universe's total entropy increases.

Free-Energy Change and Spontaneity

• The free-energy change (∆G) of a reaction determines whether it occurs spontaneously or not.
• A spontaneous process occurs without energy input and increases the entropy of the universe.
• Only processes with a negative ∆G are spontaneous and can perform work.

ATP and Energy Coupling

• ATP (adenosine triphosphate) is the cell's energy shuttle, composed of ribose, adenine, and three phosphate groups.
• Hydrolysis of ATP releases energy, which is used to drive endergonic reactions, powering cellular work such as mechanical, transport, and chemical work.