Energy, Thermodynamics, and Enzymes in Metabolism

What is the capacity to do work called?

Energy

What are the two states of energy?

Kinetic (energy of motion) and Potential (stored energy)

What is the most convenient way of measuring energy?

Heat

How much energy is required to raise 1 gram of water by 1ºC?

1 calorie

What do photosynthetic organisms do with energy from the sun?

They capture this energy and store it as potential energy in chemical bonds.

What happens during oxidation in redox reactions?

An atom or molecule loses an electron.

What happens during reduction in redox reactions?

An atom or molecule gains an electron.

What does the first law of thermodynamics state?

Energy cannot be created or destroyed; it can only change forms.

What does the second law of thermodynamics state?

Energy transformations are not 100% efficient, and entropy is continuously increasing.

What is free energy (G)?

Energy available to do work, calculated as G = H − TS.

What characterizes endergonic reactions?

They have a positive ∆G, meaning products have more free energy than reactants.

What characterizes exergonic reactions?

They have a negative ∆G, meaning products have less free energy than reactants.

What is activation energy?

The extra energy required to destabilize existing bonds and initiate a chemical reaction.

What is ATP?

Adenosine triphosphate, the chief energy currency used by all cells.

What does ATP hydrolysis yield?

ADP or AMP.

What are catalysts?

Substances that lower activation energy and increase reaction rates.

What are enzymes?

Biological catalysts, mostly proteins, that show high specificity and are not consumed in reactions.

What is the active site of an enzyme?

The pocket or cleft for substrate binding on the enzyme surface.

What is feedback inhibition?

When the end product of a pathway binds to an allosteric site on an enzyme to shut down the pathway.

What are cofactors?

Chemical components that assist enzyme function, which can include metal ions or coenzymes.

What are the two types of enzyme inhibitors?

Competitive inhibitors (compete with substrate for active site) and noncompetitive inhibitors (bind to a site other than the active site).

What is metabolism?

The total of all chemical reactions carried out by an organism.

What are anabolic reactions?

Reactions that expend energy to build up molecules.

What are catabolic reactions?

Reactions that harvest energy by breaking down molecules.

What is an enzyme-substrate complex?

The complex formed when a substrate binds to an enzyme's active site.

What is the role of ribozymes?

RNA molecules that can catalyze certain cellular reactions.

What is the significance of multienzyme complexes?

They allow subunits to work together, facilitating product delivery and preventing unwanted side reactions.