Metabolism and Energy Reactions Quiz

Study Notes

Metabolism is the collection of chemical reactions that occur in living organisms.
Metabolism is comprised of catabolism and anabolism.
Catabolism breaks down molecules, releasing energy.
Anabolism builds molecules, consuming energy.
Enzymes catalyze reactions in both catabolic and anabolic metabolic pathways.

ATP is the cell's primary energy currency.
ATP hydrolysis is an exergonic reaction that releases energy, breaking down ATP into ADP + P.
ATP synthesis is an endergonic reaction requiring energy to combine ADP + P to create ATP.
Catabolic pathways drive the regeneration of ATP through energy coupling.

ATP powers cellular work by coupling exergonic reactions with endergonic reactions.
Energy coupling involves transferring a phosphate group from ATP to specific reactants, forming a phosphorylated intermediate that is more reactive.

Enzymes are macromolecules, primarily proteins, that act as catalysts.
Enzymes speed up reactions without being consumed in the process.
Each enzyme has a unique active site that binds specifically to its substrate, the reactant molecule it acts on.
The enzyme's shape can change slightly when it binds to its substrate, called induced fit.
Enzyme activity can be described by the following: E + S → ES → P + E (where E = enzyme, S = substrate, ES = enzyme-substrate complex, and P = product).

Enzymes speed up reactions by lowering the activation energy barrier.
Activation energy is the energy required to break the bonds of reactants.
Enzymes lower the activation energy barrier by:
- Orienting substrates correctly
- Straining their bonds
- Providing a favorable microenvironment
- Covalently bonding with the substrate

Enzyme activity can be regulated by activation, inhibition, or stabilization.
Enzyme activity is affected by environmental and chemical factors.
Environmental Factors:
- Temperature: Each enzyme has an optimal temperature. Above a critical temperature, enzyme activity drops rapidly as the enzyme denatures (unfolds).
- pH: Each enzyme has an optimal pH. Changes in pH affect enzyme activity due to the acidic and basic properties of amino acids.
Chemical Factors:
- Salt concentration: Can affect enzyme structure and function.
- Cofactors: Non-protein molecules that assist enzyme activity, such as metal ions or vitamins.
- Inhibitors: Molecules that reduce enzyme function. There are two types of inhibitors: Competitive and non-competitive.
- Enzyme concentration: Increased concentration of enzyme leads to increased reaction rate.
- Allosteric regulators: Regulatory molecules bind to specific sites on the enzyme, altering its shape and function. These regulators can either activate or inhibit function.