Biochemistry: ATP Structure and Energy Types

ATP Structure and Function

• ATP (adenosine triphosphate) is composed of an adenine base, a ribose sugar, and three phosphate groups.
• Phosphate groups are connected by high-energy bonds.
• ATP is the primary energy currency in cells.
• It provides energy for various cellular processes (muscle contraction, transport, chemical reactions).
• Energy is stored in the bonds between phosphate groups.
• Hydrolysis of ATP (breaking the bond) releases energy in the form of ADP (adenosine diphosphate) and an inorganic phosphate (Pi).

Energy Types and Thermodynamics

• Potential energy is energy stored due to position or structure (e.g., chemical bonds).
• Kinetic energy is energy of motion (e.g., moving particles, heat).
• The first law of thermodynamics states energy cannot be created or destroyed, only transformed.
• Chemical potential energy in glucose can be transformed into ATP and heat.
• The second law of thermodynamics states transformations are inefficient. Some energy is lost as heat, increasing disorder (entropy).

Chemical Reactions

• Synthesis reactions combine reactants to form a larger molecule.
• Decomposition reactions break down a large molecule into smaller ones.
• Exchange reactions involve breaking and reforming bonds.
• Oxidation-reduction (redox) reactions involve electron transfer.
• Anabolic reactions build complex molecules (require energy).
• Catabolic reactions break down complex molecules (release energy).
• Endergonic reactions require energy input.
• Exergonic reactions release energy.
• Reversible reactions can proceed in both directions.
• Irreversible reactions proceed in only one direction.

Enzymes and Reaction Rates

• Reaction rate is the speed of reactant conversion to products.
• Activation energy is the minimum energy needed to start a reaction.
• Catalyzed reactions are accelerated by a catalyst (e.g., enzymes).
• Uncatalyzed reactions occur without a catalyst, typically at a slower rate.
• Enzymes are proteins with a specific 3-dimensional structure.
• The active site is the region where substrates bind.
• Enzymes lower activation energy, speeding up biochemical reactions.
• Factors affecting enzyme activity include substrate concentration, temperature, pH.

Enzyme Inhibition and Metabolism

• Competitive inhibition blocks substrate binding to the active site.
• Noncompetitive inhibition binds to a site other than the active site, changing the enzyme's shape.
• Metabolism is the sum of all chemical reactions in a cell or organism.
• Metabolic pathways often utilize negative feedback mechanisms.
• Final products inhibit earlier steps in the pathway to regulate activity.

Enzyme Mechanism

• Substrates bind to the enzyme's active site.
• Enzyme-substrate complex forms, lowering activation energy
• Products are released.
• Cofactors (non-protein molecules) assist enzymes in catalysis.