Bioenergetics- I Flashcards
What is bioenergetics?
The quantitative study of energy transformations in living cells and the chemical processes underlying these transformations. It focuses on how energy is produced, transformed, stored, and utilized in the form of ATP.
What are high-energy phosphate compounds?
Compounds that yield significant free energy (ΔG ≤ -7.3 kcal/mol or -30.1 kJ/mol) upon hydrolysis, often containing phosphate groups (e.g., ATP).
What is Gibbs free energy (ΔG)?
The amount of energy capable of doing work during a reaction at constant temperature and pressure. It predicts the energetic feasibility and direction of a reaction.
What does a negative ΔG indicate?
The reaction is exergonic (spontaneous), with a net loss of energy as the reaction proceeds.
What does a positive ΔG indicate?
The reaction is endergonic (non-spontaneous), requiring energy input to proceed.
What does ΔG = 0 signify?
The reaction is at equilibrium, with no net change in free energy.
Name three electron carriers in cellular catabolism.
NAD+, FAD, FMN.
What is the role of ATP in bioenergetics?
ATP acts as the universal energy currency, linking energy-producing (catabolic) and energy-requiring (anabolic) reactions in cells.
How do NAD+ and FAD differ in electron acceptance?
NAD+ accepts two electrons and one proton (as hydride, H–), while FAD can accept one or two electrons (as hydrogen atoms or electrons).
What is the difference between NADH and NADPH?
NADH is primarily involved in catabolic reactions (energy production), while NADPH is used in anabolic reactions (biosynthesis).
How are endergonic reactions driven forward in cells?
By coupling them with exergonic reactions, ensuring the overall ΔG of the pathway is negative.
What is the significance of the electron transport chain?
It releases free energy as electrons transferred by carriers (e.g., NADH, FADH2) move through the chain, driving ATP synthesis.
Why is ATP considered a “high-energy” compound?
Because its hydrolysis releases -7.3 kcal/mol (-30.1 kJ/mol) of free energy, making it suitable for energy coupling in biological systems.
What are the two groups of phosphate compounds in living organisms?
High-energy compounds (ΔG°’ < -25 kJ/mol, e.g., ATP, PEP).
Low-energy compounds (ΔG°’ > -25 kJ/mol, e.g., glucose-6-phosphate).
What is the squiggle symbol (~) used for in biochemistry?
It denotes high-energy bonds, such as those in ATP (~P) or creatine phosphate, which release significant energy upon hydrolysis.
Name a high-energy compound that does not contain a phosphate group.
Acetyl CoA (contains a thioester bond instead of phosphate).
How do biological oxidation-reduction reactions relate to energy flow?
Electrons transferred during redox reactions (e.g., via NADH/FADH₂) release energy, which is harnessed to synthesize ATP.
What are the three ways electrons can be transferred in biological systems?
As hydride ions (H⁻) to NAD⁺.
As hydrogen atoms (*H) to FMN, FAD, or CoQ.
As electrons (e⁻) to cytochromes.
Why is FAD considered a “flexible” electron carrier?
Unlike NAD⁺, FAD can accept 1 or 2 electrons (forms FADH or FADH₂).
How does ATP link catabolism and anabolism?
Catabolic reactions (e.g., glycolysis) generate ATP, which is then hydrolyzed to drive endergonic anabolic reactions (e.g., protein synthesis).
Give an example of energy coupling using ATP.
Glucose → Glucose-6-phosphate: The endergonic phosphorylation of glucose is coupled to ATP hydrolysis (exergonic).
Why are ΔG values additive in metabolic pathways?
Even if some steps have a positive ΔG, the pathway can proceed if the total ΔG is negative (due to coupling with exergonic reactions).
What is the clinical significance of NADH vs. NADPH?
NADH: Used in ATP production (e.g., in oxidative phosphorylation).
NADPH: Supports biosynthetic pathways (e.g., fatty acid synthesis) and antioxidant defense.
If ΔG for a reaction is +10 kJ/mol, what does this imply?
The reaction is non-spontaneous (endergonic) and requires energy input.
