Efficiency of Cellular Respiration (Unit 2) Flashcards
How are electron transport and oxidative phosphorylation related in terms of efficiency?
They are distinct and not always completely coupled. For each NADH oxidized, each pair of electrons travels down the ETC, pumping 10 H+ into the inner membrane space. 3-4 H+ are needed to flow back through ATP synthase to synthesize each ATP, resulting in up to 2 ATP made for every NADH oxidized by the ETC.
Why does the oxidation of FADH2 result in fewer ATP than NADH?
FADH2 bypasses the proton-pumping Complex I, leading to fewer protons being pumped across the membrane. Each FADH2 oxidized results in the synthesis of only 2 ATP.
How many NADH and FADH2 are oxidized by the ETC during the complete oxidation of one glucose molecule?
A total of 10 NADH, 10 H+, and 2 FADH2 are oxidized by the ETC.
How do NADH molecules produced during glycolysis access the ETC?
Since NADH produced during glycolysis is in the cytosol, two shuttle systems transfer high-energy electrons from NADH across the inner mitochondrial membranes into the matrix.
What is the malate-aspartate shuttle?
The malate-aspartate shuttle is an energy-efficient system used by many cells. NADH in the cytosol is oxidized to NAD+, and the electrons are transferred across the membrane to reduce NAD+ to NADH within the matrix.
What is the glycerol-phosphate shuttle?
The glycerol-phosphate shuttle transfers electrons across the membrane from NADH to FAD in the matrix, resulting in the formation of FADH2 and less free energy. Cells using this shuttle produce 2 ATP for every NADH produced in glycolysis.
What is the total maximum ATP yield per glucose molecule during cellular respiration?
The maximum ATP produced per glucose molecule is:
Glycolysis: 2 ATP
Citric acid cycle: 2 ATP
Electron transport: 34 ATP
Total: 38 ATP
What factors can reduce the maximum ATP yield per glucose molecule?
The inexact NADH/FADH2 to ATP ratio, energy loss due to uncoupling proteins, usage for other mitochondrial processes, and cells using the glycerol-phosphate shuttle system can all reduce the maximum ATP yield, creating 2 fewer ATP per glucose.
Why is having a constant ATP supply critical for cells?
Having a constant ATP supply is critical for cells to maintain energy for various functions, which can be particularly difficult for cells like muscle and brain cells that may need sudden bursts of ATP.
How do some organisms respond to swings in ATP demand?
Some organisms respond to swings in ATP demand by using creatine phosphate. Excess ATP is used to phosphorylate creatine, forming creatine phosphate, which can be stored and rapidly converted back to ATP when needed.
What is the role of creatine phosphate in the cell?
Creatine phosphate acts as a stored form of energy that can quickly regenerate ATP from ADP, supplementing the ATP produced by aerobic cellular respiration (ACR).
What happens when cell reserves of creatine phosphate are depleted?
Once cell reserves of creatine phosphate are depleted, they must be regenerated by ATP, which can occur later when the cell’s energy demands are lower.
What is metabolic rate?
Metabolic rate is the amount of energy expended per unit time in an organism, equivalent to the overall rate of aerobic and anaerobic respiration reactions
What is basal metabolic rate (BMR)?
Basal metabolic rate is the metabolic rate of an organism at rest, measured in kilojoules per square meter of surface area per hour (kJ/m²/h), and varies based on age, gender, growth, and health.
How is the overall rate of aerobic cellular respiration (ACR) regulated?
The overall rate of ACR is regulated to match the cell’s ATP requirements, often through feedback inhibition where end products inhibit early enzymes in the pathway.
