Cellular Respiration Flashcards
What are the two ways ATP can be produced in cellular respiration?
Substrate-level phosphorylation (simple)
Oxidative phosphorylation (complex)
What is substrate-level phosphorylation?
The direct generation of ATP in an enzyme-catalyzed reaction by transferring a phosphate group to ADP. This process is endergonic and coupled with an exergonic reaction.
What is oxidative phosphorylation?
The chemiosmotic generation of ATP, where energy from electron transport drives proton pumping to create a proton gradient across the membrane, which in turn generates ATP.
Describe the structure and function of the mitochondrion.
- Bean shaped
- Double membrane: outer membrane and inner membrane (cristae)
- Own DNA and ribosomes
- Site of oxidative phosphorylation in eukaryotic cells
- Thought to have originated from endosymbiotic bacteria
What is glycolysis, and where does it occur?
Glycolysis is the first stage of cellular respiration, occurring in the cytoplasm, where glucose is broken down to produce pyruvate, ATP, and NADH.
Chemical reaction for glycolysis.
C₆H₁₂O₆ + 2 ADP + 2 Pi + 2 NAD⁺ → 2 pyruvate + 2 ATP + 2 NADH + 2 H⁺
What is the net ATP yield per molecule of glucose in glycolysis?
2 ATP (4 ATP produced, 2 ATP used)
What are the three phases of the Calvin Cycle, and why are they important?
Carbon fixation, reduction, and regeneration. Each phase is crucial for synthesizing glucose from CO₂ in the stroma of chloroplasts.
What occurs during pyruvate oxidation?
Pyruvate enters the mitochondrial matrix, is decarboxylated to form acetyl-CoA, and produces NADH and CO₂.
Chemical reaction for pyruvate oxidation.
2 pyruvate + 2 NAD⁺ + 2 CoA → 2 Acetyl-CoA + 2 NADH + 2 H⁺ + 2 CO₂
What is the function of cristae in the mitochondria?
Cristae increase the surface area for oxidative phosphorylation, enhancing ATP production.
What role does Acetyl-CoA play in the Krebs Cycle?
Acetyl-CoA combines with oxaloacetate to form citrate, starting the Krebs Cycle.
What is the main function of the Krebs Cycle?
To generate high-energy electron carriers (NADH and FADH₂) that supply electrons to the Electron Transport Chain (ETC).
How does ATP synthase produce ATP?
Protons flow back into the mitochondrial matrix through ATP synthase, which uses this energy to convert ADP and Pi into ATP.
How many ATP are produced from one molecule of NADH?
About 3 ATP
How many ATP are produced from one molecule of FADH₂?
About 2 ATP
What is chemiosmosis?
The movement of protons down their gradient across a membrane, driving ATP synthesis by ATP synthase.
Where in the cell does the Krebs Cycle occur?
In the mitochondrial matrix.
What is the final electron acceptor in the Electron Transport Chain?
Oxygen, which combines with electrons and protons to form water.
Why is oxygen necessary for aerobic respiration?
Oxygen serves as the final electron acceptor, allowing the Electron Transport Chain to continue and prevent backup of electrons.
What is the total ATP yield from one molecule of glucose in cellular respiration?
About 36-38 ATP
How does the inner mitochondrial membrane contribute to ATP production?
Its high surface area and embedded proteins facilitate the ETC and ATP synthesis.
How does fermentation differ from aerobic respiration?
Fermentation occurs without oxygen, producing less ATP and resulting in byproducts like lactic acid or ethanol.
What happens to the electrons as they move along the ETC?
They lose energy, which is used to pump protons into the intermembrane space, creating a proton gradient.
What happens to the electrons as they move along the ETC?
They lose energy, which is used to pump protons into the intermembrane space, creating a proton gradient.
What is fermentation?
A process where hydrogen atoms from NADH are transferred to organic compounds instead of going through the ETC.
Why is pyruvate converted to ethanol or lactate during fermentation?
To regenerate NAD+ so glycolysis can continue in the absence of oxygen.
What is the byproduct when pyruvate is converted to acetaldehyde in ethanol fermentation?
Carbon dioxide (CO2).
What happens to pyruvate during lactic acid fermentation?
It is converted into lactate, which can later be used in the liver to regenerate glucose.
Why does lactic acid buildup occur in muscles during anaerobic respiration?
Because of high-intensity exercise when oxygen is limited, leading to lactate accumulation and muscle fatigue.
What is the main difference between aerobic and anaerobic respiration?
Aerobic respiration requires oxygen, while anaerobic respiration occurs without oxygen.
How much ATP is produced in aerobic respiration compared to anaerobic respiration?
Aerobic respiration produces about 32 ATP, while anaerobic respiration produces only 2 ATP per glucose molecule.
In what form is glucose stored in the body for both aerobic and anaerobic respiration?
As glycogen
Why does lactic acid buildup occur only during anaerobic respiration?
Because, in the absence of oxygen, pyruvate is converted into lactic acid instead of entering the Krebs cycle.
Why is aerobic respiration more efficient than anaerobic respiration?
Because it produces much more ATP per glucose molecule due to the complete oxidation of glucose.
