Cellular Respiration Flashcards
What is the overall purpose of cellular respiration?
Cellular respiration is a catabolic process that converts fuel molecules (primarily glucose) into ATP, the energy currency needed for cellular work.
Why are mitochondria often called “the powerhouse of the cell”?
Because they generate most of the cell’s ATP through cellular respiration, using oxygen to oxidize substrates and drive energy production.
What is the ATP cycle?
The ATP cycle is the continuous conversion of ATP (a complex molecule) to ADP and inorganic phosphate (simple molecules) during energy release, and vice versa when energy is stored.
How do catabolic and anabolic reactions differ in terms of ATP?
Catabolic reactions break down complex molecules to generate ATP, while anabolic reactions use ATP to build complex molecules from simpler ones.
What are the three main fuel sources for cellular respiration?
Carbohydrates (absorbed as simple sugars), proteins (absorbed as amino acids), and fats (absorbed as simple fats).
What is the net overall reaction of cellular respiration?
Oxygen + Glucose → Carbon Dioxide + Water + ATP
How does the body use insulin in relation to cellular respiration?
Insulin facilitates the uptake of glucose into cells, making glucose available for cellular respiration or storage as glycogen.
What role does glucagon play in energy regulation?
When blood glucose is low, glucagon is released to trigger glycogen breakdown into glucose, ensuring energy supply.
What are the four main stages of cellular respiration and where do they occur?
- Glycolysis (cytosol), 2. Pyruvate Oxidation (mitochondrial matrix), 3. Citric Acid Cycle (mitochondrial matrix), 4. Electron Transport Chain & Chemiosmosis (inner mitochondrial membrane/cristae).
What happens during glycolysis?
In the cytosol, one glucose (6 carbons) is split into 2 pyruvate molecules (3 carbons each), consuming 2 ATP and producing 4 ATP (net gain of 2 ATP) along with 2 NADH.
Is glycolysis aerobic or anaerobic, and what does that mean?
Glycolysis is anaerobic, meaning it does not require oxygen to proceed.
What occurs during pyruvate oxidation?
Pyruvate enters the mitochondrial matrix and is converted into Acetyl CoA. For each pyruvate, 1 NADH is produced and 1 CO₂ is released (doubling per glucose).
What is the role of Acetyl CoA in cellular respiration?
Acetyl CoA, containing 2 carbons, is the key substrate that enters the Citric Acid Cycle for further oxidation and energy extraction.
What takes place in the Citric Acid Cycle?
In the mitochondrial matrix, Acetyl CoA is oxidized through a series of reactions that produce ATP (by substrate-level phosphorylation), NADH, FADH₂, and CO₂ as waste.
How many molecules of ATP, NADH, FADH₂, and CO₂ are produced per glucose in the Citric Acid Cycle?
Per glucose, the cycle yields 2 ATP, 6 NADH, 2 FADH₂, and 4 CO₂ (since each glucose yields 2 Acetyl CoA).
What is substrate-level phosphorylation?
It is a direct method of ATP generation in which a phosphate group is directly transferred to ADP from a phosphorylated intermediate, as seen in glycolysis and the Citric Acid Cycle.
What is oxidative phosphorylation?
It is the process by which ATP is generated using the energy released from the oxidation of NADH and FADH₂ via the electron transport chain (ETC) and chemiosmosis.
How does the Electron Transport Chain (ETC) function?
The ETC, located in the inner mitochondrial membrane (cristae), transfers electrons from NADH and FADH₂ through a series of protein complexes, using the energy released to pump H⁺ ions into the intermembrane space.
What role does oxygen play in the ETC?
Oxygen acts as the final electron acceptor, combining with electrons and H⁺ ions to form water.
How does the proton gradient generated by the ETC lead to ATP production?
The proton gradient drives H⁺ ions back into the mitochondrial matrix through ATP synthase, which uses the energy of this flow (chemiosmosis) to phosphorylate ADP into ATP.
Approximately how many ATP molecules are produced by oxidative phosphorylation?
Oxidative phosphorylation yields about 26–28 ATP molecules per glucose molecule.
Why does oxidative phosphorylation yield more ATP than substrate-level phosphorylation?
Because it harnesses the energy from a large electrochemical proton gradient built by the ETC, allowing ATP synthase to produce many ATP molecules compared to the few generated directly by substrate-level phosphorylation.
What are some reasons given for the variability (26 or 28 ATP) in ATP yield from the ETC?
Variability arises because (1) the redox reactions and phosphorylation are not directly coupled; (2) H⁺ ions may be used in other mitochondrial functions; and (3) cytosolic NADH must transfer electrons indirectly into mitochondria, which can be less efficient.
How do fats, proteins, and complex carbohydrates enter cellular respiration?
They enter at various points along the pathway, meaning they are broken down into intermediates that feed into glycolysis, the Citric Acid Cycle, or directly into the ETC.
What is chemiosmosis?
Chemiosmosis is the movement of H⁺ ions down their concentration gradient through ATP synthase, driving the synthesis of ATP from ADP and inorganic phosphate.
What is the overall ATP yield per glucose molecule from cellular respiration?
Combining all stages, cellular respiration produces approximately 30–32 ATP per molecule of glucose.
How does negative feedback regulate cellular respiration?
High levels of ATP and citrate inhibit phosphofructokinase (PFK), slowing glycolysis, while high AMP levels stimulate PFK to increase ATP production when energy is low.
What is the rate-limiting step of glycolysis and how is it regulated?
Phosphofructokinase (PFK) is the rate-limiting enzyme; it is inhibited by high levels of ATP and citrate and stimulated by high levels of AMP.
How does the cell maintain blood glucose homeostasis after a meal?
Elevated blood glucose is detected by beta cells in the pancreas, which release insulin. Insulin promotes glucose uptake into cells, lowering blood glucose levels.
How does the body respond to low blood glucose levels?
Low blood glucose is sensed by alpha cells in the pancreas, which release glucagon. Glucagon stimulates the breakdown of glycogen in the liver and muscles to release glucose into the blood.
What is the consequence of impaired insulin production or receptor function?
Impaired insulin production (Type 1 Diabetes) or insulin resistance (Type 2 Diabetes) leads to elevated blood glucose levels, causing hyperglycemia and associated symptoms.
What are some common symptoms of Diabetes Mellitus?
Symptoms include polydipsia (excessive thirst), polyuria (frequent urination), polyphagia (increased hunger), weight loss, glycosuria (glucose in urine), fatigue, vision changes, peripheral numbness, slow wound healing, and increased infections.
How does cyanide poisoning affect cellular respiration?
Cyanide blocks Complex IV of the ETC, preventing electron transfer to oxygen, which stops ATP production and leads to cell death.
Why is oxygen essential for efficient ATP production?
Oxygen is the final electron acceptor in the ETC; without it, the entire chain backs up, the proton gradient cannot be maintained, and ATP production via oxidative phosphorylation ceases.
