Overview of Cellular Respiration and Metabolism

These flashcards cover essential concepts in enzyme characteristics, cellular respiration, and metabolism. They focus on key processes and definitions that are crucial for understanding the material comprehensively.

Enzymes are primarily composed of _.

protein. These proteins act as biological catalysts, accelerating biochemical reactions.

Enzymes act as _ to speed up the rate of cellular reactions.

organic catalysts. As organic catalysts, they increase reaction rates without being consumed in the process.

Enzymes lower the _ required for a chemical reaction to proceed.

activation energy. By lowering the activation energy, enzymes allow reactions to proceed more readily at physiological temperatures.

Cellular respiration is a collection of metabolic reactions that breaks down food molecules to produce energy in the form of _.

ATP. ATP (adenosine triphosphate) is the primary energy currency used by cells to power various activities.

Fermentation is employed in the absence of _.

O2. In the absence of oxygen, fermentation allows glycolysis to continue producing ATP by regenerating NAD+.

The first stage of cellular respiration is _.

Glycolysis. Glycolysis is an anaerobic process that occurs in the cytoplasm, breaking down glucose into pyruvate.

The intermediate product formed from pyruvate oxidation is _.

Acetyl-CoA. Acetyl-CoA is formed when pyruvate is oxidized and combined with coenzyme A, bridging glycolysis and the Krebs cycle.

During oxidative phosphorylation, the final electron acceptor is _.

oxygen. Oxygen accepts electrons and protons to form water, a crucial step enabling the continuous flow of electrons.

In glycolysis, a 6-carbon glucose molecule is broken down into two 3-carbon molecules of _.

pyruvate. This breakdown of glucose into two pyruvate molecules also yields a net gain of 2 ATP and 2 NADH.

The process of converting pyruvate into lactate is known as _ fermentation.

lactate. Lactate fermentation occurs in muscle cells during strenuous exercise and in some microorganisms.

Strict anaerobes can only perform _ for ATP production.

fermentation. These organisms cannot grow or survive in the presence of oxygen and rely exclusively on fermentation for energy.

The primary electron carriers in cellular respiration are and .

NAD+ and FAD. NAD+ and FAD accept electrons as part of redox reactions, becoming NADH and FADH2, which then deliver electrons to the electron transport chain.

The Krebs cycle occurs in the _ of eukaryotic cells.

mitochondrial matrix. In eukaryotic cells, the Krebs cycle takes place in the fluid-filled mitochondrial matrix, oxidizing acetyl-CoA.

The energy-producing process during glycolysis that directly synthesizes ATP is called _.

substrate-level phosphorylation. This process involves the direct transfer of a phosphate group from an intermediate substrate to ADP to form ATP.

The overall reaction for glycolysis can produce a net gain of _ ATP.

2. Although 4 ATP are produced in total, 2 ATP are consumed, leading to a net gain of 2 ATP.

The process of oxidative phosphorylation occurs in the _ mitochondrial membrane.

inner. The inner mitochondrial membrane houses the electron transport chain and ATP synthase, essential for this process.

The two types of fermentation are and fermentation.

lactic acid and alcoholic. Lactic acid fermentation yields lactate, while alcoholic fermentation produces ethanol and carbon dioxide.

The citric acid cycle oxidizes acetyl groups to produce and .

CO2 and NADH. It also produces FADH2 and a small amount of ATP, completing the breakdown of glucose intermediates.

The main differences between fermentation and anaerobic respiration involve the final electron acceptor; in fermentation, it is an _, while in anaerobic respiration, it is a molecule other than oxygen.

an organic molecule. In fermentation, an organic molecule (like pyruvate or acetaldehyde) serves as the final electron acceptor, whereas anaerobic respiration uses an inorganic molecule other than oxygen.

Total theoretical ATP yield from one glucose molecule during cellular respiration is _ ATP molecules.

38. This theoretical maximum yield (38 ATP) is rarely achieved in cells, with actual yields often closer to 30-32 ATP due to transport costs and proton leakage.

In feedback inhibition, excess ATP can bind to _ to regulate glycolysis.

phosphofructokinase. Phosphofructokinase is a crucial regulatory enzyme in glycolysis, whose activity is inhibited by high ATP levels.

The flow of _ across ATP synthase generates ATP through chemiosmosis.

H+. The movement of H+ ions (protons) down their electrochemical gradient through ATP synthase drives ATP synthesis.

The main products of the citric acid cycle include ATP, , and .

NADH and FADH2. These electron carriers (NADH and FADH2) are crucial for the subsequent stage of oxidative phosphorylation.

Anaerobic respiration differs from fermentation in that it utilizes an electron transport chain with a final electron acceptor that is not _.

oxygen. Instead of oxygen, anaerobic respiration uses alternative inorganic electron acceptors like nitrate, sulfate, or fumarate.

Participants in the electron transport chain include protein complexes I, III, and _.

IV. Complexes I, III, and IV pump protons into the intermembrane space, establishing a proton gradient.

ATP synthase uses the proton gradient established by the electron transport chain to synthesize _.

ATP. This enzymatic complex harnesses the energy of the proton motive force to phosphorylate ADP into ATP.

The citric acid cycle includes how many main enzymatic reactions?

eight. Each of the eight enzymatic reactions ensures the efficient cyclic processing of intermediates and regeneration of oxaloacetate.

The energy yield from each NADH during oxidative phosphorylation is approximately _ ATP.

2.5. This yield accounts for the protons pumped and the subsequent ATP produced via chemiosmosis from each NADH.

One of the main reasons organisms require oxygen is that it is the final electron acceptor in _.

aerobic respiration. Oxygen's role as the terminal electron acceptor enables the efficient, large-scale production of ATP through oxidative phosphorylation.

Beyond ATP and pyruvate, glycolysis also produces the electron carrier _.

NADH. NADH carries high-energy electrons to the electron transport chain for further ATP production.

For each glucose molecule, glycolysis produces a net of _ molecules of NADH.

2. These 2 NADH molecules will contribute to oxidative phosphorylation under aerobic conditions.

Per acetyl-CoA molecule, the Krebs cycle yields _ molecule of ATP (or GTP).

1. This ATP (or GTP) is produced via substrate-level phosphorylation within the cycle.

Each turn of the Krebs cycle, from one acetyl-CoA, produces _ molecules of NADH.

3. These 3 NADH molecules are vital electron carriers for the electron transport chain.

In the Krebs cycle, one acetyl-CoA molecule yields _ molecule of FADH2.

1. FADH2 is another critical electron carrier that delivers electrons to the electron transport chain.

For each acetyl-CoA entering the Krebs cycle, _ molecules of CO2 are released.

2. The release of CO2 completes the oxidation of the carbon atoms originally from glucose.