Energy and Respiration Quiz

Energy and Respiration

• Living organisms require energy to survive. This energy originates from the Sun or chemicals.
• Plants utilize solar energy in photosynthesis to create organic molecules from water and carbon dioxide.
• Animals break down organic molecules to produce adenosine triphosphate (ATP), the energy source for life processes.
• Energy is the ability to do work. It exists in kinetic and potential forms.
• Kinetic energy is energy of motion.
• Potential energy is stored energy. Examples include a stone on a hill or stored chemical energy.
• Energy exists in various forms like light, heat, sound, etc.
• Organisms need energy for anabolism (building complex molecules), movement (internal and external), active transport, maintenance and repair of cells, and maintaining body temperature (in endotherms).

Laws of Thermodynamics

• The first law states that energy cannot be created or destroyed, only transformed.
• The second law states that disorder (entropy) in the universe always increases. Order has less energy.

Activation Energy

• Chemical reactions require activation energy to start.
• Catalysts (e.g., enzymes) reduce the activation energy, enabling faster reaction rates or operation at lower temperatures
• Reactions can be exergonic (releasing energy) or endergonic (requiring energy).

Adenosine Triphosphate (ATP)

• ATP is the universal energy currency in cells.
• ATP is produced in mitochondria and chloroplasts.
• ATP's suitability as the energy currency is due to: rapid energy release, ease of transport, and fast regeneration from ADP.
• ATP is a small, water-soluble molecule, easily transported and involved in cellular reactions.
• The three phosphate groups in ATP are crucial. They are negatively charged, repel each other, and have a low activation energy, making them easily broken to release large amounts of energy.

Role of ATP

• ATP provides energy for anabolic processes (building complex molecules), movement, active transport across membranes, maintenance of cellular components, and body temperature regulation.

Role of Coenzymes

• Coenzymes, such as NAD (nicotinamide adenine dinucleotide) and FAD (flavine adenine dinucleotide) carry hydrogen atoms and electrons in metabolic pathways.
• NAD and FAD store energy from reactions and carry hydrogen, which is critical for energy production in oxidative phosphorylation.
• Coenzymes are frequently found as part of larger enzyme complexes.

Respiration - Glycolysis

• Glycolysis is the anaerobic breakdown of glucose into pyruvate.
• Glycolysis occurs in the cytoplasm of cells.
• It involves a series of 10 enzyme-controlled reactions that break down glucose (a 6-carbon molecule) into two molecules of pyruvate (a 3-carbon molecule), producing a small amount of ATP during substrate-level phosphorylation.
• Glycolysis yields a net gain of 2 ATP molecules and 2 NADH molecules.
• The process involves phosphorylation, splitting the sugar into two smaller units and oxidation.

Link Reaction and Krebs Cycle

• The link reaction connects glycolysis to the Krebs cycle.
• Pyruvate from glycolysis is converted into acetyl-CoA. This occurs in the mitochondrial matrix.
• Krebs Cycle: Acetyl-CoA enters the Krebs cycle, releasing carbon dioxide.
• The Krebs cycle generates reduced coenzymes (NADH and FADH₂) and a small amount of ATP (via substrate-level phosphorylation). It occurs in the matrix of the mitochondria.

Oxidative Phosphorylation

• Oxidative phosphorylation is the final stage of aerobic respiration.
• It occurs in the inner mitochondrial membrane.
• It involves an electron transport chain (ETC) where energy stored in NADH and FADH₂ is used to pump protons (H+) across the inner mitochondrial membrane to create an electrochemical gradient.
• The flow of these protons back into the mitochondria through ATP synthase drives ATP synthesis. This is a process called chemiosmosis.
• Oxygen is the final electron acceptor, forming water.

Anaerobic Respiration

• Anaerobic respiration occurs when oxygen is not available.
• In alcoholic fermentation (e.g., yeast), pyruvate is converted to ethanol and carbon dioxide, regenerating NAD+.
• In lactic acid fermentation (e.g., muscles), pyruvate is converted to lactate, regenerating NAD+.
• Anaerobic respiration results in a significantly lower ATP yield compared with aerobic respiration.

Measurement of Respiration (Respiratory Quotient)

• Respirometers are used to measure the rate of respiration.
• The respiratory quotient (RQ) is the ratio of carbon dioxide produced to oxygen consumed.
• Different respiratory substrates (e.g., carbohydrates, fats, proteins) have different RQs, allowing deductions about the types of molecules being broken down for energy.