Cellular Respiration Overview

Cellular Respiration

• Cellular respiration is the process by which cells break down glucose to produce ATP (adenosine triphosphate), the primary energy currency of cells.
• It's a catabolic process that releases energy stored in the chemical bonds of glucose.
• There are three main stages: glycolysis, the Krebs cycle (citric acid cycle), and the electron transport chain.
• Glycolysis occurs in the cytoplasm and involves the breakdown of glucose into two molecules of pyruvate.
• The Krebs cycle takes place in the mitochondrial matrix and further oxidizes pyruvate, producing NADH and FADH2 (electron carriers).
• The electron transport chain occurs in the inner mitochondrial membrane. Electron carriers (NADH and FADH2) transfer electrons, creating a proton gradient that drives ATP synthesis through chemiosmosis.
• Aerobic respiration requires oxygen as the final electron acceptor in the electron transport chain. Anaerobic respiration (fermentation) occurs without oxygen.
• Cellular respiration is highly efficient, producing a significantly larger amount of ATP compared to fermentation.
• Different types of cellular respiration exist depending on the starting molecule, but they all involve oxidation and reduction reactions releasing energy and creating usable energy for the cell.

Photosynthesis

• Photosynthesis is the process by which plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.
• It's an anabolic process that stores energy from sunlight in the chemical bonds of glucose.
• Two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).
• The light-dependent reactions occur in the thylakoid membranes of chloroplasts. Sunlight energy is captured by chlorophyll and other pigments, splitting water molecules and producing ATP and NADPH.
• Oxygen is released as a by-product of water splitting during the light-dependent reactions.
• The light-independent reactions (Calvin cycle) occur in the stroma of chloroplasts. ATP and NADPH from the light-dependent reactions provide the energy to convert carbon dioxide into glucose.
• Photosynthesis requires carbon dioxide as a source of carbon atoms for glucose synthesis.
• The rate of photosynthesis is affected by factors such as light intensity, temperature, and carbon dioxide concentration.
• Oxygen is a byproduct of this reaction, and organisms use that process for respiration.
• Plants use the glucose produced to fuel cellular processes.
• There are different types of photosynthesis including, C3, C4, and CAM, with variations within the pathways of carbon fixation in different places.

Relationship Between Cellular Respiration and Photosynthesis

• Photosynthesis and cellular respiration are essentially reverse processes.
• Photosynthesis uses sunlight to produce glucose, while cellular respiration breaks down glucose to produce ATP, the energy for cellular processes.
• The products of one process are the reactants of the other.
• Photosynthesis produces glucose and oxygen. Cellular respiration uses glucose and oxygen and produces carbon dioxide and water.
• The interdependence between photosynthesis and cellular respiration is crucial for life on Earth as it cycles essential elements between the living world and the atmosphere.