Cellular Respiration, Excretion And Growth - SS1 Biology Past Questions and Answers - page 2

Cellular respiration is the metabolic process by which cells convert glucose and oxygen into carbon dioxide, water, and ATP (adenosine triphosphate). It consists of three main stages: glycolysis, the Krebs cycle (also known as the citric acid cycle), and oxidative phosphorylation (which includes the electron transport chain). Glycolysis occurs in the cytoplasm and breaks down glucose into pyruvate, producing a small amount of ATP. The pyruvate then enters the mitochondria, where the Krebs cycle takes place, generating more ATP and electron carriers (NADH and FADH2). These electron carriers donate electrons to the electron transport chain, located in the inner mitochondrial membrane. The electron transport chain generates a large amount of ATP through oxidative phosphorylation. Overall, cellular respiration provides cells with the necessary energy (in the form of ATP) to carry out various cellular processes.

Cellular excretion refers to the removal of waste materials and metabolic byproducts from cells. This process is essential for maintaining cellular homeostasis by preventing the accumulation of toxic substances and maintaining optimal internal conditions. Cellular excretion involves various mechanisms such as diffusion, active transport, and exocytosis, which allow cells to eliminate waste products such as carbon dioxide, ammonia, urea, and excess salts. These processes ensure the proper functioning and survival of cells by preventing the build-up of harmful substances and maintaining a favorable cellular environment.