4. living organisms require energy to function and this includes each and every one of the trillions of cells that constitute the human body. Define in detail and use diagrams appropriate to show how cells extract, use and store energy including but to limited to discussion of cell respiration, glucose, pyruvic acid, glycolysis, krebs cycle, atp, nadh and fadh and electron transport. how much by the complete breakdown of glucose? why is breathing necessary for cellular respiration in animals?
Cells extract, use, and store energy through a process called cellular respiration. Cellular respiration involves the breakdown of glucose, a sugar molecule, to produce ATP (Adenosine Triphosphate), the energy currency of cells. The process occurs in multiple steps, including glycolysis, the Krebs cycle (also known as the citric acid cycle or TCA cycle), and the electron transport chain.
To better understand these processes, let's explore each step with the help of diagrams:
Glycolysis is the first step of cellular respiration. It takes place in the cytoplasm of the cell and does not require oxygen. During glycolysis, one molecule of glucose (a six-carbon sugar) is enzymatically converted into two molecules of pyruvic acid (a three-carbon compound).
Diagram of Glycolysis:
Glucose (6 carbon) -> 2 Pyruvic Acid (3 carbon)
2. Krebs Cycle:
After glycolysis, if oxygen is available, pyruvic acid molecules enter the mitochondria to undergo the Krebs cycle. Here, each pyruvic acid is converted into Acetyl-CoA, which enters a series of reactions to release energy-rich electrons.
Diagram of the Krebs Cycle:
- Each Pyruvic Acid (3 carbon) -> Acetyl-CoA (2 carbon) -> Compounds in the Krebs Cycle -> Energy-rich Electrons
3. Electron Transport Chain:
The energy-rich electrons from the Krebs cycle are transferred to electron carriers known as NADH (Nicotinamide Adenine Dinucleotide) and FADH (Flavin Adenine Dinucleotide). These electrons then move through a series of protein complexes embedded in the inner mitochondrial membrane. This movement generates energy, which is used to pump protons (H+) across the membrane.
Diagram of the Electron Transport Chain:
- Electrons from NADH and FADH -> Protein Complexes -> Proton Pumping -> Proton Gradient -> ATP Synthesis
4. ATP Synthesis:
The proton gradient created from the electron transport chain drives protons to flow back across the inner mitochondrial membrane through an enzyme called ATP synthase. This flow of protons generates ATP molecules, which are then used as an energy source for cellular processes.
Overall, the complete breakdown of glucose through cellular respiration can produce a net total of 36 to 38 ATP molecules, depending on specific factors like the efficiency of the process.
Breathing is necessary for cellular respiration in animals because it facilitates the exchange of oxygen and carbon dioxide with the environment. Oxygen is required for the final step of cellular respiration, the electron transport chain. Without sufficient oxygen, this step cannot proceed efficiently, leading to a decrease in ATP production. Breathing ensures the continuous supply of oxygen to cells and the removal of carbon dioxide, facilitating the optimal functioning of cellular respiration.