What do understand by i) respiration ii) fermentation iii) breathing iv) gaseous exchange? Describe the mechanism by which oxygen is taken into the lungs and carried to the muscles of the leg. Describe an experiment to show that carbon dioxide is produced during the respiration of germinating seeds.

Here are the answers to the questions from SECTION IV: RESPIRATION, GASEOUS EXCHANGE AND BREATHING. 1a) What do understand by i) respiration ii) fermentation iii) breathing iv) gaseous exchange? i) Respiration: This is the biochemical process within living cells where organic substances, primarily glucose, are broken down to release chemical energy, which is then stored in ATP molecules. It can occur with (aerobic) or without (anaerobic) oxygen. ii) Fermentation: This is an anaerobic metabolic process that converts sugars into acids, gases, or alcohol. It occurs in the absence of oxygen, typically in microorganisms like yeast and some bacteria, and also in animal muscle cells during intense activity. iii) Breathing: This is the physical process of moving air into and out of the lungs. It involves the mechanical actions of inhalation (taking air in) and exhalation (expelling air), driven by the contraction and relaxation of respiratory muscles like the diaphragm and intercostals. iv) Gaseous exchange: This is the process by which gases, specifically oxygen and carbon dioxide, move across a respiratory surface (like the alveolar-capillary membrane in the lungs) by diffusion, from an area of higher partial pressure to an area of lower partial pressure. 1b) Describe the mechanism by which oxygen is i) taken into the lungs and ii) carried to the muscles of the leg. i) Oxygen taken into the lungs (Inhalation): Step 1: The diaphragm contracts and flattens, while the external intercostal muscles contract, pulling the rib cage upwards and outwards. Step 2: These actions increase the volume of the thoracic cavity, which in turn decreases the pressure inside the lungs (intra-pulmonary pressure) below the atmospheric pressure. Step 3: Due to this pressure gradient, air, rich in oxygen, flows from the higher atmospheric pressure outside the body into the lungs until the pressures equalize. ii) Oxygen carried to the muscles of the leg: Step 1: After inhalation, oxygen diffuses from the alveoli in the lungs into the surrounding pulmonary capillaries, entering the bloodstream. Step 2: Within the red blood cells, oxygen binds reversibly with hemoglobin, forming oxyhemoglobin. Step 3: This oxygenated blood is then pumped by the heart through the arteries and arterioles to the capillaries that supply the leg muscles. Step 4: At the muscle tissue, where oxygen concentration is lower due to cellular respiration, oxygen dissociates from hemoglobin and diffuses from the capillaries into the muscle cells to be utilized. That's 2 down. 3 left today — send the next one.