Food holds energy, and respiration releases it in every cell. See how glucose is broken down with and without oxygen, how fish, insects and people take in oxygen, and how your lungs work.
3 lessons, about 1 h 15 min3 simulations12 problems3 practice questionsPython in every lesson
Created by StemPy LabRespiration releases the energy of food in every living cell. Glucose is first split into pyruvate in the cytoplasm. Without oxygen, yeast makes ethanol and carbon dioxide, and our muscles make lactic acid. With oxygen, in the mitochondria, pyruvate becomes carbon dioxide and water, and much more energy is released. The energy is stored as ATP.
Animals take in oxygen and give out carbon dioxide across surfaces that are large, thin and moist. Water holds far less oxygen than air, so fish breathe faster than land animals. Fish use gills, insects use air tubes, and land vertebrates use lungs. Plants exchange gases through stomata and lenticels; by day a leaf takes in carbon dioxide, and at night it gives it out.
Air passes from the nostrils through the pharynx, larynx, trachea, bronchi and bronchioles to the alveoli, where gases are exchanged with the blood. Breathing in, the ribs lift and the diaphragm flattens, so the chest gets bigger. Some residual air always stays in the lungs. Haemoglobin carries oxygen, and most carbon dioxide travels dissolved in the plasma.
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