Answer:
Hemoglobin is responsible for binding and transporting oxygen in the body. It is a tetrameric protein that is found in high concentration in red blood cells (erythrocytes, red blood cells). Each hemoglobin molecule is made up of four subunits: two of the alpha type and two of the beta type, and each subunit can bind an oxygen molecule through its heme group.
Structure studies have shown that hemoglobin can adopt two conformations, called T (tense) and R (relaxed). Deoxyhemoglobin (in blue) is in state T, and the union of oxygen (in red) causes the transition to state R. The animation shows a close view of the heme group (in white, balls and rods) of one of the subunits of hemoglobin. In the deoxygenated state (T), the iron atom is not coplanar with the rest of the heme group due to its association with the histidine side chain. The union of oxygen displaces the iron atom so that it remains coplanar with the rest of the heme group, which in turn drags histidine, producing a larger-scale conformational change that affects the entire protein.
Hemoglobin can be considered as a tetramer formed by two alpha-beta dimers. The conformational change associated with the transition from T to R mainly affects the relative position of these two dimers (rather than the interactions between the alpha and beta subunits within a dimer). This is illustrated in the last stretch of the animation (drawn in black and white).
Los seres invertebrados y los vertebrados tienen más elementos en común de lo que se pensaba. Un estudio, con participación del Consejo Superior de Investigaciones Científicas (CSIC), prueba que existe gran similitud entre los sistemas excretores de ambos grupos de animales. Según la investigación, las células encargadas de filtrar la sangre en la formación de orina, alojadas en los riñones de vertebrados, son similares a las que realizan una función análoga en invertebrados.
Answer:
We can predict the ways organisms will interact in different ecosystems by comparing the NICHE they fill.
B) carbohydrates
[: The chemical change that occurs in the leaves of green plants. It uses light energy to convert carbon dioxide and water into glucose. Oxygen is produced as a by-product of photosynthesis. ] [: A type of carbohydrate.
