Biol Cellular Respiration

Key Points: Cellular respiration begins with glucose. Glycolysis occurs in the cytoplasm and produces pyruvate. Pyruvate can be used in either anaerobic or aerobic respiration. Anaerobic respiration (fermentation) produces waste products such as lactic acid or ethanol. Aerobic respiration occurs in the mitochondria and produces ATP. The Krebs cycle produces NADH and FADH₂, which are used in the electron transport chain. The electron transport chain occurs in the inner mitochondrial membrane and produces ATP. Visual Elements: The image is a mind map or concept map. The central topic is "Cellular Respiration." The main branches are the different stages of cellular respiration: glycolysis, Krebs cycle, and electron transport chain. Sub-branches represent the processes and products involved in each stage. Arrows connect the different stages to show the flow of energy and molecules. Key Points: Photosynthesis occurs in mesophyll cells that contain chloroplasts. Chloroplasts contain thylakoids, which are stacked into grana. Light reactions occur in the thylakoid membranes. Calvin cycle occurs in the stroma. Light Reactions: Photosystems I and II absorb light energy. Photosystem II uses water to produce oxygen and electrons. Electrons are transported through the electron transport chain, producing ATP and NADPH. ATP synthase uses the energy from the electron transport chain to produce ATP. Calvin Cycle: Carbon dioxide is incorporated into organic molecules (carbon fixation). G3P is produced, which can be used to make glucose. Overall Process: Solar energy is converted into chemical energy (glucose) using light reactions and the Calvin cycle. Water is used as a source of electrons and hydrogen ions. Oxygen is released as a byproduct. To review photosynthesis, fill in the blanks in the following story. The next time you eat an apple, reflect on the apple tree's ability to make the sug- ars it contains, using sunlight to assemble simple substances from air and soil. This process is called 1 Photosynthesis. It takes place in structures called in cells of tissues called the mesophy // of the apple tree. Photosynthesis actually consists of two processes: In the • Lisht reactions, 5 Chlorophy // molecules, in chloroplast mem branes called 6 thylakouls, capture light energy. In the Kierre Calvin cycle, which takes place in the fluid & Stroma this energy is captured in molecules of sugar surrounding the thylakoids, (637) 2Chloroplasts inside the leaves Chlorophyll molecules absorb 10 photons packets of light energy. Chlorophyll absorbs only certain wavelengths, or colors, of light, mainly in the 11 Red 13 Green and 12 Blue parts of the spectrum. It reflects light. Other pigments, such as 14 xanthiphylls, can absorb colors that chlorophyll cannot use directly, and transfer this energy to chlorophyll. Chlorophyll, other pigments, and proteins are clustered on the thylakoid membranes in groups called photosystems. A photosystem consists of several pigment-and-protein light-harvesting complexes, which act as antennas to capture light energy. They pass their energy on to a central 15 reaction Cent which consists of two chlorophyll molecules and a protein called the primary electron acceptor. There are two kinds of pho- tosystems, photosystem I and photosystem II, which absorb slightly different colors of light. When light strikes a leaf, and pigment molecules absorb photons, they pass their energy to a photosystem II reaction center complex, and there the energy excites a chloro- phyll 36 electrons to a higher energy level. This electron is passed to the pri- mary electron acceptor and on to an electron transport chain. On their way down the electron transport chain, electrons from photosystem II perform important work. One of the electron carriers in the chain uses the energy released by the electrons to transport 17 19 thylakoid 20 gradient ions from the 18Stroma into the space inside the This creates a buildup of H+ ions, a concentration of H+ across the membrane. The H+ ions then diffuse through the membrane via a protein complex called 21 ATP Sunthase, which captures their en- ergy to make 22 4TP In photosynthesis, this chemiosmotic production of ATP is called 29 photophosphoy/a/because its energy source is light. H+ How does photosystem II replace its lost electrons? It gets them by splitting 24 Water . When the electrons of photosystem II are jarred loose, its reaction center complex develops a strong attraction for electrons. It obtains them by breaking apart a molecule of 25 water thylakoid space) and an 26 Oxygen This leaves two H+ ions (which pass into the atom. This atom combines with one from another water molecule to form a molecule of Oxygen gas, which diffuses out of the leaf-a product of photosynthesis important to us and other animals. energy excites an electron in a Meanwhile, 28 Licht chloroplast molecule in the reaction center complex of photosystern L. (This electron is replaced by one from the electron transport chain from photosystem II.) The primary electron 30 Dcceptor passes the electron via a short electron transport chain to NADP+, reducing it to a molecule of 31 NADPH Photosynthesis: Using Light to Make Food At this point: in the story, the cells of the apple leaf have captured the energy of the sun in molecules of NADPH and ATP, and its leaf has released some O₂ gas, but so far no sugar has been produced. NADPH and ATP are used, and sugar is made, in the 32 in the Stroms from 35 cycle, the second portion of phosathesis that takes place of the chloroplast, around the thylakoids. Using carbon obtained from the air, energy from 36 ATP and hydrogen and high-energy electrons carried by 37 NADPH the enzymes of the Calvin cycle construct 38 G-3P a high-energy three-carbon sugar molecule. In a series of steps, these molecules are combined to form the important six- carbon sugar 39 Glucose and other organic compounds. This incorporation of carbon from CO₂ into organic molecules is called carbon 40:xation The cellulose that gives an apple its crunch and the sugar that gives it its sweet taste are made from the glucose made in photosynthesis. In your intestine, the sugars enter your blood and are transported to your body cells. There the chemical pathways of cellular Respicat build 42 ATP release the energy in the sugar molecules and use it to which is in turn used to power cellular work. Energy from the sun, captured by the apple and passed on to you, enables you to see, to move, and to contemplate this amazing story.