How do living things stay alive? Cellular Respiration Burning Happens in ALL living things inside cells and has the main goal of producing ATP the fuel of life It does not matter whether the organisms is an autotroph (able to photosynthesize) or heterotroph (those that cannot make their own food from inorganic materials) All living things need to make ATP to power metabolic activities in cells Is a catabolic process: breakdown of compounds Specific organelle (Eukaryotes): Mitochondrion Photosynthesis Making the fuel of life Cellular Respiration Burning the fuel of life 1
Cellular respiration and breathing are closely related. Cellular respiration requires a cell to exchange gases with its surroundings. Cells take in oxygen gas. Glucose + O2 CO2 + H2O + ATP Cells release waste carbon dioxide gas. Breathing exchanges these same gases between the blood and outside air. Cellular level Body level O 2 Glucose H 2 O Cellular Respiration Glucose + O2 CO2 + H2O + ATP Is about producing ATP! It is the main way that chemical energy is harvested from food and converted to ATP 2 types of cellular respiration Anaerobic: no molecular (O 2 ) oxygen is used Aerobic: molecular oxygen is required in the process The Role of Oxygen in Cellular Respiration During cellular respiration, H+ and its bonding electrons change partners H+ and its electrons go from sugar to oxygen, forming water Releasing energy in the process, that is passed to the ATP This hydrogen transfer is the reason why oxygen is so vital to cellular respiration. ATP 2
A) Aerobic Cellular Respiration General equation for aerobic cellular respiration C 6 H 12 O 6 + 6O 2 + 2ATP 6 + 6H 2 O + ( Energy: Heat +38ATP) Why ATP also as a reactant? 2 ATP molecules are needed to make the glucose unstable and ready to react Covalent bonds in the glucose and subsequent by-products are broken down and e - (electrons) from H (hydrogen) atoms are used in e - transport to produce ATP Aerobic cellular respiration has 3 main parts 1). Glycolysis Takes place in the cytoplasm of the cell and does not require oxygen 2). Citric or Krebs Cycle Takes place in the matrix of mitochondria and does not require oxygen 3). Electron Transport Chain (ETC) Takes place in the inner membrane of mitochondria and does require oxygen and Electron Transport Chains The path that electrons follow from from glucose to O 2 involves many steps. The first step is an electron acceptor or carrier called NAD+ and FAD. O 2 H 2 O FADH 2 and FADH2 transports H and electron to the Electron Transport Chain during Glycolysis and Krebs The rest of the path consists of an electron transport chain, which: Involves a series of reactions That ultimately leads to the production of large amounts of ATP in the inner membrane of the mitochondria 3
1. Glycolysis Cytoplasmatic pathway Breakdown of glucose without the use of oxygen Energy (ATP) is needed to begin the reactions Summary: 4 ATPs generated -2 ATPs used = 2 NET ATPs 2 s 2 Pyruvic acids A more detailed view of glycolysis Cytoplasmatic pathway Breakdown of glucose without the use of oxygen Energy (ATP) is needed to begin the reactions 4
2. Krebs cycle Mitochondrion matrix pathway Pyruvic acid enter the mitochondrion Summary: 2 ATP is generated 6 CO2 are released 8H become attached to NAD+ and 4H to FAD When both Pyruvic acid molecules have been processed: (1) all the original C atoms from the glucose have been converted to CO2 (2) all the original H atoms from the glucose have been transferred to NAD+ and FAD energy carriers 2 Pyruvic acid 3 carbons FADH 2 ATP Enzyme 1 2 Acetyl CoA 2 carbons Oxaloacetate Enzyme 2 Enzyme 10 Enzyme 9 Enzyme 8 Krebs cycle Enzyme 7 Enzyme 6 6 carbons Enzyme 5 Enzyme 3 6 carbons Enzyme 4 5 carbons 5 carbons 3. Electron Transport Chain (ETC) Inner mitochondrion membrane pathway e- transported by and FADH 2 are released in the inner membrane system The molecules of the electron transport chain are built into the inner membranes of mitochondria. e- participate in the ETC, allowing H+ to be pumped from the (2) matrix to the inter membrane space of the mitochondria (1) H e - + H+ e- come from H atoms that split into H+ (nucleus of a H) and the e- moving around the nucleus 5
The chain works as a chemical machine, uses energy released by the fall of electrons to pump H+ across the inner mitochondrial membrane. These H+ are used to make ATP! H+ (protons) that were pumped across the membrane accumulate in the inter membrane space Summary: About 32 ATP are generated H 2 O is generated using O 2 NAD+ and FAD+ are released to be used again (3) H+ H + (4) H+ return to the original side using an enzyme as an exit ATPase (enzyme) ADP+Pi H+ H+ O 2 +4 +4e - ATP 2H 2 O (5) The energy from the H+ flow is used to make ATP, main product for cellular respiration (6) Molecular O 2 is used to receive the H+ and e- from the ETC so H 2 O is formed as a waste product when and e - combine with oxygen The Versatility of Cellular Respiration In addition to glucose, cellular respiration can burn : Diverse types of carbohydrates Fats Proteins 6
B) Fermentation: Anaerobic cellular respiration Only Glycolysis plus one extra reaction less ATP (only 2 molecules) is generated! The ultimate hydrogen acceptor is an organic molecule instead of O 2 Alcoholic fermentation Last H acceptor is an alcohol (ethanol) Yeast cells (a fungus!) when no oxygen is available Used in brewing and baking Lactic acid fermentation In humans: occurs in Red blood cells (that lack mitochondria) Muscle cells: After functioning anaerobically for about 15 seconds: Will begin to generate ATP by the process of aerobic cell respiration In Bacteria Fermentation alone is able to sustain many types of microorganisms. The lactic acid produced by microbes using fermentation is used to produce: Cheese, sour cream, and yogurt dairy products Soy sauce, pickles, olives Sausage meat products 7