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Learn about the citric acid cycle, a process that converts high-energy molecules from low-energy ones and eliminates two carbons as CO2. Understand how molecular oxygen is involved in this cycle and discover its importance in producing ATP from carrier molecules. Explore the storage of energy reserves in animal and plant cells and their utilization during periods without food. Get insights into the integration of glycolysis and the citric acid cycle in cellular metabolism.
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Glycolysis 2 Lecture 23 Pages 439 - 451
Citric Acid Cycle • Molecular oxygen is involved in this cycle and changed to form a water molecule • All three food groups may enter the citric acid cycle • It is a 8 step process • Takes place in the mitochondria of eukaryotes (or cytosol of bacterial)
This 8 step cycle is designed to remove 2 carbons at a spin. The purpose is to produce high energy molecules from low energy one and the elimination of those 2 carbons as CO2 High energy 3 NADH’s 1 FADH2 1 GTP
The structure of GTP - learn this! We have a base - Guanine We have a sugar - Ribose We have three inorganic phosphates in GTP & just 2 phosphates in GDP structure_GTP.jpg
This is the structure of FAD It is similar to GDP in that it too is made of a base (Adenine) & the sugar ribose. It has two inorganic phosphates and then a complex hydrocarbon structure. structure_FADH2.jpg If is designed to carry proton and electrons - which combine to form hydrogen in this case
Remember the names of each of the products with the letters next to their names. These are very important to the cell Even though oxygen is not used directly in the cycle, it is used in the generation of ATP from the carrier molecules. This oxygen forms water and not the CO2 that you breath out. 13_13_02_to_CO2.jpg
RECAP 13_17_final_oxidation .jpg
Starvation prevention • The cell wants to make and use energy at all times to live • Problem is that food is delivered to the cell periodically • How does the cell cope? • Answer: it stores the raw materials for its energy needs close by • Animal cells have either lipid drops or glycogen granules in the cytoplasm • Plant cells have starch and lipid drops - these are stored in the chloroplasts
Fat deposits in animal cells are stained red 13_19_store_fats.jpg
Plant Chloroplasts • Plants are able to perform photosynthesis during periods with sunlight • They make the sugars and other metabolites themselves, but also use the same processes of glycolysis as animal cells to derive energy from the breakdown of these same sugars
Seeds are high in energy because they contain lots of stored food reserves such as fats and sugars 13_21_plant seeds.jpg
In plant cells the system can be simplified as illustrated here. Note that ATP and NADH molecules are not able to leave the chloroplast membranes. So the organelle exports the sugars that it makes to other regions of the cell. 13_22_metabolites_ATP.jpg Plants consume net oxygen at night as we do. Do not sleep with too many plants in your bedroom without proper ventilation
These pathways have another function in addition to the generation of energy: that is to generate the raw materials for other cellular boichemicals 13_23_precursors.jpg
The biochemical pathways within cells are complex - here is a very simplified view showing how glycolysis and the citric acid cycle are integrated About 500 metabolites are represented here - either feeding into these two central pathways or taking molecules from them 13_24_metabolism.jpg