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Cellular Metabolism. Metabolism is the sum total of all chemical reactions within a cell. Anabolism creates larger molecules from smaller molecules (this requires an energy input).Catabolism breaks large molecules down into smaller molecules (this releases energy). . Cellular Metabolism. Anabol
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1. Chapter 4 Cellular Metabolism
2. Cellular Metabolism Metabolism is the sum total of all chemical reactions within a cell.
Anabolism creates larger molecules from smaller molecules (this requires an energy input).
Catabolism breaks large molecules down into smaller molecules (this releases energy).
3. Cellular Metabolism Anabolism provides all materials for cellular growth and repair. The chemical reaction that helps to push this process is called Dehydration Synthesis. Thru this process water is (H2O) is pulled out of two or more molecules and the two substances are joined. As the process repeats, the molecular chain extends, forming a larger molecule.
4. Cellular Metabolism Catabolism breaks down large incoming molecules into a smaller, more manageable size for the cell to handle. Hydrolysis is an example of a catabolic reaction which can decompose most organic molecules. Hydrolysis of a disaccharide, for instance, yields two monosaccharides, and hydrolysis of a protein yields amino acids.
5. Cellular Metabolism The reactions of metabolism are often reversible.
Enzymes often control metabolic reactions. Most enzymes are globular proteins that promote chemical reactions by lowering the activation energy needed to start these reactions.
Enzymes are specific. They only act on a particular molecule called a Substrate. Each enzyme must be able to recognize its substrate. This is done by shape.
All enzymes have an active site. This is the site where the enzyme binds to the substrate and the shape of the active site is very specific. This binding in turn causes a strain or change in the substrates chemical bonds that make a chemical reaction more likely to happen. The enzyme is released, unchanged, after the reaction.
6. Cellular Metabolism
7. Cellular Metabolism Sequences of enzyme controlled reactions called metabolic pathways often lead to synthesis or break-down of a particular biochemical.
The name of an enzyme often has the suffix ase added to the back of its substrates name. (lactose, lactase)
The rate at which a metabolic pathway functions is often determined by a regulatory enzyme that catalyzes one of its steps. The number of enzyme molecules available is often limited, thus when all molecules are being utilized, it is no longer possible to push a reaction any faster. The enzyme in shortest supply is often the first enzyme in a metabolic pathway and it is often referred to as the Rate Limiting Enzyme.
8. Cellular Metabolism Many enzymes may be inactive until combined with a cofactor or coenzyme. A cofactor is often an atom of a specific element such as iron or zinc. A coenzyme may be a vitamin molecule.
Almost all enzymes are proteins. As such, they are subject to the rules that proteins must obey. Factors that affect proteins will affect most enzymes. Heat, radiation, electricity, and pH can denature proteins, and thus most enzymes. The change that takes place is usually a change in the active site of the enzyme. This change usually hinders its action or makes it useless entirely.
9. Cellular Metabolism ATP is a high energy molecule that the cell uses to get work done. When one of the high energy bonds connecting a phosphorus atom is broken, energy is released for cellular work and ATP is reduced to ADP. The energy of the molecule is restored when the phosphorus molecule is reattached via phosphorylation.
10. Cellular Metabolism Cellular respiration is the process that releases energy from molecules such as glucose. The chemical reactions for respiration must occur in a specific chemical sequence, with each one controlled by a particular enzyme. Some reactions occur in the cytosol, others take place in the mitochondria.
Aerobic reactions require oxygen. Anaerobic reactions do not require oxygen, but can take place with it present.
11. Cellular Metabolism Cellular respiration has 3 stages
Glycolysis
Citric Acid Cycle
Electron Transport Chain
Glycolysis begins the break-down of carbs into a usable energy substance. It occurs in the cytosol and is completely anaerobic.
12. Cellular Metabolism Glycolysis has 3 main events:
Glucose is phosphorlyated by addition of two phosphate groups on either end.
The six carbon molecule is split into two 3-carbon molecules.
ATP is produced and two 3-carbon molecules of pyruvic acid result. This pyruvic acid goes on into the later steps.
**The net output of ATP from glycolysis is 2 molecules of ATP per molecule of glucose.
Almost all reactions will have a by-product or waste product that is a left over from their activity. The by-product of glycolysis is lactic acid. A build up of any by-product in a cell usually inhibits the reaction which built it, after a certain point.
13. Cellular Metabolism The citric acid cycle and electron transport chain are aerobic in nature. Together they produce the bulk of ATP needed by the cell, with most of it produced by the electron transport chain. This is accomplished via a complex series of enzyme catalyzed reactions.
The aerobic reactions of respiration will yield about 36 ATP, water and CO2 per molecule of glucose (2 molecules of pyruvic acid). CO2 is the waste product produced by aerobic reactions.
14. Cellular Metabolism Carbohydrate storage takes place in the cell in the form of glycogen. Most cells can synthesize this polysaccharide. Liver and muscle cells can store the greatest amounts. Unused carbs are almost always stored as neutral fat. The bodys capacity for this is almost limitless.
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