part 3 metabolism - Lecture 3: Metabolism and Bioenergetics...

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Unformatted text preview: Lecture 3: Metabolism and Bioenergetics The energy we derive from food is stored in cells in the form of adenosine triphosphase (ATP) ATP serves as the immediate source of energy for most body functions including muscle contraction ATP > ADP + Pi + Energy Energy sources + ADP +Pi > ATP Kilocalorie Energy in biological systems is measured in kilocalories All energy eventually degrades to heat One kilocalorie is the amount of heat energy needed to raise 1 kg of water from 1 C to 15 C Metabolism = sum of all chemical reactions Catabolic reactions (give off energy) Anabolic reactions (use energy, synthesis reactions) Energy Sources At rest, the body uses carbohydrate and fat almost equally for energy Protein provides little energy for cellular activity, but serves as the building blocks for the bodys tissues During intense short-duration muscular effort, the body relies mostly on carbohydrate to generate ATP Longer, less intense exercise utilizes carbohydrates and fat for sustained energy production Carbohydrate All dietary carbohydrate is ultimately converted to glucose Glucose is taken up by muscles and liver and converted to the complex sugar molecule called glycogen Glycogen is stored in the cytoplasm of muscle cells, where it can be quickly used to form ATP Glycogen is also stored in the liver, where it is converted back to glucose as needed and transported by the blood to the muscles to form ATP Fat Provides substantial energy during prolonged, low- intensity activity Body stores of fat are larger than carbohydrate reserves Fat is less readily available for cellular metabolism compared to carbohydrate Fat is stored as triglycerides and must be broken down to free fatty acids (FFAs) to be used in metabolism More energy is derived from breaking down fat (9.4 kcal/g) compared to carbohydrate (4.1 kcal/g) Protein Protein can be used as a minor source of energy, but it must be converted to glucose via glucogenesis Proteins can generate FFAs during starvation through lipogenesis Protein can supply up to 5-10% of energy during prolonged exercise Proteins must be broken down to their basic unitsamino acidsto be used for energy Energy for Cellular Metabolism...
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part 3 metabolism - Lecture 3: Metabolism and Bioenergetics...

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