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Metabolism. Metabolism. chemical reactions in making and breaking bonds carbohydrates – glucose triglycerides – glycerol and fatty acids proteins – amino acids. Lipid Metabolism. fat gives us 2X the energy of carbs and proteins efficient storage in adipose tissue
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Metabolism • chemical reactions in making and breaking bonds • carbohydrates – glucose • triglycerides – glycerol and fatty acids • proteins – amino acids
Lipid Metabolism • fat gives us 2X the energy of carbs and proteins • efficient storage in adipose tissue • food fat is converted to body fat by absorbing parts and putting back together again inside the cell • very little energy is needed Large central globule of (pure) fat
fat supplies 60% of body's energy during rest • more during activity • when needed fat (triglyceride) is dismantled and released as glycerol and fatty acids into the blood where it is easily accessible by the cells
Carbohydrate Metabolism • 1/3 of body’s glycogen is stored in liver • released as glucose to bloodstream • eat – intake glucose • liver condenses extra glucose to glycogen • blood glucose falls • liver hydrolyzes glycogen to glucose Glycogen is bulky, so we store only so much: short term energy supply Fat is the long term energy supply.
Glucose for Energy • enzymes break apart glucose – yielding energy • inadequate supply of carbohydrates • ketone bodies (fat fragments) are an alternate energy source during starvation • excess ketones can lead to ketosis: imbalance of acids in body • minimum of 50 – 100 grams of carbs/day are needed to avoid ketosis
Protein Metabolism • protein turnover • constant making and breaking of proteins • frees amino acids to “amino acid pool” • can be used to make body proteins • nonessential amino acids can be made from other amino acids
amino acid pool • stripped of nitrogens and made available for energy • deamination • can make other compounds such as melanin • make fat • amino acids are deaminated, nitrogen is excreted, carbon is converted to fat and stored • protein-rich foods can cause weight gain
Fasting • several hours after a meal, glucose is used up • protein is used for energy • shift to ketosis • suppresses appetite • hormones slow metabolism • eventually starvation