Nutrition and Metabolism

1. Nutrition and Metabolism Page 493-506

2. Why is food necessary? • A certain fraction of nutrients is used to build cellular parts • Most foods are used as metabolic fuels such as ATP • The energy value of foods is measure in units called kilocalories (kcal) or Calories (with a capital C)

3. Nutrients • Nutrients- chemical substances in food that body cells use for growth, maintenance, and repair. • Major nutrients: carbohydrates, lipids, proteins • Minor nutrients: minerals, and vitamins • Water is considered a major nutrient also as an important solvent and accounts for 60% of the volume of food we eat

4. Carbohydrates • Sugar and starches come from plants with few exceptions • Cellulose from plants is indigestible by humans • Provides roughage or fiber, which increases the bulk of the stool and aids defecation • Mainly important for ATP energy • 1g yields about 4 Kcal

5. Carbohydrate Metabolism

6. Lipids • Most fats are triglycerides • Saturated fats found in meat and dairy foods • Unsaturated fats from seeds, nuts, and most vegetable oils • Cholesterol found in egg yolk, meats and milk products • Fats are used to build cell membranes, make myelin sheaths, and insulate the body with a fatty cushion • Backup source of energy • Catabolism of 1g of fat yields twice as much energy as the breakdown of 1g of carbohydrate or protein

7. Fat Metabolism • The liver handles most lipid metabolism • Fat is broken down to acetic acid and is completely oxidized to form carbon dioxide, water and ATP • Cholesterol is never used as a cellular fuel • Excess fat is stored in depots in the hips, abdomen, breasts, and subcutaneous tissues • 1g yields about 9 Kcal

8. Protein • Chains of amino acids • Complete proteins from eggs, milk, and fish—meet all of the body’s amino acid requirements for tissue maintenance and growth • Incomplete proteins come from legumes, nuts and cereals—low in one of more of the essential amino acids • There are 8 essential amino acids out of the 20 that we cannot make on our own • The major structural components for building cell structures

9. Protein Metabolism • Once the liver has finished processing the blood draining the digestive tract and has taken its “fill” of amino acids, the remaining amino acids circulate to the body cells • Cells remove amino acids from the blood to build proteins • Excess amino acids are used to make ATP only when there is an overabundance of proteins • 1g of protein yields about 4 Kcal

10. Minerals • Minerals- 7 elements (calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium) • 4% of total body weight • Mostly in vegetables, legumes, milk and some meats • Helps regulate enzymatic reactions; excess is excreted in urine and feces.

11. Vitamins • Vitamins- organic nutrients • Function as coenzymes (act with an enzyme to accomplish a particular type of catalyst) • Fat-soluble vitamins- A, D, E, and K can’t be absorbed in adequate amounts unless ingested with lipids. • Water-soluble vitamins- B and C dissolved in water, excess is eliminated in urine. Which type is stored for longer amounts of time?

12. Metabolism • Metabolism- all chemical reactions that are necessary to maintain life • Anabolism- larger molecules or structures are built from smaller ones • Ex- joining amino acids to form proteins • Catabolism- substances are broken down to simpler substances • Ex- glucose forming ATP- cellular respiration

13. Basal Metabolic Rate • Basal metabolic rate-kilocalories needed per day to maintain essential life activities like breathing, heartbeat, kidney function- for our body • Average 60-72 kcal/hour

14. Food Pyramid • History of the Food Pyramid • More detailied food pyramid history timeline • Calorie Counting Chart • Daily Water Intake Calculator