Nutrition & Digestion

1. Nutrition & Digestion

2. Objectives: Define and Comprehend • Food processing • Human digestion • Know words on term list (available on web site) • Nutrition • 3 needs • Chemical energy • Vitamins and minerals

3. Food Processing

4. Food Processing • Most food consists of what macromolecules? • Carbohydrates, lipids, and proteins • Why is food chemically broken down? • The macromolecules are too large to pass through cell membranes • The polymers must be broken down into monomers, so that the organism can make their own polymers

5. Human Digestion System

6. Human Digestion: Oral Cavity • At sight or smell of food, salivary glands secrete saliva • Glycoprotein protects & lubricates lining of mouth • Antibacterial agents • Amylase to hydrolyze starch • Why do you chew your food? • Easier to swallow • Expose more surface area to enzymes • Tongue pushes bolus to back of oral cavity & into pharynx

7. Human Digestion: the epiglottis How does the epiglottis prevent food from moving into the trachea?

8. Human Digestion: into the esophagus

9. Human Digestion: the tum tum

10. Human Digestion: the tum tum • Why don’t we need to eat constantly? • Besides breaking down food, the stomach stores food –enough to satisfy our body for many hours • What prevents gastric juice from digesting away the stomach lining? • Pepsin, an enzyme which begins the chemical digestion of protein, is secreted in the inactive form pepsinogen • Protects the gastric gland cells • Mucus helps protect the stomach lining from both pepsin and acid • However, the stomach lining must be replaced about every 3 days

11. Human Digestion: small intestine

12. Human Digestion: small intestine • Nutrients are absorbed into the blood from the small intestine • All 4 types of macromolecules (carbohydrates, lipids, proteins, & nucleic acids) are digested in the duodenum • Carbohydrate digestion completed in rest of the small intestine • Hydrolytic enzymes breakdown polymer into monomers

13. Human Digestion: small intestine • Protein digestion • Pancreas and duodenum secrete hydrolytic enzymes that break polymer into monomers (amino acids) • Nucleic acid digestion • Pancreas and duodenum secrete hydrolytic enzymes which breakdown DNA & RNA polymers into • Nitrogenous bases, sugars, phosphates

14. Human Digestion: small intestine • Lipid digestion • Lipids reach stomach almost completely undigested • Why? • Fats are hydrophobic • Bile salts from gallbladder coat tiny fat droplets that keep them separated from each other • Why is the separation of fats into small droplets beneficial for digestion? • More surface area is exposed, which allows the enzyme to breakdown the fats quickly

15. Human Digestion: small intestine • Majority of chemical digestion has been completed by the time chyme mixture passes through duodenum • Rest of small intestine is adapted for the absorption of nutrients • Small intestine has high surface area • This allows for greater… • Absorption • Also has many folds and projections

16. Human Digestion: small intestine

17. Human Digestion: small intestine • Capillaries that drain away from the villi converge into larger blood vessels and eventually into a main vessel that leads directly to liver • Converts many of nutrients into new substances the body needs • Liver removes excess glucose and stores it as? • Glycogen in liver cells • Blood is then transported to heart, which pumps blood and nutrients to all parts of the body

18. Human Digestion: large intestine

19. Human Digestion: large intestine • Colon absorbs water –approximately 90% of the 7 liters of fluid that enters the canal a day are reclaimed (most in small intestine) • Remains of undigested food become more solid as water is absorbed • Feces • Consists mainly of plant fibers and prokaryotes • Diarrhea occurs when the colon is irritated and is less effective at reclaiming water • Constipation occurs when peristalsis moves the feces too slowly • Colon reabsorbs too much water and feces becomes too compacted • Diet low in plant fiber or lack of exercise

20. Nutrition • There are 3 needs which demand a healthy diet • Fuel to power our bodies • Organic raw materials needed to make our own molecules • Essential nutrients that we cannot make ourselves and must obtain in a prefabricated form

21. Nutrition: why we need chemical energy • The chemical processes of our bodies are fueled by? • ATP • Cellular metabolism produces ATP by oxidizing small molecules that are digested from food • Usually use carbohydrates and fats, but when required, will use proteins too • Cellular metabolism must continue or we die • Our basal metabolic rate (BMR) is approximately 1,300 to 1,800 kcal per day

22. Nutrition: too many kcal • We burn more kcal when we “move” • What happens when we take in more kcal than we use? • Muscle and liver store it as glycogen • Also stored as fat • Liver can convert excess carbohydrates and proteins into fat

23. Nutrition: too many kcal • Extremely low-carb diets • Initial weight loss is mostly WATER • Can cause fatigue and headaches, and in the long-term –muscle loss • Extremely low-fat diets • Inadequate provision of essential fatty acids, proteins, and certain minerals • Decrease absorption of fat-soluble vitamins and can cause irregular menstrual periods • Formula diets –if very low in kcal • Result in loss of body protein, may cause dry skin, thinning hair, constipation, and salt imbalance

24. Nutrition: what works? • Scientists find that the best diet to maintain a healthy body weight is… • There is no best diet • What works is the following equation • Calories in – calories out

25. Nutrition: Vitamins • If one eats a balanced diet, one does not need to take vitamins • Most serve as coenzymes or are parts of coenzymes • Used over and over again in metabolic processes • Deficiencies and excessive use can cause serious problems • Water-soluble vitamins are not harmful as excess can pass in urine and feces • Excessive fat-soluble vitamins are deposited in fat and can have toxic effects

26. Nutrition: Minerals • Must obtain minerals through dietary sources • Ex: calcium needed for normal functioning of nerves and muscles • Ex: phosphorous is an ingredient of ATP and nucleic acids