Digestion and Nutrition

1. Digestion and Nutrition

2. Nutrition

3. Major Focus Questions • What are the types of foods necessary to give us proper nutrition? • What are the major nutrients in food? • Which foods contain these nutrients? • What is the relationship between food and calories?

4. Food and Nutrition • Why do we need to eat? • Molecules of food contain chemical energy that cells use to produce ATP. • Food supplies raw materials that your body needs to build and repair tissues

5. Energy from Food: • Energy content of food is measured in Calories • When we “burn” food through cellular respiration most of the energy is converted to heat or stored in molecules of ATP • One Calorie has enough energy to raise the temperature of one liter of water by 1°C

6. Essential Nutrients • Carbohydrates • Fats • Proteins • Vitamins • Minerals • Water

7. Essential Nutrients Carbohydrates: • Major source of energy for body cells

8. Simple Carbohydrates • Monosaccharides & Disaccharides • Do not have to be digested or broken down • Ex: Fruits, honey, sugar

9. Complex Carbohydrates • Polysaccharides • Broken down by digestive system into simple sugars • Excess sugar stored in liver as glycogen • Starches found in grains, potatoes, vegetables, rice, beans, pasta • Fiber: (cellulose) a complex carb. your body cannot break down • “Roughage” • Helps move food and wastes through digestive system • Found more in “whole grain” products

11. Complex sugars are broken down (digested) into simple sugars by hydrolysis. • Breaking down molecules by adding water • Also called chemical digestion Disac.+ Water Monosac. + Monosac. C12H22O11 + H2O  C6H12O6 +C6H12O6

12. Essential Nutrients Fats (lipids): • Help body absorb fat soluble vitamins • Part of all cell membranes • Insulate nerve cells and help them function • Protect and insulate body organs

13. Important source of energy • 9 calories per gram (as opposed to carbs and proteins which have about 4 calories per gram) • Unused fat stored in fat deposits throughout body • Found in nuts, oils, dairy, meat

14. Fats • Made up of: • 1 glycerol molecule • 3 long fatty acid chains • Looks like a giant letter “E” • Also called a “triglyceride”

15. Saturated vs. Unsaturated Fats • Trans Fats: • hydrogenized unsaturated fat • Has a longer shelf life • Associated with heart disease • Saturated Fats (fatty acids all single bonds) • Most solid at room temp. (Butter, lard) • Not as healthy for you • Unsaturated Fats (fatty acids have one or more double or triple bond) • Most liquid at room temp. (vegetable oils)

16. Essential Nutrients Proteins: • Raw materials for growth and repair of tissues • Enzymes: increase chemical reaction rates • Regulatory Hormones • Transport proteins (ex: hemoglobin) • Can also be a source of energy • Body will utilize carbs and fats first though

17. Proteins are polymers made of amino acids • Body can synthesize only 12 of the 20 amino acids needed to make proteins • The other 8 are the “Essential” amino acids that must be part of our diet • Foods that contain all 8 include: • Meat, Fish, Eggs, Milk • Vegetarians: • must eat a combination of plant foods to obtain all 8 • ex: beans and rice together

18. Amino Acid: basic building block of proteins

19. Examples of Different Amino Acids

20. Biological Molecules and You: • http://www.youtube.com/watch?v=H8WJ2KENlK0&safe=active

21. Vitamins: • Organic molecules that the body needs in very small amounts • Help body perform certain chemical reactions • “Coenzymes” • Most come from food • Some are obtained by bacteria that live in our large intestine (Vitamin K and B12) • What type of symbiotic relationship is this?

22. Types of Vitamins: • Water Soluble Vitamins: • (Ex: B and C vitamins) • Dissolve in water and can’t be stored in body • Excreted in urine • Fat Soluble Vitamins • (Ex: A, D, E, K) • Can be stored in fatty tissues of body

23. Too few Vitamins: • Can result in disorders like scurvy or rickets • Too Many Vitamins • Too much of certain vitamins can be toxic and can damage organs and even be fatal

24. Minerals: inorganic nutrients Ex: • Calcium – needed for bones and teeth • Iron – needed for hemoglobin

25. Essential Nutrients Water • Most important nutrient • Necessary for chemical hydrolysis (breakdown) of food molecules into simpler forms • Lost through urine, sweat and breathing • Drink at least 1 liter each day • Dehydration: what happens?

26. Maintaining a Balanced Diet • “Balanced Diet”: • all nutrients are present in adequate amounts with enough energy to maintain a healthful weight. • Reading Food Labels: • Helps you choose healthful foods • Percent daily values based on a 2000 calorie diet • If you are more active you have greater energy needs

27. The Obesity “Epidemic” • From 1970’s to early 2000s adults considered “obese” has risen from 15% to 33% and is still rising • Causes: • high calorie diet filled with “junk foods” • lack of exercise

28. Maintaining a healthful weight • Keep an active lifestyle (exercise 30 min a day) • Limit calorie intake (especially saturated and trans fats) • Eat a balanced diet filled with whole grains and complex carbs • Many state and local governments have removed many high calorie foods with low nutritional value from schools • Is our school doing a good job? • Should government play a role in controlling obesity? • Health risks such as high blood pressure, diabetes, stroke, are increases in the obese and strain the healthcare system and the economy by reducing the number of healthy workers in the workforce

29. Digestion Focus Questions: • What is the path of food through your body? • What are the major structures and functions of the digestive system? • What are the ways we mechanically and chemically digest our food? • Where are different types of food digested and absorbed?

30. The Digestive System • Basically one long tube • Different things happen at different parts of the tube • Prepares food to be used by cells as an energy source

31. Whole Digestive System about 9 meters long! Purpose: to break food down into simple forms usable by cells

32. Ingestion: • taking in food • Digestion: • breaking down food into particles small enough to be used by cells • Physical digestion • Chemical digestion • Egestion: • elimination of undigested materials

33. Mouth: • tongue, teeth, gums, hard and soft palate

34. Mechanical Digestion: • chewing, breaks food into smaller pieces physically (mastication) • Increases surface area for chemical digestion

35. Chemical Digestion: • Carbohydrate digestion starts in mouth • Salivary glands secrete saliva into the mouth • Contains the enzyme amylase • Breaks down starch into disaccharides

36. Teeth: • Incisors: cut food • Canines: tear food • Molars: crush/grind • Made of dentin & enamel • Tooth enamel is the hardest structure in the body

37. Pulp of tooth has live tissue nerves and blood vessels • Gum tissue surrounds tooth root • Most of tooth below gum line • Problems: • gum disease, cavities

38. Tongue: • Strong muscle, helps to push food around mouth (mechanical digestion) • Pharynx at back of throat starts swallowing reflex when food pushed against it

39. Taste buds: • projections on tongue that contain cells that have “taste receptors” • Different areas of tongue taste different tastes

40. Esophagus: • Muscular tube the moves food through it by peristalsis • Involuntary wavelike muscle contractions

41. Epiglottis: • flap of skin that stops food from entering windpipe • You can’t breath when swallowing Flap opens and closes

42. Stomach • Basically just a thick walled pouch at bottom of esophagus made of smooth muscle tissue • Sphincters controls passage of food into stomach and out of stomach • Protein digestion begins here

43. Mechanical Digestion: • contraction of muscles occurs (peristalsis) • Softens the food and mixes it with digestive juices • Reverse peristalsis = throwing up • Heartburn = stomach sphincter relaxes and stomach acid enters esophagus

44. Chemical Digestion: • stomach lined with glands secreting gastric juices • Mixes with food to form chyme Two Gastric Juices • Hydrochloric Acid (HCl) • brings pH of stomach down to 2 • Kills most bacteria in food • Pepsin • Enzyme that begins breakdown of proteins by breaking peptide bonds • Can only work in a very acidic environment (provided by HCl)

45. Two Types of Digestion in Stomach

46. Why doesn’t your stomach digest itself? • Has a protective layer of mucous • Ulcer = mucous layer breaks down and acid comes in contact with wall of stomach

47. Note: • Some water, and such drugs as aspirin and ethanol are absorbed from the stomach into the blood (accounting for the quick relief of a headache after swallowing aspirin and the rapid appearance of ethanol in the blood after drinking alcohol).

48. Food stays in stomach 2-4 hours becoming a thin soupy chyme. • Slowly released into the upper part of small intestine (called the duodenum)

49. Small Intestine • Longest part of digestive system • Narrower in diameter than large intestine • Digestion is completed here • Absorption of nutrients into bloodstream happens here!!

50. Mechanical Digestion: • peristaltic muscle contractions continue • Chemical Digestion: • Secretions come from pancreas and liver that aid in digestion • Carbohydrates, proteins and fats digested here