1. Heterotrophic Nutrition
Chapter 38, Sections 1 and 2

2. Nutrition
The process of obtaining food and breaking it down to be used for metabolism
Food contains nutrients which provide energy and materials needed for metabolism (growth, repair, etc)

3. 2 Types of Nutrients Organic- proteins, carbohydrates, fats, vitamins
Inorganic- minerals and water
Minerals are chemical elements that plants absorb from soil (Fe, Ca, P, I2) and animals obtain from eating plants
Vitamins are needed as coenzymes in many reactions

4. Energy Content of Food
The energy content of food is calculated by burning food and measuring the amount of energy given off
An instrument called a calorimeter is used to do this
1 calorie is the amount of heat needed to raise 1 gram of water by 1 degree Celsius
1 calorie is a small unit, so on food labels kilocalories are used (1 kcal=1000 cal)

5. Human Nutritional Needs
Not everybody requires the same amount of calories
Young people, active people, males require more calories
When you eat more calories than you need, you gain weight
When you eat fewer calories than you need, you lose weight

6. Human Nutritional Needs (continued)
Need to eat a balanced diet (all food groups) to stay healthy
Fiber (roughage) is an important part of the diet- it stimulates the muscles in the digestive tract and decreases the risk of cancer

7. Food Pyramid
Food Guide Pyramid

8. Types of Digestion
Absorption is the process of nutrients passing through cell membranes
Digestion is the breaking down of food molecules so nutrients can be absorbed
Mechanical digestion- food cut, crushed, ground up, the surface area of food particles is increased
Chemical digestion- digestive enzymes work on the surface of food particles to break them down

9. Types of Digestion (continued)
Intracellular- occurs within the cell
Extracellular- occurs outside of the cell
Unicellular organisms have intracellular digestion
Multicellular organisms have mostly extracellular digestion

10. Digestion in the Amoeba
Intracellular digestion
Move by using pseudopodia (“false feet”)
Cyclosis-is the cytoplasm streaming
Pseudopods surround food and engulf it (phagocytosis)
Food particle joins with a lysosome, now called a food vacuole
Enzymes from the lysosome break down the food
Usable nutrients diffuse through the cell
Unusable products diffuse out of the cell

11. Digestion in Paramecium
Surrounded by cilia (hair-like structures)
Cilia sweep food into the oral groove and then gullet
Food vacuole forms with enzymes from lysosomes and digests the food
Usable products diffuse throughout the cytoplasm
Undigested products are egested through the anal pore
Intracellular digestion

12. Digestion in the Hydra Live in water attached to a plant
Has both intracellular and extracellular digestion
Has 2 layers of cells
Outer layer is ectoderm
Inner layer is endoderm
Body is a hollow tube with tentacles
Tentacles capture food and bring it into the mouth
The tentacles have stinging cells called nematocysts

13. Hydra (continued) Food moves into gastrovascular cavity
Some endoderm cells secrete enzymes into the cavity (this is extracellular digestion)
Smaller particles are absorbed into the cells where they are further broken down (this is intracellular digestion)
Undigested material is egested through the mouth
Hydra has 1 opening for food and waste

14. Digestion in the Earthworm
Complex multicellular organism
Tube within a tube body plan
Inner tube is the alimentary canal
2 openings- mouth and anus
Food travels in 1 direction from mouth to anus
Food pulled into mouth by the sucking action of the pharynx
Food moves from pharynx to esophagus to crop
Crop is a storage chamber

15. Earthworm (continued)
Food gradually released into the gizzard
Gizzard crushes food (mechanical digestion)
Food moves into the intestine, which has a large surface area
Chemical digestion occurs in the intestine
Nutrients are absorbed through the intestine into the blood
Undigested material is egested through the anus

16. Digestion in the Grasshopper
Mouth has saliva which begins chemical digestion
Mouth also has specialized mouth parts for mechanical digestion of plant material
Food then moves into esophagus and then the crop (stores food)
Food then moves into the gizzard for further mechanical digestion

17. Grasshopper (continued)
Food then moves into the stomach, where further chemical digestion and absorption occur
Usable nutrients are absorbed into blood
Undigested material moves to intestine and then rectum where water is reabsorbed and waste is eliminated through the anus

18. Digestion in Humans
Tube with specialized organs (similar to earthworm and grasshopper)
Glands secrete enzymes into the alimentary canal through ducts
Alimentary canal= digestive tract= gastrointestinal (GI) tract

19. Mouth and Pharynx Food enters here Chewing is mechanical digestion
Saliva contains amylase which begins to break down starch (chemical digestion or hydrolysis)
Saliva also moistens food and causes the food to stick together in a bolus

20. Pharynx Bolus of food enters the pharynx
Epiglottis closes to prevent food from entering the trachea
Choking occurs if food enters trachea

21. Esophagus
Bolus of food travels from pharynx to stomach through the esophagus
Bolus moves down the esophagus through peristalsis- waves of muscle contraction and relaxation

22. Stomach
Bolus of food enters the stomach through the cardiac sphincter (ring of muscles)
The stomach is a thick-walled J-shaped pouch
Bolus of food is mechanically broken down by the churning of the stomach
Bolus of food is chemically broken down by gastric juice secreted by glands in the stomach walls

23. Stomach (continued) HCl (hydrochloric acid) kills bacteria in food
Gastric juice is highly acidic because of the HCl
Gastric juice also contains pepsin, an enzyme which begins to break down proteins
Bolus becomes a soupy liquid called chyme
Chyme leaves the stomach through the pyloric sphincter

24. Small Intestine Chemical digestion is completed here
Absorption of nutrients occurs here
Is long (6.5 meters) and has a small diameter
Fluid is alkaline (basic)

25. Small Intestine (continued)
Pancreas
Accessory organ which secretes pancreatic juice into small intestine
Pancreatic juice consists of enzymes which complete the digestion of food
Amylase breaks down starch
Trypsin and proteases break down proteins
Lipase breaks down fats

26. Small Intestine (continued)
Liver-
Accessory organ that produces bile
Bile is responsible for the emulsification of fats (breaking large fats apart into smaller fat globules)
Bile is secreted through a duct into the gall bladder where it is stored and then moves into the small intestine through another duct

27. Small Intestine (continued)
Nutrients are absorbed into the blood through small finger-like projections called villi
Villi-
Have a network of blood vessels around them for the absorption of sugars and amino acids into the blood
Have a lacteal in the center for the absorption of fats into the lymph system

28. Diagram of a Villus

29. Large Intestine (Colon)
Is short (1.5 meters) and thick
Function is the reabsorption of water from the undigested material
Bacteria live here that produce vitamin K (for blood clotting) and some B vitamins
Feces is stored in the rectum and eliminated through the anus

30. Diseases of the Digestive System
Ulcers-
Mucous layer of stomach is eroded by bacteria
Is very painful
Can be treated with antibiotics
Heartburn-
Gastric reflux
Gastric juice (highly acidic) moves up into esophagus
Is painful
Treated with medication

31. Diseases (continued) Appendicitis- Diarrhea-
Appendix (pouch along large intestine) becomes infected
Is surgically removed
Diarrhea-
Too little water is reabsorbed in the large intestine
Watery feces

32. Diseases (continued) Constipation- Gallstones-
Too much water is reabsorbed in the large intestine
Occurs if not enough roughage is eaten
Gallstones-
A build up of hardened cholesterol in the gall bladder
Can be surgically removed

33. Diseases (continued) Anorexia and Bulimia-
When a person vomits frequently
Causes damage to teeth and esophagus from the acid gastric juice
There are also nutritional problems