Heterotrophic Nutrition Chapter 38, Sections 1 and 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)

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

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)

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

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

Food Pyramid Food Guide Pyramid

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

Diagram of a Villus

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

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

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

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

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