Nutrition and Digestion Chapter 41

Breaking It Down Major macromolecules: polymers monomers?

Today We Are Serving Autotrophs Heterotrophs  Consumers Herbivores Carnivores Omnivores  Decomposers

No Hands or ‘Utensils’ Baleen whales, oysters, and sponges Mosquitoes, hummingbirds, and aphids Most animals Catepillars, earthworms, and maggots

Breaking It Down

Compartmentalizing Digestion Prevents self digestion Intracellular digestion  No digestive tract Individual cells and sponges Extracellular digestion  Incomplete digestive tract Cnidarians and flatworms  Complete digestive tract Most animals

No Digestive Tract Digestion is completely intracellular Phago- or pinocytosis form food vacuoles Broken down by lysosomes Incomplete Digestive Tract Single opening to a gastrovascular cavity Starts extracellularly, but ends intracellularly

Complete Digestive Tract Mouth and anus Digestion is extracellular Specialized organs

Mammalian Digestive Tract Alimentary canal Accessory organs (green) Food moved by peristalsis Regulated by sphincters Time varies

Comparative Digestive Tracts Length related to diet  Herbivores & omnivores longer than carnivores Cellulose in plants Herbivores lose many nutrients to feces  Recycle feces to regain Ruminants have 4 chambered stomachs  Regurgitate food from 1 to another = chew cud

Mouth Mechanical digestion  Bite, tear, grind and crush  Increase SA Chemical digestion  Salivary glands release saliva Neural signal from food or association Amylase for carb digestion, bicarbonate to neutralize, and mucins to lubricate Tongue manipulates  Evaluates food via taste and olfaction  Forms a bolus

Pharynx Esophagus and trachea  Epiglottis and larynx regulation  Heimlich maneuver if fails Esophagus  Peristalsis moves bolus  Length varies b/w species  Cell types

Stomach Stores and mixes bolus Gastric juices convert to chyme (ph=2) Chemical digestion  Parietal cells: H + & Cl -  Chief cells: pepsinogen Both inactive until lumen Protects gastric glands Positive feedback  Mucus & epithelial cells Gastric ulcers (Helicobacter pylori) Sphincter regulation

The Final Breakdown Chyme and digestive juices mix in the duodenum (SI)  Pancreas: enzymes and bicarbonate solution  Liver/gallbladder: bile, emulsifier (2107 lab?) Detoxifies and maintains homeostasis Hormonal control  Positive and negative feedback  Ensures juices present only when necessary  Fig 41.4

Summary of Chemical Digestion Sucrase, maltase, and lactase

Breaking It Down

Small Intestine 3 folded regions  Duodenum  Jejunum  Ileum Increased SA increases absorption  Circular folds contain villi covered in microvilli  Diffusion or active transport to blood, lymph, and liver

Large Intestine Cecum for plant material; dead ends  Appendix Colon recovers water by osmosis  Remnants = feces  Peristalsis moves along, reclaiming more water Irritation limits absorption = diarrhea Move too slowly = constipation Rectum stores until elimination  Two sphincters (voluntary and involuntary) control

Breaking It Down

Nutritional Needs Chemical energy Organic building blocks  Carbohydrates  Proteins  Lipids Essential nutrients

Essential Nutrients Essential amino acids  8* of 20 can’t be made, must be consumed  Lacking = protein deficiency (malnutrition)  Eggs, meat, and cheese are complete; plants are incomplete Essential fatty acids  Unsaturated fatty acids  Seeds, grains, and vegetables supply plenty

Essential Nutrients (cont.) Vitamins  Organics needed in small amounts 13 ( mg/day)  Water soluble  Fat soluble Benefits of supplements Table 41.1 Minerals  Inorganics needed in small amounts Vary among species (1mg-2500mg/day) Excess can cause imbalances and toxic effects Table 41.2

Imbalances in Energy Intake Undernourishment  Deficient calories  Droughts and wars Overnourishment  Excess calories  Evolution of food hording Malnourished  Deficient nutrients  Eating habits