All organisms must obtain and process essential nutrients (food) *** Exception: Venus Fly Traps undergo photosynthesis but needs source of nitrogen

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2 All organisms must obtain and process essential nutrients (food) AUTOTROPHS self feeder makes their own food eg. Plants do not require a digestive tract *** Exception: Venus Fly Traps undergo photosynthesis but needs source of nitrogen

3 HETEROTROPH other feeder rely on other organisms for food

4 Filter Feeding filter water and extract microscopic organisms eg. blue whale, ducks, sea sponges

5 Fluid Feeding contain mouthparts adapted for piercing and sucking the juices of plants and animals eg. mosquitoes,, butterflies, leeches

6 Bulk Feeding ingest large amounts of food at a time eg. frogs, snakes, humans

7 1. Ingestion taking in food 2. Digestion breakdown of food (mechanical/chemical) 3. Absorption transport of nutrients to body 4. Elimination removal of undigested solid waste

8 Mechanical digestion: physical breakdown of food into smaller bits Chemical digestion: breakdown of macromolecules by enzymes

9 The movement of food through the digestive system is as follows: Mouth Esophagus Stomach Small Intestine Large Intestine

10 Mouth Structure: The tongue is used to mix food and move it around. Contains 3 types of teeth: Incisors: biting Canines: tearing Molars and pre-molars: grinding and crushing

11 Mouth Function: The mouth has two functions: Ingestion: taking food in Digestion: the break down of complex foods into molecules that can be used by cells Note: Both mechanical and chemical digestion occurs

12 Mechanical Digestion The physical breakdown of food (Biting, tearing, chewing) The tongue moving and mixing food

13 Chemical Digestion The use of chemicals to break down food. In the mouth, a solution called saliva is secreted from 3 pairs of salivary glands in the mouth.

14 Saliva moistens food so that it is easily swallowed Saliva contains the enzyme amylase e.g. Amylase digests starch

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16 Note: When food is ready to be swallowed, the epiglottis closes off the larynx and blocks off the respiratory tract. Food moves into the pharynx then to the esophagus. 2. Esophagus Structure A tube that connects the pharynx to the stomach. Made of muscle tissue.

17 2. Esophagus Function Muscle tissue of the esophagus contracts and relaxes in a wave like pattern. The sequence of rhythmic waves is called peristalsis Peristalsis moves food into the stomach Note: At the base of the esophagus is a ring of muscle called the cardiac sphincter. The sphincter is usually closed (constricted). Pressure exerted by food on the sphincter causes it to open, and food enters the stomach.

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19 Structure: muscular walls contains specialized cells: secrete mucous to lubricate stomach walls and protect stomach lining release of HCl when signaled secrete pepsinogen HCl + pepsinogen pepsin (low ph) (enzyme)

20 Function of Pepsin: breaks protein molecules up into short polypeptides Other Function of HCl: break up connective tissue that holds food together Note: Partially digested food leaves the stomach through the pyloric sphincter.

21 Structure: The inside of the tube is lined with fingerlike projections called villi: Villi increase the surface area for more nutrients to be absorbed On every villi there are microvilli

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23 Function: The break down of carbohydrates by amylases, proteins by peptidases, and fats by lipases. Absorption of nutrients by microvilli (monosaccharides, amino acids, fatty acids and glycerol) Note: Nutrients are absorbed through active transport and diffusion.

24 No digestion occurs here! Function: absorption of water, dissolved minerals, and vitamins (e.g. vitamin K produced by intestinal bacteria) storage of cellulose and undigested bacterial fragments until it reaches the rectum exit for solid waste

25 Pancreas Function secretes bicarbonate (a base) secretes digestive enzymes Bicarbonate neutralizes the acidity in the small intestine, enabling its enzymes to digest nutrients. Note: Insulin is also made in the pancreas

26 Liver Function Produces bile to make fats soluble Bile is stored in the gallbladder (contains bile salts) and released to small intestine Responds to glucose levels: If high, stores in liver as glycogen If low, glycogen broken down to release more

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28 Location Enzyme Substrate Digestion End Products Salivary Glands Amylase (requires high ph) Starch, glycogen Disaccharides Stomach Pepsin (requires low ph) Polypeptides Short peptides Small intestine Peptidases (just above neutral) Protein peptides Amino acids Nucleases (just above neutral) DNA, RNA Sugars and nucleic bases Lactase, maltase, sucrase Disaccharides Monosaccharides Pancreas Lipase Triglycerides Fatty acids and glycerol Trypsin Short peptides Peptides

29 Hormone Source Stimulus Action Gastrin Pylorus of the stomach Entry of food in stomach Cholecystokinin Duodenum Arrival of food in the small intestine Stimulates the secretion of HCl Stimulates the release of bile from the gallbladder. Stimulates the secretion of digestive enzymes from the pancreas. Secretin Duodenum HCl present in the duodenum Stimulates secretion of bicarbonate from pancreas